KR102280299B1 - Brillouin Optical Correlation Domain Analysis System with Injection-Locked Light Source and Analysis Method using Thereof - Google Patents

Abstract

The present invention relates to a Brillouin light correlation region analysis system based on an injection-locked light source and an analysis method using the same. a light source unit for outputting an optical signal suppressed within; an optical modulator that is optically connected to the light source, modulates the optical signal output from the light source and transmits the optical signal to the optically connected test optical fiber; and a photodetector that is optically connected to the test optical fiber and detects an optical signal by Brillouin scattering from the test optical fiber, so that signal distortion caused by intensity modulation and intensity-frequency phase delay in Brillouin optical correlation region analysis is suppressed. , Disclosed is a technique for increasing the accuracy of measurement when analyzing a Brillouin light correlation region.

Description

Brillouin Optical Correlation Domain Analysis System with Injection-Locked Light Source and Analysis Method using Thereof

The present invention relates to a Brillouin optical correlation region analysis system capable of suppressing the occurrence of signal distortion when analyzing the Brillouin optical correlation region, and an analysis method using the same.

Distribution type fiber optic sensor measures the distribution of physical quantity according to location by operating as an independent sensor in all parts of the optical fiber having a linear one-dimensional structure, and is divided into time domain, frequency domain and correlation domain according to the method of obtaining location information do.

The distributed Brillouin sensor is a sensor that measures the distribution of the Brillouin frequency, and is divided into a time domain and a correlation domain according to the implementation method.

The Brillouin light correlation domain analysis method uses amplitude modulation of the laser diode driving current to modulate the frequency of the light source. When the driving current of the laser diode is changed, the laser resonant frequency is changed by the change in carrier density and temperature change in the laser diode. Since the current change of the laser diode accompanies the output power change, frequency modulation and amplitude modulation occur together in the output light wave.

Between amplitude modulation and frequency modulation of the light wave output from the laser diode, a phase difference occurs depending on the type of laser diode, modulation frequency, and modulation amplitude, and this is called intensity-frequency phase delay (AM-FM Phase Delay). The intensity-frequency phase delay causes asymmetrical distortion in the distribution of the beat spectrum formed at each position with respect to the correlation point by the product of the frequencies of the pump light and the probe light and the two light intensities in the Brillouin light correlation domain analysis method.

The measurement signal of the Brillouin optical correlation domain analysis method is a mathematical sum of the convolutions of the bit spectrum and the Brillouin gain spectrum of each position. When there is a change in the intensity of the light source and a corresponding intensity-frequency phase delay, the bit spectrum is asymmetrically distorted around the correlation point, and an error occurs in the measured Brillouin frequency distribution.

In particular, a large error occurs at the boundary where the Brillouin frequency changes, which is a structural error of the Brillouin optical correlation domain analysis method, so it is a measurement error that is difficult to remove even by taking an average or applying other digital signal processing methods.

Republic of Korea Patent No. 10-1447090

SUMMARY OF THE INVENTION It is an object of the present invention to provide a Brillouin light correlation region analysis system capable of suppressing signal distortion when detecting Brillouin scattered light, and an analysis method using the same.

The Brillouin optical correlation region analysis system according to an embodiment of the present invention for achieving the above object includes a plurality of optically connected light sources, and outputs an optical signal whose amplitude modulation is suppressed within a certain level. light source; an optical modulator that is optically connected to the light source, modulates the optical signal output from the light source and transmits it to the optically connected test optical fiber; It may be characterized by including; a photodetector that is optically connected to the test optical fiber and detects an optical signal by Brillouin scattering from the test optical fiber.

Here, the plurality of light sources included in the light source unit are a first light source and a second light source, and the first light source outputs a first light signal of which intensity and frequency are modulated, and the second light source is from the first light source. Another feature may be that a second optical signal, which is an optical signal whose intensity modulation is suppressed within a certain level, is output by receiving the outputted first optical signal.

Here, the frequency of the second optical signal output from the second light source depends on the frequency of the first optical signal output from the first light source, and intensity modulation of the second optical signal output from the second light source is suppressed. The level may be characterized as being within 1 dB as another feature.

Here, the intensity-frequency phase delay according to the modulation frequency of the second light signal output from the second light source may be maintained at a constant level within a range between 160 degrees and 200 degrees. .

