CN117073730B - Optical fiber sensing system and optical fiber sensing method based on microwave photons - Google Patents

Abstract

This application provides an optical fiber sensing system and optical fiber sensing method based on microwave photons. The optical fiber sensing system includes: an optical signal generation unit for generating an optical signal, a microwave radio frequency oscillator for generating a first radio frequency signal and a second radio frequency signal, and a microwave-light modulation for modulating the optical signal based on the first radio frequency signal. device, a photoelectric conversion unit for converting an optical signal into a first electrical signal, a microwave phase detector and a signal acquisition and processing component. Microwave phase detectors are used to determine the operating frequency of the optical fiber sensing system before sensing changes in external physical quantities. The microwave phase detector is also used to generate a second electrical signal representing a phase difference between the first electrical signal and the second radio frequency signal. The frequencies of the first radio frequency signal and the second radio frequency signal are both working frequencies. The signal acquisition and processing component is used to demodulate the intensity of the second electrical signal to obtain information on changes in external physical quantities. The optical fiber sensing system of this application has fast response, low cost and high measurement sensitivity.

Description

Optical fiber sensing system and fiber sensing method based on microwave photons

Technical field

The present application relates to the field of optical fiber sensing technology, and in particular to an optical fiber sensing system and optical fiber sensing method based on microwave photons.

Background technique

With the continuous development of sensing technology, the requirements for the sensitivity and response speed of the sensing system are also increasing. Fast and precise measurements are of great significance in many fields. For example, in the health monitoring of structures, fast and accurate measurement results can reflect the operation of the structure in a timely manner, which is of great significance to ensuring the health of the system and achieving fast and timely equipment maintenance. During the implementation of engineering projects, in the early stages, fast and accurate measurement data is one of the key information that helps ensure the smooth progress of the project plan, which can reduce the risk of project delay, rework or restart. In the field of medical surgery, continuous and accurate measurement of tumor location, etc., can reduce unnecessary damage to adjacent tissues and reduce complications, which is crucial to ensuring human safety and health.

Fiber optic sensors have the characteristics of inherent small size, light weight, resistance to electromagnetic interference, and long sensing distance. Therefore, they have become an irreplaceable sensing solution in some application scenarios and have been widely researched and applied.

Currently, technology based on microwave photonic filters is used in fiber optic sensing systems. According to the drift of the center frequency of the passband in the system's radio frequency response, the monitoring of physical quantities such as strain, pressure, and temperature is realized. However, the sensitivity of information demodulation based on the above technology is very low, several orders of magnitude lower than methods based on spectral drift in the optical domain, and the measurement speed also needs to be improved.

Contents of the invention

This application provides an optical fiber sensing system and optical fiber sensing method based on microwave photons, which have fast response speed, low cost, and high measurement sensitivity.

This application provides an optical fiber sensing system for sensing changes in external physical quantities, including:

An optical signal generating unit is used to generate optical signals;

A microwave radio frequency oscillator, used to generate a first radio frequency signal and a second radio frequency signal;

A microwave-optical modulator, connected to the optical signal generating unit and the microwave radio frequency oscillator, used to modulate the optical signal based on the first radio frequency signal and output the modulated optical signal;

A photoelectric conversion unit, used to convert the optical signal into a first electrical signal;

A microwave phase detector is used to determine the operating frequency of the optical fiber sensing system before sensing the change information of the external physical quantity; the microwave phase detector is connected to the photoelectric conversion unit and oscillates with the microwave radio frequency The device is connected to generate a second electrical signal representing the phase difference between the first electrical signal and the second radio frequency signal; the frequencies of the first radio frequency signal and the second radio frequency signal are both the operating frequency. ;and

A signal acquisition and processing component is connected to the microwave phase detector and is used to collect and demodulate the intensity of the second electrical signal to obtain the change information of the external physical quantity.

Optionally, the microwave phase detector includes a vector network analyzer, which is used to determine the phase change rule of the external physical quantity change information before sensing the external physical quantity change information.

Optionally, the signal acquisition and processing component is used to demodulate the intensity of the second electrical signal according to the phase change rule to obtain the change information of the external physical quantity.

Optionally, the optical signal generation unit includes a light source and an interferometer component; the light source is used to generate broadband continuous light; and the interferometer component is used to optically sample the broadband continuous light to obtain a sampled optical signal.

Optionally, the interferometer assembly includes a bidirectional coupler and a first optical fiber interferometer; the bidirectional coupler includes a first port, a second port and a third port; the first port is connected to the light source, so The second port is connected to the first fiber interferometer, and the third port is connected to the microwave-light modulator; the first fiber interferometer is used to optically sample the broadband continuous light to obtain the the sampled optical signal, and transmit the sampled optical signal to the third port.

Optionally, the interferometer assembly includes a coupler and a plurality of first fiber interferometers; the coupler is connected between the second port of the bidirectional coupler and the plurality of first fiber interferometers. ; At least two of the first fiber interferometers have different free spectral ranges; the plurality of first fiber interferometers respectively perform optical sampling on the broadband continuous light to obtain a plurality of the sampled optical signals; The coupler is used to couple a plurality of the sampled optical signals. This enables multiple sensor reuse.

