Brillouin optical time domain analysis system and method

Abstract

The invention discloses a Brillouin optical time domain analysis system and method. The system comprises a master Brillouin optical time domain analysis module, a slave Brillouin optical time domain analysis module, a first to-be-tested optical fiber and a second to-be-tested optical fiber, the main Brillouin optical time domain analysis module comprises 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 comprises 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. According to the Brillouin optical time domain analysis system, the sensing distance can be further increased while the sensing precision and the spatial resolution are guaranteed by constructing a correlation architecture of the main Brillouin optical time domain analysis module and the slave Brillouin optical time domain analysis module.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of Brillouin optical time domain analysis, in particular to a Brillouin optical time domain analysis system and method. BACKGROUND

[0002] Distributed optical fiber sensing technology is widely used in the health monitoring of large infrastructure structures such as buildings, bridges, and tunnels due to its advantages such as resistance to electromagnetic interference, ability to achieve long-distance continuous monitoring, and cost adaptation to large-scale deployment. Among them, Brillouin optical time domain analysis technology (BOTDA) is a key solution for realizing long-distance distributed sensing, as it is the core technology in this field.

[0003] The core performance indicators of the Brillouin optical time domain analysis system include sensing distance, spatial resolution, and sensing accuracy, which together determine the actual application value of the system. Specifically, high spatial resolution can achieve precise positioning of structural abnormalities, and high signal-to-noise ratio is the core prerequisite for ensuring system sensing accuracy and extending effective sensing distance. However, in Brillouin optical fiber sensing technology, there is an inherent trade-off between sensing distance and spatial resolution - as the sensing distance is extended, the sensing signal inevitably attenuates during transmission in the optical fiber, resulting in a decrease in system signal-to-noise ratio, ultimately affecting sensing accuracy and effective monitoring range, which has become a key bottleneck restricting its application in ultra-long distance scenarios.

[0004] To address the above technical bottlenecks, various optimization schemes have been proposed in existing technologies, of which the two most widely used technologies are distributed Raman amplification technology and optical pulse coding technology. Among them, distributed Raman amplification technology can effectively compensate for signal attenuation to extend sensing distance and improve signal-to-noise ratio through stimulated Raman scattering effects in optical fibers, but it is limited by problems such as nonlinear effect interference, insufficient uniformity of along-the-way amplification, power and efficiency conflicts of the pumping system, and introduction of additional noise (such as spontaneous Raman scattering noise). Optical pulse coding technology can achieve a balance between "high energy transmission" and "high spatial resolution" through specific sequence modulation of pump light or probe light, using coded energy superposition and decoding recovery to improve sensing signal-to-noise ratio, optimize spatial resolution, and extend sensing distance, but 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 break through the above bottlenecks and further improve sensing distance while ensuring sensing accuracy and spatial resolution to adapt to a wider range of long-distance infrastructure monitoring scenarios. SUMMARY

[0006] The application provides a Brillouin optical time domain analysis system and method, which can further improve sensing distance while ensuring sensing accuracy and spatial resolution.

[0007] In a first aspect, the application provides a Brillouin optical time domain analysis system, comprising: a master Brillouin optical time domain analysis module, a slave Brillouin optical time domain analysis module, a first to-be-measured optical fiber, and a second to-be-measured optical fiber.

[0008] The master Brillouin optical time domain analysis module comprises: 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; and the slave Brillouin optical time domain analysis module comprises: 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.

[0009] The output end of the master laser is connected with the input end of the first coupler.

[0010] The first output end of the first coupler is connected with the first end of the first pulse modulation unit, the second end of the first pulse modulation unit is connected with the first end of the first circulator, the second end of the first circulator is connected with the first end of the first to-be-measured optical fiber, the third end of the first circulator is connected with the first signal acquisition and processing unit, the second output end of the first coupler is connected with the first end of the first frequency shift modulation unit, the second end of the first frequency shift modulation unit is connected with the first end of the second to-be-measured optical fiber, and the second end of the second to-be-measured optical fiber is connected with the second end of the second circulator.

[0011] The input end of the second coupler is connected with the output end of the slave laser, the first output end of the second coupler is connected with the first end of the second frequency shift modulation unit, the second end of the second frequency shift modulation unit is connected with the second end of the first to-be-measured optical fiber, the second output end of the second coupler is connected with the first end of the second pulse modulation unit, the second end of the second pulse modulation unit is connected with the first end of the second circulator, and the third end of the second circulator is connected with the second signal acquisition and processing unit.

[0012] Optionally, the slave Brillouin optical time domain analysis module further comprises a third coupler and a third circulator.

[0013] The third end of the second circulator is connected with the input end of the third coupler, the first output end of the third coupler is connected with the first end of the third circulator, the second end of the third circulator is connected with the output end of the slave laser, the third end of the third circulator is connected with the input end of the second coupler, and the second output end of the third coupler is connected with the second signal acquisition and processing unit.

