A Brillouin time domain analyzer

Abstract

The application belongs to the technical field of distributed optical fiber sensing, and particularly relates to a Brillouin time domain analyzer, which comprises a main laser, a detection light path, a sensing optical fiber, a pump light path, an optical signal receiving branch and a signal platform, wherein the detection light path takes the main laser as a light source, outputs continuous detection light into the sensing optical fiber, the pump light path generates pulsed pump light based on an electric signal generated by the signal platform, the pulsed pump light is input into the other end of the sensing optical fiber through a first port of a circulator, scattered light output from three ports of the circulator is divided into two paths through a beam splitter, one path is used as the input of the pump light path, frequency synchronization of the pump light and the detection light is realized through injection locking, the other path is photoelectrically converted by the optical signal receiving branch, and signal processing is performed on the signal platform to extract a Brillouin gain spectrum characteristic parameter. Compared with the prior art, the end-to-end open-loop optical path structure can realize sensing distance multiplication under the same optical fiber length, and is suitable for super-long distance distributed monitoring scenes.

Description

Technical Field

[0001] This invention relates to the field of distributed optical fiber sensing technology, and in particular to a structurally optimized Brillouin time-domain analyzer. Background Technology

[0002] Brillouin Optical Time Domain Analyzer (BOTDA), as a type of distributed fiber optic sensing technology, has the advantages of strong signal-to-noise ratio and absolute measurement, and can provide safety monitoring for large-scale infrastructure such as railways, bridges, and oil pipelines, which has attracted widespread research attention.

[0003] BOTDA is a dual-ended optical path structure where a pulsed pump beam and a continuous probe beam are incident from opposite ends of the fiber under test, resulting in stimulated Brillouin scattering (SBS). By scanning the frequency difference between the pump and probe beams and performing Lorentz fitting on the obtained Brillouin gain spectrum, the Brillouin frequency shift information of the fiber under test can be obtained. This Brillouin frequency shift is related to the temperature and strain experienced by the fiber. To ensure the frequency stability between the pump and probe beams, the widely used BOTDA optical path structure typically includes a laser source and an externally modulated frequency-shifting unit. The laser beam is split into two by a beam splitter, with the beams fed into the pump and probe branches respectively. The frequency-shifting unit is placed on the pump / probe branch to shift the frequency by approximately 11 GHz, overcoming measurement errors caused by random wavelength drift of the laser. However, this structure results in the entire optical path being loop-shaped, with the modulation systems of the pump branch and the probe branch located on the same side of the fiber under test. Consequently, the actual effective sensing distance is only half the length of the fiber under test, and resources such as the length and optical power of the fiber under test are not fully utilized. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art, which cannot fully utilize the length and optical power of the optical fiber under test, and to provide a structurally optimized Brillouin time domain analyzer.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] A Brillouin time-domain analyzer includes: a main laser, a probe optical path, a sensing optical fiber, a pump optical path, an optical signal receiving branch, and a signal platform;

[0007] The detection optical path uses the main laser as the light source and outputs continuous detection light into one end of the sensing optical fiber; the pump optical path generates pulsed pump light based on the electrical signal generated by the signal platform, which passes through the first port of the optical circulator to the second port and is then input into the other end of the sensing optical fiber.

[0008] The scattered light output from the third port of the optical circulator is split into two paths by an optical beam splitter. One path serves as the input to the pump optical path, and the pump optical path achieves frequency synchronization between the pump light and the probe light through injection locking. The other path is used for photoelectric conversion in the optical signal receiving branch and signal processing is performed on the signal platform. The Brillouin gain spectrum characteristic parameters are extracted through a time-domain demodulation algorithm.

[0009] As a preferred technical solution, the detection optical path includes an optical attenuator and an optical isolator connected in sequence;

[0010] The optical attenuator attenuates the light output from the laser to the target optical power, and then the light enters the optical isolator; the optical isolator is used to isolate the pump light coming from the opposite direction.

[0011] As a preferred technical solution, the pump optical path includes a first optical amplifier, a first optical polarization state modulation unit, an optical frequency shifting unit, an optical injection locking unit, an optical intensity modulator, a second optical amplifier, and a second optical polarization state modulation unit connected in sequence; the input of the first optical amplifier is connected to port 1 of the optical beam splitter, and the output of the second optical polarization state modulation unit is connected to port 1 of the optical circulator as the output of the pump optical path.

