Positioning type optical fiber intrusion detection system and method

Abstract

The invention provides a positioning type optical fiber intrusion detection system and method, and relates to the technical field of perimeter prevention. The device comprises an optical fiber sensor unit, an oscillator unit, a polarization state adjustment driver unit, a laser unit and a control unit, the optical fiber sensor unit adopts a bidirectional Mach-Zehnder interferometer structure; the oscillator unit is located on the interference arm and used for generating intermittent oscillation signals to generate low-frequency interference fringes; the polarization state adjusting driver unit is arranged between the laser unit and the optical fiber sensor unit; the laser unit is used for generating an optical signal and splitting the generated optical signal to the clockwise transmission loop and the anticlockwise transmission loop of the bidirectional Mach-Zehnder interferometer structure; the control unit is used for detecting two-loop interference light signals, analyzing disturbance positions, adjusting the polarization state adjusting driver and the oscillator and optimizing the polarization state of the two-loop light signals. According to the scheme, the positioning precision of the positioning type optical fiber intrusion detection system can be greatly improved while the cost is remarkably reduced.

Description

Technical Field

[0001] The present application relates to the field of perimeter protection technology, and in particular to a positioning-type optical fiber intrusion detection system and method. Background Art

[0002] Distributed fiber optic sensing technology has been widely used in perimeter defense, key infrastructure protection and other fields due to its advantages of anti-electromagnetic interference, long transmission distance and high sensitivity. In particular, the positioning fiber optic intrusion detection system can not only detect a variety of intrusion behaviors, but also locate the location of the intrusion, so it has received great attention.

[0003] Generally, products that support intrusion location functions are mainly based on the following two principles: one is to use Rayleigh scattering technology, such as OTDR-based fiber intrusion detection systems and distributed fiber vibration acoustic wave detection systems (DAS). The other is to use the principle of dual Mach-Zehnder interferometer.

[0004] Among them, the system based on Rayleigh scattering technology usually modulates the ultra-narrow linewidth laser source with pulses of appropriate width, collects and analyzes the characteristic changes of reflected light at the receiving end, and thus can determine the location of the intrusion. The technical requirements of the light source using this method are very high. They usually require complex manufacturing processes and high-end materials, so the price of such light sources is often relatively expensive.

[0005] As for the system using a dual Mach-Zehnder interferometer, it uses the optical path difference in the clockwise and counterclockwise directions to solve the position of the intrusion event, which significantly reduces the requirements for the laser source and does not require modulation. However, the positioning accuracy under this method is sensitive to the polarization state, so whether the polarization state of the system can be controlled well becomes the key. To control the polarization state, it is necessary to be able to monitor the polarization state first. However, the interference fringes of the dual Mach-Zehnder fiber interference system will not change significantly when there is no external vibration, or this slight change is not enough to identify whether the polarization state is good. Therefore, in some schemes, a certain oscillation signal is introduced, and then the quality of the polarization state is determined by the oscillation signal. For example, a frequency-adjustable Bragg grating module is equipped in the laser module of the dual Mach-Zehnder interferometer to generate a continuous high-frequency oscillation, and the polarization state control of the system is achieved by monitoring this high-frequency oscillation signal. However, the inventors have found that the laser source used in this method contains a Bragg grating oscillator, which increases the specificity, and the generation of high-frequency oscillations has led to the use of an AD data acquisition card with a higher sampling rate. These all increase the cost of the system. Summary of the invention

[0006] The purpose of the present application is to provide a positioning type fiber optic intrusion detection system and method, which can significantly reduce the cost while significantly improving the positioning accuracy of the positioning type fiber optic intrusion detection system based on Mach-Zehnder interferometer technology.

[0007] This application is implemented as follows:

[0008] In a first aspect, the present application provides a positioning optical fiber intrusion detection system, comprising:

[0009] The optical fiber sensor unit adopts a bidirectional Mach-Zehnder interferometer structure; the oscillator unit is arranged on two interference arms of the bidirectional Mach-Zehnder interferometer structure, and is used to generate intermittent oscillation signals to obtain low-frequency interference fringes; the polarization state adjustment driver unit is arranged between the laser unit and the optical fiber sensor unit; the laser unit is used to generate an optical signal, and split the generated optical signal into two optical signals, one of which is sent to the clockwise transmission loop of the bidirectional Mach-Zehnder interferometer structure, and the other optical signal is sent to the counterclockwise transmission loop of the bidirectional Mach-Zehnder interferometer structure; the control unit is used to control the oscillator unit to generate an intermittent oscillation signal, and when the oscillator is turned on, the polarization states of the optical signals of the clockwise transmission loop and the counterclockwise transmission loop are monitored and adjusted; when the oscillator unit is stopped, the two interference optical signals output from the clockwise transmission loop and the counterclockwise transmission loop of the bidirectional Mach-Zehnder interferometer structure are received and detected, and the position of the disturbance on the bidirectional Mach-Zehnder interferometer structure is determined by using the optical path difference in the clockwise and counterclockwise directions.

