CN110601752B

CN110601752B - Chirp measuring device and method, computer readable storage medium

Info

Publication number: CN110601752B
Application number: CN201910760199.0A
Authority: CN
Inventors: 陈宏刚; 张博; 胡蕾蕾; 李凤; 丁兰; 甘霖飞
Original assignee: Accelink Technologies Co Ltd
Current assignee: Accelink Technologies Co Ltd
Priority date: 2019-08-16
Filing date: 2019-08-16
Publication date: 2021-04-09
Anticipated expiration: 2039-08-16
Also published as: CN110601752A

Abstract

The embodiment of the invention discloses a chirp measuring device and method and a computer readable storage medium, comprising the following steps: the device comprises a first laser, a second laser, an optical signal modulation circuit, an optical coupler, a sampling circuit and a processor; the output end of the first laser is connected with the input end of the optical signal modulation circuit, the input end of the optical coupler is respectively connected with the output end of the optical signal modulation circuit and the output end of the second laser, the output end of the optical coupler is connected with the input end of the sampling circuit, and the output end of the sampling circuit is connected with the processor; the processor is used for calculating phase shift coefficients of the direct current component, the first harmonic component, the second harmonic component and the third harmonic component output by the sampling circuit to obtain a phase shift conversion factor, and calculating to obtain a chirp parameter according to a preset chirp measurement model and the phase shift conversion factor; the preset chirp measurement model is used for measuring the chirp parameter of the optical signal modulation circuit.

Description

Chirp measuring device and method, computer readable storage medium

Technical Field

The present invention relates to the field of optical communications, and in particular, to a chirp measurement apparatus and method, and a computer-readable storage medium.

Background

In recent years, silicon photonics technology has received increasing attention as a high-speed optoelectronic hybrid integrated device with a small package, which can be compatible with existing CMOS technology to achieve low cost, where a silicon optical modulator has been used in optical interconnection backbone network transmission as a core device in silicon photonics technology. The silicon optical modulator is based on the dispersion effect of nonlinear plasma, and causes the change of the refractive index of the waveguide active region, thereby realizing the phase modulation of optical signals. However, such a modulation method not only changes the phase of the optical signal, but also changes the intensity of the optical signal, which causes a chirp effect in the optical fiber transmission of the modulated optical signal, resulting in distortion of the phase and intensity of the optical signal.

The accurate measurement of the chirp of the silicon optical modulator is crucial to the evaluation of the modulation characteristics of the silicon optical modulator, and in the center of the existing test technology, when the chirp parameter of the silicon optical modulator is measured by a chirp measurement device, a test signal is usually added to a radio frequency pin of the silicon optical modulator, and the test signal is monitored by a spectrometer, so as to obtain the chirp parameter.

Disclosure of Invention

The invention mainly provides a chirp measurement device and method and a computer readable storage medium, which can improve the accuracy of chirp parameter measurement.

The technical scheme of the invention is realized as follows:

in a first aspect, an embodiment of the present invention provides a chirp measurement apparatus, including:

the device comprises a first laser, a second laser, an optical signal modulation circuit, an optical coupler, a sampling circuit and a processor;

the output end of the first laser is connected with the input end of the optical signal modulation circuit, the input end of the optical coupler is respectively connected with the output end of the optical signal modulation circuit, the output end of the second laser is connected with the output end of the optical coupler, the output end of the optical coupler is connected with the input end of the sampling circuit, and the output end of the sampling circuit is connected with the processor;

the processor is used for calculating phase shift coefficients of the direct current component, the first harmonic component, the second harmonic component and the third harmonic component output by the sampling circuit to obtain a phase shift conversion factor, and calculating a chirp parameter according to a preset chirp measurement model and the phase shift conversion factor; the preset chirp measurement model is used for measuring chirp parameters of the optical signal modulation circuit;

the optical signal modulation circuit modulates an input optical signal generated by the first laser to obtain a modulated optical signal, the optical coupler mixes the modulated optical signal with a local oscillator optical signal generated by the second laser to obtain a mixed optical signal, the sampling circuit samples the mixed optical signal, and the direct current component, the first harmonic component, the second harmonic component and the third harmonic component output by the sampling circuit are sent to the processor to calculate the chirp parameter.

In the above aspect, the sampling circuit includes: a photoelectric signal converter and a sampler;

the input end of the photoelectric signal converter is connected with the output end of the optical coupler;

the input end of the sampler is connected with the output end of the photoelectric signal converter;

the output end of the sampler is connected with the processor;

and converting the mixing optical signal into a first voltage signal through the photoelectric signal converter, and sampling the first voltage signal through the sampler to obtain the direct current component, the first harmonic component, the second harmonic component and the third harmonic component.

In the above scheme, the sampling circuit further includes: a transimpedance amplifier;

the input end of the transimpedance amplifier is connected with the output end of the photoelectric signal converter;

the output end of the transimpedance amplifier is connected with the input end of the sampler;

and converting the mixing optical signal into a current signal through the photoelectric signal converter, converting the current signal into a second voltage signal by using the transimpedance amplifier, and sending the second voltage signal into the sampler for sampling to obtain the direct current component, the first harmonic component, the second harmonic component and the third harmonic component.

In the foregoing scheme, a frequency offset exists between the input optical signal generated by the first laser and the local oscillator optical signal generated by the second laser.

In the above aspect, the optical signal modulation circuit includes: the device comprises a silicon optical modulator, a test signal generator and a direct current voltage source;

the output end of the first laser is connected with the silicon optical modulator, and the output end of the silicon optical modulator is connected with the input end of the optical coupler;

the test signal generator is connected with the silicon optical modulator;

the direct current voltage source is connected with the silicon optical modulator;

and inputting a test signal to the silicon optical modulator through a test signal generator, inputting direct current bias and radio frequency bias to the silicon optical modulator through the direct current voltage source, and modulating the input optical signal and the test signal by using the silicon optical modulator to obtain the modulated optical signal.

In the above aspect, the silicon optical modulator includes: the optical signal input end, the first optical path, the second optical path and the optical signal output end;

the optical signal input end is connected with the output end of the first laser, and the optical signal output end is connected with the input end of the optical coupler;

said first optical path and said second optical path diverging from said optical signal input and converging at said optical signal output;

and receiving an input optical signal through the optical signal input end, modulating the input optical signal by using a first optical path and a second optical path, and obtaining and outputting the modulated optical signal at the optical signal output end.

In a second aspect, an embodiment of the present invention provides a chirp measurement method applied to the chirp measurement apparatus in any one of the first aspects, including:

generating an input optical signal through a first laser, and generating a local oscillator optical signal through a second laser;

modulating the input optical signal to obtain a modulated optical signal;

mixing the modulated optical signal and the local oscillator optical signal to obtain a mixed optical signal;

sampling the mixed optical signal to obtain a direct current component, a first harmonic component, a second harmonic component and a third harmonic component of the mixed optical signal;

calculating phase shift coefficients of the direct current component, the first harmonic component, the second harmonic component and the third harmonic component to obtain a phase shift conversion factor, and calculating according to a preset chirp measurement model and the phase shift conversion factor to obtain a chirp parameter; the chirp measurement model is used for measuring the chirp parameter of the optical signal modulation circuit.

In the above scheme, the calculating a phase shift coefficient for the dc component, the first harmonic component, the second harmonic component, and the third harmonic component to obtain a phase shift transformation factor includes:

acquiring a preset light complex field intensity model, and performing Fourier transform on the preset light complex field intensity model to obtain a first frequency spectrum model and a second frequency spectrum model;

respectively substituting the direct current component, the first harmonic component, the second harmonic component and the third harmonic component into the first frequency spectrum model and the second frequency spectrum model, and respectively calculating a first direct current output, a second direct current output, a first harmonic output, a second first harmonic output, a first second harmonic output, a second harmonic output, a first third harmonic output and a second third harmonic output;

calculating a phase shift coefficient by adopting the first direct current output and the second direct current output to obtain a direct current phase shift factor;

calculating phase shift coefficients by using the first primary harmonic output and the second primary harmonic output to respectively obtain a primary sum phase shift factor and a primary difference phase shift factor;

calculating a phase shift coefficient according to the first second harmonic output and the second harmonic output to respectively obtain a second sum phase shift factor and a second difference phase shift factor;

calculating a phase shift coefficient by using the first third harmonic output and the second third harmonic output to respectively obtain a third sum phase shift factor and a third difference phase shift factor;

and adopting the direct current phase shift factor, the primary sum phase shift factor, the primary difference phase shift factor, the secondary sum phase shift factor, the secondary difference phase shift factor, the tertiary sum phase shift factor and the tertiary difference phase shift factor as the phase shift transformation factor.

In the foregoing solution, the calculating a phase shift coefficient by using the first dc output and the second dc output to obtain a dc phase shift factor includes:

obtaining a direct current difference value result by adopting the difference between the first direct current output and the second direct current output;

summing the first direct current output and the second direct current output to obtain a direct current sum result;

comparing the DC difference result with the DC sum result, and taking the obtained ratio as the DC phase shift factor.

In the above scheme, the calculating the phase shift coefficient by using the first harmonic output and the second first harmonic output to obtain the first sum phase shift factor and the first difference phase shift factor respectively includes:

obtaining a first difference value result by adopting the difference between the first harmonic output and the second first harmonic output;

summing the first harmonic output and the second first harmonic output to obtain a first sum result,

comparing the primary sum result with the direct current sum result to obtain the primary sum phase shift factor, and comparing the primary difference result with the direct current difference result to obtain the primary difference phase shift factor.

In the foregoing solution, the performing phase shift coefficient calculation according to the first second harmonic output and the second harmonic output to obtain a second sum phase shift factor and a second difference phase shift factor respectively includes:

obtaining a second order difference value result by adopting the difference between the first second order harmonic output and the second order harmonic output;

summing the first second harmonic output and the second harmonic output to obtain a second sum result;

and comparing the secondary sum result with the direct current sum result to obtain the secondary sum phase shift factor, and comparing the secondary difference result with the direct current difference result to obtain the secondary difference phase shift factor.

In the foregoing solution, the calculating a phase shift coefficient by using the first third harmonic output and the second third harmonic output to obtain a third sum phase shift factor and a third difference phase shift factor respectively includes:

subtracting the first third harmonic output from the second third harmonic output to obtain a third difference result;

summing the first third harmonic output and the second third harmonic output to obtain a third sum result;

and comparing the third sum result with the direct current sum result to obtain the third sum phase shift factor, and comparing the third difference result with the direct current difference result to obtain the third difference phase shift factor.

In the foregoing solution, the calculating a chirp parameter according to a preset chirp measurement model and the phase shift transformation factor includes:

acquiring a phase shift difference of an optical signal modulation circuit;

calculating a chirp molecule part according to the direct current phase shift factor, the first sum phase shift factor, the first difference phase shift factor, the second sum phase shift factor, the second difference phase shift factor, the first cosine harmonic, the third sum phase shift factor, the third difference phase shift factor, the second cosine harmonic and the sine value of the phase shift difference;

calculating a chirp denominator part according to the direct current phase shift factor, the first sum phase shift factor, the first difference phase shift factor, the second sum phase shift factor, the second difference phase shift factor, the first cosine harmonic, the third sum phase shift factor, the third difference phase shift factor, the second cosine harmonic and a cosine value of the phase shift difference;

and comparing the chirp numerator part with the chirp denominator part, and integrating the obtained ratio in a time domain to obtain the chirp parameter.