Here, the first light source may be a master laser diode, and the second light source may be a slave laser diode, but may be a laser diode excluding an internal isolator.

Here, the light source unit includes a signal generator for applying a sine wave current modulation to the master laser diode; and a first optical circulator optically connected to the master laser diode and the slave laser diode.

The light modulator may include: a light splitter that receives the second light signal output from the second light source side of the light source unit and divides it into probe light and pump light; a single side wave modulator optically connected to the optical splitter, receiving the probe light from the optical splitter, and modulating it into an optical signal including a sideband signal; a polarization switch optically connected to the single side wave modulator to receive and polarize the probe light transmitted from the single side wave modulator; an advertising filter optically connected to the polarization switch and configured to suppress the pump light from proceeding from the test optical fiber toward the single side wave modulator; a phase modulator optically connected to the optical splitter and modulating by receiving the pump light from the optical splitter, and an optical amplifier optically connected to the phase modulator and amplifying the pump light transmitted from the phase modulator; It may be characterized as another feature to include.

Here, the photodetector may include: a second optical circulator optically connected to the test optical fiber and branching Brillouin scattered light generated from the test optical fiber; a photodetector for receiving the Brillouin scattered light branched from the second optical cycler and converting it into an electrical signal; Another feature may include a lock amplifier electrically connected to the photodetector, receiving the electrical signal converted by the photodetector, and intermittently detecting it according to a predetermined phase lock signal.

Here, the photodetector may further include a data collector that converts the electrical signal received from the lock amplifier into the form of a Brillouin gain spectrum.

The analysis method using the Brillouin optical correlation region analysis system according to an embodiment of the present invention for achieving the above object is an output step in which an optical signal whose intensity modulation is suppressed within a certain level is output from a light source unit including a plurality of light sources ; a modulation step of receiving and modulating the optical signal output from the output step, modulating the optical signal, and transmitting the optical signal to the test optical fiber; and a detection step of detecting Brillouin light scattering generated in the test optical fiber by the optical signal transmitted in the modulation step.

Here, in the output step, the optical signal output by suppressing the intensity modulation within a certain level is a second optical signal, and in the output step, the intensity and frequency are obtained from the master laser diode included in the plurality of light sources of the light source unit. a first optical signal output step of outputting a modulated first optical signal; and the first optical signal output in the first optical signal output step is injected into a slave laser diode included in the plurality of light sources of the light source unit, and intensity modulation from the slave laser diode is suppressed to a level within 1 dB. A second optical signal output step of outputting two optical signals may be included as another feature.

According to the Brillouin optical correlation domain analysis system and the analysis method using the same according to the present invention, signal distortion caused by intensity modulation and intensity-frequency phase delay, that is, a phenomenon in which the bit spectrum is asymmetrically distorted in the Brillouin optical correlation domain analysis Since it is suppressed, the occurrence of errors in the measured Brillouin frequency distribution is suppressed. Therefore, there is an effect of improving the measurement accuracy when analyzing the Brillouin light correlation region.

1 is a conceptual diagram schematically showing the configuration of a Brillouin optical correlation region analysis system according to an embodiment of the present invention.
2 is a graph schematically illustrating intensity modulation characteristics of an optical signal output from a light source unit in a Brillouin optical correlation region analysis system according to an embodiment of the present invention.
3 is a graph schematically illustrating a measurement of intensity-frequency phase delay according to a modulation frequency of an optical signal output from a light source in the Brillouin optical correlation region analysis system according to an embodiment of the present invention.
4 is a flowchart schematically illustrating an analysis method using a Brillouin optical correlation region analysis system according to an embodiment of the present invention.
5 is a graph schematically showing the results measured by the conventional Brillouin optical correlation region analysis system.
6 is a graph schematically illustrating a result of measurement using the Brillouin optical correlation region analysis system according to an embodiment of the present invention.

Hereinafter, a preferred embodiment will be described with reference to the accompanying drawings so that the present invention can be understood in more detail.

1 is a conceptual diagram schematically showing the configuration of a Brillouin optical correlation region analysis system according to an embodiment of the present invention.

Referring to FIG. 1 , the Brillouin optical correlation region analysis system according to an embodiment of the present invention includes a light source unit 100 , a light modulator 200 , and a light detection unit 300 . In addition, the test optical fiber may be disposed at a position to measure a change in a physical quantity using Brillouin scattering on the optical path.