[0012] As a preferred technical solution, the first optical polarization state modulation unit includes an optical polarizer and an optical polarizer connected in sequence;

[0013] The optical polarizer is used to randomly perturb the polarization state of the input continuous light, and the output light with a stable polarization state is obtained after passing through the optical polarizer.

[0014] As a preferred technical solution, the optical frequency shifting unit includes a Mach-Zehnder intensity modulator, a voltage-controlled oscillator, a radio frequency amplifier, a bias controller, and an optical filter, which are used to arbitrarily shift the input continuous laser within a certain frequency range centered on the Brillouin frequency shift of the optical fiber material.

[0015] The bias controller drives the Mach-Zehnder intensity modulator to operate in carrier-suppressed mode, modulating the input light intensity to generate symmetrical positive and negative first-order sidebands.

[0016] The voltage-controlled oscillator is used for radio frequency signals, and the radio frequency signal amplifier is used to amplify the output radio frequency signal of the voltage-controlled oscillator. The frequency range of the radio frequency signal covers the Brillouin frequency of the sensing fiber. The radio frequency signal is loaded onto a Mach-Zehnder intensity modulator to control the frequency difference between the sidebands.

[0017] The output of the Mach-Zehnder intensity modulator is connected to the input of the optical filter to filter out the high-frequency sidebands.

[0018] As a preferred technical solution, the optical injection locking unit includes a polarization controller, a circulator, an isolator-free distributed feedback laser and its temperature control platform, used for optical frequency locking between the detection optical path and the pump optical path;

[0019] The output of the polarization controller is connected to the first port of the circulator;

[0020] The second port of the circulator is connected to the distributed feedback laser, and the third port is connected to the optical intensity modulator as the output of the optical injection lock.

[0021] The temperature control platform adjusts the temperature and current parameters to make the center wavelength of the distributed feedback laser close to the center wavelength of the input seed light. The distributed feedback laser maintains the same oscillation frequency as the seed light. At this time, the wavelength output by the distributed feedback laser has the same optical characteristics as the main laser (11).

[0022] As a preferred technical solution, the light intensity modulator is used to modulate the input continuous light intensity into pulsed light of a coded sequence.

[0023] As a preferred technical solution, the optical signal receiving branch includes an optical filtering unit and a photodetector;

[0024] The optical filtering unit includes a Bragg grating and a circulator. The center wavelength of the Bragg grating is aligned with the center wavelength of the main laser to filter out backscattering noise generated by the pump light. The photodetector is an avalanche photodetector with analog bandwidth, used to convert the backscattering signal into an electrical signal.

[0025] As a preferred technical solution, the signal platform includes: a first signal generator, a second signal generator, a signal acquisition unit, and a computer;

[0026] The first signal generator outputs an electrical signal to drive the optical frequency shifting unit to perform a specified frequency shift on its input light, and continuously changes the amplitude of the electrical signal so that the input light is scanned point by point within a certain frequency range;

[0027] The second signal generator outputs a pulse electrical signal with a specified coded sequence, which drives the light intensity modulator to generate a pulse optical signal with the corresponding coded sequence.

[0028] The signal acquisition unit is connected to the output of the photodetector and converts the captured photoelectric signals into digital signals.

[0029] The first signal generator, the second signal generator, and the signal acquisition unit maintain clock synchronization and trigger synchronization.

[0030] The computer executes the system control program, which cyclically generates coded pulses and frequency sweep signals, as well as demodulates the signals, to complete the scanning of the Brillouin gain spectrum and extract the Brillouin frequency shift information.

[0031] As a preferred technical solution, the system control program is executed as follows:

[0032] The first signal generator changes the frequency shift of the frequency shift unit point by point within a certain range;

[0033] In each frequency shift of the frequency shifting unit, the second signal generator generates a pulse electrical signal with a specified coded sequence and drives the intensity modulator; the signal acquisition unit performs analog-to-digital conversion on the acquired electrical signal; the above modulation and acquisition process is repeated several times, and the acquired time-domain signal is averaged and denoised in the computer and the corresponding decoding operation is performed to obtain the Brillouin gain corresponding to the single pulse.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] 1) This invention proposes a structurally optimized Brillouin time-domain analyzer that achieves full utilization of the sensing fiber length and enables long-distance sensing. In this invention, the probe optical path and pump optical path are located on opposite sides of the fiber under test, forming an end-to-end open-circuit structure. After passing through the fiber under test, a portion of the probe light directly reaches the input end of the pump optical path, serving as a seed light to ensure frequency stability between the pump and probe light. This open-circuit structure avoids the waste of sensing fiber length resources inherent in traditional loop-structured Brillouin time-domain analyzers, effectively doubling the sensing distance.

