A Brillouin optical time domain analysis system

Abstract

The utility model discloses a kind of Brillouin optical time domain analysis systems, the system includes: main Brillouin optical time domain analysis module, slave Brillouin optical time domain analysis module, first to-be-measured optical fiber and second to-be-measured optical fiber;Main Brillouin optical time domain analysis module includes: main laser, first coupler, first pulse modulation unit, first frequency shift modulation unit, first circulator and first signal acquisition processing unit;Slave Brillouin optical time domain analysis module includes: slave laser, second coupler, second pulse modulation unit, second frequency shift modulation unit, second circulator and second signal acquisition processing unit.The utility model can further improve sensing distance while guaranteeing sensing accuracy and spatial resolution by constructing main Brillouin optical time domain analysis module and slave Brillouin optical time domain analysis module to the architecture of shooting.

Description

Technical Field

[0001] This utility model relates to the field of Brillouin optical time-domain analysis technology, and in particular to a Brillouin optical time-domain analysis system. Background Technology

[0002] Distributed fiber optic sensing technology, due to its advantages such as resistance to electromagnetic interference, ability to achieve long-distance continuous monitoring, and deployment cost adaptability to large-scale scenarios, is widely used in the structural health monitoring of large infrastructure such as buildings, bridges, and tunnels, showing broad application prospects in long-distance measurement scenarios. Among them, Brillouin Optical Time Domain Analysis (BOTDA) is a core technology in this field and a key solution for realizing long-distance distributed sensing at the hundred-kilometer level.

[0003] The core performance indicators of a Brillouin optical time-domain analysis system include sensing distance, spatial resolution, and sensing accuracy, all of which jointly determine the system's practical application value. Specifically, high spatial resolution enables precise location of structural anomalies, while a high signal-to-noise ratio (SNR) is a crucial prerequisite for ensuring system sensing accuracy and extending the effective sensing distance. However, in Brillouin fiber optic sensing technology, sensing distance and spatial resolution are inherently mutually restrictive—as the sensing distance increases, the sensing signal inevitably attenuates during transmission through the fiber, leading to a decrease in the system's SNR and ultimately affecting sensing accuracy and effective monitoring range. This has become a key bottleneck restricting its application in ultra-long-distance scenarios.

[0004] To address the aforementioned technical bottlenecks, various optimization schemes have been proposed in existing technologies. Among them, the two most widely used technologies are distributed Raman amplification and optical pulse coding. While distributed Raman amplification can amplify the sensing signal along the path through stimulated Raman scattering in optical fibers, effectively compensating for signal attenuation to extend the sensing distance and improve the signal-to-noise ratio, it is limited by nonlinear interference, insufficient uniformity of amplification along the path, the contradiction between pump system power and efficiency, and the introduction of additional noise (such as spontaneous Raman scattering noise). Optical pulse coding, on the other hand, can achieve a balance between "high energy transmission" and "high spatial resolution" by modulating the pump light or probe light with a specific sequence, utilizing the superposition of encoded energy and decoding recovery, thereby improving the sensing signal-to-noise ratio, optimizing spatial resolution, and extending the sensing distance. However, it faces challenges such as increased decoding algorithm complexity, difficulty in balancing measurement time and performance, and decoding sidelobe interference.

[0005] Therefore, a new technical solution is needed to overcome the above bottlenecks, and to further improve the sensing distance while ensuring sensing accuracy and spatial resolution, so as to adapt to a wider range of long-distance infrastructure monitoring scenarios. Utility Model Content

[0006] This invention provides a Brillouin optical time-domain analysis system that can further improve the sensing distance while ensuring sensing accuracy and spatial resolution.

[0007] This utility model provides a Brillouin optical time-domain analysis system, including: a main Brillouin optical time-domain analysis module, a slave Brillouin optical time-domain analysis module, a first optical fiber under test, and a second optical fiber under test; The master Brillouin optical time-domain analysis module includes: a master laser, a first coupler, a first pulse modulation unit, a first frequency shift modulation unit, a first circulator, and a first signal acquisition and processing unit; the slave Brillouin optical time-domain analysis module includes: a slave laser, a second coupler, a second pulse modulation unit, a second frequency shift modulation unit, a second circulator, and a second signal acquisition and processing unit. The output end of the main laser is connected to the input end of the first coupler; The first output terminal of the first coupler is connected to the first terminal of the first pulse modulation unit, the second terminal of the first pulse modulation unit is connected to the first terminal of the first circulator, and the second terminal of the first circulator is connected to the first terminal of the first optical fiber under test; the third terminal of the first circulator is connected to the first signal acquisition and processing unit; the second output terminal of the first coupler is connected to the first terminal of the first frequency shift modulation unit, the second terminal of the first frequency shift modulation unit is connected to the first terminal of the second optical fiber under test, and the second terminal of the second optical fiber under test is connected to the second terminal of the second circulator. The input terminal of the second coupler is connected to the output terminal of the laser; the first output terminal of the second coupler is connected to the first terminal of the second frequency shift modulation unit; the second terminal of the second frequency shift modulation unit is connected to the second terminal of the first optical fiber under test; the second output terminal of the second coupler is connected to the first terminal of the second pulse modulation unit; the second terminal of the second pulse modulation unit is connected to the first terminal of the second circulator; and the third terminal of the second circulator is connected to the second signal acquisition and processing unit.

[0008] Optionally, the Brillouin optical time-domain analysis module further includes a third coupler and a third circulator; The third end of the second circulator is connected to the input end of the third coupler, the first output end of the third coupler is connected to the first end of the third circulator, the second end of the third circulator is connected to the output end of the laser, the third end of the third circulator is connected to the input end of the second coupler, and the second output end of the third coupler is connected to the second signal acquisition and processing unit.

[0009] Optionally, the first signal acquisition and processing unit includes a first filtering unit, a first photodetector, and a first data acquisition processor. The third end of the first circulator is connected to the first end of the first filtering unit, the second end of the first filtering unit is connected to the first end of the first photodetector, and the electrical signal output end of the first photodetector is electrically connected to the first data acquisition processor. The second signal acquisition and processing unit includes a second filtering unit, a second photodetector, and a second data acquisition processor. The second output terminal of the third coupler is connected to the first terminal of the second filtering unit, the second terminal of the second filtering unit is connected to the first terminal of the second photodetector, and the electrical signal output terminal of the second photodetector is electrically connected to the second data acquisition processor. Preferably, the first filtering unit includes one of a fiber Bragg grating and a Fabry-Perot filter, and / or the second filtering unit includes one of a fiber Bragg grating and a Fabry-Perot filter.