Optionally, the light source includes an amplified spontaneous emission light source or a superluminescent diode.

Optionally, the photoelectric conversion unit includes a dispersion component and a photodetector; the dispersion component is used to disperse the modulated optical signal to obtain a dispersed optical signal; the photodetector is used to convert the dispersion The optical signal is converted into the first electrical signal.

Optionally, the optical fiber sensing system includes an amplifier connected between the optical signal generating unit and the photodetector for amplifying the optical signal.

Optionally, the dispersion component includes at least one of a single-mode fiber, a multi-mode fiber, and a dispersion compensation fiber.

Optionally, the microwave radio frequency oscillator includes a vector network analyzer.

Optionally, the microwave-light modulator includes one of an electro-optical modulator, a Mach-Zehnder modulator, and a phase modulator.

This application also provides an optical fiber sensing method based on microwave photons, which is applied to the optical fiber sensing system to sense changes in external physical quantities, including:

Determine the operating frequency of the optical fiber sensing system;

generate light signals;

Modulate the optical signal based on the first radio frequency signal to obtain a modulated optical signal;

convert the optical signal into a first electrical signal;

Generate a second electrical signal representing the phase difference between the first electrical signal and the second radio frequency signal; wherein the frequencies of the second radio frequency signal and the first radio frequency signal are both the operating frequency;

Demodulate the intensity of the second electrical signal to obtain the change information of the external physical quantity.

Optionally, determining the operating frequency of the optical fiber sensing system includes:

Produce broadband continuous light;

Optically sample the broadband continuous light to obtain a sampled optical signal;

Modulate the sampled optical signal based on a wide-band radio frequency sweep signal to obtain a modulated optical signal;

Perform dispersion on the modulated optical signal to obtain a dispersed optical signal;

Convert the dispersion optical signal into a third electrical signal;

Determine any frequency within the radio frequency passband as the operating frequency according to the strength of the third electrical signal;

According to the phase of the third electrical signal, the phase change rule of the external physical quantity change information is determined.

Optionally, before demodulating the intensity of the second electrical signal, the optical fiber sensing method further includes:

removing the direct current information of the intensity of the second electrical signal;

Noise information from the intensity of the second electrical signal is removed.

In some embodiments, the first radio frequency signal and the second radio frequency signal have the same frequency, the microwave-optical modulator modulates the optical signal based on the first radio frequency signal, and the microwave phase detector generates a signal that is representative of the first electrical signal and the second radio frequency signal. The second electrical signal with phase difference, so that the optical fiber sensing system does not need a frequency sweep process, has a fast response speed and low cost of single-frequency working devices; by demodulating the intensity of the second electrical signal, the first electrical signal and the second radio frequency are obtained The phase difference information of the signal can then be used to obtain information about changes in external physical quantities. In this way, the measurement sensitivity of the optical fiber sensing system is high.

It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and do not limit the present application.

Description of the drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the application and together with the description, serve to explain the principles of the application.

Figure 1 shows a structural block diagram of an embodiment of the optical fiber sensing system of the present application.

Figure 2 shows a structural block diagram of another embodiment of the optical fiber sensing system of the present application.

FIG. 3 is a schematic spectrum diagram of an optical signal of an embodiment of the light source shown in FIG. 2 .

FIG. 4 shows a schematic spectrum diagram of the spectrum diagram shown in FIG. 3 after being sampled by the interferometer assembly shown in FIG. 2 .

FIG. 5 is a schematic structural diagram of an embodiment of the interferometer assembly shown in FIG. 2 .

FIG. 6 is a schematic structural diagram of another embodiment of the interferometer assembly shown in FIG. 2 .

FIG. 7 is a schematic structural diagram of another embodiment of the interferometer assembly shown in FIG. 2 .

FIG. 8 is a schematic structural diagram of another embodiment of the interferometer assembly shown in FIG. 2 .

FIG. 9 is a schematic structural diagram of an embodiment of the first optical fiber interferometer shown in FIG. 5 .

FIG. 10 is a schematic structural diagram of an embodiment of the second optical fiber interferometer shown in FIG. 7 .

FIG. 11 is a schematic structural diagram of an embodiment of the second optical fiber interferometer shown in FIG. 7 .

FIG. 12 is a schematic structural diagram of an embodiment of the second optical fiber interferometer shown in FIG. 7 .

Figure 13 is a flow chart of an embodiment of the optical fiber sensing method of the present application.

Figure 14 is a structural block diagram of another embodiment of the optical fiber sensing system of the present application.

Figure 15 is a flow chart of an embodiment of the step "determining the operating frequency of the optical fiber sensing system" in Figure 13.

Figure 16 is a waveform diagram of an embodiment of a third electrical signal.

FIG. 17 is a waveform diagram of a phase of an embodiment of a third electrical signal.

Figure 18 is a device diagram of another embodiment of the optical fiber sensing system.

Figure 19 is a spectrum diagram of the optical signal after sampling of the optical fiber sensing system shown in Figure 18.

Figure 20 is a schematic diagram of the radio frequency passband signal intensity measured by the optical fiber sensing system shown in Figure 18.