[0010] In the second aspect, the present application provides a positioning type optical fiber intrusion detection method, wherein the optical fiber sensor part adopts a bidirectional Mach-Zehnder interferometer structure, a polarization state adjustment driver unit is provided between the light source and the optical fiber sensor, and two interference arms of the bidirectional Mach-Zehnder interferometer structure are provided with an oscillator unit, and the oscillator unit is used to generate an intermittent oscillation signal to obtain low-frequency interference fringes. The method comprises the following steps: controlling the oscillator unit to generate an intermittent oscillation signal, so as to monitor and adjust the polarization state of the optical signal of the clockwise transmission loop and the counterclockwise transmission loop when the oscillator unit is turned on; when the oscillator unit is stopped, receiving and detecting the two-way interference optical signal outputted from the clockwise transmission loop and the counterclockwise transmission loop of the bidirectional Mach-Zehnder interferometer structure, and determining the position of the disturbance on the bidirectional Mach-Zehnder interferometer structure by using the optical path difference in the clockwise and counterclockwise directions.

[0011] Compared with the prior art, the present invention has at least the following advantages or beneficial effects:

[0012] 1) Compared with the system based on Rayleigh scattering technology, the present application uses a conventional laser as a light source, does not require pulse modulation of the light source, and has no strict restrictions and requirements, which significantly reduces the production cost.

[0013] 2) Compared with the existing scheme based on Mach-Zehnder interferometer, the oscillator unit in the present application is an independent component, which is more economical and practical because of its low oscillation frequency and relatively simple design and manufacture. At the same time, since the oscillator adopts intermittent oscillation mode, no additional filter is required. In addition, since the frequency of the oscillator is relatively low, there is no need to use an AD acquisition card with a high sampling rate, which significantly reduces the cost.

[0014] 3) Compared with the existing solutions based on Mach-Zehnder interferometer, this application uses conventional lasers as light sources and can flexibly select lasers of different powers according to the actual engineering distance, thus getting rid of the dependence on special laser components. It not only saves the cost of light source equipment, but also greatly enhances the flexibility of the system, thereby improving the economic benefits and practicality of the entire fiber optic intrusion detection system. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0016] Figure 1 This is a structural block diagram of an embodiment of a positioning optical fiber intrusion detection method of the present application;

[0017] Figure 2 1 is a flow chart of a controller controlling an oscillator unit to generate an intermittent oscillation signal in an embodiment of the present application. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various different configurations.

[0019] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for protection, but merely represents the selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present application. In addition, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation in this article, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations.

[0020] In conjunction with the accompanying drawings, some embodiments of the present application are described in detail below. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0021] Example 1

[0022] See also Figure 1 The positioning type optical fiber intrusion detection system comprises: an optical fiber sensor unit, which adopts a bidirectional Mach-Zehnder interferometer structure; an oscillator unit, which is arranged on two interference arms of the bidirectional Mach-Zehnder interferometer structure, and is used to generate an intermittent oscillation signal to obtain low-frequency interference fringes; a polarization state adjustment driver unit, which is arranged between the laser unit and the optical fiber sensor unit; a laser unit, which is used to generate an optical signal and split the generated optical signal into two optical signals, one of which is sent to the clockwise transmission loop of the bidirectional Mach-Zehnder interferometer structure, and the other is sent to the clockwise transmission loop of the bidirectional Mach-Zehnder interferometer structure. The signal is sent to the counterclockwise transmission loop of the bidirectional Mach-Zehnder interferometer structure; the control unit is used to control the oscillator unit to generate an intermittent oscillation signal, and when the oscillator unit is turned on, the polarization state of the optical signal of the clockwise transmission loop and the counterclockwise transmission loop is monitored and adjusted; when the oscillator unit is stopped, the two-way interference optical signal output from the clockwise transmission loop and the counterclockwise transmission loop of the bidirectional Mach-Zehnder interferometer structure is received and detected, and the position of the disturbance on the bidirectional Mach-Zehnder interferometer structure is determined by using the optical path difference in the clockwise and counterclockwise directions.