In the above scheme, the calculating a chirp molecule part according to the dc phase shift factor, the first sum phase shift factor, the first difference phase shift factor, the second sum phase shift factor, the second difference phase shift factor, the first cosine harmonic, the third sum phase shift factor, the third difference phase shift factor, the second cosine harmonic, and the sine value of the phase shift difference includes:

calculating primary chirp molecules according to the direct current phase shift factor, the primary sum phase shift factor, the primary difference phase shift factor and the sine value of the phase shift difference;

calculating secondary chirp molecules by using the direct current phase shift factor, the secondary sum phase shift factor, the secondary difference phase shift factor, the sine value of the phase shift difference and the primary cosine harmonic;

calculating a third chirp molecule according to the direct current phase shift factor, the third sum phase shift factor, the third difference phase shift factor, the sine value of the phase shift difference and the second cosine harmonic;

and accumulating the primary chirp molecules, the secondary chirp molecules and the tertiary chirp molecules to obtain the chirp molecule part.

In the above solution, the calculating a chirp denominator part according to the dc phase shift factor, the first sum shift factor, the first difference phase shift factor, the second sum shift factor, the second difference phase shift factor, the first cosine harmonic, the third sum shift factor, the third difference phase shift factor, the second cosine harmonic, and the cosine value of the phase shift difference includes:

calculating a primary chirp denominator according to the direct current phase shift factor, the primary sum phase shift factor, the primary difference phase shift factor and the cosine value of the phase difference;

calculating a secondary chirp denominator by using the direct current phase shift factor, the secondary sum phase shift factor, the secondary difference phase shift factor, the cosine value of the phase difference and the primary cosine harmonic;

calculating a third chirp denominator according to the direct current phase shift factor, the third sum phase shift factor, the third difference phase shift factor, a cosine value of the phase difference and the second cosine harmonic;

and accumulating the primary chirp denominator, the secondary chirp denominator and the tertiary chirp denominator to obtain the chirp denominator part.

In the foregoing solution, before the generating an input optical signal by the first laser and generating a local oscillation optical signal by the second laser, the method further includes:

acquiring a preset light complex field intensity model and a preset chirp calculation model;

expanding and simplifying the preset light complex field intensity model to obtain an instantaneous light intensity function and an instantaneous phase function of the modulated light signal;

combining and simplifying the preset chirp calculation model, the instantaneous light intensity function and the instantaneous phase function to obtain an instantaneous chirp measurement model;

and integrating the instantaneous chirp measurement model to obtain the preset chirp measurement model.

In a third aspect, an embodiment of the present invention provides a chirp measurement apparatus, including:

the generating module is used for generating an input optical signal through a set first laser and generating a local oscillator optical signal through a set second laser;

the optical processing module is used for modulating the input optical signal to obtain a modulated optical signal; mixing the modulated optical signal and the local oscillator optical signal to obtain a mixed optical signal;

the sampling module is used for sampling the frequency mixing optical signal to obtain a direct current component, a first harmonic component, a second harmonic component and a third harmonic component of the frequency mixing optical signal;

the calculation module is used for calculating phase shift coefficients of the direct current component, the first harmonic component, the second harmonic component and the third harmonic component to obtain a phase shift conversion factor, and calculating a chirp parameter according to a preset chirp measurement model and the phase shift conversion factor; the chirp measurement model is used for measuring the chirp parameter of the optical signal modulation circuit.

In a fourth aspect, an embodiment of the present invention provides a chirp measurement apparatus, including: a memory and a processor;

the memory is used for storing executable chirp measurement instructions;

the processor is configured to execute the executable chirp measurement instruction stored in the memory to implement the method according to any one of the second aspect.

In a fifth aspect, an embodiment of the present invention provides a computer-readable storage medium storing executable chirp measurement instructions for causing a processor to perform the method according to any one of the second aspects.

In an embodiment of the present invention, a chirp measurement apparatus includes: the device comprises a first laser, a second laser, an optical signal modulation circuit, an optical coupler, a sampling circuit and a processor; the output end of the first laser is connected with the input end of the optical signal modulation circuit, the input end of the optical coupler is respectively connected with the output end of the optical signal modulation circuit and the output end of the second laser, the output end of the optical coupler is connected with the input end of the sampling circuit, and the output end of the sampling circuit is connected with the processor; the processor is used for calculating phase shift coefficients of the direct current component, the first harmonic component, the second harmonic component and the third harmonic component output by the sampling circuit to obtain a phase shift conversion factor, and calculating to obtain a chirp parameter according to a preset chirp measurement model and the phase shift conversion factor; the preset chirp measurement model is used for measuring the chirp parameter of the optical signal modulation circuit. Therefore, chirp measurement can carry out optical frequency mixing on a modulated optical signal and a local oscillator optical signal by using an optical coupler, so that a sampling circuit can obtain a direct current component, a first harmonic component, a second harmonic component and a third harmonic component when sampling the frequency mixing optical signal, then a chirp measurement device calculates the frequency spectrum components by using a processor to obtain a phase shift conversion factor, and finally, a preset chirp measurement model deduced according to an optical complex field intensity model of an optical signal modulator is used for calculating a chirp parameter, so that the nonlinear modulation effect of a silicon optical modulator is fully considered, and the accuracy of chirp parameter measurement is improved.

Drawings

Fig. 1 is a schematic structural diagram of a chirp measurement apparatus according to an embodiment of the present invention;

fig. 2(a) is a simulation diagram of a signal corresponding to a first spectrum expression provided in an embodiment of the present invention;

fig. 2(b) is a simulation diagram of a signal corresponding to a second spectrum expression provided in the embodiment of the present invention;

fig. 3 is a graph illustrating chirp parameters varying with the voltage of a test signal according to an embodiment of the present invention;

fig. 4 is a schematic structural diagram of a chirp measurement apparatus according to an embodiment of the present invention;

FIG. 5 is a schematic diagram of an internal structure of a silicon optical modulator according to an embodiment of the present invention;

fig. 6 is a flowchart of a chirp measurement method according to an embodiment of the present invention;

fig. 7 is an equivalent structural diagram of an optical signal modulator according to an embodiment of the present invention;

FIG. 8(a) is a phase shift graph of a silicon optical modulator according to an embodiment of the present invention;

FIG. 8(b) is a graph showing the absorption loss of a silicon optical modulator according to an embodiment of the present invention;

fig. 9 is a schematic diagram illustrating a relationship between an instantaneous chirp parameter and a splitting ratio according to an embodiment of the present invention;

fig. 10 is a schematic structural diagram of a chirp measurement apparatus provided in an embodiment of the present invention;

fig. 11 is a schematic structural diagram of a chirp measurement apparatus according to an embodiment of the present invention.

Detailed Description

The technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

Optical communication is a communication method using light waves as carriers, has advantages such as large communication capacity and long relay distance, and has been widely used in the field of communication. The silicon photonic technology can realize the transmission and reception of optical information between a computer and other electronic devices by using standard silicon, has the advantage of high speed, can be compatible with Complementary Metal Oxide Semiconductor (CMOS), and plays an important role in optical communication. The silicon optical modulator is a core device of a silicon photon technology, and the modulation principle is based on a nonlinear photoelectric effect, namely a plasma dispersion effect of a silicon material, and the concentration of carriers in a silicon waveguide is changed by loading a high-speed modulation signal to the silicon optical modulator, so that the refractive index of an active region of the waveguide is changed, and the phase modulation of an optical signal is realized. However, when the silicon optical modulator modulates the optical signal, not only the phase of the optical signal but also the intensity of the optical signal is changed, that is, extra intensity modulation is added to the optical signal, which causes a chirp effect to occur in the modulated optical signal during optical fiber transmission, that is, the silicon optical modulator has a chirp effect.

The chirp effect refers to a characteristic that an instantaneous frequency of an optical signal changes with time, and when the optical signal is transmitted in an optical fiber for a medium-long distance, the chirp effect may aggravate a dispersion effect of the optical signal in the optical fiber, so that a phase and an intensity of the optical signal are distorted. In order to ensure that the Optical Signal is not distorted during transmission, the influence of the silicon Optical modulator on various parameters during the transmission of the Optical Signal needs to be evaluated, such as a constellation diagram, an Optical Signal Noise Ratio (OSNR), and the like. The chirp effect is commonly used to evaluate the influence of the silicon optical modulator on various parameters in the optical signal transmission process, so a measurement device is required to measure the parameters of the chirp effect of the silicon optical modulator, that is, the chirp parameters.

The chirp measuring device in the related art still uses the measuring method for the lithium niobate modulator to measure the chirp parameters of the silicon optical modulator, that is, a sine signal generator adds a test signal to a pin of the modulator, a spectrometer monitors the amplitude of the first harmonic of the test signal, and the obtained monitoring result is used as the chirp parameters. However, the lithium niobate modulator modulates the optical signal by using a linear electro-optical effect, which only modulates the phase of the optical signal, and does not have an additional intensity modulation for the optical signal, and the phase of the optical signal is linearly changed. However, as can be seen from the above description, the silicon optical modulator utilizes the nonlinear electro-optic effect to realize modulation, and when measuring the chirp parameter, it is necessary to consider not only the nonlinear phase change caused by the silicon optical modulator, but also the intensity modulation caused by the silicon optical modulator, so that the chirp measuring apparatus continues to use the measuring method of the lithium niobate modulator, which results in low accuracy in measuring the chirp parameter.

Based on the above-mentioned problems in measuring chirp parameters by chirp, the basic idea of the embodiments of the present invention is to provide a measuring apparatus, which can apply a test signal to a silicon optical modulator, detect a multi-level harmonic component of an output signal of the silicon optical modulator, and calculate a chirp parameter with high accuracy according to the multi-level harmonic component.

Based on the above idea, an embodiment of the present invention provides a chirp measurement apparatus, which is shown in fig. 1 and includes:

a first laser 10, a second laser 11, an optical signal modulation circuit 12, an optical coupler 13, a sampling circuit 14 and a processor 15;

the output end of the first laser 10 is connected with the input end of the optical signal modulation circuit 12, the input end of the optical coupler 13 is respectively connected with the output end of the optical signal modulation circuit 12 and the output end 11 of the second laser, the output end of the optical coupler 13 is connected with the input end of the sampling circuit 14, and the output end of the sampling circuit 14 is connected with the processor 15;

the processor 15 is configured to perform phase shift coefficient calculation on the direct current component, the first harmonic component, the second harmonic component, and the third harmonic component output by the sampling circuit 14 to obtain a phase shift conversion factor, and calculate a chirp parameter according to a preset chirp measurement model and the phase shift conversion factor; the preset chirp measurement model is used for measuring the chirp parameter of the photoelectric signal modulation circuit 12;

an input optical signal generated by the first laser 10 is modulated by the optical signal modulation circuit 12 to obtain a modulated optical signal, the modulated optical signal is mixed with a local oscillator optical signal generated by the second laser 11 by the optical coupler 13 to obtain a mixed optical signal, the mixed optical signal is sampled by the sampling circuit 14, a direct current component, a first harmonic component, a second harmonic component and a third harmonic component output by the sampling circuit are sent to the processor 15, and a chirp parameter is calculated.