Figure 21 is the time domain information of the signal measured by the optical fiber sensing system shown in Figure 18.

Figure 22 is the frequency domain information of the signal measured by the optical fiber sensing system shown in Figure 18.

Detailed ways

Exemplary embodiments will be described in detail herein, examples of which are illustrated in the accompanying drawings. When the following description refers to the drawings, the same numbers in different drawings refer to the same or similar elements unless otherwise indicated. The implementations described in the following exemplary embodiments do not represent all implementations consistent with this application. Rather, they are merely examples of apparatus and methods consistent with aspects of the application as detailed in the appended claims.

The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. Unless otherwise defined, the technical terms or scientific terms used in this application shall have the usual meaning understood by a person with ordinary skills in the field to which this application belongs. The "first", "second" and similar words used in the description and claims of this application do not indicate any order, quantity or importance, but are only used to distinguish different components. Likewise, "a" or "one" and similar words do not indicate a quantitative limit, but rather indicate the presence of at least one. "Multiple" or "several" means two or more than two. Unless otherwise indicated, similar terms such as "front", "rear", "lower" and/or "upper" are for convenience of description only and are not intended to limit one position or one spatial orientation. "Including" or "including" and other similar words mean that the elements or objects appearing before "includes" or "includes" cover the elements or objects listed after "includes" or "includes" and their equivalents, and do not exclude other elements. or objects. Words such as "connected" or "connected" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect.

The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used in this application and the appended claims, the singular forms "a," "the" and "the" are intended to include the plural forms as well, unless the context clearly dictates otherwise. It will also be understood that the term "and/or" as used herein refers to and includes any and all possible combinations of one or more of the associated listed items.

The optical fiber sensing system based on microwave photons in the embodiment of the present application includes: an optical signal generation unit for generating an optical signal, a microwave radio frequency oscillator for generating a first radio frequency signal and a second radio frequency signal, and a microwave radio frequency oscillator for generating a first radio frequency signal. A microwave-light modulator for signal modulating optical signals, a photoelectric conversion unit for converting the optical signal into a first electrical signal, a microwave phase detector and a signal acquisition and processing component. Microwave phase detectors are used to determine the operating frequency of the optical fiber sensing system before sensing changes in external physical quantities. The microwave phase detector is also used to generate a second electrical signal representing a phase difference between the first electrical signal and the second radio frequency signal. Wherein, the frequencies of the first radio frequency signal and the second radio frequency signal are both working frequencies. The signal acquisition and processing component is used to acquire and demodulate the phase of the second electrical signal to obtain information on changes in external physical quantities. The optical fiber sensing system of the present application has fast response speed, low cost, and high measurement sensitivity.

This application provides an optical fiber sensing system and optical fiber sensing method based on microwave photons. The microwave photon-based optical fiber sensing system and optical fiber sensing method of the present application will be described in detail below with reference to the accompanying drawings. Features in the following embodiments and implementations may be combined with each other without conflict.

Figure 1 shows a structural block diagram of an embodiment of the optical fiber sensing system 10 of the present application. The optical fiber sensing system 10 of the present application is used to sense information on changes in external physical quantities. Information on changes in external physical quantities can be temperature, pressure, vibration, sound waves, strain, etc. As shown in Figure 1, the optical fiber sensing system 10 includes: an optical signal generation unit 11, a microwave radio frequency oscillator 12, a microwave-light modulator 13, a photoelectric conversion unit 14, a microwave phase detector 15 and a signal acquisition and processing component 16.

The optical signal generating unit 11 is used to generate optical signals. The optical signal changes with the change of external physical quantity information.

The microwave radio frequency oscillator 12 is used to generate a first radio frequency signal and a second radio frequency signal. The fiber optic sensing system 10 has an operating frequency. The frequencies of the first radio frequency signal and the second radio frequency signal are both working frequencies.

The microwave-optical modulator 13 is connected to the optical signal generation unit 11 and the microwave radio frequency oscillator 12, and is used to modulate the optical signal based on the first radio frequency signal to obtain a modulated optical signal. The microwave-light modulator 13 receives the optical signal generated by the optical signal generating unit 11 and the first radio frequency signal generated by the microwave radio frequency oscillator 12, and modulates the optical signal based on the first radio frequency signal to generate a modulated optical signal. In some embodiments, the microwave-light modulator 13 includes one of an electro-optic modulator, a Mach-Zehnder modulator, and a phase modulator.

The photoelectric conversion unit 14 is used to convert the optical signal into a first electrical signal. After the optical signal is converted into the first electrical signal, the first electrical signal is easier to detect and analyze.

The microwave phase detector 15 is used to determine the operating frequency of the optical fiber sensing system 10 before sensing the change information of external physical quantities. Before sensing changes in external physical quantities, the optical fiber sensing system 10 needs to be pre-calibrated to determine the operating frequency. The operating frequency determines the frequencies of the first radio frequency signal and the second radio frequency signal. In some embodiments, microwave phase detector 15 includes a vector network analyzer.