[0010] Optionally, an isolator is further connected in series between the main laser and the first coupler; and / or, A polarization controller or analyzer is connected in series between the first output terminal of the third coupler and the first terminal of the third circulator.

[0011] Optionally, the first frequency shift modulation unit includes a first electro-optic modulator and a first microwave signal source. The first end of the first electro-optic modulator is connected to the second output end of the first coupler, the second end of the first electro-optic modulator is connected to the first end of the second optical fiber under test, and the radio frequency signal output end of the first microwave signal source is electrically connected to the radio frequency signal input end of the first electro-optic modulator. Preferably, the first frequency shift modulation unit further includes a first polarization processing device, which is connected in series between the second end of the first electro-optic modulator and the first end of the second optical fiber under test. Preferably, the first polarization processing device includes one of a polarization scrambler, a polarization diversity receiving system, a polarization state feedback control system, and a depolarizer; Preferably, the first frequency shift modulation unit further includes a second optical amplifier, which is connected in series in the optical path between the second end of the first electro-optic modulator and the first polarization processing device.

[0012] Optionally, the second frequency shift modulation unit includes a second photoelectric modulator and a second microwave signal source; The first end of the second opto-modulator is connected to the first output end of the second coupler, the second end of the second opto-modulator is connected to the second end of the first optical fiber under test, and the RF output end of the second microwave signal source is electrically connected to the RF input end of the second opto-modulator. Preferably, the second frequency shift modulation unit further includes a second polarization processing device, which is connected in series between the second end of the second optoelectronic modulator and the first optical fiber under test; Preferably, the second polarization processing device includes one of a polarization scrambler, a polarization diversity receiving system, a polarization state feedback control system, and a polarization depolarizer; Preferably, the second frequency shift modulation unit further includes a third optical amplifier, which is connected in series in the optical path between the second end of the second photoelectric modulator and the second polarization processing device.

[0013] Optionally, the first pulse modulation unit includes a first pulse generation module and a first pulse driver. The first end of the first pulse generation module is connected to the first output end of the first coupler, the second end of the first pulse generation module is connected to the first end of the first circulator, and the electrical drive signal output end of the first pulse driver is electrically connected to the electrical drive signal input end of the first pulse generation module. Preferably, the first pulse modulation unit further includes a first optical amplifier, which is connected in series between the second end of the first pulse generation module and the first end of the first circulator; Preferably, the first pulse generation module includes one of a semiconductor optical amplifier, an electro-optic modulator, and an acousto-optic modulator; Optionally, the second pulse modulation unit includes a second pulse generation module and a second pulse driver. The first end of the second pulse generation module is connected to the second output end of the second coupler, the second end of the second pulse generation module is connected to the first end of the second circulator, and the electrical drive signal output end of the second pulse driver is electrically connected to the electrical drive signal input end of the second pulse generation module. Preferably, the second pulse modulation unit further includes a fourth optical amplifier, which is connected in series between the second end of the second pulse generation module and the first end of the second circulator; Preferably, the second pulse generation module includes one of a semiconductor optical amplifier, an electro-optic modulator, and an acousto-optic modulator.

[0014] Optionally, the Brillouin optical time-domain analysis system further includes a communication optical fiber; the main Brillouin optical time-domain analysis module further includes a main module control unit and a main-end optical fiber transceiver; the slave Brillouin optical time-domain analysis module further includes a slave module control unit and a slave-end optical fiber transceiver. The main fiber optic transceiver, the main laser, the first signal acquisition and processing unit, the first pulse modulation unit, and the first frequency shift modulation unit are electrically connected to the main module control unit, respectively. The slave fiber optic transceiver, the slave laser, the second signal acquisition and processing unit, the second pulse modulation unit, and the second frequency shift modulation unit are respectively electrically connected to the slave module control unit; The master fiber optic transceiver and the slave fiber optic transceiver are connected via the communication fiber optic cable. Optionally, the master Brillouin optical time domain analysis module further includes a master module controller and a master remote communication module; the slave Brillouin optical time domain analysis module further includes a slave module controller and a slave remote communication module. The main remote communication module, the main laser, the first signal acquisition and processing unit, the first pulse modulation unit, and the first frequency shift modulation unit are electrically connected to the main module controller, respectively. The remote communication module, the laser, the second signal acquisition and processing unit, the second pulse modulation unit, and the second frequency shift modulation unit are electrically connected to the slave module controller, respectively. The master remote communication module and the slave remote communication module establish a communication connection wirelessly.

[0015] This utility model provides a Brillouin optical time-domain analysis system with the following advantages: a through-beam architecture of a main Brillouin optical time-domain analysis module and a slave Brillouin optical time-domain analysis module is constructed through a first test fiber and a second test fiber. By performing continuous pulsed light bidirectional through-beaming in the first test fiber and the second test fiber respectively, a basic structure for long-distance measurement is built. While ensuring sensing accuracy and spatial resolution, the sensing distance can reach four times that of a traditional single BOTDA.

[0016] It should be understood that the description in this section is not intended to identify key or important features of the embodiments of this utility model, nor is it intended to limit the scope of this utility model. Other features of this utility model will become readily apparent from the following description. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this utility model, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0018] Figure 1This is a schematic diagram of the structure of a Brillouin optical time-domain analysis system in the prior art; Figure 2 This is a schematic diagram of the structure of a Brillouin optical time-domain analysis system provided by an embodiment of this utility model; Figure 3 This is a schematic diagram of another Brillouin optical time-domain analysis system provided by an embodiment of this utility model; Figure 4 This is a schematic diagram of the communication method of a Brillouin optical time-domain analysis system provided by an embodiment of this utility model; Figure 5 This is a schematic diagram of the communication method of another Brillouin optical time-domain analysis system provided by this utility model embodiment.