The light source unit 100 includes a plurality of optically connected light sources, and outputs a laser light signal (hereinafter simply referred to as an optical signal) in which amplitude modulation is suppressed within a predetermined level.

The light source unit 100 includes a first light source 120 and a second light source 130 , and may include a signal generator 110 and a first light circulator 140 .

The first light source 120 outputs a first light signal whose intensity and frequency are modulated. In addition, the second light source 130 receives the first light signal output from the first light source 120 and outputs a second light signal that is an optical signal whose intensity modulation is suppressed within a predetermined level.

Preferably, the first light source 120 and the second light source 130 are laser diodes, and the light output from the first light source 120 is injected into the second light source 130 . Accordingly, the first light source 120 may be a master laser diode, and the second light source 130 may be a slave laser diode.

인 제1광신호를 얻을 수 있게 된다.The signal generator 110 applies a sinusoidal current modulation to the first light source 120 to output an optical signal from the master laser diode, which is the first light source 120 . By modulating the supply current with the master laser diode 120 as the first light source using the signal generator 110, it is modulated in the form of a sine wave having a predetermined modulation frequency, and the width of frequency modulation is

It is possible to obtain the first optical signal.

The first light source 120 receiving the sinusoidal current modulation from the signal generator 110 outputs a first optical signal having a sinusoidal frequency modulation.

When the first light source 120 receives a sinusoidal current modulation from the signal generator 110 , it outputs an optical signal in which amplitude and frequency are modulated. In addition, the first light signal output from the first light source 120 is injected into the second light source 130 .

The second light source 130 receives the first light signal output from the first light source 120 and outputs the second light signal. The second optical signal output from the second light source 130 is transmitted to the optically connected optical modulator 200 . The second light source 130 is a slave laser diode, and is preferably a laser diode from which an internal isolator is excluded in order to allow a large injection power.

As described above, the injection lock method is to inject an optical signal output by modulating intensity and frequency from the master laser diode, which is the first light source, into the second light source, that is, a slave laser diode without an ad particle, and output laser light from the slave laser diode. A light source to which this injection locking method is applied can be called an injection-locked light source.

The first light circulator 140 is optically connected to the first light source 120 and the second light source 130 . The second optical signal output from the second light source 130 is transmitted to the optical modulator 200 via the first optical circulator 140 .

Further reference is made here to FIGS. 2 and 3 . 2 is a graph schematically illustrating intensity modulation characteristics of an optical signal output from a second light source of a light source unit in a Brillouin optical correlation region analysis system according to an embodiment of the present invention, and FIG. 3 is a Brillouin light correlation region analysis system according to an embodiment of the present invention. It is a graph schematically showing the measurement of the intensity-frequency phase delay according to the modulation frequency of the optical signal output from the light source in the Rouen optical correlation region analysis system.

The frequency of the second light signal output from the second light source 130 depends on the frequency of the first light signal output from the first light source 120 , and as shown in FIG. 2 , the second light source 130 is the slave. The level at which modulation of the intensity of the second optical signal output from the laser diode is suppressed is preferably within 1 dB.

In addition, as shown in FIG. 3 , the intensity-frequency phase delay according to the modulation frequency of the second optical signal output from the slave laser diode, which is the second light source 130 , is within a range between 160 degrees and 200 degrees. It is desirable to maintain it at a certain level in

The light modulator 200 is optically connected to the light source unit 100 side, modulates the second optical signal output from the second light source of the light source unit 100, and transmits the probe light and the pump light to the test optical fiber side.

The optical modulator 200 includes an optical splitter 205 , a single side wave modulator 210 , a polarization switch 220 , an advertisement splitter 230 , a phase modulator 260 , and an optical amplifier 270 .

The optical splitter 205 divides and distributes the second optical signal output from the second light source 130 and transmitted through the optical circulator 140 into a probe beam and a pump beam. The light output from the light source unit 100 is divided into a pump light and a probe light at a ratio of approximately 50:50 and distributed.

The probe light is transmitted from the optical splitter 205 to the single side wave modulator 210 of the optical modulator 200 , and the pump light is transmitted from the optical splitter 205 to the phase modulator 260 .

The test optical fiber may be disposed at a position to measure a change in a physical quantity using Brillouin scattering on the optical path.