[0023] In the above embodiment, the laser unit is the light source of the whole system and is responsible for generating a stable optical signal. This optical signal is continuous, unmodulated, and has a specific wavelength and power. In this system, the optical signal generated by the laser is divided into two paths by a beam splitter (which may be an optical coupler or a beam splitter) and sent to the clockwise and counterclockwise transmission loops of the bidirectional Mach-Zehnder interferometer (DMZI) structure respectively.

[0024] Optical fiber sensor unit (bidirectional Mach-Zehnder interferometer structure), DMZI structure consists of two equal but independent interference arms, which carry both clockwise and counterclockwise laser signals. Interference occurs when the clockwise laser is transmitted through the two arms to OM3, and interference occurs when the counterclockwise laser is transmitted through the two arms to OM2.

[0025] That is, the two optical signals split from the laser unit enter the two directions of DMZI respectively and share two interference arms. During the transmission process, if the optical fiber is subject to external disturbances (such as vibration, pressure changes, etc.), these disturbances will change the phase of the optical signal, thereby changing the law of interference fringes. The output signals (i.e., interference fringes) of the two directions of DMZI are then sent to the control unit for detection and analysis.

[0026] The oscillator unit is located on the two interference arms of the DMZI structure. It is driven by the controller to make the interference fringes on OM2 and OM3 produce intermittent oscillation. The oscillation signal is used to monitor and adjust the polarization state. The start-up time period of the oscillator is much shorter than the stop-oscillation time period.

[0027] The polarization state adjustment driver unit is used to adjust the polarization state of the optical signal to overcome the polarization drift problem that may occur during optical fiber transmission. By changing the polarization direction or state of the optical signal, it is possible to ensure that the optical signal maintains a stable interference effect in the DMZI structure. Among them, the polarization state adjustment driver unit is connected to the two interference arms of the DMZI structure, and can adjust the polarization state in the clockwise and counterclockwise directions respectively. The polarization state adjustment driver unit executes the instructions of the control unit to adjust the polarization state.

[0028] The control unit is the core of the entire system, responsible for receiving and detecting the two optical signals (i.e., interference fringes) output by the DMZI structure. By performing digital signal processing (such as filtering, amplification, phase resolution, etc.) on these signals, the control unit can determine the location where the fiber disturbance occurs. At the same time, the control unit also monitors the oscillator signals received from both clockwise and counterclockwise directions to determine whether the system's polarization state is good. Once it is detected that the polarization state has deteriorated to an unacceptable level, an adjustment instruction is issued to the polarization state adjustment drive unit to maintain the system's polarization state in a good state.

[0029] In summary, this application aims to improve the detection performance, stability and economy of the system:

[0030] 1) Compared with the system based on Rayleigh scattering technology, the present application uses a conventional laser as a light source, does not require pulse modulation of the light source, and has no strict restrictions and requirements, which significantly reduces the production cost.

[0031] 2) Compared with the existing scheme based on Mach-Zehnder interferometer, the oscillator unit in the present application is an independent component, which is more economical and practical because of its low oscillation frequency and relatively simple design and manufacture. At the same time, since the oscillator adopts intermittent oscillation mode, no additional filter is required. In addition, since the frequency of the oscillator is relatively low, there is no need to use an AD acquisition card with a high sampling rate, which significantly reduces the cost.

[0032] 3) Compared with the existing solutions based on Mach-Zehnder interferometer, this application uses conventional lasers as light sources and can flexibly select lasers of different powers according to the actual engineering distance, thus getting rid of the dependence on special laser components. It not only saves the cost of light source equipment, but also greatly enhances the flexibility of the system, thereby improving the economic benefits and practicality of the entire fiber optic intrusion detection system.

[0033] Based on the above solution, in some implementations of the present application, a circulator is further provided between the polarization state adjustment driver unit and the optical fiber sensor unit to isolate reflection and reduce light loss, thereby achieving the effect of isolating reflection and reducing light loss.

[0034] In the above implementation, the introduction of the circulator effectively isolates the reflected light in the optical fiber transmission, including reflections caused by connectors, optical fiber end faces or internal defects. This greatly reduces the interference of reflected light on the original optical signal, improves the quality and purity of the optical signal, and provides a better basis for subsequent signal processing and analysis. At the same time, reflected light and optical attenuation are important factors affecting the stability of optical fiber sensors. By isolating reflections and reducing optical attenuation, the circulator significantly improves the stability of the system and reduces performance fluctuations and failure rates caused by environmental factors or device aging. In addition, after reducing the interference of reflected light and optical attenuation, the optical fiber sensor can receive and process optical signals more accurately, thereby improving positioning accuracy and detection sensitivity.