[0019] Icon labels: A. First fiber under test; B. Second fiber under test; 100. Main Brillouin optical time-domain analysis module; 110. Main laser; 120. First coupler; 130. First pulse modulation unit; 131. First pulse generation module; 132. First pulse driver; 140. First frequency shift modulation unit; 141. First electro-optic modulator; 142. First microwave signal source; 143. First polarization processing device; 144. Second optical amplifier; 150. First circulator; 160. First signal acquisition and processing unit; 161. First filtering unit; 162. First photodetector; 163. First data acquisition processor; 170. Isolator; 200. From Brillouin optical time-domain analysis module; 210. From laser; 220. Second coupler; 230. Second pulse modulation unit; 231. Second pulse generation module; 232. Second pulse driver; 240. Second frequency shift modulation unit; 241. Second optoelectronic modulator; 242. Second microwave signal source; 243. Second polarization processing device; 244. Third optical amplifier; 250. Second circulator; 260. Second signal acquisition and processing unit; 261. Second filtering unit; 262. Second photodetector; 263. Second data acquisition processor; 270. Third circulator; 280. Third coupler; 290. Polarization controller; C. Optical fiber for communication; 311. Master module control unit; 312. Master-end fiber optic transceiver; 321. Slave module control unit; 322. Slave-end fiber optic transceiver; 411. Master module controller; 412. Master remote communication module; 421. Slave module controller; 422. Slave remote communication module. Detailed Implementation

[0020] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort should fall within the scope of protection of the present invention.

[0021] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this utility model are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the utility model described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0022] Figure 1 This is a schematic diagram of the structure of a Brillouin optical time-domain analysis system in the prior art, for reference. Figure 1 The existing Brillouin optical time-domain analysis system includes a main laser 110, a first coupler 120, a first pulse modulation unit 130, a first frequency shift modulation unit 140, a first circulator 150, and a first signal acquisition and processing unit 160. The output terminal of the main laser 110 is connected to the input terminal of the first coupler 120, the first output terminal of the first coupler 120 is connected to the first terminal of the first pulse modulation unit 130, the second terminal of the first pulse modulation unit 130 is connected to the first terminal of the first circulator 150, the second terminal of the first circulator 150 is connected to the first terminal of the first optical fiber under test A, and the third terminal of the first circulator 150 is connected to the first signal acquisition and processing unit 160.

[0023] If the length of the first fiber A under test in the prior art is 2L, then the sensing distance of the prior art Brillouin optical time-domain analysis system is L. To further improve the sensing distance while ensuring sensing accuracy and spatial resolution, and to adapt to a wider range of long-distance infrastructure monitoring scenarios, this utility model provides a Brillouin optical time-domain analysis system that, without reducing the signal-to-noise ratio (i.e., sensing accuracy) and spatial resolution, can increase the effective sensing distance to four times that of a traditional single BOTDA, i.e., 4L. Specifically: Figure 2This is a schematic diagram of the structure of a Brillouin optical time-domain analysis system provided by an embodiment of this utility model, with reference to... Figure 2 The system includes a main Brillouin optical time-domain analysis module 100, a slave Brillouin optical time-domain analysis module 200, a first fiber under test A, and a second fiber under test B. The main Brillouin optical time-domain analysis module 100 includes a main laser 110, a first coupler 120, a first pulse modulation unit 130, a first frequency shift modulation unit 140, a first circulator 150, and a first signal acquisition and processing unit 160; the slave Brillouin optical time-domain analysis module 200 includes a slave laser 210, a second coupler 220, a second pulse modulation unit 230, a second frequency shift modulation unit 240, a second circulator 250, and a second signal acquisition and processing unit 260.

[0024] Continue to refer to Figure 2 The output end of the main laser 110 is connected to the input end of the first coupler 120, the first output end of the first coupler 120 is connected to the first end of the first pulse modulation unit 130, the second end of the first pulse modulation unit 130 is connected to the first end of the first circulator 150, the second end of the first circulator 150 is connected to the first end of the first optical fiber under test A, and the third end of the first circulator 150 is connected to the first signal acquisition and processing unit 160. The second output terminal of the first coupler 120 is connected to the first terminal of the first frequency shift modulation unit 140, the second terminal of the first frequency shift modulation unit 140 is connected to the first terminal of the second fiber under test B, and the second terminal of the second fiber under test B is connected to the second terminal of the second circulator 250. The input terminal of the second coupler 220 is connected to the output terminal of the laser 210, the first output terminal of the second coupler 220 is connected to the first terminal of the second frequency shift modulation unit 240, and the second terminal of the second frequency shift modulation unit 240 is connected to the second terminal of the first fiber under test A. The second output terminal of the second coupler 220 is connected to the first terminal of the second pulse modulation unit 230, and the second terminal of the second pulse modulation unit 230 is connected to the first terminal of the second circulator 250. The third terminal of the second circulator 250 is connected to the second signal acquisition and processing unit 260.

[0025] Understandably, the light emitted by the main laser 110 is split into two paths by the first coupler 120: one path enters the first pulse modulation unit 130, is modulated into pulse light, and is injected into the first fiber under test A through the first circulator 150; the other path enters the first frequency shift modulation unit 140, generates sideband modulated continuous light with a specific frequency, and is injected into the second fiber under test B.

[0026] Similarly, the light emitted from the laser 210 is split into two paths by the second coupler 220: one path enters the second pulse modulation unit 230, is modulated into pulse light, and is injected into the second fiber under test B through the second circulator 250; the other path enters the second frequency shift modulation unit 240 to generate sideband modulated continuous light with a specific frequency.

[0027] On one hand, the pulsed light modulated by the first pulse modulation unit 130 and the sideband modulated continuous light generated by the second frequency shift modulation unit 240 undergo stimulated Brillouin scattering in the first fiber under test A. After the continuous light emitted from the Brillouin optical time-domain analysis module 200 to the first fiber under test A through the second frequency shift modulation unit 240 and the pulsed light emitted from the main Brillouin optical time-domain analysis module 100 to the first fiber under test A through the first pulse modulation unit 130 undergo stimulated Brillouin scattering in the first fiber under test A, they enter the first signal acquisition and processing unit 160 through the first circulator 150. The sideband modulated signal is filtered out by the first signal acquisition and processing unit 160 and converted into an electrical signal. After acquisition and processing, it can be used to obtain the temperature strain distribution of the first half of the first fiber under test A (that is, the effective area of ​​the first half of the entire fiber link, i.e., the first half of the first fiber under test A, i.e., from the first end of the first fiber under test A as the measurement start point to the midpoint of the first fiber under test A as the measurement end point). In some implementations, it is possible to obtain the data corresponding to the temperature strain distribution along the entire length of the first fiber A under test, but it is possible to select only the data corresponding to the temperature strain distribution along the first half of the first fiber A under test.