A single band modulator 210 is optically connected to the optical splitter 205 . Then, the probe light is received from the optical splitter 205, modulated into an optical signal including a side band signal, and outputted.

The single-side modulator 210 may output a down-shifted modulation frequency among the up-shifted modulation frequency and the down-shifted modulation frequency.

Accordingly, a probe light signal having a frequency shifted down by the offset frequency with respect to the frequency may be output.

Alternatively, an up-shifted modulation frequency among the up-shifted modulation frequency and the down-shifted modulation frequency may be output as a probe light signal.

The polarization switch 220 is optically connected to the single side wave modulator 210 . Then, the probe light transmitted from the single side wave modulator 210 is received and polarized.

For example, the polarization switch 220 may alternately rotate the polarization of the probe light signal by 0 degrees once and 90 degrees the other time. Alternatively, in another embodiment, the polarization switch 220 may periodically change the polarization of the probe light signal at a different angle.

Induced Brillouin scattering amplification occurs when the polarizations of the pump light signal and the probe light signal match, but the polarizations of the pump light signal and/or the probe light signal may change with time or space. Therefore, the polarization problem can be solved by performing the measurement while changing the polarization of the probe light signal using the polarization switch and using the average value of the measured values.

The advertisement particle device 230 is optically connected to the polarization switch. In addition, the pump light is prevented from proceeding from the test optical fiber toward the single side wave modulator 210 .

In addition, the optical modulator 200 may further include a delay optical fiber. In a general Brillouin optical correlation domain analysis method, the positions of the correlation points can be adjusted by changing the modulation frequency. However, in the center of the optical fiber constituting the entire optical path, the position of the Brillouin gain peak does not change even if the modulation frequency is changed. It has easy features. Therefore, in the absence of the delayed optical fiber, the peak where the position of the correlation point cannot be adjusted is located in the center of the test optical fiber.

Therefore, for this reason, a delayed optical fiber can be used. By properly adjusting the length of the delay fiber, any one of the Brillouin gain peaks far from the center of the entire optical path can be located on the test fiber.

The delayed optical fiber is optically connected to the test optical fiber through the optical fiber 230, and the pump optical signal passing through the test optical fiber is blocked by the optical fiber 230 and not input to the delayed optical fiber, so Brillouin scattered light is generated only in the test optical fiber can be

The delay optical fiber may be made of the same material as the test optical fiber.

The phase modulator 260 is optically connected to the light splitter 205 and receives the pump light from the light splitter 205 . The optical signal modulated by the phase modulator 260 has the same frequency before and after input and output, and the frequency of the pump light is the frequency of the second optical signal output from the aforementioned slave laser diode 130 .

The optical amplifier 270 is optically connected to the phase modulator 260 . Then, the pump light transmitted from the phase modulator 260 is amplified. The optical amplifier 270 serves to amplify the intensity of the pump signal to generate the induced Brillouin scattering effect to make it greater than or equal to the Brillouin threshold.

The photodetector 300 is optically connected to the test optical fiber, and detects Brillouin scattered light generated from the test optical fiber, that is, an amplified signal of the probe optical signal due to induced Brillouin scattering.

The photodetector 300 includes a photodetector 310 and a lock amplifier 320 , and further includes a photocirculator 305 and a data collection unit 350 .

The second optical circulator 305 is optically connected to the test optical fiber, and branches Brillouin scattered light generated from the test optical fiber.

The photodetector 310 receives the Brillouin scattered light branched from the second photocirculator 305 and converts it into an electrical signal. A photodiode may be used as the photodetector 310 .

The lock amplifier 320 is electrically connected to the photodetector, receives the electrical signal converted by the photodetector 310, and intermittently detects it according to a predetermined phase lock signal. The lock amplifier 320 may include an AC signal channel, a mixer, a DC amplifier, and a low-pass filter, but is not limited thereto.

The data acquisition unit (Data Acquisition; DAQ) 350 receives the signal output from the lock amplifier 320 and converts the received signal into the form of a Brillouin gain spectrum to measure the physical change of the test optical fiber. there is. However, this is an example, and in another embodiment, signal processing and analysis may be performed using one or more different data processing means.

When the Brillouin optical correlation domain is analyzed using the Brillouin optical correlation domain analysis system as described above, signal distortion due to intensity modulation and intensity-frequency phase delay is suppressed, thereby ensuring measurement accuracy.