[0014] Optionally, the first signal acquisition and processing unit comprises a first filter unit, a first photoelectric detector and a first data acquisition processor, the third end of the first circulator is connected with the first end of the first filter unit, the second end of the first filter unit is connected with the first end of the first photoelectric detector, and the electrical signal output end of the first photoelectric detector is electrically connected with the first data acquisition processor.

[0015] The second signal acquisition and processing unit comprises a second filter unit, a second photoelectric detector and a second data acquisition processor, the second output end of the third coupler is connected with the first end of the second filter unit, the second end of the second filter unit is connected with the first end of the second photoelectric detector, and the electrical signal output end of the second photoelectric detector is electrically connected with the second data acquisition processor.

[0016] Preferably, the first filter unit comprises one of a fiber Bragg grating and a Fabry-Perot filter, and / or the second filter unit comprises one of a fiber Bragg grating and a Fabry-Perot filter.

[0017] Optionally, an isolator is further connected in series between the master laser and the first coupler; and / or,

[0018] A polarization controller or a polarization analyzer is connected in series between the first output end of the third coupler and the first end of the third circulator.

[0019] Optionally, the first frequency shift modulation unit comprises a first electro-optical modulator and a first microwave signal source, the first end of the first electro-optical modulator is connected with the second output end of the first coupler, the second end of the first electro-optical modulator is connected with the first end of the second to-be-measured optical fiber, and the radio frequency signal output end of the first microwave signal source is electrically connected with the radio frequency signal input end of the first electro-optical modulator.

[0020] Preferably, the first frequency shift modulation unit further comprises a first polarization processing device, which is connected in series between the second end of the first electro-optical modulator and the first end of the second to-be-measured optical fiber.

[0021] Preferably, the first polarization processing device comprises one of a depolarizer, a polarization diversity receiving system, a polarization state feedback control system and a depolarizer.

[0022] Preferably, the first frequency shift modulation unit further comprises a second optical amplifier, which is connected in series in the optical path between the second end of the first electro-optical modulator and the first polarization processing device.

[0023] Optionally, the second frequency shift modulation unit comprises a second electro-optical modulator and a second microwave signal source;

[0024] The first end of the second electro-optical modulator is connected with the first output end of the second coupler, the second end of the second electro-optical modulator is connected with the second end of the first to-be-measured optical fiber, and the radio frequency output end of the second microwave signal source is electrically connected with the radio frequency input end of the second electro-optical modulator;

[0025] Preferably, the second frequency shift modulation unit further comprises a second polarization processing device, which is connected in series in the optical path between the second end of the second electro-optical modulator and the first to-be-measured optical fiber;

[0026] Preferably, the second polarization processing device comprises one of a depolarizer, a polarization diversity receiving system, a polarization state feedback control system, and a depolarizer.

[0027] Preferably, the second frequency shift modulation unit further comprises a third optical amplifier, which is connected in series in the optical path between the second end of the second electro-optical modulator and the second polarization processing device.

[0028] Optionally, the first pulse modulation unit comprises a first pulse generation module and a first pulse driver, the first end of the first pulse generation module is connected with the first output end of the first coupler, the second end of the first pulse generation module is connected with the first end of the first circulator, and the electric driving signal output end of the first pulse driver is electrically connected with the electric driving signal input end of the first pulse generation module; Preferably, the first pulse modulation unit further comprises 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 comprises one of a semiconductor optical amplifier, an electro-optical modulator, and an acousto-optic modulator.

[0029] and / or,

[0030] The second pulse modulation unit comprises a second pulse generation module and a second pulse driver, a first end of the second pulse generation module is connected with a second output end of the second coupler, a second end of the second pulse generation module is connected with a first end of the second circulator, and an electrical driving signal output end of the second pulse driver is electrically connected with an electrical driving signal input end of the second pulse generation module; preferably, the second pulse modulation unit further comprises 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 comprises one of a semiconductor optical amplifier, an electro-optical modulator and an acousto-optical modulator.

[0031] Optionally, the Brillouin optical time domain analysis system further comprises a communication optical fiber, the master Brillouin optical time domain analysis module further comprises a master module control unit and a master end optical fiber transceiver, and the slave Brillouin optical time domain analysis module further comprises a slave module control unit and a slave end optical fiber transceiver; the master end optical fiber transceiver, the master laser, the first signal acquisition and processing unit, the first pulse modulation unit and the first frequency shift modulation unit are electrically connected with the master module control unit respectively, the slave end optical fiber transceiver, the slave laser, the second signal acquisition and processing unit, the second pulse modulation unit and the second frequency shift modulation unit are electrically connected with the slave module control unit respectively, and the master end optical fiber transceiver and the slave end optical fiber transceiver are communicatively connected through the communication optical fiber.