[0028] On the other hand, the pulsed light modulated by the second pulse modulation unit 230 and the sideband modulated continuous light generated by the first frequency shift modulation unit 140 undergo stimulated Brillouin scattering in the second fiber under test B. This stimulated scattering is then acquired and processed by the second signal acquisition and processing unit 260. Specifically, the second signal acquisition and processing unit 260 filters out the sideband modulated signal and converts it into an electrical signal before acquisition and processing. Ultimately, this signal can be used to obtain the temperature strain distribution of the second half of the second fiber under test B (i.e., the effective region of the second half of the entire fiber link, i.e., the second half of the second fiber under test B, from the second end of the second fiber under test as the measurement start point to the midpoint of the second fiber under test B as the measurement end point). In some embodiments, it is possible to obtain the temperature strain distribution data corresponding to the entire length of the second fiber under test B, but only the data corresponding to the temperature strain distribution of the second half of the second fiber under test B can be selected. Explanatoryly, the improvements in the embodiments of this application only relate to the structure of the Brillouin optical time-domain analysis system and do not involve improvements to the data processing methods.

[0029] In summary, the embodiments of this utility model construct a through-beam architecture of a master Brillouin optical time-domain analysis module 100 and a slave Brillouin optical time-domain analysis module 200 through a first test fiber A and a second test fiber B. By performing continuous pulsed light bidirectional through-beaming in the first test fiber A and the second test fiber B respectively, a basic structure for long-distance measurement is established. While ensuring sensing accuracy and spatial resolution, the sensing distance can reach four times that of a traditional single BOTDA. That is, assuming the sensing distance of a traditional single BOTDA is L, the first half of the first test fiber A corresponds to a sensing distance of 2L, and the second half of the second test fiber B corresponds to a sensing distance of 2L, for a total sensing distance of 4L.

[0030] Furthermore, Figure 3 This is a schematic diagram of another Brillouin optical time-domain analysis system provided by an embodiment of this utility model. Based on the above embodiment, refer to... Figure 3 The Brillouin optical time-domain analysis module also includes a third coupler 280 disposed between the third end of the second circulator 250 and the second signal acquisition and processing unit, and a third circulator 270 disposed between the output end of the laser 210 and the input end of the second coupler 220; the third end of the second circulator 250 is connected to the input end of the third coupler 280, the first output end of the third coupler 280 is connected to the first end of the third circulator 270, the second end of the third circulator 270 is connected to the output end of the laser 210, the third end of the third circulator 270 is connected to the input end of the second coupler 220, and the second output end of the third coupler 280 is connected to the second signal acquisition and processing unit.

[0031] Understandably, the optical signal received by laser 210 from the main laser 110 and transmitted through the second fiber under test B is split into two branches after passing through the second circulator 250 and entering the third coupler 280. One branch from the third coupler 280 enters the slave laser 210, and then passes through the second coupler 220 to the second frequency shift modulation unit 240 and the second pulse modulation module 230, respectively. The second frequency shift modulation unit 240 generates sideband modulated continuous light, which is then modulated by the second pulse modulation unit 230 to form pulsed light. The sideband modulated continuous light generated by the second frequency shift modulation unit 240 and the pulsed light modulated by the first pulse modulation unit 130 undergo stimulated Brillouin scattering in the first fiber under test A. The continuous light emitted from the Brillouin optical time-domain analysis module 200 to the first fiber under test A via the second frequency-shift modulation unit 240, and the pulsed light emitted from the main Brillouin optical time-domain analysis module 100 to the first fiber under test A via the first pulse modulation unit 130, undergo stimulated Brillouin scattering in the first fiber under test A. After passing through the first circulator 150, the light enters the first signal acquisition and processing unit 160. The first signal acquisition and processing unit 160 filters out the sideband modulation signal and converts it into an electrical signal for acquisition and processing. The pulsed light modulated by the second pulse modulation unit 230 and the sideband modulated continuous light generated by the first frequency-shift modulation unit 140 undergo stimulated Brillouin scattering in the second fiber under test B. The other path, split by the third coupler 280, passes through the second signal acquisition and processing unit 260. The second signal acquisition and processing unit 260 filters out the sideband modulation signal and converts it into an electrical signal for acquisition and processing.

[0032] In this embodiment of the invention, the continuous light emitted by the master laser 110 passes through the second fiber under test B and the second circulator 250 into the third coupler 280. By setting the third coupler 280, the light can be split into one path and injected into the slave laser 210. Furthermore, by introducing injection locking technology, the output wavelengths of the master Brillouin optical time-domain analysis module 100 and the slave Brillouin optical time-domain analysis module 200 can be controlled, which helps ensure that their wavelengths are consistent. Explanatoryly, the corresponding injection locking method can be achieved using existing technology.

[0033] Optionally, based on the above implementation methods, continue to refer to... Figure 2 or Figure 3 The first signal acquisition and processing unit 160 includes a first filtering unit 161, a first photodetector 162, and a first data acquisition processor 163; the third end of the first circulator 150 is connected to the first end of the first filtering unit 161, the second end of the first filtering unit 161 is connected to the first end of the first photodetector 162, and the electrical signal output end of the first photodetector 162 is electrically connected to the first data acquisition processor 163.

[0034] The first filtering unit 161 is used to filter out the sideband modulation signal, the first photodetector 162 is used to convert the optical signal after the sideband modulation signal is filtered out by the first filtering unit 161 into an electrical signal, and the first data acquisition processor 163 is used to acquire and process the electrical signal, which can then be used to obtain the temperature strain information of the first half of the first optical fiber A under test.

[0035] The second signal acquisition and processing unit 260 includes a second filtering unit 261, a second photodetector 262, and a second data acquisition processor 263; the second output terminal of the third coupler 280 is connected to the first terminal of the second filtering unit 261, the second terminal of the second filtering unit 261 is connected to the first terminal of the second photodetector 262, and the electrical signal output terminal of the second photodetector 262 is electrically connected to the second data acquisition processor 263.

[0036] The second filtering unit 261 is used to filter out the sideband modulation signal, the second photodetector 262 is used to convert the optical signal after the sideband modulation signal is filtered out by the second filtering unit 261 into an electrical signal, and the second data acquisition processor 263 is used to acquire and process the electrical signal, which can then be used to obtain the temperature strain distribution of the second half of the second optical fiber B under test.

[0037] In some embodiments, the first filtering unit 161 includes one of a fiber Bragg grating and a Fabry-Perot filter.

[0038] In some embodiments, the second filtering unit 261 includes one of a fiber Bragg grating and a Fabry-Perot filter.

[0039] It should be noted that the main function of a fiber Bragg grating is wavelength selection and band-stop filtering, while the main function of a Fabry-Perot filter is ultra-narrow bandpass filtering and fine wavelength selection. The first filtering unit 161 and the second filtering unit 261 can be selected from either a fiber Bragg grating or a Fabry-Perot filter according to actual usage requirements.