[0036] 2) The pump optical path of the present invention includes multiple optoelectronic devices, wherein the optical polarization modulation unit polarizes the input continuous light, and then the intensity is modulated by the optical frequency shifting unit to generate symmetrical positive and negative first-order sidebands; then the optical injection locking unit passively locks the wavelength of the laser to the wavelength of the input light of the optical frequency shifting unit, ensuring the frequency stability between the probe optical path and the pump optical path; finally, the intensity of the input continuous light is modulated into pulse light of the coded sequence, and a stable and adjustable pump light is output.

[0037] 3) The signal platform of this invention drives the optical frequency shifting unit to perform a specified frequency shift on its input light to obtain a swept frequency signal, and drives the optical intensity modulator to encode the pump pulse through a specified coding sequence to generate a pulsed optical signal with the corresponding coding sequence, and performs analog-to-digital conversion on the acquired electrical signal. By repeatedly executing the frequency sweep and encoding, and averaging and denoising the acquired time-domain signal and performing the corresponding decoding operation, the scanning of the Brillouin gain spectrum and the extraction of Brillouin frequency shift information are completed. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the system structure of a structurally optimized Brillouin time-domain analyzer according to the present invention.

[0039] Figure 2 This is a block diagram illustrating the implementation scheme of the optical frequency shifting unit in an embodiment of the present invention;

[0040] Figure 3 A block diagram illustrating the implementation scheme of a typical optical injection locking unit;

[0041] Figure 4 This is a graph showing the results of the actual measurement of Brillouin frequency shift and its temperature fitting curve in an embodiment of the present invention.

[0042] The following are the labels in the diagram: 11. Main laser; 12. Optical circulator; 13. Optical beam splitter; 2. Probe optical path; 21. Optical isolator; 3. Sensing fiber; 4. Pump optical path; 41. First optical amplifier; 42. First optical polarization state modulation unit; 43. Optical frequency shifting unit; 44. Optical injection locking unit; 45. Optical intensity; 46. Second optical amplifier; 47. Second optical polarization state modulation unit; 5. Optical signal receiving branch; 51. Optical filtering unit; 52. Photodetector; 6. Signal platform; 61. First signal generator; 62. Second signal generator; 63. Signal acquisition unit; 64. Computer. Detailed Implementation

[0043] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0044] Example 1

[0045] This invention proposes a structurally optimized Brillouin time-domain analyzer. The probe optical path 2 uses a main laser 11 as the light source, outputting continuous light into the sensing fiber 3. The pump optical path 4 generates pulsed pump light based on the electrical signal generated by the signal platform 6. This pulsed pump light passes through the first port to the second port of the optical circulator 12 and is input to the other end of the sensing fiber 3. The scattered light output from the third port of the optical circulator 12 is split into two paths by the optical beam splitter 13. One path serves as the input to the pump optical path 4, and frequency synchronization between the pump light and the probe light is achieved through injection locking. The other path is used in the optical signal receiving branch 5 for photoelectric conversion, and signal processing is performed on the signal platform 6. A time-domain demodulation algorithm is used to extract the Brillouin gain spectrum characteristic parameters to reconstruct the temperature / strain distribution. This invention proposes an end-to-end open-loop optical path structure, which can double the sensing distance for the same fiber length, making it suitable for ultra-long-distance distributed monitoring scenarios.

[0046] As one specific embodiment of the present invention, such as Figure 1As shown, the Brillouin time-domain analyzer in this embodiment includes: a main laser 11, a probe optical path 2, a sensing optical fiber 3, a pump optical path 4, an optical signal receiving branch 5, and a signal platform 6. The continuous single-frequency laser generated by the main laser 11 is input to the probe optical path 2 as the main light source. The output of the probe optical path 2 is connected to one end of the optical fiber under test 3. The output of the pump optical path 4 is connected to the other end of the optical fiber under test 3 through ports 1 to 2 of the circulator 12. The output of port 3 of the circulator 12 is sent to the optical beam splitter 13, and its output is split into two paths. One path is connected to the input end of the pump optical path 4, and the other path is received by the optical signal receiving branch 5. The signal platform 6 is used to perform analog-to-digital conversion and signal demodulation on the output of the optical signal receiving branch 5, and at the same time generate an electrical signal to control the pump optical path 4.