[0035] Based on the aforementioned scheme, in some implementations of the present application, the system also includes: a coupler unit, which is used to split the optical signal on the clockwise transmission loop or the counterclockwise transmission loop of the bidirectional Mach-Zehnder interferometer structure, or to merge the two optical signals to form interference.

[0036] It should be noted that the coupler unit is an optical device that can split a beam of optical signals into multiple optical signals while maintaining the phase relationship between the optical signals. Figure 1As shown, in this system, the coupler unit is set at both ends of the two interference arms of the bidirectional Mach-Zehnder interferometer (DMZI) structure to split the optical signal, or merge the two beams of light to form interference. In the clockwise direction, OM2 is split and OM3 is merged, while in the counterclockwise direction, OM3 is split and OM2 is merged. The optical signals after interference in the clockwise and counterclockwise directions are sent to the control unit, converted into analog electrical signals through photoelectric conversion, and then sampled and quantized into digital signals, and then sent to the CPU for subsequent deep digital signal processing.

[0037] It should be further explained that the coupler OM2 has a 3×3 structure. In the clockwise direction, OM2 plays a splitting role, and in the counterclockwise direction, OM2 plays a coupling role. In terms of splitting effect, the clockwise laser is divided into three beams by OM2, two of which are sent to the two arms of the interferometer, and the middle port of OM2 is abandoned. In terms of coupling effect, the counterclockwise optical signals on the two arms of DMZI are interfered on OM2, and the interfered optical signals appear on the three ports 1, port 2, and port 3 at the output end of OM2, and the interference signals of these three ports have a phase difference of 120 degrees. Using this feature, the three signals are compared with the interference signal obtained in the clockwise direction in turn, and there will be more opportunities to select a signal combination with a good polarization state. In other words, the adjustment efficiency of the polarization state is doubled, the adjustment is easier, and the effect is better.

[0038] That is to say, the coupler unit OM2 splits the optical signal on the clockwise transmission loop of the bidirectional Mach-Zehnder interferometer structure on the one hand, and merges the two counterclockwise optical signals on the other hand to obtain three interference signals with a phase difference of 120 degrees. The controller compares the three interference optical signals of different phases with the interference optical signal of the clockwise transmission loop, so that the two interference optical signals with the most matching polarization states can be determined more quickly. If the interference optical signal with matching polarization states cannot be found, the polarization state will be adjusted immediately through the control unit until a combination of interference optical signals with matching polarization states is found. This multi-phase port detection method increases the probability of finding the best interference fringes, shortens the time to adjust the polarization state, and helps the system to quickly and accurately position.

[0039] Based on the introduction of the coupler unit, in some implementations of the present application, the coupler unit includes a 3×3 coupler for splitting the interference light signal at the output position of the counterclockwise transmission loop of the bidirectional Mach-Zehnder interferometer structure into three ports, and the phase difference of the light signals of the three ports is 120 degrees.

[0040] Furthermore, in some implementations of the present application, the control unit is further used to start the oscillator unit within a first time period based on the interference light signals of the three ports received and the clockwise interference light signals, monitor and adjust the polarization states of the optical signals of the clockwise transmission loop and the counterclockwise transmission loop: sequentially detect whether the polarization states of the three ports are qualified, wherein if at least one port is qualified, it is recorded as the polarization state is normal, and the oscillator unit is turned off within a second time period to continue positioning detection; if all three ports are unqualified, the polarization state adjustment driver is started to adjust the polarization state of the clockwise transmission loop or the counterclockwise transmission loop.

[0041] In the above implementation, by combining the interference optical signals received from the three ports with the clockwise interference optical signal, the control unit can more accurately monitor and adjust the polarization states of the optical signals in the clockwise transmission loop and the counterclockwise transmission loop to ensure the stability and accuracy of the system.

[0042] In order to enable those skilled in the art to understand the present application more intuitively, a specific example will be used here to illustrate.

[0043] like Figure 1 As shown, it shows a schematic diagram of the structure of the positioning optical fiber intrusion detection system in a specific application scenario. At this time, the system includes a laser source, a polarization state adjustment driver, an oscillator, two circulators, two 2×2 couplers (OM1 and OM2), a 3×3 coupler OM2, and four photoelectric converters ( Figure 1 O / E in the system), four A / D acquisition cards, four detectors (DET1, DET2, DET3 and DET4), and a processor CPU.

[0044] Among them, the laser source is used to emit a light beam, and it can flexibly select conventional lasers of different powers according to the actual length of the project distance. The light beam emitted by the laser source is divided into two beams after passing through the coupler OM1. One beam passes through the first circulator to the coupler OM2, and is divided into three beams at the coupler OM2. The middle beam is discarded, and the other two beams are sent to the R and S interference arms, and then form interference at the coupler OM3, and then reach the second circulator through the optical fiber G, and finally reach the detector DET1 after passing through the photoelectric converter (O / E) and the A / D acquisition card, completing the clockwise transmission.