[0040] Optionally, based on the above embodiments, refer to Figure 3 An isolator 170 is connected in series between the main laser 110 and the first coupler 120. The isolator 170 is used to allow the optical signal to pass through in one direction while effectively blocking the light transmitted in the opposite direction, which can ensure the stable operation of the optical system.

[0041] In some embodiments, a polarization controller 290 or an analyzer is connected in series between the first output terminal of the third coupler 280 and the first terminal of the third circulator 270. The polarization controller 290 is used to actively adjust the polarization state of the light, and the analyzer is used to select and pass light with a specific polarization direction.

[0042] Optionally, in some implementations, reference continues to be made to... Figure 2 The first frequency shift modulation unit 140 includes a first electro-optic modulator 141 and a first microwave signal source 142. The first end of the first electro-optic modulator 141 is connected to the second output end of the first coupler 120, and the second end of the first electro-optic modulator 141 is connected to the first end of the second optical fiber under test (B). The radio frequency (RF) signal output end of the first microwave signal source 141 is electrically connected to the RF signal input end of the first electro-optic modulator 141. The first microwave signal source 142 generates a high-precision, high-stability microwave signal with adjustable parameters (such as frequency and amplitude). Based on the electro-optic effect, the first electro-optic modulator 141 loads this microwave signal onto a continuous laser beam, thereby generating a probe beam whose frequency matches the Brillouin frequency shift. The coordinated operation of these two components enables scanning of the Brillouin gain spectrum and is the core module determining the system's measurement accuracy and spatial resolution.

[0043] In some embodiments, the first frequency shift modulation unit 140 further includes a first polarization processing device 143, which is connected in series between the second end of the first electro-optic modulator 141 and the first end of the second optical fiber B under test.

[0044] In some embodiments, the first polarization processing device 143 includes one of a polarization scrambler, a polarization diversity receiving system, a polarization state feedback control system, and a depolarizer. In the above embodiments, random fluctuations in the polarization state introduce significant polarization fading noise, directly affecting the measurement accuracy, system stability, and repeatability of the Brillouin gain spectrum. To suppress this critical problem, the first polarization processing device can be selected from the polarization scrambler, polarization diversity receiving system, polarization state feedback control system, and depolarizer according to the specific requirements of the system. Specifically, the polarization scrambler eliminates polarization uncertainty in test calibration by traversing the input polarization state; the polarization diversity receiving system overcomes random changes in signal polarization at the receiving end, avoiding deep fading; the polarization state feedback control system actively locks the optimal polarization operating point to meet ultra-high precision measurement requirements; and the depolarizer passively disrupts the polarization state of light, making it approach polarization-free characteristics in the time domain, thereby stabilizing the Brillouin scattering process and simplifying system design. These solutions all aim to improve the robustness of the BOTDA system against polarization disturbances and can be selected based on the requirements for system accuracy, complexity, and cost.

[0045] In some embodiments, the first frequency shift modulation unit 140 further includes a second optical amplifier 144, which is connected in series in the optical path between the second end of the first electro-optic modulator 141 and the first polarization processing device 143.

[0046] Optionally, in some implementations, reference continues to be made to... Figure 3The second frequency shift modulation unit 240 includes a second optoelectronic modulator 241 and a second microwave signal source 242. The first end of the second optoelectronic modulator 241 is connected to the first output end of the second coupler 220, the second end of the second optoelectronic modulator 241 is connected to the second end of the first optical fiber under test A, and the radio frequency output end of the second microwave signal source 242 is electrically connected to the radio frequency input end of the second optoelectronic modulator 241. The second optoelectronic modulator 241 and the second microwave signal source 242 are used to generate high-precision, high-stability microwave electrical signals with adjustable parameters (such as frequency and amplitude).

[0047] In some embodiments, the second frequency shift modulation unit 240 further includes a second polarization processing device 243, which is connected in series between the second end of the second optoelectronic modulator 241 and the first optical fiber under test A.

[0048] In some embodiments, the second polarization processing device 243 includes one of a polarization scrambler, a polarization diversity receiving system, a polarization state feedback control system, and a depolarizer. The second polarization processing device 243 is used to perform specific processing on the polarization state of a signal, and the second polarization processing device 243 can be selected from one of the polarization scrambler, polarization diversity receiving system, polarization state feedback control system, and depolarizer according to actual usage requirements.

[0049] In some embodiments, the second frequency shift modulation unit 240 further includes a third optical amplifier 244, which is connected in series in the optical path between the second end of the second optoelectronic modulator 241 and the second polarization processing device 243.

[0050] Optionally, in some implementations, reference continues to be made to... Figure 3 The first pulse modulation unit 130 includes a first pulse generation module 131 and a first pulse driver 132. The first end of the first pulse generation module 131 is connected to the first output end of the first coupler 120, the second end of the first pulse generation module 131 is connected to the first end of the first circulator 150, and the electrical drive signal output end of the first pulse driver 132 is electrically connected to the electrical drive signal input end of the first pulse generation module 131. In some embodiments, the first pulse modulation unit 130 further includes a first optical amplifier 133, which is connected in series between the second end of the first pulse generation module 131 and the first end of the first circulator 150. In some embodiments, the first pulse generation module 131 includes one of a semiconductor optical amplifier, an electro-optic modulator, and an acousto-optic modulator; wherein, when the first pulse generation module 131 is a first acousto-optic modulator, it modulates the input continuous laser into the required time-domain pulse light based on the acousto-optic effect to drive the first pulse generation module 131 to complete efficient and stable pulse modulation.

[0051] In some embodiments, the second pulse modulation unit 230 includes a second pulse generation module 231 and a second pulse driver 232. The first end of the second pulse generation module 231 is connected to the second output end of the second coupler 220, the second end of the second pulse generation module 231 is connected to the first end of the second circulator 250, and the electrical drive signal output end of the second pulse driver 232 is electrically connected to the electrical drive signal input end of the second pulse generation module 231.

[0052] In some embodiments, the second pulse modulation unit 230 further includes a fourth optical amplifier 233, which is connected in series between the second terminal of the second pulse generation module 231 and the first terminal of the second circulator 250.

[0053] In some embodiments, the second pulse generation module 231 includes one of a semiconductor optical amplifier, an electro-optic modulator, and an acousto-optic modulator. When the second pulse generation module 231 is a second acousto-optic modulator, it modulates the input continuous light into the desired time-domain pulse light based on the acousto-optic effect, thereby driving the second pulse generation module 231 to complete highly efficient and stable pulse modulation.