Next, an analysis method using the Brillouin optical correlation region analysis system according to an embodiment of the present invention will be described with further reference to FIG. 4 .

4 is a flowchart schematically illustrating an analysis method using a Brillouin optical correlation region analysis system according to an embodiment of the present invention.

Referring to FIG. 4 , the analysis method using the Brillouin optical correlation region analysis system according to an embodiment of the present invention includes an output step (S110), a modulation step (S120), and a detection step (S130).

<< S110 >>

The output step ( S110 ) is a step of outputting an optical signal whose intensity modulation is suppressed within a predetermined level from the light source unit 100 including a plurality of light sources in the Brillouin optical correlation region analysis system.

Here, the plurality of light sources includes a first light source 120 and a second light source 130 . And, the optical signal output by suppressing the intensity modulation within a certain level is the second optical signal output from the slave laser diode 130 which is the second light source 130 as described above.

This output step (S110) includes a first optical signal output step (S111) and a second optical signal output step (S113).

<< S111 >>

The first optical signal output step S111 is a step of outputting a first optical signal whose intensity and frequency are modulated from the master laser diode 120 which is a first light source included in the plurality of light sources of the light source unit 100 .

Current modulation is applied from the signal generator 110 to the master laser diode 120 as the first light source. The first optical signal output from the master laser diode 120 to which the current modulation is applied is injected into the slave laser diode 130 as a second light source.

<< S113 >>

Next, in the second optical signal output step S113 , the first optical signal output in the first optical signal output step S111 is sent to the slave laser diode 130 as a second light source included in the plurality of light sources of the light source unit 100 . is injected Then, a second optical signal in which intensity modulation is suppressed to a level within 1 dB is output from the slave laser diode 130 . ,

The second optical signal output from the slave laser diode 130 is transmitted to the optical splitter 205 of the optical modulator 200 via the optical circulator 140 .

<< S120 >>

The modulation step (S120) is a step in which the optical modulator 200 receives and modulates the optical signal output in the output step (S110), that is, the second optical signal output from the slave laser diode 130, and transmits it to the test optical fiber. .

When the second optical signal output from the slave laser diode 130 is input to the optical splitter 205 , the optical splitter 205 divides it into a pump light and a probe light.

The probe light distributed from the optical splitter 205 is transferred to the single side wave modulator 210 of the optical modulator 200 , and the pump light is transferred from the optical splitter 205 to the phase modulator 260 .

The single side wave modulator 210 receives the probe light from the optical splitter 205, modulates it into an optical signal including a side band signal, and outputs it.

The probe light signal modulated and output from the single side wave modulator 210 is transmitted to the polarization switch 220 . The polarization switch 220 polarizes the input probe light signal.

The polarization switch 220 may alternately rotate the polarization of the probe light signal by 0 degrees once and 90 degrees at the other time, for example. Alternatively, the polarization of the probe light signal may be periodically changed to a different angle.

The probe optical signal polarized by the polarization switch 220 proceeds to one end of the test optical fiber through the delay optical fiber.

Then, the pump light distributed from the light splitter 205 is input to the phase modulator 260 .

The pump light input to the phase modulator 260 is modulated and transmitted to the optical amplifier 270 . The optical amplifier 270 receiving the pump light amplifies the intensity of the pump signal so as to generate the induced Brillouin scattering effect, and makes it greater than or equal to the Brillouin threshold.

The pump light amplified by the optical amplifier 270 is input to the other end of the test optical fiber.

Accordingly, the probe light is input to one end of the test optical fiber and the pump light is input to the other end of the test optical fiber, thereby generating induced Brillouin scattering.

<< S130 >>

The detection step S130 is a step of detecting Brillouin light scattering generated from the test optical fiber. That is, Brillouin scattered light generated from the test optical fiber, that is, the amplified signal of the probe optical signal due to induced Brillouin scattering is detected.

The second optical circulator 305 diverges Brillouin scattered light generated from the test optical fiber.

Then, the photodetector 310 receives the Brillouin scattered light branched from the second optical cycler 305 and converts it into an electrical signal. A photodiode may be used as the photodetector 310 .

The lock amplifier 320 receives the electrical signal converted by the photodetector 310 and intermittently detects it according to a predetermined phase lock signal.