[0047] The main laser 11 outputs a continuous single-frequency laser, and its linewidth should be much smaller than the width of the stimulated Brillouin scattering spectrum of the sensing fiber. In this embodiment, the laser output power is 10dBm and the center wavelength is 1550nm.

[0048] The detection optical path 2 includes an optical attenuator and an optical isolator 21 connected in sequence. The optical attenuator attenuates the light output from the laser to -10dBm, and then enters the optical isolator 21 to isolate the pump light coming from the opposite direction and prevent it from damaging the laser.

[0049] The sensing fiber 3 used in this embodiment is 80km long and is a single-mode silica fiber.

[0050] The pump optical path 4 contains multiple optoelectronic devices, which are arranged in the following order according to the propagation sequence of the optical signal: first optical amplifier 41, first optical polarization state modulation unit 42, optical frequency shifting unit 43, optical injection locking unit 44, optical intensity modulator 45, second optical amplifier 46, and second optical polarization state modulation unit 47. The input of the first optical amplifier 41 is connected to port 1 of the optical beam splitter 13, and the output of the second optical polarization state modulation unit 47 is connected to port 1 of the optical circulator 12 as the output of the pump optical path 4.

[0051] The first optical polarization state modulation unit 42 includes an optical polarizer and a polarizer. The optical polarizer perturbs the polarization state of the input continuous light at a certain frequency and then inputs it into the polarizer so that the output light has a stable polarization state.

[0052] The optical frequency shifting unit 43 includes a Mach-Zehnder intensity modulator, a voltage-controlled oscillator, an RF amplifier, a bias controller, and an optical filter, such as... Figure 2As shown, the Mach-Zehnder intensity modulator is biased by a bias controller to operate in carrier-suppressed mode, while simultaneously modulating the input light to generate symmetrical ±1st-order sidebands. The frequency difference between the sidebands is related to the radio frequency (RF) signal applied to the Mach-Zehnder modulator. In this embodiment, a voltage-controlled oscillator (VCO) is used to generate the corresponding RF signal, and an RF signal amplifier is used to amplify the output RF signal of the VCO to drive the modulator. The frequency range of the RF signal covers the Brillouin frequency of single-mode silica fiber, approximately 11 GHz. The output of the modulator is connected to the input of an optical filter to filter out the high-frequency sidebands, enabling subsequent stimulated Brillouin scattering (SBS).

[0053] The optical injection locking unit 44 includes a polarization controller, a circulator, an isolator-free distributed feedback laser, and its temperature control platform, such as... Figure 3 As shown. The output of the polarization controller is connected to port 1 of the circulator, port 2 of the circulator is connected to the laser, and port 3, as the output of the optical injection lock, is connected to the optical intensity modulator 45. By adjusting parameters such as temperature and current of the temperature control platform, the center wavelength of the distributed feedback laser is made close to the center wavelength of the input seed light. At this time, the distributed feedback laser will maintain the same oscillation frequency as the seed light, and its output will have the same optical frequency, linewidth, and other optical characteristics as the seed light (i.e., the main laser 11). Injection lock ensures the frequency stability between the probe optical path and the pump optical path. The output of the laser output injection lock unit is then injected into the optical intensity modulator for subsequent modulation.

[0054] The function of the light intensity modulator 45 is to modulate the input continuous light intensity into pulse light of the coded sequence. In this embodiment, an acousto-optic modulator is selected to realize pulse shaping. Its extinction ratio is as high as 60dB and its response speed is fast. The pulse light of the coded sequence it generates has a symbol pulse width of 50ns, corresponding to a spatial resolution of 5m.

[0055] Both the first optical amplifier 41 and the second optical amplifier 46 are erbium-doped fiber amplifiers. The former is used to amplify the optical power entering the optical injection locking unit 44, so that the injection locking has a larger locking range. The latter is used to amplify the encoded pulse sequence to meet the threshold of stimulated Brillouin scattering.

[0056] The second optical polarization state modulation unit 47 is an optical polarizer that randomly perturbs the polarization state of the pump light to overcome the polarization fading phenomenon in the stimulated Brillouin scattering process.

[0057] The optical signal receiving branch 5 includes an optical filtering unit 51 and a photodetector 52. In this embodiment, the optical filtering unit 51 uses a combination of a Bragg grating and a circulator. The center wavelength of the Bragg grating is aligned with the center wavelength of the main laser to filter out the back Rayleigh scattering noise generated by the pump light. In this embodiment, an avalanche photodetector with an analog bandwidth of 400MHz is selected to convert the back Brillouin scattering signal into an electrical signal.