The chirp measuring device provided by the embodiment of the invention is used for measuring chirp parameters generated when an optical signal modulation circuit modulates an optical signal.

In the embodiment of the present invention, a first laser 10 is used to generate an input optical signal, a chirp measuring device obtains the input optical signal through the first laser 10, and sends the input optical signal into an optical signal modulation circuit 12 through a polarization-maintaining optical fiber, a test signal is loaded to the input optical signal through the optical signal modulation circuit 12, modulation is completed, and a modulated optical signal is obtained, a second laser 11 is used to generate a local oscillator optical signal, similarly, after the chirp measuring device generates the local oscillator optical signal through the second laser 11, the local oscillator optical signal and the modulated optical signal simultaneously enter an optical coupler 13 through the polarization-maintaining optical fiber to perform optical mixing, so as to obtain a mixed optical signal, and then the chirp measuring device sends the mixed optical signal into a sampling circuit 14 through the polarization-maintaining optical fiber, converts the mixed optical signal into an electrical signal through the sampling circuit 14, and then samples the obtained electrical signal, and finally, the chirp measuring device sends the frequency spectrum components into the processor 15 by using a wire for operation to obtain the chirp parameters to be measured finally.

It should be noted that, in the embodiment of the present invention, the first laser 10 may be a continuous output laser having a stable operating state, or may be another type of laser, and the embodiment of the present invention is not limited in detail herein. Correspondingly, the second laser 11 may be the same type of laser as the first laser 10, or may be a different type of laser.

For example, when the first laser 10 is a continuous output laser, the second laser 11 may be a continuous output laser, and may also be another type of laser.

It should be noted that the polarization maintaining fiber is an optical fiber capable of ensuring that the linear polarization direction is unchanged and improving the signal-to-noise ratio of the optical signal. According to the embodiment of the invention, the polarization-maintaining optical fiber is used for connecting each device, so that the birefringence phenomenon of the optical signal in the optical fiber can be weakened, and the measured direct current component, the first harmonic component, the second harmonic component and the third harmonic component are more accurate.

It should be noted that, in the embodiment of the present invention, the optical signal modulation circuit 12 has a test signal generator therein, and can generate a test signal. In the embodiment of the present invention, the test signal may be a continuous signal or may be another type of signal, and the embodiment of the present invention is not limited in detail herein. Illustratively, the test signal may be a sine signal, a cosine signal, or other types of continuous signals.

In the embodiment of the present invention, when the optical coupler 13 optically mixes the modulated optical signal and the local oscillator optical signal, the chirp test apparatus may first obtain the frequency of the modulated optical signal and the frequency of the local oscillator optical signal through the optical coupler 13, then sum the frequency of the modulated optical signal and the local oscillator optical signal through the optical coupler 13 according to the frequency of the modulated optical signal and the frequency of the local oscillator optical signal to obtain a sum frequency signal, and difference the frequency of the local oscillator optical signal of the modulated optical signal to obtain a difference frequency signal, and finally use the sum frequency signal and the difference frequency signal together as the mixed optical signal. It is understood that, in the embodiment of the present invention, the frequency of the modulated optical signal is different from the frequency of the local oscillator optical signal.

It should be noted that the chirp test apparatus may also mix the modulated optical signal and the local oscillator optical signal by using other ways through the optical coupler 13, and the embodiment of the present invention is not limited herein.

It should be noted that the optical coupler in the embodiment of the present invention may be any type of optical coupler, and the embodiment of the present invention is not limited herein.

It can be understood that, in the embodiment of the present invention, when the chirp measurement apparatus samples the mixed optical signal through the sampling circuit 14, the processor 15 performs Fourier transform, for example, Fast Fourier Transform (FFT), on a preset optical complex field intensity model to obtain a spectrum expression of the mixed optical signal, sets the phase shift offset to 0 to obtain a first spectrum expression, sets the phase shift offset to pi to obtain a second spectrum expression, and then samples, through the sampling circuit 14, a signal corresponding to the first spectrum expression and a signal corresponding to the second spectrum expression that are obtained respectively to obtain a dc component, a first harmonic component, a second harmonic component, and a third harmonic component, and sends these spectrum components to the processor 15.

Illustratively, when the chirp measuring apparatus modulates a 200MHz sinusoidal test signal and an input optical signal by the optical signal modulation circuit 12 to obtain a modulated optical signal, and mixes the modulated optical signal with a local oscillator optical signal by the optical coupling 13 to obtain a mixed optical signal, the chirp measuring apparatus performs FFT on a preset optical complex field intensity model by the processor 15, sets the offset phase shift to 0 to obtain a signal corresponding to a first spectral expression, and simulates the signal corresponding to the first spectral expression to obtain a simulation diagram as shown in fig. 2(a), where the horizontal axis of fig. 2(a) is frequency, the unit is MHz, the vertical axis is normalized spectrum, and the unit is dB, at this time, a dc component to be collected by the chirp measuring apparatus by the sampling circuit 15 is a dc component at the frequency of 0, a first harmonic component at the frequency of 200MHz, a first harmonic component, a second harmonic component at the frequency of 200MHz, and a third harmonic component, The second harmonic component at a frequency of 400MHz and the third harmonic component at a frequency of 600 MHz. Similarly, fig. 2(b) is a simulation result of a signal corresponding to the second spectral expression obtained when the chirp measuring apparatus sets the offset phase shift to pi, and at this time, the chirp measuring apparatus acquires, through the sampling circuit 15, a direct current component at a frequency of 0, a first harmonic component at a frequency of 200MHz, a second harmonic component at a frequency of 400MHz, and a third harmonic component at a frequency of 600 MHz.

In the embodiment of the present invention, when the chirp measurement apparatus performs phase shift coefficient calculation on the direct current component, the first harmonic component, the second harmonic component, and the third harmonic component through the processor 15 to obtain a phase shift conversion factor, a preset optical complex field intensity model of the optical signal modulation circuit is obtained first, and fourier transform is performed on the preset optical complex field model to obtain a first spectrum model and a second spectrum model. Specifically, the chirp measurement apparatus sets the offset phase shift to 0 to obtain a first spectral expression while performing fourier transform by the processor 15, and sets the offset phase shift to pi to obtain a second spectral expression.

Then, the chirp measurement apparatus substitutes the dc component, the first harmonic component, the second harmonic component, and the third harmonic component into the first spectrum model and the second spectrum model respectively through the processor 15, and calculates and obtains a first dc output, a second dc output, a first harmonic output, a second first harmonic output, a first second harmonic output, a second harmonic output, a first third harmonic output, and a second third harmonic output. At this time, the chirp measuring device substitutes the direct current components into the first spectral expression and the second spectral expression respectively through the processor 15 to obtain a first direct current output and a second direct current output; respectively substituting the first harmonic component into the first frequency spectrum expression and the second frequency spectrum expression to respectively obtain first harmonic output and second first harmonic output; respectively substituting the second harmonic component into the first frequency spectrum expression and the second frequency spectrum expression to respectively obtain a first second harmonic output and a second harmonic output; and substituting the third harmonic component into the first frequency spectrum expression and the second frequency spectrum expression respectively to obtain a first third harmonic output and a second third harmonic output respectively.

Then, the chirp measuring device calculates a phase shift coefficient by using the first dc output and the second dc output through the processor 15 to obtain a dc phase shift factor, that is, a difference between the first dc output and the second dc output corresponding to the dc component is used to obtain a dc difference result, and the first dc output and the second dc output are summed to obtain a dc sum result, and finally, the dc difference result is compared with the dc sum result, and the obtained ratio is used as the dc phase shift factor. Then, the chirp measuring device calculates the phase shift coefficient by using the first harmonic output and the second first harmonic output through the processor 15 to obtain a first sum phase shift factor and a first difference phase shift factor, respectively, that is, sums the first harmonic output and the second first harmonic output corresponding to the first harmonic component to obtain a first sum result, compares the first sum result with the dc sum result to obtain a first sum phase shift factor, and meanwhile, performs subtraction on the first harmonic output and the second first harmonic output to obtain a first difference result, and compares the first difference result with the dc difference result to obtain a first difference phase shift factor. Similarly, the chirp test apparatus performs phase shift sparse calculation according to the first second harmonic output and the second harmonic output by the processor 15 to obtain a second sum phase shift factor and a second difference phase shift factor, respectively, that is, sums the first second harmonic output and the second harmonic output to obtain a second sum result, and compares the second sum result with the dc sum result to obtain a second sum phase shift factor; and comparing the second difference result with the direct current difference result to obtain a second difference phase shift factor. Then, the chirp test device calculates a phase shift coefficient by using the first third harmonic output and the second third harmonic output through the processor 15 to obtain a third sum phase shift factor and a third difference phase shift factor respectively, i.e. the first third harmonic output and the second third harmonic output are summed to obtain a third sum result, and the third sum result is compared with the direct current sum result to obtain a third sum phase shift factor; and (3) subtracting the first third harmonic output from the second third harmonic output, taking double of the ratio as a third difference result, and comparing the third difference result with the direct current difference result to obtain a third difference phase shift factor.

After the chirp measuring apparatus obtains the dc phase shift factor, the primary sum phase shift factor, the primary difference phase shift factor, the secondary sum phase shift factor, the secondary difference phase shift factor, the tertiary sum phase shift factor, and the tertiary difference phase shift factor through the processor 15, all the phase shift factors are used as the phase shift conversion factors. Thus, the chirp test apparatus can obtain the phase shift transformation factor through the processor 15.

It can be understood that, when the chirp measuring apparatus further uses the scale operation to convert the phase shift conversion factor, the obtained ratio is enlarged to 2 times of the original ratio, and then each phase shift conversion factor is obtained.

For example, the embodiment of the present invention shows a formula for calculating a phase shift transformation factor, as shown in formulas (1) to (7):

wherein, w₀Is a direct current component, P_{OUT_0}(w₀) Denotes a first DC output, P_{OUT_π}(w₀) Second DC output, γ_normThen a dc phase shift factor is indicated.

Wherein, w₀Is a direct current component, w₀+w₁Is a first harmonic component, P_{OUT_0}(w₀+w₁) Representing the first harmonic inputOut, P_{OUT_π}(w₀+w₁) Representing the second harmonic output, P_{OUT_0}(w₀) Denotes a first DC output, P_{OUT_π}(w₀) A second DC output, A₁A primary sum shift factor is indicated.

Wherein, w₀Is a direct current component, w₀+w₁Is a first harmonic component, P_{OUT_0}(w₀+w₁) Representing the first harmonic output, P_{OUT_π}(w₀+w₁) Representing the second harmonic output, P_{OUT_0}(w₀) Denotes a first DC output, P_{OUT_π}(w₀) Second DC output, B₁A first order differential phase shift factor is indicated.

Wherein, w₀Is a direct current component, w₀+2w₁Is the second harmonic component, P_{OUT_0}(w₀+2w₁) Representing the first second harmonic output, P_{OUT_π}(w₀+2w₁) Representing the second harmonic output, P_{OUT_0}(w₀) Denotes a first DC output, P_{OUT_π}(w₀) A second DC output, A₂A quadratic sum shift factor is indicated.

