KR100345236B1 - Apparatus and method for stabilizing beating frequency of two laser diodes - Google Patents

Abstract

The present invention relates to a bit frequency stabilization apparatus and method for two laser diodes to stabilize the bit frequency by a simple structure and a software process, without the existing complicated hardware structure for controlling the laser diode driver and the temperature controller, A bit frequency detector 30 which detects bit frequency signals of optical signals transmitted from the two light sources 10a and 10b and is transmitted through the corresponding optical fibers 11a and 11b and converts them into electrical signals; A valid signal extracting unit 40 for extracting only valid signal components from the converted electrical signal; A spectrum analyzer 50 for analyzing frequency components of the extracted signal; And a driver 12 for comparing the analyzed frequency component with data about a predetermined bit frequency component and controlling the output of one light source 10b of the two light sources 10a and 10b based on the comparison result. ) And the control unit 60, and stabilize the frequency in software as compared to the existing device that required a separate hardware device for frequency stabilization, the existing device is applied by the characteristics of the laser diode While there is a limitation in that it can be usefully applied to any laser diode.

Description

Apparatus and method for stabilizing beating frequency of two laser diodes}

The present invention relates to an apparatus and a method for stabilizing the bit frequency of two laser diodes, and more particularly to the bit frequency by a simple structure and a software process, excluding the conventional complicated hardware structure for controlling the laser diode driver and the temperature controller. The present invention relates to a bit frequency stabilization device and a method for stabilizing two laser diodes.

Beat frequency control refers to using a difference between two frequencies by mixing two lights rather than directly controlling the optical frequency of the laser diode.

The conventional bit frequency stabilization device requires a separate precise hardware device for installing a current driver and a temperature controller for each laser diode and controlling the current driver and the temperature controller to obtain a desired stable bit frequency. This not only complicates the structure of the device but also takes a long time to stabilize the laser diode.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object thereof is to provide a bit frequency stabilization apparatus and method for two laser diodes which are designed to stabilize a bit frequency within a short time while simplifying a hardware structure.

1 is a block diagram of a bit frequency stabilization apparatus of two laser diodes according to an embodiment of the present invention;

2 is a flowchart illustrating a bit frequency stabilization method of two laser diodes according to an exemplary embodiment of the present invention.

3 is a detailed flowchart of the control method of step S240 of FIG.

※ Explanation of code for main part of drawing

10a, 10b: laser diode 11a, 11b: optical fiber

12: drive unit 20a, 20b: optical isolator

30: bit frequency detection unit 31, 32, 33: optical fiber coupler

34: photodiode 40: effective signal extraction unit

41: amplifier 42: low pass filter

50: spectrum analyzer 60: control unit

In order to achieve the above object, the bit frequency stabilization apparatus of two laser diodes according to the present invention includes: detection means for detecting a bit frequency signal of an optical signal output from two light sources and transmitted through a corresponding optical fiber and converting the signal into an electrical signal ; Extraction means for extracting only a valid signal component from the converted electrical signal; Analyzing means for analyzing frequency components of the extracted signal; And control means for comparing the analyzed frequency component with data about a preset bit frequency component and controlling the output of one of the two light sources based on the comparison result.

The detecting means branches the optical signals transmitted through the respective optical fibers at a predetermined ratio, and converts the two divided optical signals into optical signals having bit frequencies corresponding to the frequency differences between the two light sources. Preferably, the converted optical signal is configured to convert into an electrical signal, and the extracting means is configured to amplify and filter the converted electrical signal.

In order to achieve the above object, the bit frequency stabilization apparatus of two laser diodes according to the present invention comprises: a first step of detecting a bit frequency signal for two optical signals transmitted and converting the signal into an electrical signal; Extracting only valid signal components from the converted electrical signals; A third step of analyzing a frequency of the extracted signal component; And a fourth step of comparing the analyzed frequency with a magnitude of a preset bit frequency and controlling an optical frequency of one of the two optical signals based on the comparison result.