The microwave phase detector 15 is connected to the photoelectric conversion unit 14 and to the microwave radio frequency oscillator 12 for generating a second electrical signal representing the phase difference between the first electrical signal and the second radio frequency signal. The microwave phase detector 15 receives the first electrical signal and the second radio frequency signal, detects the phase difference between the first electrical signal and the second radio frequency signal, and generates a second electrical signal based on the phase difference. In some embodiments, the second electrical signal is a voltage value reflecting the phase difference.

The signal acquisition and processing component 16 is connected to the microwave phase detector 15 and is used to collect and demodulate the intensity of the second electrical signal to obtain information on changes in external physical quantities. The signal acquisition and processing component 16 can collect the second electrical signal, and obtain the change information of the external physical quantity through intensity demodulation of the second electrical signal.

In some embodiments, the first radio frequency signal and the second radio frequency signal have the same frequency, the microwave-optical modulator 13 modulates the optical signal based on the first radio frequency signal, and the microwave phase detector 15 generates an electrical signal representative of the first electrical signal and the second radio frequency signal. The phase difference of the second electrical signal of the signal, so that the optical fiber sensing system 10 does not need a frequency sweeping process, has a fast response speed and a low cost of single-frequency working devices; by demodulating the intensity of the second electrical signal, the first electrical signal and The phase difference information of the second radio frequency signal can then be used to obtain the change information of external physical quantities. In this way, the measurement sensitivity of the optical fiber sensing system 10 is high.

Before sensing the change information of the external physical quantity, the optical fiber sensing system 10 needs to be pre-calibrated to determine the phase change law of the change information of the external physical quantity. The phase change rule represents the change rule of the intensity of the second electrical signal as the external physical quantity changes. The phase change law is used to demodulate the change information of physical quantities.

The microwave phase detector 15 is used to determine the phase change rule of the change information of the external physical quantity before sensing the change information of the external physical quantity.

The signal acquisition and processing component 16 is used to demodulate the intensity of the second electrical signal according to the phase change rule to obtain information on changes in external physical quantities. The signal acquisition and processing component 16 corresponds the intensity of the second electrical signal to the external physical quantity change information according to the phase change rule determined during pre-calibration, demodulates the second electrical signal, and obtains the external physical quantity change information.

Figure 2 shows a structural block diagram of another embodiment of the optical fiber sensing system 10 of the present application.

The optical signal generating unit 11 includes a light source 17 and an interferometer assembly 18 .

The light source 17 is used to generate broadband continuous light. In some embodiments, light source 17 includes an amplified spontaneous emission light source or a superluminescent diode.

The interferometer component 18 is used to optically sample broadband continuous light to obtain a sampled optical signal. The interferometer component 18 is a sensing element of the optical fiber sensing system 10. It can be an interferometer or a combination of multiple interferometers. It performs optical sampling on the spectrum of broadband continuous light generated by the light source 17. Changes in external physical quantities cause changes in the sampled spectrum. changes, thus enabling multiple sensor reuse. ω is the angular frequency of broadband continuous light, the transfer function of the interferometer component 18 is T(ω), and the sampled optical signal can be expressed as S(ω)×T(ω).

FIG. 3 is a schematic spectrum diagram of an optical signal of an embodiment of the light source 17 shown in FIG. 2 .

FIG. 4 shows a schematic spectrum diagram of the spectrum diagram shown in FIG. 3 after being sampled by the interferometer assembly 18 shown in FIG. 2 .

Referring to Figures 3 and 4, the spectrum of the optical signal generated by the light source 17 is Gaussian. The spectrum sampled by the interferometer assembly 18 exhibits a continuous sinusoidal shape.

Referring to FIG. 2 , the photoelectric conversion unit 14 includes a dispersion component 141 and a photodetector 142 . The dispersion component 141 is used to disperse the modulated optical signal to obtain a dispersed optical signal. The dispersion component 141 can introduce dispersion into the signal and introduce the frequency domain characteristics of the signal into the time domain, thereby obtaining a passband signal in the radio frequency domain and forming a passband radio frequency filter. The dispersion component 141 can minimize high-order dispersion through optimized design, and can reduce the nonlinearity of the phase detected by the microwave phase detector 15 that changes with information about changes in external physical quantities. In some embodiments, the dispersion component 14 includes at least one of a single-mode optical fiber, a multi-mode optical fiber, and a dispersion-compensating optical fiber.

The photodetector 142 is used to convert the dispersion optical signal into a first electrical signal.

The complex frequency response of the fiber optic sensing system 10 can be expressed by the following formula:

Wherein, Ω is the angular frequency of the first radio frequency signal and the second radio frequency signal; H is the complex transfer function of the dispersion component 141; m is the modulation coefficient of the light field output by the microwave-light modulator 13.

In some embodiments, the optical fiber sensing system 10 includes an amplifier connected between the optical signal generating unit 11 and the photodetector 142 for amplifying the optical signal. In some embodiments, an amplifier is connected between the interferometer assembly 18 and the microwave-light modulator 13 for amplifying the sampled optical signal. In some embodiments, an amplifier is connected between the microwave-light modulator 13 and the dispersion component 141 for amplifying the modulated optical signal. In some embodiments, an amplifier is connected between the dispersion component 141 and the photodetector 142 for amplifying the dispersion optical signal. Amplifiers can increase signal strength to facilitate subsequent detection.