[0032] Or,

[0033] The master Brillouin optical time domain analysis module further comprises a master module controller and a master remote communication module, and the slave Brillouin optical time domain analysis module further comprises a slave module controller and a slave remote communication module; the master remote communication module, the master laser, the first signal acquisition and processing unit, the first pulse modulation unit and the first frequency shift modulation unit are electrically connected with the master module controller respectively, the slave remote communication module, the slave laser, the second signal acquisition and processing unit, the second pulse modulation unit and the second frequency shift modulation unit are electrically connected with the slave module controller respectively, and the master remote communication module and the slave remote communication module are communicatively connected through a wireless mode.

[0034] In a second aspect, the embodiments of the present application provide a Brillouin optical time domain analysis method, which is implemented by using the Brillouin optical time domain analysis system in the first aspect, and the Brillouin optical time domain analysis method comprises the following steps.

[0035] Acquiring data collected by the master Brillouin optical time domain analysis module and the slave Brillouin optical time domain analysis module;

[0036] Processing the acquired data of the master Brillouin optical time domain analysis module and the slave Brillouin optical time domain analysis module to determine temperature strain distribution of the first half of the first to-be-measured optical fiber and the second half of the second to-be-measured optical fiber.

[0037] Optionally, before acquiring the data collected by the master Brillouin optical time domain analysis module and the slave Brillouin optical time domain analysis module, the method further comprises starting the master Brillouin optical time domain analysis module and the slave Brillouin optical time domain analysis module; when it is detected that the master Brillouin optical time domain analysis module and the slave Brillouin optical time domain analysis module establish communication, initializing and configuring the master Brillouin optical time domain analysis module; preferably, after the initializing and configuring of the master Brillouin optical time domain analysis module, the method further comprises parameter debugging and injection locking of the slave laser; optimizing parameters of the master Brillouin optical time domain analysis module and parameter debugging of the slave Brillouin optical time domain analysis module.

[0038] and / or,

[0039] After processing the acquired data of the master Brillouin optical time domain analysis module and the slave Brillouin optical time domain analysis module to determine temperature strain distribution of the first half of the first to-be-measured optical fiber and the second half of the second to-be-measured optical fiber, the method further comprises splicing data of the full optical fiber link to determine a distributed measurement result of the full optical fiber link.

[0040] Advantages of the present application:

[0041] The Brillouin optical time domain analysis system provided by the embodiment of the present application constructs a pair of the master Brillouin optical time domain analysis module and the slave Brillouin optical time domain analysis module through the first to-be-measured optical fiber and the second to-be-measured optical fiber, and builds a basic structure for long-distance measurement by bidirectional pair of continuous pulse light in the first to-be-measured optical fiber and the second to-be-measured optical fiber, which guarantees the sensing accuracy and spatial resolution while the sensing distance can reach four times of the sensing distance of the traditional single BOTDA.

[0042] It should be understood that the content described in this part is not intended to identify key or important features of the embodiments of the present application, nor to limit the scope of the present application. Other features of the present application will become apparent from the following description. BRIEF DESCRIPTION OF DRAWINGS

[0043] In order to make the technical solutions in the embodiments of the present application clearer, the drawings needed in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort based on these drawings.

[0044] Figure 1 is a structural schematic diagram of a Brillouin optical time domain analysis system in the prior art;

[0045] Figure 2 is a structural schematic diagram of a Brillouin optical time domain analysis system provided by the embodiments of the present application;

[0046] Figure 3 is a structural schematic diagram of another Brillouin optical time domain analysis system provided by the embodiments of the present application;

[0047] Figure 4 is a communication mode schematic diagram of a Brillouin optical time domain analysis system provided by the embodiments of the present application;

[0048] Figure 5 is a communication mode schematic diagram of another Brillouin optical time domain analysis system provided by the embodiments of the present application;

[0049] Figure 6 is a flow chart of a Brillouin optical time domain analysis method provided by the embodiments of the present application;

[0050] Figure 7 is a flow chart of another Brillouin optical time domain analysis method provided by the embodiments of the present application.

[0051] Reference numerals:

[0052] A first to-be-measured optical fiber; B, a second to-be-measured optical fiber;

[0053] 100, a main Brillouin optical time domain analysis module; 110, a main laser; 120, a first coupler; 130, a first pulse modulation unit; 131, a first pulse generation module; 132, a first pulse driver; 140, a first frequency shift modulation unit; 141, a first electro-optic modulator; 142, a first microwave signal source; 143, a first polarization processing device; 144, a second optical amplifier; 150, a first circulator; 160, a first signal acquisition and processing unit; 161, a first filter unit; 162, a first photoelectric detector; 163, a first data acquisition processor; 170, an isolator;

[0054] 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 electro-optical modulator; 242, second microwave signal source; 243, second polarization processing device; 244, third optical amplifier; 250, second circulator; 260, second signal acquisition processing unit; 261, second filter unit; 262, second photoelectric detector; 263, second data acquisition processor; 270, third circulator; 280, third coupler; 290, polarization controller;

[0055] C, communication optical fiber;

[0056] 311, master module control unit; 312, master end fiber transceiver; 321, slave module control unit; 322, slave end fiber transceiver;

[0057] 411, master module controller; 412, master remote communication module; 421, slave module controller; 422, slave remote communication module. DETAILED DESCRIPTION

[0058] In order to make the personnel in the technical field better understand the present application scheme, the technical scheme in the embodiments of the present application will be described clearly and completely in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by the person skilled in the art without creative labor should belong to the scope of protection of the present application.