[0054] Understandably, optical amplifiers can be flexibly configured according to optical power requirements, and can be omitted if the energy of continuous pulsed light meets the requirements.

[0055] For example, continue to refer to Figure 3 In the main Brillouin optical time-domain analysis module 100, the light emitted by the main laser 110 is injected into the first coupler 120 after passing through the isolator 170, and is split into two transmission paths: one path of light split from the first coupler 120 enters the first pulse generation module 131 (first acousto-optic modulator), and is driven by the first pulse driver 132 to generate pulse light. After being amplified by the first optical amplifier 133, it is injected into the first fiber under test A through the first circulator 150. The pulse light and the light emitted from the Brillouin optical time-domain analysis module 200 undergo stimulated Brillouin scattering (SBS) in the first fiber under test A. The scattered light enters the first filter unit 161 through the first circulator 150. The first filter unit 161 can be a fiber Bragg grating. The -1st order sideband (loss-type BOTDA) is filtered out by the fiber Bragg grating. After being converted into an electrical signal by the first photodetector 162, it is sent to the first data acquisition processor 163 for analysis. Another beam of light split off from the first coupler 120 enters the first electro-optic modulator 141, where it is driven by the first microwave signal source 142 to achieve sideband modulation. After being amplified by the second optical amplifier 144, it is injected into the second fiber under test B through the first polarization processing device 143 and undergoes the SBS effect with the light emitted from the Brillouin optical time domain analysis module 200 in the second fiber under test B.

[0056] The optical signal transmitted through the second fiber under test B passes through the second circulator 250 and enters the third coupler 280, where it splits into two branches: one branch from the third coupler 280 has its polarization state adjusted by the polarization controller 290 to match its polarization characteristics with those of the laser 210, and then enters the laser 210. The light output from the laser 210 passes through the third circulator 270 and is injected into the second coupler 220, where it splits into two paths: one branch from the second coupler 220 enters the second optoelectronic modulator 241, where it is driven by the second microwave signal source 242 to complete sideband modulation, and then passes through the third optical amplifier. After being amplified by the amplifier 244, the light is injected into the first fiber under test A, where it undergoes the SBS effect with the pulsed light from the first pulse generation module 131 (first acousto-optic modulator) of the main Brillouin optical time-domain analysis module 100. Another path, split off by the second coupler 220, enters the second pulse generation module 231, where a driving signal is provided by the second pulse driver 232 to generate pulsed light. After being amplified by the fourth optical amplifier 233, the light is injected into the second fiber under test B through the second circulator 250, where it undergoes the SBS effect with the sideband modulated light generated by the first electro-optic modulator 141 of the main Brillouin optical time-domain analysis module 100. Another optical signal, split off by the third coupler 280, enters the second filtering unit 261. The second filtering unit 261 can be a fiber Bragg grating, which filters out the -1st order sideband (loss-type BOTDA). After being converted into an electrical signal by the second photodetector 262, it is sent to the second data acquisition processor 263 for analysis.

[0057] Optionally, both the first pulse modulation unit 130 and the second pulse modulation unit 230 may be implemented using any of the following combinations: a pulse driver and a semiconductor optical amplifier, or a pulse driver and an electro-optic modulator.

[0058] It should be noted that the pulse driver is used to generate electrical pulse signals with precise timing, specific pulse width, and high power. When configured as a "pulse driver and semiconductor optical amplifier," the semiconductor optical amplifier, driven by the electrical pulse, directly performs high-speed switching and amplification of the injected continuous laser, generating the required high extinction ratio and high peak power optical pulses. When configured as a "pulse driver and electro-optic modulator," the electro-optic modulator, based on the electrical pulse, rapidly modulates the intensity of the continuous laser through the electro-optic effect, thereby generating optical pulses that meet the system requirements. These optional solutions provide a flexible and reliable technical path for the system to generate pump and probe pulses.

[0059] Furthermore, the Brillouin optical time-domain analysis system provided in this embodiment mainly includes a main Brillouin optical time-domain analysis module 100 and a slave Brillouin optical time-domain analysis module 200, which can achieve parameter adjustment, acquisition synchronization, and data transmission through communication optical fibers. The lengths of the first fiber under test A and the second fiber under test B can be equal or unequal. Alternatively, parameter adjustment, acquisition synchronization, and data transmission can also be achieved through wireless communication.

[0060] Furthermore, Figure 4 This is a schematic diagram of the communication method of a Brillouin optical time-domain analysis system provided by an embodiment of this utility model. Based on the above embodiment, refer to... Figure 4 The Brillouin optical time-domain analysis system also includes a communication optical fiber C; the main Brillouin optical time-domain analysis module 100 also includes a main module control unit 311 and a main-end optical transceiver 312; the slave Brillouin optical time-domain analysis module 200 also includes a slave module control unit 321 and a slave-end optical transceiver 322; the main-end optical transceiver 312, the main laser 110, the first signal acquisition and processing unit 160, the first pulse modulation unit 130, and the first frequency shift modulation unit 140 are electrically connected to the main module control unit 311; the slave-end optical transceiver 322, the slave laser 210, the second signal acquisition and processing unit 260, the second pulse modulation unit 230, and the second frequency shift modulation unit 240 are electrically connected to the slave module control unit 321; the main-end optical transceiver 312 and the slave-end optical transceiver 322 are connected via the communication optical fiber C.

[0061] It should be noted that the master and slave Brillouin optical time domain analysis modules achieve wired communication through parallel independent communication optical fibers C. The control commands generated by the master module control unit 311 are transmitted to the master fiber optic transceiver 312. The master fiber optic transceiver 312 converts the electrical signal into a laser signal of a specific wavelength and transmits it through the communication optical fiber. After receiving the optical signal, the slave fiber optic transceiver 322 restores it to an electrical signal, which is then parsed and adjusted by the slave module control unit 321. At the same time, the status feedback signal generated by the slave module control unit 321 is transmitted back to the master module control unit 311 along the same path. Thus, the coordination between the fiber optic transceiver and the control unit ensures the synchronization of the master and slave devices and avoids interference between communication and measurement signals. The unique advantages of this method lie in the physical isolation of communication and measurement signals, stable transmission, and strong scalability: On the one hand, the independent communication fiber does not occupy the fiber resources under test, and can completely avoid mutual interference between communication signals and probe light, pump light, and backscattered signals, making it particularly suitable for long-distance fiber optic testing scenarios with high measurement accuracy requirements; on the other hand, wired transmission is resistant to electromagnetic interference and has strong environmental immunity (such as adapting to complex outdoor environments such as overhead power lines and oil and gas pipelines), and wavelength division multiplexing modules can be superimposed as needed to realize the parallel transmission of multiple control commands and status feedback signals without worrying about signal congestion, ensuring the stability of master-slave module collaboration.