Wherein, w₀Is a direct current component, w₀+2w₁Is the second harmonic component, P_{OUT_0}(w₀+2w₁) Representing the first second harmonic output, P_{OUT_π}(w₀+2w₁) Representing the second harmonic output, P_{OUT_0}(w₀) Denotes a first DC output, P_{OUT_π}(w₀) Second DC output, B₂The quadratic difference phase shift factor is indicated.

Wherein, w₀Is a direct current component, w₀+3w₁Is the third harmonic component, P_{OUT_0}(w₀+3w₁) Representing the first third harmonic output, P_{OUT_π}(w₀+3w₁) Representing the second third harmonic output, P_{OUT_0}(w₀) Denotes a first DC output, P_{OUT_π}(w₀) A second DC output, A₃A cubic sum value shift factor is indicated.

Wherein, w₀Is a direct current component, w₀+3w₁Is the third harmonic component, P_{OUT_0}(w₀+3w₁) Representing the first third harmonic output, P_{OUT_π}(w₀+3w₁) Representing the second third harmonic output, P_{OUT_0}(w₀) Denotes a first DC output, P_{OUT_π}(w₀) Second DC output, B₃Then the cubic difference phase shift factor is indicated.

Chirp measuring device obtaining dc component w by sampling circuit 14₀First harmonic component w₀+w₁Second harmonic component w₀+2w₁And a third harmonic component w₀+3w₁The dc component w may then be processed by the processor 15₀In the formula (1), the DC phase shift factor gamma is calculated_normThe first harmonic component w₀+w₁Respectively substituting into formula (2) and formula (3), respectively calculating primary sum value shift factor A₁And a first difference phase shift factor B₁Then, the second harmonic component w is₀+2w₁Respectively generation by generationCalculating a quadratic sum shift factor A in the formula (4) and the formula (5)₂And a quadratic difference phase shift factor B₂The third harmonic component w₀+3w₁Respectively substituting in formula (6) and formula (7), calculating cubic sum value shift factor A₃And the third order difference phase shift factor B₃. Finally, the chirp measuring device passes through a processor 15, which converts the gamma_norm、A₁、B₁、A₂、B₂、A₃And B₃As a phase shift transformation factor.

After the chirp measurement device obtains the phase shift transformation factors through the processor 15, the phase shift transformation factors are substituted into a preset chirp measurement model for calculation, so as to obtain final chirp parameters.

It should be noted that the preset chirp model is derived by the chirp measuring apparatus through the processor 15 according to the preset light complex field intensity model of the light signal modulation circuit and the preset chirp calculation model, and is stored in the processor 15.

When the chirp measurement device calculates the chirp parameter by using the preset chirp measurement model through the processor 15, the chirp measurement device firstly obtains the phase shift difference of the optical signal modulation circuit, and then calculates the chirp molecular part according to the direct current phase shift factor, the primary sum phase shift factor, the primary difference phase shift factor, the secondary sum phase shift factor, the secondary difference phase shift factor, the primary cosine harmonic, the tertiary sum phase shift factor, the tertiary difference phase shift factor, the secondary cosine harmonic and the sine value of the phase shift difference. Specifically, the chirp measuring device calculates a primary chirp molecule by the processor 15 according to the dc phase shift factor, the primary sum phase shift factor, the primary difference phase shift factor, and the sine value of the phase shift difference; calculating secondary chirp molecules according to the direct current phase shift factor, the secondary sum phase shift factor, the secondary difference phase shift factor, the sine value of the phase shift difference and the primary cosine harmonic; and then calculating third chirp molecules according to the direct current phase shift factor, the third sum phase shift factor, the third difference phase shift factor, the sine value of the phase shift difference and the second pre-harmonic, and finally accumulating the first chirp molecules, the second chirp molecules and the third chirp molecules by the chirp measuring device through the processor 15 to obtain a chirp molecule part.

Similarly, the chirp measurement apparatus can calculate the chirp denominator part by the processor 15 based on the dc phase shift factor, the primary sum phase shift factor, the primary difference phase shift factor, the secondary sum phase shift factor, the secondary difference phase shift factor, the primary cosine harmonic, the tertiary sum phase shift factor, the tertiary difference phase shift factor, and the cosine value of the predicted phase shift difference of the secondary cosine harmonic. Specifically, the chirp measuring device calculates a primary chirp denominator through the processor 15 according to the dc phase shift factor, the primary sum value shift factor, the primary difference value shift factor, and the cosine value of the phase difference; calculating a second chirp denominator according to the direct current phase shift factor, the second sum phase shift factor, the second difference phase shift factor, the cosine value of the phase difference and the first cosine harmonic; and then calculating a third chirp denominator according to the direct current phase shift factor, the third sum phase shift factor, the third difference phase shift factor, the cosine value of the phase difference and the second cosine harmonic, accumulating the first chirp denominator, the second chirp denominator and the third chirp denominator, and taking the obtained accumulation result as a chirp denominator part.

The chirp measuring apparatus obtains the chirp numerator portion and the chirp denominator portion through the processor 15, compares the chirp numerator portion with the chirp denominator portion, and integrates the obtained ratio result in the time domain, and uses the finally obtained integration result as the chirp parameter.

For example, the preset chirp measurement model may be represented by equation (8), as follows:

wherein, γ_normIs a DC phase shift factor, A₁As a primary sum-shift factor, B₁Is a first order differential phase shift factor, A₂As a quadratic sum shift factor, B₂Is a quadratic difference phase shift factor, A₃As a cubic sum-shift factor, B₃For the third order difference phase shift factor,t represents time, NT_sRepresents the time integral phi_{RF_A}And phi_{RF_B}Is a phase shift of the optical signal modulation circuit, which is an inherent parameter of the optical signal modulation circuit, cosw₁t denotes the first cosine harmonic, cos2w₁t denotes the second cosine harmonic.

The chirp measuring device obtains the phase shift by calculating the direct current component, the first harmonic component, the second harmonic component and the third harmonic component through the processor 15, and the direct current phase shift factor gamma_normA first sum shift factor A₁First order difference phase shift factor B₁Quadratic sum shift factor a₂Second order difference phase shift factor B₂Cubic sum shift factor A₃And a cubic difference phase shift factor B₃While obtaining the phase shift phi of the optical signal modulation circuit_{RF_A}And phi_{RF_B}And calculating the phase shift difference, and then substituting the parameters and the phase shift difference into an equation (8), so that the chirp measuring device can obtain the chirp parameters.

Illustratively, as shown in fig. 3, the embodiment of the present invention shows a graph of chirp parameter variation with voltage of the test signal, where the horizontal axis represents the voltage of the test signal, and the horizontal axis represents the range of [0, 1], which is expressed by V, and the vertical axis represents the chirp parameter, which is expressed by the range of [ -0.02, -0.06 ]. As can be seen from fig. 3, when the voltage of the test signal is gradually increased from 0V to 1V, the value of the chirp parameter is gradually decreased, that is, the absolute value of the chirp parameter is gradually increased, and in practice, the absolute value of the chirp parameter is increased as the voltage of the test signal is increased, so that it can be seen that in the embodiment of the present invention, the chirp measurement apparatus uses the preset chirp measurement model, and the result of the chirp parameter is in accordance with the rule of practical use.

The processor 15 in the embodiment of the present invention may be a microprocessor with a computing function, or may be an electronic device such as a personal computer or a notebook computer, and the embodiment of the present invention is not limited in particular herein.

In the embodiment of the invention, chirp measurement can perform optical frequency mixing on a modulated optical signal and a local oscillator optical signal by using an optical coupler, so that a sampling circuit can perform direct current component, first harmonic component, second harmonic component and third harmonic component when sampling the frequency-mixed optical signal, then a chirp measurement device calculates the frequency spectrum components by using a processor to obtain phase shift conversion factors, and finally, a preset chirp measurement model deduced according to an optical complex field intensity model of an optical signal modulator is used for calculating chirp parameters, the structure of the optical signal modulator is fully considered, and the accuracy of chirp parameter measurement is improved.

In some embodiments of the present invention, sampling circuit 14 comprises: a photoelectric signal converter and a sampler;

the input end of the photoelectric signal converter is connected with the output end of the optical coupler 13;

the output end of the sampler is connected with the processor 15;

the mixed optical signal is converted into a first voltage signal by the photoelectric signal converter, and then the chirp measuring device samples the first voltage signal by the sampling circuit 15 to obtain a direct current component, a first harmonic component, a second harmonic component and a third harmonic component.

It can be understood that the optical-to-electrical signal converter converts the mixed optical signal into a current by using the photovoltaic effect through the silicon-based material inside the converter, and then converts the current signal into a first voltage signal by using the resistor inside the converter. In the embodiment of the present invention, the type of the optical-to-electrical signal converter may be determined according to actual requirements, and the embodiment of the present invention is not limited herein.

It should be noted that, in the embodiment of the present invention, the sampler may be an Oscilloscope having a sampling function, such as a high-speed real-time sampling Oscilloscope (high speed real-time sampling Oscilloscope), a Digital Storage Oscilloscope (DSO), or other electronic devices having a sampling function, and the embodiment of the present invention is not limited herein.

In the embodiment of the invention, the chirp measuring device firstly converts the frequency mixing optical signal into the first voltage signal through the photoelectric signal converter, and then samples the obtained first voltage signal by using the sampler, so that the chirp measuring device can obtain the direct current component, the first harmonic component, the second harmonic component and the third harmonic component through sampling, and the calculation of subsequent chirp parameters is facilitated.

In some embodiments of the present invention, the sampling circuit 14 further comprises: a transimpedance amplifier;

the output end of the trans-impedance amplifier is connected with the input end of the sampler;

the mixed signal is converted into a current signal through a photoelectric signal converter and output, then the current signal is converted into a second voltage signal through a trans-impedance amplifier and sent into a sampler, and the second voltage signal is sampled through the sampler to obtain a direct current component, a first harmonic component, a second harmonic component and a third harmonic component.

It is understood that in the embodiment of the present invention, the transimpedance amplifier converts the current mode into the second voltage signal by using ohm's law. In the embodiment of the present invention, the type of the transimpedance amplifier may be selected according to actual situations, and the embodiment of the present invention is not limited herein.

In the embodiment of the invention, the chirp measuring device can also convert the frequency mixing optical signal into the current signal, and then convert the current signal into the second voltage information by using the transimpedance amplifier, so that the chirp measuring device can collect the direct current component, the first harmonic component, the second harmonic component and the third harmonic component no matter aiming at the current signal or the voltage signal.

In some embodiments of the present invention, the input optical signal generated by the first laser 10 is offset in frequency from the local optical signal generated by the second laser 11.

In the embodiment of the present invention, the chirp measuring apparatus is configured such that the first laser 10 and the optical signal modulation circuit 12 are connected to each other through a polarization maintaining fiber, and the second laser 11 and the optical coupler 13 are connected to each other through a polarization maintaining fiber.

It should be noted that, since the optical signal modulator 12 does not change the frequency of the input optical signal when modulating the input optical signal, in order to enable the chirp measurement apparatus to optically mix the modulated optical signal and the local oscillator optical signal through the optical coupler 13, the frequencies of the input optical signal generated by the first laser 10 and the local oscillator optical signal generated by the second laser 11 should be different, that is, there is a frequency offset, so that the chirp measurement apparatus can correctly generate the sum frequency signal and the difference frequency signal through the optical coupler 13.