Then, the data acquisition unit (Data Acquisition; DAQ) 350 receives the signal output from the lock amplifier 320, converts the received signal into the form of a Brillouin gain spectrum to measure the physical change of the test optical fiber can do.

FIG. 5 is a graph schematically showing the results measured by the conventional Brillouin optical correlation region analysis system, and FIG. 6 is a schematic diagram showing the results measured using the Brillouin optical correlation region analysis system according to an embodiment of the present invention. It is a graph diagram shown.

As shown in FIG. 5 , looking at the measurement results in the conventional Brillouin optical correlation region analysis system to which no injection-locked light source is applied, the difference between the actual value (B) and the measured value (A) of the Brillouin frequency change is shown. Although there is a large difference, as shown in FIG. 6 , when looking at the measurement results in the Brillouin optical correlation region analysis system to which the injection-locked light source according to the embodiment of the present invention is applied, the actual value (B) of the Brillouin frequency change and The difference between the measured values (A) is insignificant. As described above, it can be seen that the occurrence of signal distortion is suppressed in the Brillouin optical correlation region analysis system to which the injection-locked light source is applied according to the embodiment of the present invention.

As described above, according to the Brillouin optical correlation region analysis system according to the present invention, an optical signal whose intensity and frequency are modulated is output from the master laser diode to which current modulation is applied. The optical signal output from the master laser diode is injected into the slave laser diode without an ad particle, and the optical signal output from the slave laser diode is used as a light source for Brillouin optical correlation region analysis. The frequency of the optical signal output from the slave laser diode depends on the frequency of the optical signal injected from the master laser diode, but the change in intensity is suppressed.

The optical signal output from the slave laser diode has the same frequency change as the light output from the master laser diode, but the change in intensity is suppressed to a level of less than 10%. In addition, when analyzing the Brillouin optical correlation region, the intensity-frequency phase delay is maintained around 180 degrees where signal distortion is minimized.

As described above, according to the Brillouin optical correlation domain analysis system and the analysis method using the same according to the present invention, signal distortion due to intensity modulation and intensity-frequency phase delay in the Brillouin optical correlation domain analysis, that is, the bit spectrum is asymmetrically distorted. Since the phenomenon is suppressed, the occurrence of errors in the measured Brillouin frequency distribution is suppressed. Accordingly, there is an advantage in that the measurement accuracy is increased when analyzing the Brillouin light correlation region.

In addition, since there is no need to control the frequency of the reference signal according to the laser diode modulation frequency in the measurement signal processing process using the lock amplifier, the Brillouin optical correlation domain analysis system is simplified.

As described above, the detailed description of the present invention has been made by the embodiments with reference to the accompanying drawings, but since the above-described embodiments have only been described with reference to the preferred embodiments of the present invention, the present invention It should not be construed as being limited only to the embodiments, and the scope of the present invention should be understood as the following claims and their equivalents.

10: Brillouin optical correlation region analysis system
100: light source unit
110: signal generator 120: first light source (master laser diode)
140: optical cycler 130: second light source (slave laser diode)
200: light modulator
205: optical splitter 210: modulator
220: polarization switch 230: advertising granularity
260: phase modulator 270: optical amplifier
300: photodetector
305: photocirculator 310: photodetector
320: lock-in amplifier 350: data collector

Claims (7)