[0059] It should be noted that the terms "first", "second" and the like in the specification and claims of the present application and the above-described drawings are used to distinguish similar objects, and do not necessarily indicate a specific order or a chronological sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the present application described herein can be implemented in an order other than that illustrated or described herein. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device including a series of steps or units does not have to be limited to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0060] Figure 1 is a structural schematic diagram of a Brillouin optical time domain analysis system of the prior art, referring to Figure 1The prior art 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 end of the main laser 110 is connected with the input end of the first coupler 120, the first output end of the first coupler 120 is connected with the first end of the first pulse modulation unit 130, the second end of the first pulse modulation unit 130 is connected with the first end of the first circulator 150, the second end of the first circulator 150 is connected with the first end of the first to-be-measured optical fiber A, and the third end of the first circulator 150 is connected with the first signal acquisition and processing unit 160.

[0061] If the length of the first to-be-measured optical fiber A in the prior art is 2L, the sensing distance of the prior art Brillouin optical time domain analysis system is L. In order to further improve the sensing distance while ensuring the sensing accuracy and spatial resolution to adapt to a wider long-distance infrastructure monitoring scene, the Brillouin optical time domain analysis system and method provided by the embodiment of the present application can improve the effective sensing distance to four times the sensing distance of the traditional single BOTDA, that is, 4L, under the premise of ensuring the sensing accuracy and spatial resolution. Specifically as follows:

[0062] Figure 2 is a structural schematic diagram of a Brillouin optical time domain analysis system provided by the embodiment of the present application, referring 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 to-be-measured optical fiber A, and a second to-be-measured optical fiber 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.

[0063] Continuing to refer to Figure 2The 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.

[0064] 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.

[0065] 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.

[0066] 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. The signal is then acquired and processed to finally 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.

[0067] 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 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, 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) can be obtained. 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.

[0068] In summary, the embodiments of the present invention 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 using 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.

[0069] Furthermore, based on the Brillouin optical time-domain analysis system, a "segmented precision measurement" logic can be established. The main Brillouin optical time-domain analysis module can be responsible for measuring only the first half of the effective area of ​​the entire optical fiber link (from the first end of the first fiber under test as the measurement start point to the midpoint of the first fiber under test as the measurement end point), and the secondary Brillouin optical time-domain analysis module can be responsible for measuring only the second half of the effective area of ​​the entire optical fiber link (from the second end of the second fiber under test as the measurement start point to the midpoint of the second fiber under test as the measurement end point). This eliminates the need for a single device to cover the entire link, thus overcoming distance limitations from both hardware and measurement logic perspectives. Moreover, based on the Brillouin optical time-domain analysis system and the "segmented measurement" logic, the main and secondary Brillouin optical time-domain analysis modules each focus on the temperature and strain measurements of their respective half of the link (the first and second half of the effective area), eliminating the need to address the signal attenuation accumulation problem during the entire link transmission. This allows for a measurement distance of up to four times that of a traditional single BOTDA while maintaining sensing accuracy and spatial resolution. Interpretive, ensuring sensing accuracy means ensuring the signal-to-noise ratio is not reduced.

[0070] Furthermore, Figure 3 This is a schematic diagram of another Brillouin optical time-domain analysis system provided by an embodiment of the present invention. Based on the above embodiments, 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.

[0071] Understandably, the optical signal received from the main laser 110 and transmitted through the second fiber under test B is received from the laser 210. This optical signal passes through the second circulator 250 and enters the third coupler 280, where it is split into two branches: one branch from the third coupler 280 enters the laser 210 for injection locking, matching the wavelength and Brillouin frequency shift of the light emitted from the laser 210 with those of the main laser 110, and locking and amplifying the fundamental frequency of the sideband modulated continuous light; the amplified light is then sent 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-shifting 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, which is then acquired and processed to obtain the temperature strain distribution of the first half of the first fiber under test A (i.e., the effective region of the first half of the entire fiber link, i.e., the first half of the first fiber under test A, from the first end of the first fiber under test as the measurement start point to the midpoint of the first fiber under test A as the measurement end point). In some embodiments, it is possible to obtain the data corresponding to the temperature strain distribution of the entire first fiber under test A, but it is possible to select only the data corresponding to the temperature strain distribution of the first half of the first fiber under test A. 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 off by the third coupler 280, passes through the second signal acquisition and processing unit 260. After the second signal acquisition and processing unit 260 filters out the sideband-modulated signal and converts it into an electrical signal, it is acquired and processed. This signal can then be used to obtain the temperature strain distribution of the latter half of the second fiber under test (i.e., the effective region of the latter half of the entire fiber link, i.e., the latter half of the second fiber under test, from the second end of the second fiber under test as the measurement start point to the midpoint of the second fiber under test 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 latter half of the second fiber under test (B) can be selected.