It may be understood that, in the embodiment of the present invention, the frequency of the input optical signal may be greater than the frequency of the local oscillator optical signal, or the frequency of the input optical signal may be smaller than the frequency of the local oscillator optical signal, which is not limited herein.

In the embodiment of the invention, the frequency offset exists between the frequency of the input optical signal generated by the first signal laser and the frequency of the local oscillator optical signal generated by the second laser, so that the chirp measuring device can perform frequency mixing on the modulated optical signal and the local oscillator optical signal to obtain the frequency mixing optical signal.

In some embodiments of the present invention, optical signal modulation circuitry 12 comprises: the device comprises a silicon optical modulator, a test signal generator and a direct current voltage source;

the output end of the first laser 10 is connected with a silicon optical modulator, and the output end of the silicon optical modulator is connected with the input end of the optical coupler 13;

the test signal generator is connected with the silicon optical modulator;

the chirp measuring device inputs a test signal to the silicon optical modulator through the test signal generator, inputs direct current bias and radio frequency bias to the silicon optical modulator through the direct current voltage source, and modulates the input optical signal and the test signal by using the silicon optical modulator to obtain a modulated optical signal.

It can be understood that the silicon optical modulator is used for modulating the input optical signal to obtain a modulated optical signal and outputting the modulated optical signal, therefore, the input end of the silicon optical modulator is connected to the first laser through the polarization maintaining fiber, the output end of the silicon optical modulator is also connected to the optical coupler 13 through the polarization maintaining fiber, and the test signal generator and the dc voltage source generate electrical signals, and therefore, the test signal generator and the dc voltage source are connected to the silicon optical modulator through a wire.

It should be noted that, in the embodiment of the present invention, the test signal generator may be a sinusoidal signal generator, or may be another signal generator, and a specific test signal generator may be set according to actual needs, and the embodiment of the present invention is not limited specifically herein.

In the embodiment of the present invention, the dc voltage source may be a dual-path dc voltage source, or may be another type of dc voltage source, and the embodiment of the present invention is not limited herein.

In some embodiments of the present invention, a dc bias pin and a rf bias pin are disposed on the silicon optical modulator; the direct current voltage source is provided with a radio frequency bias output end and a direct current bias output end; the modulation bias output end is connected with the radio frequency bias pin, and the direct current output end is connected with the direct current bias pin.

The chirp measuring device sends the radio frequency bias generated by the direct current voltage source to the silicon optical modulator through the radio frequency bias output end and the radio frequency bias pin, and sends the direct current bias generated by the direct current voltage source to the silicon optical modulator through the direct current bias output end and the direct current bias pin.

It should be noted that the dc bias generated by the dc voltage source is used to control the dc bias point of the silicon optical modulator, that is, to control whether the silicon optical modulator modulates the intensity or modulates the phase of the input optical signal.

Illustratively, when the direct current bias point is an orthogonal (quad) point, the chirp measuring device performs intensity modulation on an input optical signal through a silicon optical modulator; when the direct current bias point is a zero (null) point, the chirp measuring device performs phase modulation on the input optical signal through the silicon optical modulator.

In some embodiments of the present invention, the optical signal modulation circuit 12 further comprises: a radio frequency signal amplifier; the output end of the test signal generator is connected with the input end of the radio frequency signal amplifier.

The chirp measuring device differentiates the test signal through the radio frequency amplifier to obtain a first differential signal and a second differential signal, and inputs the first differential signal and the second differential signal into the silicon optical modulator.

It can be understood that, in the embodiment of the present invention, the silicon optical modulator may be a silicon optical modulator based on a push-pull structure, that is, when the silicon optical modulator modulates the input optical signal, the silicon optical modulator may firstly divide the input optical signal into two paths for modulation, so that the chirp measurement apparatus may differentiate the test signal through the radio frequency signal amplifier to obtain two paths of differential signals, and send the two paths of differential signals into the silicon optical modulator, so that the chirp measurement apparatus may modulate the two paths of optical signals through the silicon optical modulator.

In some embodiments of the present invention, the rf signal amplifier has a first differential signal output terminal and a second differential signal output terminal, and the silicon optical modulator is provided with a first differential signal pin and a second differential signal pin; the first differential signal output end is connected with the first differential signal pin through a wire, and the second differential signal output end is connected with the second differential signal pin;

the chirp measuring device sends a first differential signal generated by the radio frequency signal amplifier to the silicon optical modulator through the first differential signal output end and the first differential signal pin, and sends a second differential signal generated by the radio frequency signal amplifier to the silicon optical modulator through the second differential signal output end and the second differential signal pin.

Illustratively, the embodiment of the present invention provides a structural schematic of a chirp measurement apparatus, as shown in fig. 4, a first laser and a second laser are both continuous output lasers, the continuous output laser 4-1 is connected to a silicon optical modulator 4-4 through a polarization maintaining fiber 4-3, the continuous output laser 4-2 is also connected to the silicon optical modulator 4-4 through a polarization maintaining fiber, a test Signal generator 4-5 is connected to a radio frequency Signal amplifier 4-6, a first differential Signal output end (not shown) of the radio frequency Signal amplifier 4-6 is connected to a first differential Signal pin RF _ Signal + of the silicon optical modulator 4-4, the second differential Signal output terminal (not shown) of the RF Signal generator 4-6 is connected to the second differential pin RF _ Signal-of the silicon optical modulator 4-4. A double-pass direct-current voltage source 4-7 is used as a direct-current voltage source of the chirp measuring device, a direct-current Bias output end (not shown) of the double-pass direct-current voltage source 4-7 is connected with a direct-current Bias pin Bias of the silicon optical modulator 4-4, and a radio-frequency Bias output end (not shown) of the double-pass direct-current voltage source 4-7 is connected with a radio-frequency Bias pin PN of the silicon optical modulator 4-4. The output end of the silicon optical modulator 4-4 is connected with the input end of the optical coupler 4-8 through a polarization maintaining optical fiber, the output end of the optical coupler 4-8 is connected with the input end of the photoelectric signal converter 4-9, the output end of the photoelectric signal converter 4-9 is connected with the high-speed transimpedance amplifier 4-10, the output end of the high-speed transimpedance amplifier 4-10 is connected with the high-speed real-time sampling oscilloscope 4-11 which is used as a sampler of the chirp measuring device, and finally, the output end of the high-speed real-time sampling oscilloscope 4-11 is connected with the input end of the processor 4-12. By the structure, the chirp measuring device can generate an input optical signal by using the continuous laser output optical device 4-1, generate a local oscillation optical signal by using the continuous output optical device 4-2, generate a test signal by using the test signal generator 4-5, and convert the test signal into two paths of differential signals after being processed by the radio frequency amplifier 4-6 and provide the two paths of differential signals for the silicon optical modulator 4-4; meanwhile, the chirp measuring device provides the silicon optical modulator 4-4 with the direct current bias and the radio frequency bias which are necessary when the modulation signal is provided by the double-path direct current voltage source 4-7, and then the input optical signal can be modulated into a modulation optical signal through the silicon optical modulator 4-4 and output; the chirp measuring device receives a modulated optical signal through an optical coupler 4-8, then mixes the modulated optical signal with a local oscillator optical signal to obtain a mixed optical signal, converts the mixed optical signal into a current signal through an optical-electrical signal converter 4-9, and converts the current signal into a voltage signal through a high-speed transimpedance amplifier 4-10, so that a high-speed real-time sampling oscilloscope 4-11 can acquire and obtain a direct current component, a first harmonic component, a second harmonic component and a third harmonic component; finally, the frequency spectrum components are sent to the processor 4-14 for operation, and the chirp parameters to be measured are obtained.

In the embodiment of the invention, the test signal generator provides a test signal for the silicon optical modulator, and the direct current voltage source provides direct current bias and radio frequency bias required by modulation for the silicon optical modulator, so that the silicon optical modulator can modulate an input optical signal to obtain a debugging optical signal.

In some embodiments of the invention, a silicon optical modulator comprises: the optical signal input end, the first optical path, the second optical path and the optical signal output end;

the optical signal input end is connected with the output end of the first laser 10, and the optical signal output end is connected with the input end of the optical coupler 13;

a first optical path and a second optical path which are separated from the optical signal input terminal and joined at the optical signal output terminal;

the input optical signal is received through the optical signal input end, the input optical signal is modulated by the first optical path and the second optical path, and the modulated optical signal is obtained and output at the optical signal output end.

It should be noted that, in the embodiment of the present invention, a first radio frequency phase shifter is disposed on the first optical path, and a thermo-optic phase shifter and a second radio frequency phase shifter are disposed on the second optical path; the first radio frequency phase shifter and the second radio frequency phase shifter are respectively connected with the test signal generator; an on-chip inductor is arranged between the first light path and the second light path and connected with the radio frequency offset pin.

The chirp measuring device receives radio frequency offset through an on-chip inductor, sets a modulation phase through a thermo-optic phase shifter, and modulates an input optical signal and a test signal by using a first radio frequency phase shifter and a second radio frequency phase shifter to obtain a modulated optical signal.

It is understood that, in the embodiment of the present invention, the types of the first radio frequency phase shifter, the second radio frequency phase shifter, and the thermo-optic phase shifter may be selected according to actual situations, and the embodiment of the present invention is not particularly limited herein.

It should be noted that the type of the on-chip inductor, i.e., the parameter, may be set according to actual situations, and the embodiment of the present invention is not limited herein.

In some embodiments of the present invention, a first reverse PN junction is embedded in the positive electrode of the first radio frequency phase shifter, and the first optical path is connected to the first radio frequency phase shifter through the first reverse PN junction; and a second reverse PN junction is embedded in the negative electrode of the second radio frequency phase shifter, and the second light path is connected with the second radio frequency phase shifter through the second reverse PN junction.

In some embodiments of the present invention, the cathode of the first reverse PN junction is connected in series with the cathode of the second reverse PN junction as a common pole of the first reverse PN junction and the second reverse PN junction.

The chirp measuring device sends an input optical signal into the first radio frequency phase shifter through the first reverse PN junction, and sends the input optical signal into the second radio frequency phase shifter through the second reverse PN junction so as to complete the modulation of the input optical signal.

It is to be understood that the first reverse PN junction and the second reverse PN junction may be two PN junctions with the same parameter or two PN junctions with different parameters, and the types of the first reverse PN junction and the second reverse PN junction may be determined according to actual situations, which is not limited herein in the embodiments of the present invention.

In some embodiments of the present invention, the first rf phase shifter is provided with a first termination resistor, and the second rf phase shifter is provided with a second termination resistor; the first radio frequency phase shifter is connected with the ground point through a first terminal resistor, and the second radio frequency phase shifter is connected with the ground point through a second terminal resistor.

The chirp measuring device prevents the modulated optical signal from being reflected by the first termination resistor and the second termination resistor.

It should be noted that the resistance values of the first terminal resistor and the second terminal resistor may be the same or different, and the specific resistance value of the first terminal resistor and the specific resistance value of the second terminal resistor may be determined according to actual conditions, which is not limited herein in the embodiment of the present invention.