a light source unit including a plurality of optically connected light sources and outputting an optical signal in which amplitude modulation is suppressed within a predetermined level;
an optical modulator that is optically connected to the light source, modulates the optical signal output from the light source and transmits it to the optically connected test optical fiber;
A photodetector that is optically connected to the test optical fiber and detects an optical signal by Brillouin scattering from the test optical fiber;
The light source unit is configured to include a signal generator for applying a sine wave type current modulation,
The light modulator,
a light splitter that receives the optical signal output from the light source and divides it into probe light and pump light;
a single side wave modulator optically connected to the optical splitter, receiving the probe light from the optical splitter, and modulating it into an optical signal including a sideband signal;
a polarization switch optically connected to the single side wave modulator to receive and polarize the probe light transmitted from the single side wave modulator;
an advertising particle device optically connected to the polarization switch and suppressing the pump light from proceeding from the test optical fiber toward the single side wave modulator;
and a delay optical fiber that optically connects the probe optical signal polarized in the polarization switch to the test optical fiber through the optical particle device,
The plurality of light sources included in the light source unit are a first light source and a second light source,
The first light source outputs a first light signal whose intensity and frequency are modulated,
The second light source receives the first optical signal output from the first light source and outputs a second optical signal that is an optical signal in which the intensity modulation is suppressed within a certain level,
The frequency of the second optical signal output from the second light source depends on the frequency of the first optical signal output from the first light source,
The level at which the intensity modulation of the second light signal output from the second light source is suppressed is within 1 dB,
The light modulator,
a phase modulator optically connected to the light splitter and modulated by receiving the pump light from the light splitter; and
Further comprising an optical amplifier optically connected to the phase modulator and amplifying the pump light transmitted from the phase modulator,
The optical signal modulated by the phase modulator has the same frequency before and after input and output, characterized in that the frequency of the pump light is the frequency of the second optical signal,
Brillouin Optical Correlation Area Analysis System. The method of claim 1,
The intensity-frequency phase delay according to the modulation frequency of the second light signal output from the second light source is maintained at a constant level within a range between 160 degrees and 200 degrees,
Brillouin Optical Correlation Area Analysis System. 3. The method of claim 2,
The first light source is a master laser diode,
The second light source is a slave laser diode, characterized in that it is a laser diode excluding an internal isolator,
Brillouin Optical Correlation Area Analysis System. 4. The method of claim 3,
The signal generator is
Applying a sinusoidal current modulation to the master laser diode,
The light source unit,
Characterized in that it further comprises a first optical circulator optically connected to the master laser diode and the slave laser diode,
Brillouin Optical Correlation Area Analysis System. The method of claim 1,
The photodetector,
a second optical circulator optically connected to the test optical fiber and branching Brillouin scattered light generated from the test optical fiber;
a photodetector for receiving the Brillouin scattered light branched from the second optical cycler and converting it into an electrical signal;
and a lock amplifier electrically connected to the photodetector, receiving the electrical signal converted by the photodetector, and intermittently detecting it according to a predetermined phase lock signal;
Brillouin Optical Correlation Area Analysis System. 6. The method of claim 5,
The photodetector,
Characterized in that it further comprises a data collector for converting the electrical signal received from the lock amplifier into the form of a Brillouin gain spectrum,
Brillouin Optical Correlation Area Analysis System. an output step of outputting an optical signal whose intensity modulation is suppressed within a predetermined level from a light source unit including a plurality of light sources;
a modulation step of receiving and modulating the optical signal output from the output step, modulating the optical signal, and transmitting the optical signal to the test optical fiber; and
A detection step of detecting Brillouin light scattering generated in the test optical fiber by the optical signal transmitted in the modulation step;
In the output step, the light source unit is configured to include a signal generator for applying a current modulation in the form of a sine wave,
In the modulation step, the light modulator,
a light splitter that receives the optical signal output from the light source and divides it into probe light and pump light;
a single side wave modulator optically connected to the optical splitter, receiving the probe light from the optical splitter, and modulating it into an optical signal including a sideband signal;
a polarization switch optically connected to the single side wave modulator to receive and polarize the probe light transmitted from the single side wave modulator;
an advertising particle device optically connected to the polarization switch and suppressing the pump light from proceeding from the test optical fiber toward the single side wave modulator;
and a delay optical fiber that optically connects the probe optical signal polarized in the polarization switch to the test optical fiber through the optical particle device,
In the output step,
The optical signal output by suppressing the intensity modulation within a certain level is a second optical signal,
The output step is
a first optical signal output step of outputting a first optical signal of which intensity and frequency are modulated from a master laser diode included in the plurality of light sources in the light source unit; and
The first optical signal output in the first optical signal output step is injected into a slave laser diode included in the plurality of light sources of the light source unit, and the intensity modulation from the slave laser diode is suppressed to a level within 1 dB. a second optical signal output step in which an optical signal is output;
The frequency of the second optical signal output from the slave laser diode depends on the frequency of the first optical signal output from the master laser diode,
The light modulator,
a phase modulator optically connected to the light splitter and modulated by receiving the pump light from the light splitter; and
Further comprising an optical amplifier optically connected to the phase modulator and amplifying the pump light transmitted from the phase modulator,
The optical signal modulated by the phase modulator has the same frequency before and after input and output, characterized in that the frequency of the pump light is the frequency of the second optical signal,
Analysis method using Brillouin optical correlation region analysis system.

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