[0062] Figure 5 This is a schematic diagram of the communication method of another Brillouin optical time-domain analysis system provided by an embodiment of this utility model. In some embodiments, reference is made to... Figure 5 The main Brillouin optical time domain analysis module 100 also includes a main module controller 411 and a main remote communication module 412; the slave Brillouin optical time domain analysis module 200 also includes a slave module controller 421 and a slave remote communication module 422; the main remote communication module 412, the main laser 110, the first signal acquisition and processing unit 160, the first pulse modulation unit 130, and the first frequency shift modulation unit 140 are electrically connected to the main module controller 411; the slave remote communication module 422, the slave laser 210, the second signal acquisition and processing unit 260, the second pulse modulation unit 230, and the second frequency shift modulation unit 240 are electrically connected to the slave module controller 421; the main remote communication module 412 and the slave remote communication module 422 establish a communication connection wirelessly.

[0063] It should be noted that the master and slave Brillouin optical time-domain analysis modules are each equipped with a remote communication module, establishing a communication connection wirelessly. The remote communication module must directly interact with the master / slave device controller of its respective module. The pump light and probe light coordinated control commands, measurement synchronization signals, and other electrical signals generated by the master module controller 411 are transmitted to the master remote communication module 412, where they are converted into wireless signals (such as industrial-grade GPRS signals) and sent. The slave remote communication module 422 receives these wireless signals, converts them back into electrical signals, and feeds them back to the slave module controller 421. The slave module controller 421 analyzes the signals and adjusts the states of components such as the pump light source, while simultaneously generating a device operating status feedback signal, which is wirelessly transmitted back to the master remote communication module 412 via the slave remote communication module 422. No additional optical fiber is required throughout the process. Through the collaboration between the remote communication module and the control unit, stable interaction of commands and feedback between the master and slave devices is achieved, ensuring collaborative long-distance fiber optic measurements. The unique advantages of this approach are its flexible deployment and high resource utilization: if wireless communication (such as GPRS) is used, there is no need to lay additional communication optical fibers, which can significantly reduce the deployment cost and difficulty in complex terrains (such as mountainous areas and cross-river areas), and is especially suitable for scenarios with good wireless signal coverage; at the same time, the remote communication module has a high degree of integration and can be directly linked with the control unit of the master-slave analysis module without the need to build an additional complex signal conversion structure, resulting in a lower overall size and complexity of the device.

[0064] In the preferred embodiment of this invention, the Brillouin optical time-domain analysis system constructs a through-beam architecture of a main Brillouin optical time-domain analysis module 100 and a slave Brillouin optical time-domain analysis module 200 via a first fiber under test (A) and a second fiber under test (B). By performing continuous pulsed light bidirectionally through the first fiber under test (A) and the second fiber under test (B), a basic structure for long-distance measurement is established. While ensuring sensing accuracy and spatial resolution, the sensing distance can reach four times that of a traditional single BOTDA. Furthermore, it physically avoids the dependence on complex amplification or encoding techniques for single-device end-to-end measurement, solving the nonlinearity, noise, and efficiency problems of Raman amplification, as well as the poor real-time performance and algorithm complexity of optical pulse encoding. Moreover, its measurement efficiency is higher than that of encoding schemes, ultimately achieving a balance between long-distance, high-precision, and high-stability measurement. In addition, the continuous light emitted by the main laser 110 enters the third coupler 280 through the second fiber under test B and the second circulator 250. By setting the third coupler 280, the light can be split into one path and injected into the slave laser 210. Furthermore, by introducing injection locking technology, the output light wavelengths of the main Brillouin optical time domain analysis module 100 and the slave Brillouin optical time domain analysis module 200 can be controlled, which helps to ensure that the wavelengths of the two are consistent.

[0065] The specific embodiments described above do not constitute a limitation on the scope of protection of this utility model. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this utility model should be included within the scope of protection of this utility model.

Claims

1. A Brillouin optical time-domain analysis system, characterized in that, include: The main Brillouin optical time-domain analysis module, the slave Brillouin optical time-domain analysis module, the first optical fiber under test, and the second optical fiber under test; The main Brillouin optical time-domain analysis module includes a main laser, a first coupler, a first pulse modulation unit, a first frequency shift modulation unit, a first circulator, and a first signal acquisition and processing unit; the slave Brillouin optical time-domain analysis module includes a slave laser, a second coupler, a second pulse modulation unit, a second frequency shift modulation unit, a second circulator, and a second signal acquisition and processing unit. The output end of the main laser is connected to the input end of the first coupler; The first output terminal of the first coupler is connected to the first terminal of the first pulse modulation unit, the second terminal of the first pulse modulation unit is connected to the first terminal of the first circulator, the second terminal of the first circulator is connected to the first terminal of the first optical fiber under test, and the third terminal of the first circulator is connected to the first signal acquisition and processing unit; the second output terminal of the first coupler is connected to the first terminal of the first frequency shift modulation unit, the second terminal of the first frequency shift modulation unit is connected to the first terminal of the second optical fiber under test, and the second terminal of the second optical fiber under test is connected to the second terminal of the second circulator. The input terminal of the second coupler is connected to the output terminal of the laser; the first output terminal of the second coupler is connected to the first terminal of the second frequency shift modulation unit; the second terminal of the second frequency shift modulation unit is connected to the second terminal of the first optical fiber under test; the second output terminal of the second coupler is connected to the first terminal of the second pulse modulation unit; the second terminal of the second pulse modulation unit is connected to the first terminal of the second circulator; and the third terminal of the second circulator is connected to the second signal acquisition and processing unit.

2. The Brillouin optical time-domain analysis system according to claim 1, characterized in that, The Brillouin optical time-domain analysis module also includes a third coupler and a third circulator; The third end of the second circulator is connected to the input end of the third coupler, the first output end of the third coupler is connected to the first end of the third circulator, the second end of the third circulator is connected to the output end of the laser, the third end of the third circulator is connected to the input end of the second coupler, and the second output end of the third coupler is connected to the second signal acquisition and processing unit.