[0072] In some embodiments of the present invention, the 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. The third coupler 280 splits the light into one path and injects it into the slave laser 210. 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 precisely controlled, which helps to ensure that the wavelengths of the two are consistent. It does not require a highly complex wavelength calibration module, which helps to reduce system energy consumption and heat dissipation requirements, and provides a basic guarantee for the accuracy of segmented measurement.

[0073] 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. 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.

[0074] 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.

[0075] 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.

[0076] In some embodiments, the first filtering unit 161 includes one of a fiber Bragg grating and a Fabry-Perot filter.

[0077] In some embodiments, the second filtering unit 261 includes one of a fiber Bragg grating and a Fabry-Perot filter.

[0078] 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.

[0079] Optionally, in some implementations, 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.

[0080] 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.

[0081] Optionally, in some implementations, reference continues to be made to... Figure 3 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.

[0082] Optionally, 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.

[0083] Optionally, 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. Furthermore, 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 issue, the first polarization processing device 143 can be selected from the polarization scrambler, polarization diversity receiving system, polarization state feedback control system, and depolarizer according to specific system requirements: 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.

[0084] Optionally, 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.

[0085] Optionally, in some implementations, reference continues to be made to... Figure 3 The 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).

[0086] 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.

[0087] 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.

[0088] 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.

[0089] In some implementations, reference continues. 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.

[0090] 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.

[0091] 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.

[0092] 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.

[0093] 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.

[0094] 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.

[0095] 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.

[0096] 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. Finally, it can be used to obtain the temperature strain distribution results of the first half of the first fiber under test A. 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.

[0097] The optical signal transmitted through the second fiber under test B enters the third coupler 280 via the second circulator 250 and is then split into two branches: one branch from the third coupler 280 is polarized by the polarization controller 290 to match the polarization characteristics of the light with those of the slave laser 210, and then enters the slave laser 210 to achieve injection lock (ensuring that the wavelength and Brillouin frequency shift of the slave laser 210 match those of the master laser 110, and locking and amplifying the fundamental frequency of the sideband modulated continuous light); the amplified light from the slave laser 210 is injected into the second coupler 220 via the third circulator 270, and then splits into two paths: one branch from the second coupler 220 enters the second optoelectronic modulator 241, and is then... The second microwave signal source 242 provides a driving signal to complete sideband modulation. After being amplified by the third optical amplifier 244, it is injected into the first fiber under test A, where it undergoes the SBS effect with the pulse 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 the second pulse driver 232 provides a driving signal to generate pulse light. After being amplified by the fourth optical amplifier 233, it 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, and can ultimately be used to obtain the temperature strain distribution results of the second half of the second fiber under test B. The optical path coordination and signal processing of the master Brillouin optical time domain analysis module 100 and the slave Brillouin optical time domain analysis module 200 provided by the embodiments of the present invention can be used to realize distributed measurement of the first half of the first fiber under test A and the second half of the second fiber under test B.

[0098] Furthermore, in some implementations, based on the distributed measurement data of the first half of the first fiber under test A and the second half of the second fiber under test B, the complete temperature strain distribution of the all-fiber link between the master and slave devices can be obtained after data splicing, which meets the requirements of high-precision monitoring of long-distance fiber optic links.

[0099] 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.

[0100] 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.

[0101] Furthermore, some embodiments of the present invention provide a Brillouin optical time-domain analysis system, which mainly includes a main Brillouin optical time-domain analysis module 100 and a slave Brillouin optical time-domain analysis module 200. The two modules can achieve parameter adjustment, acquisition synchronization, and data transmission via optical fiber, or they can use wireless communication to achieve the same. The lengths of the first optical fiber under test A and the second optical fiber under test B can be equal or unequal.

[0102] Figure 4 This is a schematic diagram of the communication method of a Brillouin optical time-domain analysis system provided by an embodiment of the present invention. Optionally, 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.

[0103] It should be noted that the master and slave Brillouin optical time domain analysis modules transmit the control commands generated by the master module control unit 311 to the master fiber optic transceiver 312 through parallel independent communication optical fibers C. 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 C. The slave fiber optic transceiver 322 receives the optical signal and 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 synchronization of the master and slave devices is ensured through the coordination of fiber optic transceivers and control units, reducing 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 C does not occupy the fiber resources under test, which 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.

[0104] Figure 5 This is a schematic diagram of another communication method for a Brillouin optical time-domain analysis system provided in an embodiment of the present invention. (Reference) 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.

[0105] 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.

[0106] Figure 6 This is a flowchart of a Brillouin optical time-domain analysis method provided by an embodiment of the present invention, implemented using any of the Brillouin optical time-domain analysis systems provided in the above embodiments, with reference to... Figure 6 The Brillouin optical time-domain analysis method includes:

[0107] S610: Acquire data from the main Brillouin optical time domain analysis module and the data collected from the slave Brillouin optical time domain analysis module.