Illustratively, the embodiment of the present invention provides a schematic internal structure of a silicon optical modulator, as shown in fig. 5, the silicon optical modulator is divided into two optical paths, i.e. a first optical path 5-2 and a second optical path 5-3, starting from an optical signal input end 5-1, and the first optical path 5-2 and the second optical path 5-3 are combined into one path at an optical signal output end 5-4 and connected to an optical coupler 5-5. A first radio frequency phase shifter 5-21 is arranged on the first light path 5-2; the second optical path 3 is provided with thermo-optic phase shifters 5-31 and second radio frequency phase shifters 5-32. The first optical path 5-2 is connected with the first radio frequency phase shifter 5-21 through a first reverse PN junction, and similarly, the second radio frequency phase shifter 5-32 is connected with the second optical path 5-3 through a second reverse PN junction. The first reverse PN junction and the second reverse PN junction share a common cathode. The first rf phase shifter 5-21 has a termination resistor 5-210 and similarly the second rf phase shifter 5-32 has a termination resistor 5-320 to prevent reflection of the modulated optical signal, both termination resistors being connected to the ground. In addition, an on-chip inductor 5-6 is arranged between the first optical path 5-2 and the second optical path 5-3, and the on-chip inductor 5-6 is connected with a direct current bias pin PN. The first radio frequency phase shifter 5-21 and the second radio frequency phase shifter 5-32 are both connected to the radio frequency source 5-7 and receive the test signal. The chirp measuring device can divide an input optical signal into two paths through a silicon optical modulator with the structure shown in fig. 5, respectively modulate the two paths, and obtain a modulated optical signal at the final optical signal output end 5-4.

In the embodiment of the invention, the chirp measuring device obtains the input optical signal from the optical signal input end through the silicon optical modulator, divides the input optical signal into two paths, modulates the two paths with the first optical path and the second optical path respectively by setting, and finally converges the two paths at the optical signal output end, so that the chirp measuring device can complete the modulation of the input optical signal.

An embodiment of the present invention provides a chirp measurement method, which is applied to any one of the chirp measurement apparatuses in the embodiments of the present invention described above, and with reference to fig. 6, the method includes:

s101, generating an input optical signal through a set first laser, and generating a local oscillator optical signal through a set second laser.

The chirp measuring device generates an input optical signal through a first laser arranged inside the chirp measuring device, wherein the frequency of the input optical signal can be determined according to a chirp parameter to be measured, namely the chirp parameter of which frequency needs to be measured, and the input optical signal of which frequency is generated through the first laser. Meanwhile, a local oscillator optical signal is generated through a second laser arranged in the chirp measuring device, and the frequency of the local oscillator optical signal is different from that of the input optical signal.

S102, modulating the input optical signal to obtain a modulated optical signal.

The chirp measuring device generates a test signal through the optical signal modulation circuit, and superposes the test signal on the input optical signal through the optical signal modulation circuit to complete the modulation process of the input optical signal and obtain a modulated optical signal. In this process, it is also necessary to determine the modulation bias point by the optical signal modulation circuit to determine whether to perform phase modulation or intensity modulation on the input optical signal.

And S103, mixing the modulated optical signal and the local oscillator optical signal to obtain a mixed optical signal.

The chirp measuring device firstly obtains the frequency of a modulated optical signal and the frequency of a local oscillator optical signal through an optical coupler in the chirp measuring device, then performs optical sum frequency on the modulated optical signal and the local oscillator optical signal according to the frequency of the modulated optical signal and the frequency of the local oscillator optical signal to obtain a signal with the frequency being the sum of the frequency of the modulated optical signal and the frequency of the local oscillator optical signal, performs optical difference frequency on the modulated optical signal and the local oscillator optical signal to obtain a signal with the frequency being the difference between the frequency of the modulated optical signal and the frequency of the local oscillator optical signal, and uses the obtained signal as a mixing optical signal.

And S104, sampling the mixed optical signal to obtain a direct current component, a first harmonic component, a second harmonic component and a third harmonic component of the mixed optical signal.

The chirp measuring device conducts FFT on the frequency mixing optical signal through the sampler, then obtains a first spectrum expression and a second spectrum expression according to different phase shift offsets, then samples signals corresponding to the first spectrum expression and signals corresponding to the second spectrum expression through the sampler respectively, and obtains a direct current component, a first harmonic component, a second harmonic component and a third harmonic component, so that a subsequent chirp measuring device can calculate according to the spectrum components.

S105, calculating phase shift coefficients of the direct current component, the first harmonic component, the second harmonic component and the third harmonic component to obtain phase shift conversion factors; calculating according to a preset chirp measurement model and a phase shift conversion factor to obtain a chirp parameter; the preset chirp measurement model is used for measuring the chirp parameters of the optical signal modulation circuit.

After the chirp measuring device obtains the direct current component, the first harmonic component, the second harmonic component and the third harmonic component through the sampler, the processor calculates phase shift coefficients of the frequency spectrum components, and uses the obtained direct current phase shift factor, the first sum phase shift factor, the first difference phase shift factor, the second sum phase shift factor, the second difference phase shift factor, the third sum phase shift factor and the third difference phase shift factor as phase shift conversion factors, and then the chirp measuring device substitutes the phase shift conversion factors into a preset chirp measuring model deduced through the processor to calculate chirp parameters.

It should be noted that the process of calculating the phase shift transformation factor and the form of the preset chirp measurement model in the embodiment of the present invention are the same as those described in the above embodiment of the present invention, and are not described herein again.

In the embodiment of the application, the chirp measurement model can perform optical frequency mixing on a modulated optical signal and a local oscillator optical signal, so that a chirp measurement device can perform direct current component, first harmonic component, second harmonic component and third harmonic component when sampling the frequency-mixed optical signal, then the chirp measurement device calculates the frequency spectrum components through a processor to obtain phase shift conversion factors, and finally, a preset chirp measurement model derived according to an optical complex field intensity model of an optical signal modulator is used for calculating chirp parameters, the structure of the optical signal modulator is fully considered, and the accuracy of chirp parameter measurement is improved.

In some embodiments of the present invention, before generating the input optical signal by the first laser and generating the local oscillator optical signal by the second laser, i.e., before S101, the method further includes: S106-S109, as follows:

and S106, acquiring a preset light complex field intensity model and a preset chirp calculation model.

When the processor deduces the preset chirp measurement model, the chirp measurement device needs to first acquire a preset optical complex field intensity model corresponding to the optical signal modulation circuit and a preset chirp calculation model for defining chirp parameters, wherein the preset optical complex field intensity model is stored in the processor in advance.

It should be noted that the structure and parameters of the optical signal modulation circuit determine the intensity and phase of the modulated optical signal, and therefore, the preset optical complex field intensity model is determined by the structure of the optical signal modulation circuit.

For example, an equivalent structure diagram of an optical signal modulator is provided in the embodiment of the present invention, as shown in fig. 7, the equivalent structure diagram is an equivalent structure diagram of the optical signal modulator in fig. 7. DC bias voltage V_PNThe test signal is applied to a DC bias pin PN, and is loaded on a first differential signal pin S + (1) and a second differential signal pin S- (3) respectively after being subjected to differential by a radio frequency amplifier. In order to ensure that two PN junctions which are connected in series reversely work in a reverse modulation state in silicon optical modulation, V must be ensured_PNAnd when the maximum input voltage is greater than the maximum input voltages of S + (1) and S- (3), the preset light complex field intensity model corresponding to the equivalent structure can be obtained as shown in the formula (9):

wherein E is_INGamma is the splitting ratio of the first and second light paths of the silicon light modulator, w is the complex amplitude of the input light field₀For the frequency of the input optical signal, alpha_{RF_A}(t) is the absorption loss factor, α, of the first optical path_{RF_B}(t) is the absorption loss factor of the second optical path, phi_{RF_A}(t) is the phase shift of the first optical path, phi_{RF_B}(t) is the phase shift of the second optical path, phi_BiasA phase offset set for the thermo-optic phase shifter on the second optical path.

It should be noted that, the chirp measurement model uses the processor, the first derivative of the phase modulation in time is compared with the first derivative of the intensity modulation in time, the obtained ratio result is multiplied by 2 times of the intensity modulation, and the final obtained product is used as the preset chirp calculation model.

Illustratively, the embodiment of the present invention provides a preset chirp calculation model, as shown in equation (10):

where θ (t) denotes phase modulation, P_OUT(t) denotes intensity modulation, α_chirpRepresenting the chirp parameter.

And S107, expanding and simplifying the preset light complex field intensity model to obtain an instantaneous light intensity function and an instantaneous phase function of the modulated light signal.

After the chirp measuring device obtains the preset optical complex field intensity model through the processor, the intensity and the phase of the preset optical complex field intensity model are extracted to obtain an instantaneous light intensity function and an instantaneous phase function of the modulated light signal.

It should be noted that, when the preset optical complex field intensity model is expanded, the intensity of the preset optical complex field model is extracted as an instantaneous light intensity function, and the phase of the preset optical complex field intensity model is extracted as an instantaneous phase function.

Illustratively, when the preset light complex field intensity model is equation (9), the extracted instantaneous light intensity function and instantaneous phase function are respectively expressed by equation (11) and equation (12):

And S108, combining and simplifying the preset chirp calculation model, the instantaneous light intensity function and the instantaneous phase function to obtain an instantaneous chirp measurement model.

After the chirp measuring device obtains an instantaneous light intensity function and an instantaneous phase function through the processor, the instantaneous light intensity function and the instantaneous phase function are substituted into a preset chirp calculation model to be combined, and then a preset optical complex field intensity model is unfolded and rewritten through direct current bias, the amplitude of a test signal, the frequency of the test signal, the radio frequency phase shift of an optical signal modulator and the absorption loss of the optical signal modulator to obtain an instantaneous chirp measuring model.

Illustratively, the chirp measuring apparatus substitutes equation (12) into equation (11) by the processor while assuming χ_A＝exp(-2α_{A_RF}(t)),χ_B＝exp(-2α_{B_RF}(t)),χ_AB＝exp(-α_{A_RF}(t)-α_{B_RF}(t)), equation (13) can be obtained as follows:

wherein' denotes the first derivative in time, and gamma is the splitting ratio of the first and second optical paths of the silicon optical modulator, phi_{RF_A}Is the phase shift of the first optical path, phi_{RF_B}Is the phase shift of the second optical path, phi_BiasA phase offset set for the thermo-optic phase shifter on the second optical path.

As can be seen from equation (13), the chirp parameter is offset from the phase of the thermo-optic phase shifter by φ_BiasIn connection with, when

When is intensity modulation, when_BiasIn null, phase modulation is performed, and in both modulation modes, the chirp test method is consistent, so equation (13) can be further simplified to equation (14):

wherein' denotes the first derivative, χ, over time_AB＝exp(-α_{A_RF}(t)-α_{B_RF}(t))，φ_{RF_A}Is the phase shift of the first optical path, phi_{RF_B}Is the phase shift of the second optical path, phi_BiasA phase offset set for the thermo-optic phase shifter on the second optical path.