[0058] Signal platform 6 includes: a first signal generator 61, a second signal generator 62, a signal acquisition unit 63, and a computer 64, wherein,

[0059] The first signal generator 61 outputs an electrical signal to drive the optical frequency shifting unit 43 to perform a specified frequency shift on its input light;

[0060] The second signal generator 62 outputs a pulse electrical signal with a specified encoding sequence, which drives the light intensity modulator 45 to generate a pulse optical signal with the corresponding encoding sequence. In this embodiment, a 127-bit Simplex encoding sequence is selected to encode the pump pulse.

[0061] The signal acquisition unit 63 is connected to the output of the photodetector 52 and converts the captured photoelectric signal into a digital signal.

[0062] In this embodiment, both the first signal generator 61 and the second signal generator 62 are arbitrary waveform generation boards with a sampling rate of 400MSa / s, an analog bandwidth of 250MHz, and an output voltage range of 5V.

[0063] The first signal generator 61, the second signal generator 62, and the signal acquisition unit 63 maintain strict clock synchronization and trigger synchronization;

[0064] The computer 64 executes the system control program, which cyclically generates coded pulses and sweep frequency signals, as well as demodulates the signals.

[0065] In the system control program, under each frequency shift of the frequency shift unit controlled by the first signal generator 61, the second signal generator 62 cyclically generates a pulse electrical signal of a 127-bit Simplex encoded sequence to drive the intensity modulator 45. The signal acquisition unit 63 performs analog-to-digital conversion on the acquired electrical signal. The above process is repeated several times to improve the signal-to-noise ratio. In the computer 64, the time-domain signal is averaged and denoised, and corresponding decoding operations are performed to obtain the Brillouin gain corresponding to the single pulse.

[0066] In the system control program, the first signal generator 61 changes the frequency shift of the frequency shift unit point by point within a certain range (10.61GHz to 10.80GHz), the second signal generator 62 repeatedly performs the encoding operation, and the computer 64 repeatedly performs the averaging denoising and decoding operations to complete the scanning of the Brillouin gain spectrum and the extraction of Brillouin frequency shift information.

[0067] To test system performance, approximately 40 meters of fiber optic cable at the end of the sensing fiber (79.840km-79.880km) was placed in a water bath, and its Brillouin frequency shift was measured at different temperatures (18.9℃, 25℃, 30.7℃, 36℃, 41.7℃, 46.6℃). A linear fit was then performed between the measured Brillouin frequency shift and the applied temperature information. Figure 4 The results showed that the two have a good linear relationship, with a slope coefficient of 1.10MHz / ℃, which is consistent with the parameter characteristics of quartz optical fiber.

[0068] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A Brillouin time-domain analyzer, characterized in that, include: The main laser (11), the probe optical path (2), the sensing optical fiber (3), the pump optical path (4), the optical signal receiving branch (5), and the signal platform (6). The detection optical path (2) uses the main laser as the light source and outputs continuous detection light into one end of the sensing optical fiber (3); the detection optical path (2) includes an optical attenuator and an optical isolator (21) connected in sequence. The optical attenuator attenuates the light output from the laser to the target optical power, and then enters the optical isolator (21); the optical isolator (21) is used to isolate the pump light coming from the opposite direction; The pump optical path (4) generates pulsed pump light based on the electrical signal generated by the signal platform (6), which is then input to the other end of the sensing fiber (3) after passing through the first port to the second port of the optical circulator (12); the pump optical path (4) includes a first optical amplifier (41), a first optical polarization state modulation unit (42), an optical frequency shifting unit (43), an optical injection locking unit (44), an optical intensity modulator (45), a second optical amplifier (46), and a second optical polarization state modulation unit (47) connected in sequence; the input of the first optical amplifier (41) is connected to port 1 of the optical beam splitter (13), and the output of the second optical polarization state modulation unit (47) is connected to port 1 of the optical circulator (12) as the output of the pump optical path (4); The first optical polarization state modulation unit (42) includes an optical polarizer and an optical polarizer connected in sequence; The optical polarizer is used to randomly perturb the polarization state of the input continuous light, and the output light with a stable polarization state is obtained after passing through the optical polarizer. The optical injection locking unit (44) includes a polarization controller, a circulator, a distributed feedback laser without isolators and its temperature control platform, used to detect the optical frequency lock between the optical path (2) and the pump optical path (4); The output of the polarization controller is connected to the first port of the circulator; The second port of the circulator is connected to the distributed feedback laser, and the third port is connected to the optical intensity modulator (45) as the output of the optical injection lock. The temperature control platform adjusts the temperature and current parameters to make the center wavelength of the distributed feedback laser close to the center wavelength of the input seed light. The distributed feedback laser maintains the same oscillation frequency as the seed light. At this time, the wavelength output by the distributed feedback laser has the same optical characteristics as the main laser (11). The scattered light output from the third port of the optical circulator (12) is split into two paths by the optical beam splitter (13). One path serves as the input to the pump optical path (4), which achieves frequency synchronization between the pump light and the probe light through injection locking. The other path is used for photoelectric conversion in the optical signal receiving branch (5) and signal processing is performed on the signal platform (6). The Brillouin gain spectrum characteristic parameters are extracted through the time-domain demodulation algorithm.