FIG. 5 is a schematic structural diagram of an embodiment of the interferometer assembly 18 shown in FIG. 2 .

The interferometer assembly 18 includes a bidirectional coupler 181 and a first fiber optic interferometer 182 . The bidirectional coupler 181 includes a first port T1, a second port T2, and a third port T3. The first port T1 is connected to the light source 17 and receives broadband continuous light. The second port T2 is connected to the first optical fiber interferometer 182 . The third port T3 is connected to the microwave-optical modulator 13 . The first optical fiber interferometer 182 is used to optically sample broadband continuous light, obtain a sampled optical signal, and transmit the sampled optical signal to the third port T3. The sampled optical signal is transmitted to the microwave-optical modulator through the third port T3. Device 13.

FIG. 6 is a schematic structural diagram of another embodiment of the interferometer assembly 18 shown in FIG. 2 .

The interferometer assembly 18 includes a coupler 183 and a plurality of first fiber interferometers 182 . The coupler 183 is connected between the second port T2 of the bidirectional coupler and the plurality of first fiber interferometers 182 . At least two first optical fiber interferometers 182 have different free spectral ranges and can detect physical quantity change information at multiple measurement points. The plurality of first optical fiber interferometers 182 respectively perform optical sampling on the broadband continuous light to obtain a plurality of sampled optical signals. The coupler 183 is used to couple multiple sampled optical signals and transmit them to the microwave-optical modulator 13 through the third port T3. The signal acquisition and processing component 16 can demodulate the radio frequency signals corresponding to different sampled optical signals, and then obtain the physical quantity change information of multiple measurement points, so that multiple sensors can be multiplexed.

FIG. 7 is a schematic structural diagram of another embodiment of the interferometer assembly 18 shown in FIG. 2 . Interferometer assembly 18 includes a second fiber optic interferometer 184 . The input end of the second optical fiber interferometer 184 is connected to the light source 17, and after optical sampling of the broadband continuous light, the sampled optical signal is transmitted to the microwave-light modulator 13 through the output end.

FIG. 8 is a schematic structural diagram of another embodiment of the interferometer assembly 18 shown in FIG. 2 .

Interferometer assembly 18 includes coupler 185 , coupler 186 and a plurality of second fiber optic interferometers 184 . The broadband continuous light is input to a plurality of second optical fiber interferometers 184 through the coupler 185 . At least two second optical fiber interferometers 184 have different free spectral ranges and can detect physical quantity change information at multiple measurement points. A plurality of second optical fiber interferometers 184 sample broadband continuous light to obtain multiple sampled optical signals. The coupler 186 couples the multiple sampled optical signals and outputs them. The signal acquisition and processing component 16 can demodulate different sampled optical signals. The radio frequency signal corresponding to the signal can then be used to obtain the physical quantity change information of multiple measurement points, so that multiple sensors can be reused.

FIG. 9 is a schematic structural diagram of an embodiment of the first optical fiber interferometer 182 shown in FIG. 5 . The first fiber optic interferometer 182 includes a Fabry-Borot interferometer. The first optical fiber interferometer 182 includes two reflection points 191 and 192, and the optical fiber between the reflection point 191 and the reflection point 192 is a sensing section.

FIG. 10 is a schematic structural diagram of an embodiment of the second optical fiber interferometer 184 shown in FIG. 7 .

The second fiber optic interferometer 184 includes a Sagnac interferometer. The second optical fiber interferometer 184 includes two couplers 193 and 194, a reference optical fiber 195, a delay optical fiber 196 and a reflection point 197. The optical fiber between the coupler 194 and the reflection point 197 is the sensing section.

FIG. 11 is a schematic structural diagram of an embodiment of the second optical fiber interferometer 184 shown in FIG. 7 .

The second fiber optic interferometer 184 includes a Mach-Zehnder interferometer. It includes two couplers 193 and 194, a reference optical fiber 195, and a delay optical fiber 196. The delay section optical fiber 196 is the sensing section of the system.

FIG. 12 is a schematic structural diagram of an embodiment of the second optical fiber interferometer 184 shown in FIG. 7 .

The second fiber optic interferometer 184 includes a Michelson interferometer. The second optical fiber interferometer 184 includes a coupler 193, a reference optical fiber 195, a delay optical fiber 196, and two reflection points 197 and 198. The delay section optical fiber 196 is the sensing section.

Figure 13 is a flow chart of an embodiment of the optical fiber sensing method 20 of the present application.

The optical fiber sensing method 20 is applied to the optical fiber sensing system 10 to sense external physical quantity change information. The optical fiber sensing method 20 includes: steps 21 to 26.

Step 21: Determine the operating frequency of the optical fiber sensing system 10. Step 21 is to determine the operating frequency of the microwave radio frequency oscillator 12 in the optical fiber sensing system 10 .

Step 22, generate an optical signal. The optical signal is generated by the optical signal generating unit 11 . The optical signal changes with the change of external physical quantity information.