In practice, the electric absorption effect of the silicon optical modulator is much smaller than the corresponding electric refraction effect, and therefore, the electric absorption effect is much smaller, and therefore, the losses of the first optical path and the second optical path of the silicon optical modulator caused by the electric absorption effect can be expressed by the average absorption coefficient, as shown in formula (15) -formula (18),

α_{RF_A_mean}＝δ_{RF_A_1}+δ_{RF_A_2}V_PN+δ_{RF_A_3}V_PN ²+δ_{RF_A_4}V_PN ³ (15)

α_{RF_B_mean}＝δ_{RF_B_1}+δ_{RF_B_2}V_PN+δ_{RF_B_3}V_PN ²+δ_{RF_B_4}V_PN ³ (16)

α_{RF_A}(t)≈α_{RF_A_mean} (17)

α_{RF_B}(t)≈α_{RF_B_mean} (18)

for example, the embodiment of the present invention provides a phase shift curve of a silicon optical modulator, as shown in fig. 8(a), the horizontal axis represents applied reverse voltage in V, and the vertical axis represents phase shift in rad, and as can be seen from fig. 8(a), when the applied reverse voltage increases in the absence of a test signal, the phase shift of the optical signal on the first optical path of the silicon optical modulator increases correspondingly, and the phase shift of the optical signal on the second optical path also increases correspondingly. Fig. 8(b) is an absorption loss curve of the silicon optical modulator, where the horizontal axis is the applied reverse voltage, the unit is V, and the vertical axis is the absorption loss, the unit is dB, and it can be seen from fig. 8(b) that when the applied reverse voltage is increased, the loss due to the first optical path electro-absorption of the silicon optical modulator is gradually reduced, and the loss due to the second optical path electro-absorption is also gradually reduced, indicating that at a larger modulation voltage, the loss due to the electro-absorption is much smaller than the electro-refraction effect, and therefore, the losses of the first optical path and the second optical path can be expressed by the average absorption coefficient.

In this case, equation (13) can be simplified to equation (19) as follows:

wherein' denotes the first derivative, χ, over time_AB＝exp(-α_{A_RF}(t)-α_{B_RF}(t))，χ_AB' ≈ 0, assuming γ_norm≈γχ_AB，φ_{RF_A}Is the phase shift of the first optical path, phi_{RF_B}Is the phase shift of the second optical path, phi_BiasA phase offset set for the thermo-optic phase shifter on the second optical path.

The chirp measuring apparatus can calculate the chirp parameter after obtaining the equations (18) and (19).

When the chirp measuring apparatus rewrites the above formula with the dc offset, the amplitude of the test signal, the frequency of the test signal, the radio frequency phase shift of the optical signal modulator, and the absorption loss of the optical signal modulator, it is assumed that V is applied to the silicon optical modulator in the optical signal modulator_PNApplying an amplitude V to the silicon optical modulator_RFFrequency of w₁When testing the signal, the radio frequency phase shift alpha of the first optical path of the silicon optical modulator_{RF_A}(t) radio frequency phase shift α of the second optical path_{RF_B}(t) absorption loss phi of the first optical path_{RF_A}(t) and absorption loss phi of the second optical path_{RF_B}(t) can be written as a third order polynomial of the reverse voltage of the PN junction within the silicon light modulator, as shown in equations (20) -23:

α_{RF_A}(t)＝δ_{RF_A_1}+δ_{RF_A_2}(V_PN-V_RFcosw₁t)+δ_{RF_A_3}(V_PN-V_RFcosw₁t)²+δ_{RF_A_4}(V_PN-V_RFcosw₁t)³ (22)

α_{RF_B}(t)＝δ_{RF_B_1}+δ_{RF_B_2}(V_PN+V_RFcosw₁t)+δ_{RF_B_3}(V_PN+V_RFcosw₁t)²+δ_{RF_B_4}(V_PN+V_RFcosw₁t)³ (23)

wherein,

and

respectively, the polynomial factors of the rf phase shift of the first optical path of the silicon optical modulator with respect to the reverse bias voltage,

and

polynomial factor alpha of the radio frequency phase shift of the second optical path of the silicon optical modulator relative to the reverse bias voltage_{RF_A_1}、α_{RF_A_2}、α_{RF_A_3}、α_{RF_A_4}Respectively polynomial factors of the absorption loss of the first optical path of the silicon optical modulator with respect to the reverse bias voltage,

polynomial factor, V, of absorption loss of the second optical path of the respective silicon optical modulator with respect to reverse bias_PNIs a dc bias voltage. Phase shift phi of first optical path of silicon optical modulator in absence of test signal_{REF_A}And phase shift phi of the second optical path_{REF_B}And may be expressed as formula (24) to formula (25), the absorption loss α of the first optical path of the silicon optical modulator_{RF_A_mean}And the absorption loss sum of the second optical path_{RF_B_mean}And can be expressed as formula (26) to formula (27) as follows:

α_{RF_A_mean}＝δ_{RF_A_1}+δ_{RF_A_2}V_PN+δ_{RF_A_3}V_PN ²+δ_{RF_A_4}V_PN ³ (26)

α_{RF_B_mean}＝δ_{RF_B_1}+δ_{RF_B_2}V_PN+δ_{RF_B_3}V_PN ²+δ_{RF_B_4}V_PN ³ (27)

the chirp measuring device uses the processor to measure phi in the formula (20)_{RF_A}Phi in (t) and formula (21)_{RF_B}(t) expanding, and respectively using A as the zeroth order term, the first order term, the second order term and the third order term in the expansion₀、A₁、A₂、A₃And B₀、B₁、B₂、B₃In this case, the following expression (28) to expression (35) can be obtained:

at this time, phi_{RF_A}(t) and phi_{RF_B}(t) can be rewritten as formula (36) to formula (37):

φ_{RF_A}(t)＝A₀+A₁cosw₁t+A₂cos2w₁t+A₃cos3w₁t (36)

φ_{RF_B}(t)＝B₀+B₁cosw₁t+B₂cos2w₁t+B₃cos3w₁t (37)

it can be seen that when measuring the chirp parameter, a needs to be calculated first₀、A₁、A₂、A₃And B₀、B₁、B₂、B₃The numerical value of (c).

For calculation convenience, the chirp measuring device firstly carries out FFT (fast Fourier transform) on a preset optical complex field intensity model and sets the offset phase shift of the thermo-optic phase shifter to be 0 and pi, namely phi is measured_Bias0 and phi_BiasAt this time, a spectrum expression of the preset light complex field intensity model can be obtained, as shown in equations (38) to (39):

wherein E is_INFor complex amplitude of the input light field, alpha_{RF_A_mean}Is the absorption loss of the first optical path, a_{RF_B_mean}δ is the pulse function for the absorption loss of the second optical path.

At this time, A₀、A₁、A₂、A₃And B₀、B₁、B₂、B₃Can be obtained according to the formulae (1) to (7).

Therefore, the chirp test device can obtain the instantaneous chirp measurement model by only substituting the formulas (1) to (7) into the formula (19) through the processor, as shown in the formula (40):

wherein, w₀Is a direct current component, w₀+w₁Is a first harmonic component, w₀+2w₁Is a second harmonic component, w₀+3w₁Is the third harmonic component, phi_{RF_A}Is the phase shift of the first optical path, phi_{RF_B}Is the phase shift of the second optical path.

Further, as can be seen from the instantaneous chirp measurement model, the instantaneous chirp parameter is related to the splitting ratio γ. For example, the embodiment of the present invention provides a schematic diagram of the relationship between the instantaneous chirp parameter and the splitting ratio, as shown in fig. 9, where the horizontal axis represents time and the unit is e^-11s, the vertical axis represents the instantaneous chirp parameter, and the three curves in fig. 9 are graphs of the chirp parameter when γ is 0.9, γ is 1, and γ is 1.1, respectively. As can be seen from fig. 9, when the split ratio γ is 0.9, the absolute value of the chirp parameter is generally small, and is close to 0.1 at the maximum and 0 at the minimum, and when the split ratio γ is 1 and the split ratio γ is 1.1, the absolute value of the instantaneous chirp parameter is large, and the maximum exceeds even 0.3, and the minimum is close to 0.1. Thereby can beIn practical applications, the instantaneous chirp can be reduced by setting the splitting ratio.

And S109, integrating the instantaneous chirp measurement model to obtain a preset chirp measurement model.

After the chirp measuring device obtains the instantaneous chirp measurement model, the instantaneous chirp measurement model is integrated in the time domain, and the obtained integration model is used as the final preset chirp measurement model and is stored in the processor so as to calculate the chirp parameters later.

It should be noted that, in practice, the chirp parameter of the optical signal modulator is usually characterized by using the average chirp, and therefore, the chirp measurement apparatus needs to further integrate the instantaneous chirp measurement model from 0 to the end of the preset integration time to obtain the preset chirp measurement model capable of calculating the average chirp.

It is understood that the preset integration time may be set according to actual requirements, and the embodiment of the present invention is not limited herein.

Illustratively, when the instantaneous chirp model is the equation (40), the chirp measuring apparatus integrates the equation (40) in the time domain by the processor to obtain a preset chirp measurement model, i.e., equation (8).

In the embodiment of the present invention, before the chirp measurement process is performed, the processor may first derive the preset chirp model for calculating the chirp parameter from the preset optical complex field intensity model of the optical signal modulator, so that the chirp measurement apparatus can subsequently calculate the chirp parameter according to the preset chirp measurement model.

In some embodiments of the present invention, as shown in fig. 10, an embodiment of the present invention provides a chirp measurement apparatus 2 including:

the generating module 20 is configured to generate an input optical signal through a first set laser, and generate a local oscillator optical signal through a second set laser;

the optical processing module 21 is configured to modulate the input optical signal to obtain a modulated optical signal; mixing the modulated optical signal and the local oscillator optical signal to obtain a mixed optical signal;

a sampling module 22, configured to sample the mixed optical signal to obtain a direct current component, a first harmonic component, a second harmonic component, and a third harmonic component of the mixed optical signal;

a calculating module 23, configured to perform phase shift coefficient calculation on the direct current component, the first harmonic component, the second harmonic component, and the third harmonic component to obtain a phase shift transformation factor, and calculate a chirp parameter according to a preset chirp measurement model and the phase shift transformation factor; the chirp measurement model is used for measuring the chirp parameter of the optical signal modulation circuit.

In some embodiments of the present invention, the calculating module 23 is specifically configured to obtain a preset light complex field intensity model, and perform fourier transform on the preset light complex field intensity model to obtain a first spectrum model and a second spectrum model; respectively substituting the direct current component, the first harmonic component, the second harmonic component and the third harmonic component into the first frequency spectrum model and the second frequency spectrum model, and respectively calculating a first direct current output, a second direct current output, a first harmonic output, a second first harmonic output, a first second harmonic output, a second harmonic output, a first third harmonic output and a second third harmonic output; calculating a phase shift coefficient by adopting the first direct current output and the second direct current output to obtain a direct current phase shift factor; calculating phase shift coefficients by using the first primary harmonic output and the second primary harmonic output to respectively obtain a primary sum phase shift factor and a primary difference phase shift factor; calculating a phase shift coefficient according to the first second harmonic output and the second harmonic output to respectively obtain a second sum phase shift factor and a second difference phase shift factor; calculating a phase shift coefficient by using the first third harmonic output and the second third harmonic output to respectively obtain a third sum phase shift factor and a third difference phase shift factor; and adopting the direct current phase shift factor, the primary sum phase shift factor, the primary difference phase shift factor, the secondary sum phase shift factor, the secondary difference phase shift factor, the tertiary sum phase shift factor and the tertiary difference phase shift factor as the phase shift transformation factor.

In some embodiments of the present invention, the calculating module 23 is specifically configured to obtain a direct current difference result by taking a difference between the first direct current output and the second direct current output; summing the first direct current output and the second direct current output to obtain a direct current sum result; comparing the DC difference result with the DC sum result, and taking the obtained ratio as the DC phase shift factor.