[0108] S620. Process the data acquired from the master Brillouin optical time-domain analysis module and the slave Brillouin optical time-domain analysis module to determine the temperature strain distribution of the first half of the first fiber under test and the second half of the second fiber under test.

[0109] Specifically, for step S620, it may be to obtain the temperature strain distribution corresponding to the entire length of the first fiber A and the entire length of the second fiber B, and then take the temperature strain distribution of the first half of the first fiber A and the second half of the second fiber B.

[0110] Furthermore, Figure 7 This is a flowchart of another Brillouin optical time-domain analysis method provided by an embodiment of the present invention, see reference. Figure 7 The method further includes steps S710-S720 before acquiring the data from the main Brillouin optical time-domain analysis module and the data acquired from the Brillouin optical time-domain analysis module:

[0111] S710, start the main Brillouin optical time domain analysis module and the slave Brillouin optical time domain analysis module.

[0112] S720: After detecting that the main Brillouin optical time domain analysis module and the slave Brillouin optical time domain analysis module have established communication, the main Brillouin optical time domain analysis module is initialized and configured.

[0113] It is understandable that the master Brillouin optical time domain analysis module 100 and the slave Brillouin optical time domain analysis module 200 can adopt... Figure 4 or Figure 5 Communication is established using the communication method described in the diagram. Establishing communication between the master Brillouin optical time domain analysis module 100 and the slave Brillouin optical time domain analysis module 200 has the following significance: 1. It ensures synchronization between the master and slave Brillouin optical time domain analysis modules 100 and 200; 2. It ensures data transmission between the master and slave modules 100; 3. Generally, the Brillouin optical time domain analysis system needs to be connected to a debugging computer to complete the debugging of both the master and slave modules. However, considering the practical limitations of scenarios such as maritime locations and inconvenient transportation, the operation procedure can be adjusted: first, at the deployment site of the slave Brillouin optical time domain analysis module 200, its local parameter configuration is completed. After arriving at the location of the master Brillouin optical time domain analysis module 100, the final debugging of both modules is completed using the established communication link between the master and slave modules.

[0114] Furthermore, in some embodiments, steps S730 and S740 may be included after step S720.

[0115] S730 performs parameter adjustment and injection locking on the laser.

[0116] Specifically, when adjusting the parameters and locking the injection of the slave laser 210, it is necessary to ensure that the wavelength and Brillouin frequency shift of the slave laser 210 match those of the master laser 110, and to lock and amplify the fundamental frequency of the sideband modulated continuous light.

[0117] In some implementations, parameter tuning includes: 1. The optical power of continuous and pulsed light in the main Brillouin optical time-domain analysis module 100 and the slave Brillouin optical time-domain analysis module 200 is controlled by adjusting the optical amplifiers corresponding to each branch. 2. Sensing distance: Setting the required sensing distance for the main Brillouin optical time-domain analysis module 100 and the slave Brillouin optical time-domain analysis module 200; 3. Spatial resolution: Setting an appropriate spatial resolution to match the site requirements; 4. Frequency sweep range: Setting the frequency sweep range of the equipment to match the actual operating conditions on site.

[0118] Key evaluation criteria for successful commissioning include: 1. High Brillouin signal-to-noise ratio: The peak value of the Brillouin gain spectrum is significantly higher than the fluctuation range of the background noise. 2. Symmetrical spectral shape: The Brillouin gain or loss spectrum is observed to have a Lorentzian shape, without obvious distortion such as a steep slope on one side and a gentle slope on the other. 3. Smooth, burr-free spectral lines: The spectral lines are smooth and fluid, without obvious, sharp burrs or abnormal fluctuations. 4. Sufficient dynamic range: The Brillouin spectrum curves corresponding to the highest and lowest points on the system measurement curve are complete, and the entire spectrum has a certain margin from the start and end frequencies of the measurement boundary.

[0119] In some implementations, the specific method for injecting lock is as follows:

[0120] 1. Provide a reference light source: The main laser 110 generates a continuous beam of light with a stable frequency and extremely narrow linewidth, which serves as the optical frequency reference for the entire system.

[0121] 2. Generation of Injection and Probe Signals: The light output from the main laser 110 is split into two paths. One path enters the probe link of the main Brillouin optical time-domain analysis module 100, and the other path enters the first frequency-shifting modulation unit 140. It should be clearly stated that this module simultaneously outputs two types of optical signals: one is the frequency-shifted light it generates, which will serve as the continuous probe light from the Brillouin optical time-domain analysis module 200, used to induce stimulated Brillouin scattering with pulsed light in the fiber under test. The second is the original fundamental frequency light whose frequency has not shifted after passing through this module; this pure fundamental frequency light is specifically extracted and used as the injection signal for injection locking.

[0122] 3. Implement frequency locking: The generated fundamental frequency injection optical signal is directionally injected into the resonant cavity of the slave laser from the Brillouin optical time domain analysis module through the third coupler 280.