3. The Brillouin optical time-domain analysis system according to claim 2, characterized in that, The first signal acquisition and processing unit includes a first filtering unit, a first photodetector, and a first data acquisition processor. The third end of the first circulator is connected to the first end of the first filtering unit, the second end of the first filtering unit is connected to the first end of the first photodetector, and the electrical signal output end of the first photodetector is electrically connected to the first data acquisition processor. The second signal acquisition and processing unit includes a second filtering unit, a second photodetector, and a second data acquisition processor. The second output terminal of the third coupler is connected to the first terminal of the second filtering unit, the second terminal of the second filtering unit is connected to the first terminal of the second photodetector, and the electrical signal output terminal of the second photodetector is electrically connected to the second data acquisition processor.

4. The Brillouin optical time-domain analysis system according to claim 3, characterized in that, The first filtering unit includes one of a fiber Bragg grating and a Fabry-Perot filter, and / or the second filtering unit includes one of a fiber Bragg grating and a Fabry-Perot filter.

5. The Brillouin optical time-domain analysis system according to claim 2, characterized in that, An isolator is also connected in series between the main laser and the first coupler; And / or, a polarization controller or analyzer is connected in series between the first output terminal of the third coupler and the first terminal of the third circulator.

6. The Brillouin optical time-domain analysis system according to claim 1, characterized in that, The first frequency shift modulation unit includes a first electro-optic modulator and a first microwave signal source. The first end of the first electro-optic modulator is connected to the second output end of the first coupler, the second end of the first electro-optic modulator is connected to the first end of the second optical fiber under test, and the radio frequency signal output end of the first microwave signal source is electrically connected to the radio frequency signal input end of the first electro-optic modulator.

7. The Brillouin optical time-domain analysis system according to claim 6, characterized in that, The first frequency shift modulation unit further includes a first polarization processing device, which is connected in series between the second end of the first electro-optic modulator and the first end of the second optical fiber under test.

8. The Brillouin optical time-domain analysis system according to claim 7, characterized in that, The first polarization processing device includes one of a polarization scrambler, a polarization diversity receiving system, a polarization state feedback control system, and a polarization depolarizer.

9. The Brillouin optical time-domain analysis system according to claim 7, characterized in that, The first frequency shift modulation unit further includes a second optical amplifier, which is connected in series in the optical path between the second end of the first electro-optic modulator and the first polarization processing device.

10. The Brillouin optical time-domain analysis system according to claim 1, characterized in that, The second frequency shift modulation unit includes a second optoelectronic modulator and a second microwave signal source. The first end of the second optoelectronic modulator is connected to the first output end of the second coupler, the second end of the second optoelectronic modulator is connected to the second end of the first optical fiber under test, and the radio frequency output end of the second microwave signal source is electrically connected to the radio frequency input end of the second optoelectronic modulator.

11. The Brillouin optical time-domain analysis system according to claim 10, characterized in that, The second frequency shift modulation unit further includes a second polarization processing device, which is connected in series between the second end of the second optoelectronic modulator and the first optical fiber under test.

12. The Brillouin optical time-domain analysis system according to claim 11, characterized in that, The second polarization processing device includes one of a polarization scrambler, a polarization diversity receiving system, a polarization state feedback control system, and a depolarizer.

13. The Brillouin optical time-domain analysis system according to claim 11, characterized in that, The second frequency shift modulation unit further includes a third optical amplifier, which is connected in series in the optical path between the second end of the second photoelectric modulator and the second polarization processing device.

14. The Brillouin optical time-domain analysis system according to claim 1, characterized in that, The first pulse modulation unit includes a first pulse generation module and a first pulse driver. The first end of the first pulse generation module is connected to the first output end of the first coupler, the second end of the first pulse generation module is connected to the first end of the first circulator, and the electrical drive signal output end of the first pulse driver is electrically connected to the electrical drive signal input end of the first pulse generation module.

15. The Brillouin optical time-domain analysis system according to claim 14, characterized in that, The first pulse modulation unit further includes a first optical amplifier, which is connected in series between the second end of the first pulse generation module and the first end of the first circulator.

16. The Brillouin optical time-domain analysis system according to claim 14, characterized in that, The first pulse generation module includes one of a semiconductor optical amplifier, an electro-optic modulator, and an acousto-optic modulator.

17. The Brillouin optical time-domain analysis system according to claim 1, characterized in that, The second pulse modulation unit includes a second pulse generation module and a second pulse driver. The first end of the second pulse generation module is connected to the second output end of the second coupler, the second end of the second pulse generation module is connected to the first end of the second circulator, and the electrical drive signal output end of the second pulse driver is electrically connected to the electrical drive signal input end of the second pulse generation module.

18. The Brillouin optical time-domain analysis system according to claim 17, characterized in that, The second pulse modulation unit further includes a fourth optical amplifier, which is connected in series between the second end of the second pulse generation module and the first end of the second circulator.

19. The Brillouin optical time-domain analysis system according to claim 17, characterized in that, The second pulse generation module includes one of a semiconductor optical amplifier, an electro-optic modulator, and an acousto-optic modulator.

20. The Brillouin optical time-domain analysis system according to claim 1, characterized in that, The Brillouin optical time-domain analysis system also includes a communication optical fiber; the main Brillouin optical time-domain analysis module also includes a main module control unit and a main-end optical fiber transceiver; the slave Brillouin optical time-domain analysis module also includes a slave module control unit and a slave-end optical fiber transceiver. The main fiber optic transceiver, the main laser, the first signal acquisition and processing unit, the first pulse modulation unit, and the first frequency shift modulation unit are electrically connected to the main module control unit, respectively. The slave fiber optic transceiver, the slave laser, the second signal acquisition and processing unit, the second pulse modulation unit, and the second frequency shift modulation unit are respectively electrically connected to the slave module control unit; The master fiber optic transceiver and the slave fiber optic transceiver are connected via the communication fiber optic cable.

21. The Brillouin optical time-domain analysis system according to claim 1, characterized in that, The master Brillouin optical time domain analysis module further includes a master module controller and a master remote communication module; the slave Brillouin optical time domain analysis module further includes a slave module controller and a slave remote communication module. The main remote communication module, the main laser, the first signal acquisition and processing unit, the first pulse modulation unit, and the first frequency shift modulation unit are electrically connected to the main module controller, respectively. The remote communication module, the laser, the second signal acquisition and processing unit, the second pulse modulation unit, and the second frequency shift modulation unit are electrically connected to the slave module controller, respectively. The master remote communication module and the slave remote communication module establish a communication connection wirelessly.

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