In some embodiments of the present invention, the calculating module 23 is specifically configured to obtain a first difference result by performing a difference between the first harmonic output and the second first harmonic output; summing the first harmonic output and the second first harmonic output to obtain a first sum result, comparing the first sum result with the direct current sum result to obtain the first sum shift factor, and comparing the first difference result with the direct current difference result to obtain the first difference shift factor.

In some embodiments of the present invention, the calculating module 23 is specifically configured to obtain a second difference result by subtracting the first second harmonic output from the second harmonic output; summing the first second harmonic output and the second harmonic output to obtain a second sum result; and comparing the secondary sum result with the direct current sum result to obtain the secondary sum phase shift factor, and comparing the secondary difference result with the direct current difference result to obtain the secondary difference phase shift factor.

In some embodiments of the present invention, the calculating module 23 is specifically configured to perform a difference between the first third harmonic output and the second third harmonic output to obtain a third difference result; summing the first third harmonic output and the second third harmonic output to obtain a third sum result; and comparing the third sum result with the direct current sum result to obtain the third sum phase shift factor, and comparing the third difference result with the direct current difference result to obtain the third difference phase shift factor.

In some embodiments of the present invention, the calculating module 23 is specifically configured to obtain a phase shift difference of the optical signal modulation circuit; calculating a chirp molecule part according to the direct current phase shift factor, the first sum phase shift factor, the first difference phase shift factor, the second sum phase shift factor, the second difference phase shift factor, the first cosine harmonic, the third sum phase shift factor, the third difference phase shift factor, the second cosine harmonic and the sine value of the phase shift difference; calculating a chirp denominator part according to the direct current phase shift factor, the first sum phase shift factor, the first difference phase shift factor, the second sum phase shift factor, the second difference phase shift factor, the first cosine harmonic, the third sum phase shift factor, the third difference phase shift factor, the second cosine harmonic and a cosine value of the phase shift difference; and comparing the chirp numerator part with the chirp denominator part, and integrating the obtained ratio in the time domain to obtain the chirp parameter.

In some embodiments of the present invention, the calculating module 23 is specifically configured to calculate the primary chirp molecule according to the dc phase shift factor, the primary sum phase shift factor, the primary difference phase shift factor, and a sine value of the phase shift difference; calculating secondary chirp molecules by using the direct current phase shift factor, the secondary sum phase shift factor, the secondary difference phase shift factor, the sine value of the phase shift difference and the primary cosine harmonic; calculating a third chirp molecule according to the direct current phase shift factor, the third sum phase shift factor, the third difference phase shift factor, the sine value of the phase shift difference and the second cosine harmonic; and accumulating the primary chirp molecules, the secondary chirp molecules and the tertiary chirp molecules to obtain the chirp molecule part.

In some embodiments of the present invention, the calculating module 23 is specifically configured to calculate a primary chirp denominator according to the dc phase shift factor, the primary sum phase shift factor, the primary difference phase shift factor, and a cosine value of the phase difference; calculating a secondary chirp denominator by using the direct current phase shift factor, the secondary sum phase shift factor, the secondary difference phase shift factor, the cosine value of the phase difference and the primary cosine harmonic; calculating a third chirp denominator according to the direct current phase shift factor, the third sum phase shift factor, the third difference phase shift factor, a cosine value of the phase difference and the second cosine harmonic; and accumulating the primary chirp denominator, the secondary chirp denominator and the tertiary chirp denominator to obtain the chirp denominator part.

In some embodiments of the present invention, the calculating module 23 is further configured to obtain a preset light complex field intensity model and a preset chirp calculation model; expanding and simplifying the preset light complex field intensity model to obtain an instantaneous light intensity function and an instantaneous phase function of the modulated light signal; combining and simplifying the preset chirp calculation model, the instantaneous light intensity function and the instantaneous phase function to obtain an instantaneous chirp measurement model; and integrating the instantaneous chirp measurement model to obtain the preset chirp measurement model.

In some embodiments of the present invention, fig. 11 is a schematic structural diagram of a chirp measurement apparatus according to an embodiment of the present invention, and as shown in fig. 11, a chirp measurement apparatus according to an embodiment of the present invention may include a processor 01 and a memory 02 storing instructions executable by the processor 01. The processor 01 is configured to execute the executable chirp measurement instruction stored in the memory, so as to implement the chirp measurement method provided by the embodiment of the present invention.

In an embodiment of the present invention, the Processor 01 may be at least one of an Application Specific Integrated Circuit (ASIC), a Digital Signal Processor (DSP), a Digital Signal Processing Device (DSPD), a ProgRAMmable Logic Device (PLD), a Field ProgRAMmable Gate Array (FPGA), a CPU, a controller, a microcontroller, and a microprocessor. It will be appreciated that the electronic devices used to implement the processor functions described above may be other devices, and embodiments of the present invention are not limited in particular. The terminal further comprises a memory 02, which memory 02 may be connected to the processor 01, wherein the memory 02 may comprise a high speed RAM memory, and may further comprise a non-volatile memory, such as at least two disk memories.

In practical applications, the Memory 02 may be a volatile Memory (volatile Memory), such as a Random-Access Memory (RAM); or a non-volatile Memory (non-volatile Memory), such as a Read-Only Memory (ROM), a flash Memory (flash Memory), a Hard Disk (Hard Disk Drive, HDD) or a Solid-State Drive (SSD); or a combination of the above types of memories and provides instructions and data to the processor 01.

In addition, each functional module in this embodiment may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit. The integrated unit can be realized in a form of hardware or a form of a software functional module.

Based on the understanding that the technical solution of the present embodiment essentially or a part contributing to the prior art, or all or part of the technical solution, may be embodied in the form of a software product stored in a storage medium, and include several instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) or a processor (processor) to execute all or part of the steps of the method of the present embodiment. And the aforementioned storage medium includes: u disk, removable hard disk, read only memory, random access memory, magnetic or optical disk, etc. for storing program codes.

The embodiment of the invention provides a computer readable storage medium, which stores executable chirp measurement instructions and is applied to a chirp measurement device, and when the program is executed by a processor, the program realizes a chirp measurement method provided by the embodiment of the invention.

As will be appreciated by one skilled in the art, embodiments of the present invention may be provided as a method, system, or computer program product. Accordingly, the present invention may take the form of a hardware embodiment, a software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, optical storage, and the like) having computer-usable program code embodied therein.

The present invention has been described with reference to flowchart illustrations and/or block diagrams of implementations of methods, apparatus (systems) and computer program products according to embodiments of the invention. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart block or blocks and/or flowchart block or blocks.

These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart block or blocks.

These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart block or blocks in the flowchart and/or block diagram block or blocks.

In the following description, suffixes such as "module", "component", or "unit" used to denote elements are used only for the convenience of explanation of the present disclosure, and have no specific meaning in themselves. Thus, "module", "component" or "unit" may be used mixedly.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention.

Claims

1. A chirp measurement apparatus, characterized in that the measurement apparatus comprises:

the processor is used for calculating phase shift coefficients of the direct current component, the first harmonic component, the second harmonic component and the third harmonic component output by the sampling circuit to obtain a phase shift conversion factor; calculating according to a preset chirp measurement model and the phase shift conversion factor to obtain a chirp parameter; the preset chirp measurement model is used for measuring chirp parameters of the optical signal modulation circuit;

2. The chirp measurement device according to claim 1,

the sampling circuit includes: a photoelectric signal converter and a sampler;

the output end of the sampler is connected with the processor;

3. The chirp measurement device of claim 2, wherein the sampling circuit further comprises: a transimpedance amplifier;

4. The chirp measurement device according to claim 1,

the input optical signal generated by the first laser and the local oscillator optical signal generated by the second laser have frequency offset.

5. The chirp measurement device according to claim 1,

the optical signal modulation circuit includes: the device comprises a silicon optical modulator, a test signal generator and a direct current voltage source;

the test signal generator is connected with the silicon optical modulator;

6. The chirp measurement device according to claim 5,

the silicon optical modulator includes: the optical signal input end, the first optical path, the second optical path and the optical signal output end;

7. A chirp measurement method applied to the chirp measurement apparatus according to any one of claims 1 to 6, the method comprising:

modulating the input optical signal to obtain a modulated optical signal;

performing phase shift coefficient calculation on the direct current component, the first harmonic component, the second harmonic component and the third harmonic component to obtain a phase shift transformation factor; calculating according to a preset chirp measurement model and the phase shift conversion factor to obtain a chirp parameter; the chirp measurement model is used for measuring the chirp parameter of the optical signal modulation circuit.

8. The method of claim 7, wherein the performing phase shift coefficient calculations on the dc component, the first harmonic component, the second harmonic component, and the third harmonic component to obtain phase shift transform factors comprises:

9. The method of claim 8, wherein said calculating a phase shift coefficient using said first dc output and said second dc output to obtain a dc phase shift factor comprises:

10. The method of claim 8, wherein the performing phase shift coefficient calculations using the first harmonic output and the second first harmonic output to obtain a first sum phase shift factor and a first difference phase shift factor, respectively, comprises:

summing the first harmonic output and the second first harmonic output to obtain a first sum result;

11. The method of claim 8, wherein the performing phase shift coefficient calculations based on the first second harmonic output and the second harmonic output to obtain a second sum phase shift factor and a second difference phase shift factor, respectively, comprises:

12. The method of claim 8, wherein the performing phase shift coefficient calculations using the first third harmonic output and the second third harmonic output to obtain a third sum phase shift factor and a third difference phase shift factor, respectively, comprises:

13. The method of claim 7, wherein calculating the chirp parameter according to a preset chirp measurement model and the phase shift transformation factor comprises:

acquiring a phase shift difference of an optical signal modulation circuit;

14. The method of claim 13, wherein calculating the fraction of chirped molecules based on the dc phase shift factor, the first sum shift factor, the first difference phase shift factor, the second sum shift factor, the second difference phase shift factor, the first cosine harmonic, the third sum shift factor, the third difference phase shift factor, the second cosine harmonic, and the sine of the phase shift difference comprises:

15. The method of claim 13 or 14, wherein the calculating a chirp denominator portion from the dc phase shift factor, the primary sum shift factor, the primary difference phase shift factor, the secondary sum shift factor, the secondary difference phase shift factor, the primary cosine harmonic, the tertiary sum shift factor, the tertiary difference phase shift factor, the secondary cosine harmonic, and the cosine value of the phase shift difference comprises:

calculating a primary chirp denominator according to the direct current phase shift factor, the primary sum phase shift factor, the primary difference phase shift factor and a cosine value of the phase difference;

16. The method of claim 7, wherein before the generating an input optical signal by a first laser and generating a local oscillator optical signal by a second laser, the method further comprises:

17. A chirp measurement apparatus, characterized in that the chirp measurement apparatus comprises:

18. A chirp measurement apparatus, characterized in that the chirp measurement apparatus comprises: a memory and a processor;

the memory is used for storing executable chirp measurement instructions;

the processor, configured to execute the executable chirp measurement instructions stored in the memory, to implement the method of any one of claims 7-16.

19. A computer-readable storage medium having stored thereon executable chirp measurement instructions for causing a processor to perform the method of any one of claims 7-16 when executed.