[0123] 4. Locking process completed: By precisely controlling the power of the fundamental frequency injected optical signal, it is brought into the injection locking capture range of the laser 210. Under nonlinear interaction, the output light from the laser 210 will abandon its original free oscillation frequency, and its instantaneous frequency and phase will be continuously "pulled" until it finally maintains a fixed phase relationship with the fundamental frequency injected optical signal, achieving complete synchronization of frequency and phase.

[0124] 5. Establishing Stable Detection: After successful locking, the frequency of the light output from laser 210 will be exactly equal to the fundamental frequency of the main laser 110. At this time, the frequency difference between the pulsed light propagating in the main Brillouin optical time-domain analysis module 100 and the continuous probe light (i.e., the frequency-shifted light generated by the first frequency-shifting modulation unit 140) propagating from the Brillouin optical time-domain analysis module 200, i.e., the beat frequency required for Brillouin sensing, is determined only by the frequency shift of the first frequency-shifting modulation unit 140 and is independent of the frequency drift of the laser itself, thereby establishing a highly stable dual-end Brillouin distributed sensing system.

[0125] S740. Optimize the parameters of the main Brillouin optical time domain analysis module and debug the parameters of the slave Brillouin optical time domain analysis module.

[0126] In some implementations, parameter optimization of the main Brillouin optical time-domain analysis module 100 may include optimization of frequency shift parameters, sensing distance, pulse parameters, and amplification parameters.

[0127] Specifically, regarding the frequency shift parameters: the frequency shift amount is set by the first frequency shift modulation unit 140 based on the measured temperature and strain range of the first fiber A under test.

[0128] Regarding sensing distance: The sensing distance will be determined based on the requirements of on-site testing.

[0129] Regarding pulse parameters: based on the spatial resolution and sensing distance requirements, the pulse width (e.g., 10ns corresponds to 1m) and repetition frequency (preferably, the repetition frequency is ≤ twice the light transmission time of the sensing distance to avoid crosstalk) are set by the first pulse modulation unit 130.

[0130] Regarding amplification parameters: Adjusting the first optical amplifier 133 and the second optical amplifier 143 controls the output optical power of pulsed and continuous light, thereby ensuring the signal strength at the end of the link without introducing nonlinear effects.

[0131] In some implementations, parameter tuning of the Brillouin optical time domain analysis module 200 may include continuous light and frequency shift parameters, amplification parameters, and synchronous configuration of the parameters of the slave Brillouin optical time domain analysis module 200 based on the pulse parameters (pulse width, repetition frequency) and sensing distance of the master Brillouin optical time domain analysis module 100.

[0132] Specifically, regarding continuous light and frequency shift parameters: based on the test temperature and strain range of the second fiber under test B, the frequency shift amount is set through the second frequency shift modulation unit 240 to generate continuous probe light; the output power of the laser 210 is adjusted, and combined with the gain of the third amplifier 244, the power difference of the pulse light of the main Brillouin optical time domain analysis module 100 is matched (which can ensure the effective excitation of Brillouin scattering).

[0133] In addition, based on the pulse parameters (pulse width, repetition frequency) and sensing distance of the main Brillouin optical time domain analysis module 100, the parameters of the slave Brillouin optical time domain analysis module 200 are configured synchronously, including: keeping the pulse width consistent with the main Brillouin optical time domain analysis module 100 (to match spatial resolution requirements), keeping the repetition frequency the same as the main Brillouin optical time domain analysis module 100 (to avoid spatiotemporal signal crosstalk), and calibrating the sensing distance of the slave Brillouin optical time domain analysis module 200 to align with the main Brillouin optical time domain analysis module 100.

[0134] Regarding amplification parameters: the gain of the fourth optical amplifier 233 is adjusted to control the output power of the pulsed light from the Brillouin optical time-domain analysis module 200, so that the power difference between the pulsed light and the continuous light from the main Brillouin optical time-domain analysis module 100 is matched, ensuring effective excitation of Brillouin scattering while avoiding nonlinear effects.

[0135] Optionally, after step S620 of the above embodiment, which processes the data obtained from the master Brillouin optical time-domain analysis module and the slave Brillouin optical time-domain analysis module to determine the temperature strain distribution of the first half of the first fiber under test and the second half of the second fiber under test, step S770 may also be included.

[0136] S770: The data from the all-fiber link are spliced ​​together to determine the distributed measurement results of the all-fiber link.

[0137] Data splicing of an all-fiber link refers to splicing the temperature strain distribution of the first half of the first fiber under test A and the second half of the second fiber under test B.

[0138] Specifically, the splicing method can be to calibrate the position of the second fiber B according to the position calibration rules of the first fiber A to be tested.

[0139] For example, when calibrating the first fiber A under test, the first end of the first fiber A under test is calibrated to the 0m position, and the second end of the first fiber A under test is calibrated to the 4Lm position; when determining the temperature strain at each position of the first fiber A under test according to the optical time domain analysis method, the calibrated position coordinates of the first fiber A under test are the actual physical position coordinates corresponding to a certain temperature strain.