Step 23: Modulate the optical signal based on the first radio frequency signal to obtain a modulated optical signal. The microwave-light modulator 13 receives the optical signal generated by the optical signal generating unit 11 and the first radio frequency signal generated by the microwave radio frequency oscillator 12, and modulates the optical signal based on the first radio frequency signal to generate a modulated optical signal.

Step 24: Convert the optical signal into a first electrical signal. The photoelectric conversion unit 14 converts the optical signal into a first electrical signal.

Step 25: Generate a second electrical signal representing the phase difference between the first electrical signal and the second radio frequency signal. Wherein, the frequencies of the second radio frequency signal and the first radio frequency signal are both working frequencies. The microwave phase detector 15 receives the first electrical signal and the second radio frequency signal, detects the phase difference between the first electrical signal and the second radio frequency signal, and generates a second electrical signal based on the phase difference.

Step 26: Demodulate the intensity of the second electrical signal to obtain information on changes in external physical quantities. The signal acquisition and processing component 16 collects and demodulates the phase of the second electrical signal to obtain information on changes in external physical quantities.

In some embodiments, the optical fiber sensing method 20 further includes: removing DC information of the intensity of the second electrical signal; removing noise information of the intensity of the second electrical signal. In this way, information on changes in external physical quantities can be obtained more accurately.

Figure 14 is a structural block diagram of another embodiment of the optical fiber sensing system 10 of the present application. This embodiment is used to determine the operating frequency and phase change rules before measuring physical quantities, that is, a pre-calibration process. The calibration system 210 includes: an optical signal generation unit 11 , a microwave-light modulator 13 , a photoelectric conversion unit 14 , a signal acquisition and processing component 16 and a vector network analyzer 19 . The optical signal generation unit 11, microwave-light modulator 13, photoelectric conversion unit 14, and signal acquisition and processing component 16 are consistent with those in the optical fiber sensing system 10 shown in Figure 2.

The vector network analyzer 19 is connected to the microwave-optical modulator 13 to provide a wide-band radio frequency sweep signal for modulating the optical signal generated by the optical signal generation unit 11, thereby generating a radio frequency pass-band electrical signal after passing through the photoelectric conversion unit 14.

The vector network analyzer 19 is connected to the photoelectric conversion unit 14 and is used to collect the radio frequency passband electrical signal generated by the photoelectric conversion unit 14, that is, the third electrical signal.

The signal acquisition and processing component 16 is connected to the vector network analyzer 19 to collect and process radio frequency pass electrical signals. According to the intensity information of the third electrical signal, the operating frequency of the optical fiber sensing system 10 is determined. According to the phase information of the third electrical signal, the phase change rule of the optical fiber sensing system 10 as the external physical quantity changes is determined.

FIG. 15 is a flow chart of an embodiment of step 21 in FIG. 13 .

Step 21 includes: steps 211 to 216. When performing step 21, the calibration system 210 shown in FIG. 14 is used, that is, the microwave radio frequency oscillator 12 and the microwave phase detector 15 are replaced by the vector network analyzer 19.

Step 211, generate broadband continuous light. The light source 17 generates broadband continuous light.

Step 212: Optically sample the broadband continuous light to obtain a sampled optical signal. The interferometer component 18 optically samples the broadband continuous light to obtain a sampled optical signal.

Step 213: Modulate the sampled optical signal based on the broadband radio frequency sweep signal to obtain the modulated optical signal. The vector network analyzer can provide a broadband radio frequency sweep signal. The microwave-optical modulator 13 modulates the sampled optical signal based on the broadband radio frequency sweep signal to obtain a modulated optical signal.

Step 214: Disperse the modulated optical signal to obtain the dispersed optical signal. The dispersion component 141 disperses the modulated optical signal, introduces the frequency domain characteristics of the signal into the time domain, thereby obtaining a passband signal in the radio frequency domain, forms a passband radio frequency filter, and obtains the dispersed optical signal.

Step 215: Convert the dispersion optical signal into a third electrical signal. The photodetector 142 converts the dispersed optical signal into a third electrical signal.

Step 216: Determine any frequency within the radio frequency passband as the operating frequency according to the strength of the third electrical signal. The vector network analyzer is connected to the photodetector 142 to measure the intensity of the third electrical signal. Figure 15 is a waveform diagram of an embodiment of a third electrical signal. As shown in Figure 16, the radio frequency passband is between frequency f1 and frequency f2. Any frequency within the radio frequency passband can be used as the operating frequency, for example, frequency f3, frequency f4, frequency f. If the optical fiber sensing system 10 includes multiple sensors, then there will be multiple radio frequency passbands of the signal detected by the photodetector 142, and the frequency corresponding to the radio frequency passband of the corresponding sensor is selected as the operating frequency of the optical fiber sensing system 10, that is, The sensing information of the corresponding sensor can be measured and obtained.

Step 217: Based on the phase of the third electrical signal, determine the phase change rule of the information of the optical fiber sensing system 10 as the external physical quantity changes. The vector network analyzer 19 measures the phase of the third electrical signal, changes the external physical quantity to be measured, and obtains the phase change rule of the external physical quantity change information.