Hereinafter, a bit frequency stabilization apparatus and method for two laser diodes according to an exemplary embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram of an apparatus for stabilizing bit frequencies of two laser diodes according to an embodiment of the present invention, which includes two first and second laser diodes LD # 1, LD # 2 10a and 10b as light sources; Two isolators 20a outputted from the respective laser diodes 10a and 10b to prevent reverse propagation of the optical signals transmitted through the optical fibers 11a and 11b to prevent instability of the transmitted optical signal frequencies. , 20b); First and second optical fiber couplers 31 and 32 that branch by 10% of the total optical signals output through the isolators 20a and 20b, and the first and second optical fiber couplers 31 and 32. A third optical fiber coupler 33 for inputting two optical signals branched by and converting the optical signal into an optical signal having a bit frequency corresponding to the frequency difference between the two light sources, and outputting from the third optical fiber coupler 33 Photodiode 34 which detects the optical signal to be converted into an electrical signal and outputs it, and outputs from the two laser diode (10a, 10b) and transmitted through the corresponding optical fiber (11a, 11b) A bit frequency detector 30 for detecting a bit frequency of the signal and converting the bit frequency into an electrical signal; An amplifier (AMP) 41 for amplifying the electrical signal converted by the photodiode 34 of the bit frequency detector 30, and a low pass filter LPF for low-pass filtering the output signal of the amplifier 41. A valid signal extracting unit (40) having a 42, for extracting only a valid signal component from an electrical signal output through the photodiode 34; A spectrum analyzer (50) for inputting a signal output from the low pass filter (42) of the effective signal extractor (40) and analyzing a frequency component of the input signal; The second laser diode, which is one of the two laser diodes 10a and 10b, is compared with each other by comparing the frequency component analyzed by the spectrum analyzer 50 with data about a preset bit frequency component. The controller 60 controls the driving current of the second laser diode 10b by providing a control signal CS1 for controlling the output of the second laser diode 10b to the driver 12 of the second laser diode 10b. It is.

In FIG. 1, reference numeral 70 denotes a 90% optical signal branched from the first and second polarization maintaining optical fiber couplers 31 and 32 to input a difference, that is, a bit frequency, between the two input optical signals. The measurement system and the equipment to be applied to the corresponding application field according to the control signal CS2 of the control unit 60 are shown.

FIG. 2 is a flowchart illustrating a method for stabilizing bit frequencies of two laser diodes according to an exemplary embodiment of the present invention, which is applied to the apparatus of the present invention as shown in FIG.

First, the bit frequency signal is detected by the bit frequency detector 30 for two optical signals output from the first and second laser diodes 10a and 10b and transmitted through the corresponding optical fibers 11a and 11b. In more detail, the output optical signal of the first laser diode 10a is passed through the first isolator 20a by the first optical fiber coupler 31, whereby 90% of the two lasers have a constant frequency difference. To the measuring system and equipment 70, such as a measuring instrument or system requiring light, and the remaining 10% is branched to the third optical fiber coupler 33 side and at the same time the second laser diode 10b 90% is transmitted by the second optical fiber coupler 32 through the second isolator 20b to the measurement system and the equipment 70, and the remaining 10% is Branched to the third optical fiber coupler 33 and transmitted, and the third optical fiber coupler 33 receives the two optical signals branched by 10% by the first and second optical fiber couplers 31 and 32 Converted into an optical signal having a bit frequency, that is, a frequency of 10.9 GHz corresponding to the frequency difference between the two laser diodes (10a, 10b), the photodiode 34 is output from the third optical fiber coupler 33 The optical signal is detected and converted into an electrical signal and output (S210).

Subsequently, the valid signal extractor 40 extracts and outputs only a valid signal component from the electrical signal converted through the photodiode 34. In detail, the electrical signal output from the photodiode 34 Amplified by the amplifier 41, unnecessary components are removed through the low pass filter 42 (S220).

The signal output from the low pass filter 42 is input to the spectrum analyzer 50 for analysis (S230), and finally, the controller 60 measures the value of the signal analyzed by the spectrum analyzer 50 the most. After reading the amplitude of the high place and storing the frequency f at that time in the buffer, and comparing the stored frequency f with data for the preset bit frequency, the two laser diodes 10a and 10b are based on the comparison result. Drive current of the second laser diode 10b by providing a control signal CS2 for controlling the output of the second laser diode 10b to the driver 12 of the second laser diode 10b. To control the bar (S240), the control method of the step S240 implemented in the control unit 60 will be described in more detail with reference to FIG.

3 is a detailed flowchart of the control method of the step S240 of FIG.

First, the controller 60 reads the frequency f (or frequency f stored in the buffer of the controller 60) analyzed by the spectrum analyzer 50 (S241), and the frequency f is a preset bit frequency. After determining whether it is larger (S242), if it is determined to be large or small, by applying a control signal CS1 corresponding to the difference magnitude to the driver 12, the magnitude of the driving current of the second laser diode 10b is lowered. To increase or increase (S243). That is, when it is determined that the size is large, the driving current of the second laser diode 10b is reduced, and when it is determined that the size is small, the driving current of the second laser diode 10b is increased.