2. The Brillouin time-domain analyzer according to claim 1, characterized in that, The optical frequency shifting unit (43) includes a Mach-Zehnder intensity modulator, a voltage-controlled oscillator, a radio frequency amplifier, a bias controller, and an optical filter, which are used to arbitrarily shift the input continuous laser within a certain frequency range centered on the Brillouin frequency shift of the optical fiber material. The bias controller drives the Mach-Zehnder intensity modulator to operate in carrier-suppressed mode, modulating the input light intensity to generate symmetrical positive and negative first-order sidebands. The voltage-controlled oscillator is used for radio frequency signals, and the radio frequency signal amplifier is used to amplify the output radio frequency signal of the voltage-controlled oscillator. The frequency range of the radio frequency signal covers the Brillouin frequency of the sensing fiber (3). The radio frequency signal is loaded onto the Mach-Zehnder intensity modulator to control the frequency difference between the sidebands. The output of the Mach-Zehnder intensity modulator is connected to the input of the optical filter to filter out the high-frequency sidebands.

3. A Brillouin time-domain analyzer according to claim 1, characterized in that, The light intensity modulator (45) is used to modulate the input continuous light intensity into pulse light of a coded sequence.

4. A Brillouin time-domain analyzer according to claim 1, characterized in that, The optical signal receiving branch (5) includes an optical filtering unit (51) and a photodetector (52); The optical filtering unit (51) includes a Bragg grating and a circulator. The center wavelength of the Bragg grating is aligned with the center wavelength of the main laser to filter out the back Rayleigh scattering noise generated by the pump light. The photodetector (52) is an avalanche photodetector with analog bandwidth, used to convert the back Brillouin scattering signal into an electrical signal.

5. A Brillouin time-domain analyzer according to claim 1, characterized in that, The signal platform (6) includes: a first signal generator (61), a second signal generator (62), a signal acquisition unit (63), and a computer (64). The first signal generator (61) outputs an electrical signal to drive the optical frequency shifting unit (43) to perform a specified frequency shift on its input light and continuously change the amplitude of the electrical signal so that the input light is scanned point by point within a certain frequency range; The second signal generator (62) outputs a pulse electrical signal of a specified encoding sequence, which drives the light intensity modulator (45) to generate a pulse optical signal of the corresponding encoding sequence; The signal acquisition unit (63) is connected to the output of the photodetector (52) and converts the captured photoelectric signal into a digital signal. The first signal generator (61), the second signal generator (62), and the signal acquisition unit (63) maintain clock synchronization and trigger synchronization; The computer (64) executes the system control program, repeatedly executing the generation of encoded pulses and frequency sweep signals, as well as signal demodulation, to complete the scanning of the Brillouin gain spectrum and extract the Brillouin frequency shift information.

6. A Brillouin time-domain analyzer according to claim 5, characterized in that, The system control program executes as follows: The first signal generator (61) changes the frequency shift of the frequency shift unit (43) point by point within a certain range; In each frequency shift of the frequency shift unit (43), the second signal generator (62) generates a pulse electrical signal with a specified coded sequence and drives the intensity modulator (45); the signal acquisition unit (63) performs analog-to-digital conversion on the acquired electrical signal; The above modulation and acquisition process is repeated several times. The acquired time-domain signal is averaged and denoised in the computer (64) and the corresponding decoding operation is performed to obtain the Brillouin gain corresponding to the single pulse.

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