In some embodiments, step 216 includes determining the microwave frequency within the radio frequency passband as the operating frequency. Because when the sensing element is subject to large-scale fluctuations, its phase changes may cause phase wrapping. At this time, the amplitude change characteristics are used to unwrap the phase signal, and a wide range of measurements can be achieved.

FIG. 17 is a waveform diagram of a phase of an embodiment of a third electrical signal. In the embodiment shown in Figure 17, the dispersion component 141 has no third-order dispersion. The phase within the signal passband changes linearly with frequency. Therefore, when using the optical fiber sensing system 10 for sensing and detection, the phase change of the system detection caused by the passband frequency drift caused by changes in external physical quantities also shows a linear trend. Through pre-calibration, the phase change rule with the external physical quantity is obtained, and the phase change value can be corresponding to the change value of the physical quantity to achieve demodulation.

FIG. 18 is a device diagram of another embodiment of the optical fiber sensing system 10. In this embodiment, this device is used as both the fiber optic sensing system 10 and the calibration system 210 . When this device is used as an optical fiber sensing system 10, a vector network analyzer (VNA) is used as a microwave phase detector 15 and also as a microwave radio frequency oscillator 12. At this time, the radio frequency signal output by the first port of the VNA is used as both the first radio frequency signal and the second radio frequency signal of the microwave radio frequency oscillator 12 .

In the embodiment shown in FIG. 18 , the light source 17 uses an amplified spontaneous emission light source (ASE). The central wavelength of the light source 17 is 1545.5 nm and the spectrum width is 35 nm. The interferometer assembly 18 is a Fabry-Perot (FP) cavity. The light emitted by the ASE is coupled into a Fabry-Porot (FP) cavity composed of hollow core fiber (HCF) and single-mode fiber (SMF) after passing through the circulator. Here, the two end surfaces at the welding point of SMF and HCF are used as the two reflective surfaces of the FP cavity. The cavity length of the FP cavity, that is, the length of the hollow-core fiber, is approximately 300 μm. After optical sampling by the FP cavity, the spectrum reflected back by the sampled optical signal is output through the third port of the circulator and coupled to the erbium-doped fiber amplifier (EDFA).

FIG. 19 is a spectrum diagram of the sampled optical signal of the optical fiber sensing system 10 shown in FIG. 18 .

It can be seen from Figure 19 that the free spectral range (FSR) of the FP cavity is 3.95nm, and the calculated cavity length is 303μm. The microwave-optical modulator 13 uses an electro-optical modulator (EOM). After the signal is amplified by EDFA, it enters the electro-optical modulator (EOM) to achieve radio frequency modulation. The RF signal is provided by the first port of the vector network analyzer (VNA). The RF signal input into the EOM is a linear sweep signal with a sweep range of 10kHz~500MHz. The optical signal is modulated by radio frequency in the EOM and then input into the dispersion compensation fiber (DCF) module. The total dispersion introduced by the DCF module is -997ps/nm. The signal after DCF is detected by a photodetector with a bandwidth of 1.6GHz and then input to the second port of the VNA for processing and display to obtain the signal intensity and phase information. After the VNA, the signal acquisition and processing module is connected for signal acquisition and processing.

The radio frequency passband signal strength measured by the system is shown in Figure 20. According to the signal strength information, the passband center frequency f is obtained to be 248.4MHz, and the pre-calibration process is completed.

After obtaining the passband center frequency, the optical fiber sensing method 20 is used to measure the external physical quantities. Set the frequency of the RF signal output by the first port of the VNA to the passband center frequency f, and load the continuous RF signal with frequency f onto the EOM for modulation. The optical fiber FP cavity is tightly wound around the periphery of the tubular piezoelectric ceramic (PZT). A sinusoidal electrical signal with a frequency of 10Hz and an amplitude of 10Vpp is loaded on the PZT to drive the PZT to vibrate.

The signal after DCF is detected by the photodetector and then input to the second port of the VNA for processing and display, and the phase information of the signal is obtained. The VNA's IF Bandwidth is set to 100Hz. In actual engineering applications, the system can use lower-cost microwave phase detectors to achieve higher economic benefits.

After the measured phase information has been processed to remove DC and noise, the conversion relationship between phase and strain is obtained through the calibration process of strain and phase change. The final time domain information of the vibration signal is shown in Figure 21, and the power spectral density (PSD) in the frequency domain is shown in Figure 21. From Figure 21 and Figure 22, it can be seen that the vibration signal with a frequency of 10Hz is well analyzed in the time domain. was restored, and the signal-to-noise ratio was above 43.7dB. This proves the high detection sensitivity of the optical fiber sensing system 10 provided by this application.

Other embodiments of the present application will be readily apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary technical means in the technical field that are not disclosed in this application. . It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the application being indicated by the following claims.

It is to be understood that the present application is not limited to the precise structures described above and illustrated in the accompanying drawings, and that various modifications and changes may be made without departing from the scope thereof. The scope of the application is limited only by the appended claims.