Subsequently, after storing the frequency f value data analyzed by the spectra analyzer 50 in the buffer in step S244, it is determined whether a stop key is set (S245), and if the stop key is not set, When the process starts again, the process starts again from the step S241, and when it is set, the data stored in the buffer is finally stored on the disk and then terminated (S246).

As described in detail above, according to the bit frequency stabilization apparatus and method of the two laser diodes according to the present invention, if it takes a lot of time to actually stabilize the bit frequency, it is difficult to configure a variety of devices to stabilize the bit frequency within a short time This is essential to improve the reliability and measurement accuracy of the equipment. According to the present invention, it is possible to eliminate the configuration of complex hardware devices by stabilizing the frequency by software in comparison with the existing devices which required a separate hardware device for frequency stabilization. In addition, while the existing device is limited in its application by the characteristics of the laser diode, there is an advantage that can be usefully applied to any laser diode.

In addition, the bit frequency stabilization device according to the present invention is a useful invention that can be applied to optical communication equipment, such as optical detection equipment, microwave signal processing, heterodyne laser radar, MMIC test, long range antenna system and especially Brillouin strain measurement equipment .

Claims (10)

In the bit frequency application device using the frequency difference between the two optical signals by mixing the optical signals output from the two light sources, Detecting means for detecting a bit frequency signal of an optical signal outputted from the two light sources and transmitted through a corresponding optical fiber and converting the signal into an electrical signal; Extraction means for extracting only a valid signal component from the converted electrical signal; Analyzing means for analyzing frequency components of the extracted signal; And Two lasers comprising control means for comparing the analyzed frequency component with data about a predetermined bit frequency component and controlling the output of one of the two light sources based on the comparison result. Bit frequency stabilization of diodes. The method of claim 1, The detecting means may include: first and second optical fiber couplers for branching the optical signal transmitted through each optical fiber at a predetermined ratio; A third optical fiber coupler for inputting two optical signals branched by the first and second optical fiber couplers and converting the optical signals into optical signals having bit frequencies corresponding to the frequency differences between the two light sources; And And a photo detector which detects an optical signal output from the third optical fiber coupler, converts the optical signal into an electrical signal, and outputs the electrical signal. The method of claim 2, And the polarization ratios of the first optical fiber coupler, the second optical fiber coupler, and the third optical fiber coupler are 90:10, 90:10, and 50:50, respectively. The method according to claim 1 or 2, Two laser diodes, characterized in that it further comprises an isolator installed in the optical fiber portion of the front end of the detection means in order to prevent the reverse progress of the optical signals output from the two light sources and transmitted through the corresponding optical fiber, respectively. Bit frequency stabilization device. The method of claim 1, The extraction means includes an amplifier for amplifying the converted electrical signal; And And a low pass filter for low pass filtering the output signal of the amplifier. The method of claim 1, And said analyzing means detects and tracks the difference frequencies of the two lasers. The method of claim 1, And the control means controls the driving current provided to the light source so as to correspond to the difference between the analyzed frequency and the preset bit frequency. In a method of using a bit frequency that is the difference between two frequencies by mixing two optical signals output from two laser diodes, A first step of detecting bit frequency signals of two optical signals output from the two laser diodes and transmitting the two laser diodes and converting the signal into electrical signals; Extracting only valid signal components from the converted electrical signals; A third step of analyzing a frequency of the extracted signal component; And And comparing a size of the analyzed frequency with a preset bit frequency and controlling an output size of one of the two laser diodes based on the comparison result. Method of stabilizing the beat frequency of laser diodes. The method of claim 8, The first step is, A lower step of dividing the two transmitted optical signals at a predetermined ratio, respectively; A lower second step of generating a bit frequency signal that is a difference signal between the two split optical signals; And And a lower third step of converting the generated optical signal into an electrical signal. The method of claim 8, The fourth step, A first step of determining whether the size of the analyzed frequency is greater than the size of the preset bit frequency; And If it is determined in the lower first step that the driving current of the laser diode is reduced, and if it is determined that the small driving current of the laser diode is increased, the frequency of one optical signal of the two optical signals to vary Bit frequency stabilization method of the two laser diodes, characterized in that comprises a lower two steps.