[0140] At this point, the actual physical position of the second end of the second fiber B under test is 4Lm. When the Brillouin optical time-domain analysis module 200 determines the temperature strain at each position of the second fiber B under test according to its own optical time-domain analysis method, the Brillouin optical time-domain analysis module 200 will calibrate the second end of the second fiber B under test as the 0m reference position. Therefore, it is necessary to readjust the position data corresponding to the second half of the temperature strain distribution of the second fiber B under test according to the position calibration rules of the first fiber A under test, that is, to calibrate the 0m reference position as the 4Lm position. In this way, the calibration of the second half of the temperature strain distribution of the second fiber B under test can be completed according to the position calibration rules of the first fiber A under test.

[0141] Finally, by combining the temperature strain distribution of the first half of the fiber under test A and the temperature strain distribution of the second half of the fiber under test B after the above adjustments, the splicing of the entire fiber link data (temperature strain distribution of the first half of the fiber under test A and the second half of the fiber under test B) can be completed.

[0142] Of course, in some other alternative implementations, data splicing and adjustment may not be necessary, as long as the position of the temperature strain on the corresponding first fiber A or second fiber B under test can be determined.

[0143] In summary, the optimal embodiment of this invention employs a master Brillouin optical time-domain analysis module 100 and a slave Brillouin optical time-domain analysis module 200 in a counter-beam configuration. Without reducing the signal-to-noise ratio (i.e., sensing accuracy) and spatial resolution, the effective sensing distance can be increased to four times that of a traditional single BOTDA. This physically avoids the reliance on complex amplification or encoding techniques in existing single-device end-to-end measurements, directly 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. Furthermore, the injection-locking technology ensures strict wavelength consistency between the master laser 110 and the slave laser 210, eliminating the need for a complex external wavelength calibration module, which helps reduce system power consumption and complexity, providing a core guarantee for accurate synchronization and seamless stitching of the two data segments. Furthermore, based on the logic of segmented synchronous acquisition and data stitching, complete data with an effective sensing distance four times that of a traditional single BOTDA can be obtained; in addition, its measurement efficiency is higher than that of the encoding scheme, ultimately achieving a balance between long distance, high precision, and high stability.

[0144] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. 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 invention should be included within the scope of protection of this invention.

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. 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.

4. 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.

5. 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. 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.

6. 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. 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.

7. 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. A first end of the first pulse generation module is connected to a first output end of the first coupler, and a second end of the first pulse generation module is connected to a first end of the first circulator. 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. And / or, The second pulse modulation unit includes a second pulse generating module and a second pulse driver. The first end of the second pulse generating module is connected to the second output end of the second coupler, and the second end of the second pulse generating module is connected to the first end of the second circulator. 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 generating 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 generating module and the first end of the second circulator. Preferably, the second pulse generating module includes one of a semiconductor optical amplifier, an electro-optic modulator, and an acousto-optic modulator.

8. 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 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-end optical fiber 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. The slave-end optical fiber transceiver, the slave 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 control unit. The main-end optical fiber transceiver and the slave-end optical fiber transceiver are communicatively connected through the communication optical fiber. or, The main Brillouin optical time-domain analysis module further includes a main module controller and a main 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. The slave remote communication module, the slave 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. The main remote communication module and the slave remote communication module establish a communication connection wirelessly.

9. A Brillouin optical time-domain analysis method, characterized in that, The Brillouin optical time-domain analysis system according to any one of claims 1-8 is used, and the Brillouin optical time-domain analysis method includes: Acquire data from the main Brillouin optical time-domain analysis module and the slave Brillouin optical time-domain analysis module; The data acquired from the master Brillouin optical time-domain analysis module and the slave Brillouin optical time-domain analysis module are processed to determine the temperature strain distribution of the first half of the first fiber under test and the second half of the second fiber under test.

10. The Brillouin optical time-domain analysis method according to claim 9, characterized in that, Before acquiring data from the master Brillouin optical time-domain analysis module and the slave Brillouin optical time-domain analysis module, the method further includes starting the master Brillouin optical time-domain analysis module and the slave Brillouin optical time-domain analysis module; after detecting that the master Brillouin optical time-domain analysis module and the slave Brillouin optical time-domain analysis module have established communication, the master Brillouin optical time-domain analysis module is initialized and configured; preferably, after initializing and configuring the master Brillouin optical time-domain analysis module after detecting that the master Brillouin optical time-domain analysis module and the slave Brillouin optical time-domain analysis module have established communication, the method further includes parameter debugging and injection locking of the slave laser; optimizing the parameters of the master Brillouin optical time-domain analysis module and debugging the parameters of the slave Brillouin optical time-domain analysis module; And / or, After processing the data acquired from the master Brillouin optical time-domain analysis module and the slave Brillouin optical time-domain analysis module to determine the temperature strain distribution of the first half of the first fiber under test and the second half of the second fiber under test, the data of the entire fiber link is spliced ​​together to determine the distributed measurement results of the entire fiber link.

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