Claims (12)

1. An optical fiber sensing system based on microwave photons, for sensing external physical quantity change information, comprising:

an optical signal generating unit for generating an optical signal; the optical signal is changed along with the change of the external physical quantity change information;

the microwave radio frequency oscillator is used for generating a first radio frequency signal and a second radio frequency signal;

the microwave-optical modulator is connected with the optical signal generating unit and the microwave radio frequency oscillator and is used for modulating the optical signal based on the first radio frequency signal and outputting a modulated optical signal;

a photoelectric conversion unit for converting the optical signal into a first electrical signal;

the microwave phase detector is used for determining the working frequency of the optical fiber sensing system before sensing the external physical quantity change information; the microwave phase detector is connected with the photoelectric conversion unit and the microwave radio frequency oscillator and is used for generating a second electric signal representing the phase difference of the first electric signal and the second radio frequency signal; the frequencies of the first radio frequency signal and the second radio frequency signal are the working frequency; and

The signal acquisition and processing assembly is connected with the microwave phase detector and is used for acquiring and demodulating the intensity of the second electric signal to obtain the external physical quantity change information;

the photoelectric conversion unit comprises a dispersion component and a photoelectric detector; the dispersion component is used for dispersing the modulated optical signal to obtain a dispersed optical signal; the photodetector is configured to convert the dispersed optical signal into the first electrical signal;

the optical signal generating unit comprises a light source and an interferometer assembly; the light source is used for generating broadband continuous light; the interferometer component is used for carrying out optical sampling on the broadband continuous light to obtain a sampled optical signal.

2. The fiber optic sensing system of claim 1, wherein the microwave phase detector comprises a vector network analyzer for determining a phase change law of the external physical quantity change information prior to sensing the external physical quantity change information.

3. The optical fiber sensing system according to claim 2, wherein the signal acquisition processing component is configured to demodulate the intensity of the second electrical signal according to the phase change rule, so as to obtain the external physical quantity change information.

4. The fiber optic sensing system of claim 1, wherein the interferometer assembly comprises a bi-directional coupler and a first fiber optic interferometer; the bi-directional coupler includes a first port, a second port, and a third port; the first port is connected with the light source, the second port is connected with the first optical fiber interferometer, and the third port is connected with the microwave-optical modulator; the first optical fiber interferometer is used for optically sampling the broadband continuous light to obtain the sampled optical signal, and transmitting the sampled optical signal to the third port.

5. The fiber optic sensing system of claim 1, wherein the interferometer assembly comprises a bi-directional coupler; the bi-directional coupler includes a first port, a second port, and a third port; the first port is connected with the light source; the third port is connected with the microwave-optical modulator; the interferometer assembly further comprises a coupler and a plurality of first fiber optic interferometers; the coupler is connected between the second port of the bi-directional coupler and a plurality of the first fiber interferometers; at least two of the first fiber interferometers have different free spectral ranges; the plurality of first optical fiber interferometers respectively carry out optical sampling on the broadband continuous light to obtain a plurality of sampled optical signals; the coupler is used for coupling a plurality of sampled optical signals and transmitting the sampled optical signals to the microwave-optical modulator through the third port.

6. The fiber optic sensing system of claim 1, wherein the light source comprises an amplified spontaneous emission light source or a superluminescent light emitting diode.

7. The optical fiber sensing system according to claim 1, wherein the optical fiber sensing system comprises an amplifier connected between the optical signal generating unit and the photodetector for amplifying the optical signal.

8. The fiber optic sensing system of claim 1, wherein the dispersion component comprises at least one of a single mode fiber, a multimode fiber, a dispersion compensating fiber.

9. The fiber optic sensing system of claim 1, wherein the microwave radio frequency oscillator comprises a vector network analyzer; and/or

The microwave-optical modulator comprises one of an electro-optic modulator, a Mach-Zehnder modulator, a phase modulator.

10. An optical fiber sensing method based on microwave photons, applied to the optical fiber sensing system of any one of claims 1-9 for sensing external physical quantity change information, comprising:

determining the working frequency of the optical fiber sensing system;

generating an optical signal; the optical signal is changed along with the change of the external physical quantity change information;

modulating the optical signal based on a first radio frequency signal to obtain a modulated optical signal;

converting the optical signal into a first electrical signal;

generating a second electrical signal representative of a phase difference of the first electrical signal and a second radio frequency signal; the frequencies of the second radio frequency signal and the first radio frequency signal are the working frequency;

demodulating the intensity of the second electric signal to obtain the external physical quantity change information.

11. The fiber optic sensing method of claim 10, wherein the determining the operating frequency of the fiber optic sensing system comprises:

generating broadband continuous light;

optical sampling is carried out on the broadband continuous light to obtain a sampled optical signal;

modulating the sampled optical signal based on a broadband radio frequency sweep signal to obtain a modulated optical signal;

dispersing the modulated optical signal to obtain a dispersed optical signal;

converting the dispersed optical signal into a third electrical signal;

determining any frequency in a radio frequency passband as the operating frequency according to the intensity of the third electrical signal;

and determining the phase change rule of the external physical quantity change information according to the phase of the third electric signal.

12. The fiber optic sensing method of claim 10, wherein prior to the demodulating the intensity of the second electrical signal, the fiber optic sensing method further comprises:

removing direct current information of the intensity of the second electric signal;

noise information of the intensity of the second electrical signal is removed.