[0045] In the counterclockwise direction, another beam of light separated by the coupler OM1 goes through the second circulator and the optical fiber G to the coupler OM3, where it is evenly divided into the two interference arms R and S, and then forms interference on the coupler OM2. Among them, the subtlety of the 3×3 coupler OM2 is that it can divide the interfered optical signal into 3 paths, and the 3 outputs differ in phase by 120 degrees. The 3 interfered optical signals are respectively sent to their respective detectors (sent to detectors DET1, DET2 and DET3) after photoelectric conversion and A / D conversion.

[0046] Polarization state adjustment driver: used to adjust the polarization state of light propagating in opposite directions in the two arms of the interferometer, so as to ensure the best quality of their respective interference signals.

[0047] Oscillator: Under the condition of no external interference, the interference intensity obtained by the interferometer in the clockwise and counterclockwise directions is relatively stable, that is, the change of the interference fringes is weak and not obvious, and it is difficult to determine and adjust the polarization state based on this. For this reason, the present application introduces an oscillator, which works intermittently with a specific period, the first time period is the start of oscillation, the second time period is the stop of oscillation, and the first time period is much smaller than the second time period.

[0048] Processor CPU: This processor is used to receive the output of detectors DET1, DET2, DET3 and DET4, and deeply process and analyze these data to determine intrusion events and solve positioning information. The processor controls the intermittent operation of the oscillator, analyzes the data received from the detector, monitors the polarization state changes in the clockwise and counterclockwise directions of the interferometer, and dynamically adjusts the polarization states of the two opposite directions of the lasers in the two arms of the bidirectional Mach-Zehnder interferometer to ensure good visibility and correlation.

[0049] That is, the 3×3 coupler OM2 divides the interference light in the counterclockwise direction into three paths, and the three outputs differ in phase by 120 degrees. By comparing the three interference signals with a phase difference of 120 degrees obtained in the counterclockwise direction with the interference signals obtained in the clockwise direction, it is possible to quickly select a pair of interference signals with a qualified polarization state. If the combined polarization state of the three pairs of signals is not qualified, the polarization state is immediately adjusted by the processor CPU using the polarization state adjustment driver and oscillator until a pair of interference signal combinations with a qualified polarization state is found. This significantly increases the probability of successful polarization state adjustment and shortens the time required for polarization state adjustment, thereby ensuring the accuracy of solving the disturbance position of the long-distance interferometer.

[0050] Example 2

[0051] Based on the same inventive concept as the positioning type fiber optic intrusion detection system, an embodiment of the present application provides a positioning type fiber optic intrusion detection method, wherein the fiber optic sensor part adopts a bidirectional Mach-Zehnder interferometer structure, a polarization state adjustment driver unit is provided between the light source and the fiber optic sensor, and two interference arms of the bidirectional Mach-Zehnder interferometer structure are provided with oscillator units, and the oscillator unit is used to generate an intermittent oscillation signal to obtain low-frequency interference fringes; the method comprises the following steps: controlling the oscillator unit to generate an intermittent oscillation signal to monitor and adjust the polarization states of the optical signals of the clockwise transmission loop and the counterclockwise transmission loop when the oscillator unit is turned on; when the oscillator unit stops, receiving and detecting the two interference optical signals outputted from the clockwise transmission loop and the counterclockwise transmission loop of the bidirectional Mach-Zehnder interferometer structure, and determining the position where the disturbance occurs on the bidirectional Mach-Zehnder interferometer structure by using the optical path difference in the clockwise and counterclockwise directions.

[0052] In the above embodiment, the oscillator unit is installed on the two interference arms of the bidirectional DMZI structure to generate intermittent oscillation signals. These intermittent oscillation signals act on the two interference arms to generate interference fringes. The polarization state adjustment driver unit is placed between the laser unit and the optical fiber sensor unit to dynamically adjust the polarization state of the optical signal. Since the disturbance in the optical fiber may affect the polarization state of the optical signal, this influence can be compensated by adjusting the polarization state adjustment driver, making the interference effect more stable and reliable. In addition, the adjustment of the polarization state also helps to improve the sensitivity of the system to weak disturbance signals and further improve the detection performance.

[0053] That is, the combined use of the oscillator unit and the polarization state adjustment driver unit in the above embodiment improves the sensitivity of the system to weak disturbance signals, and its implementation cost is low, and it has good cost performance and practicality.

[0054] For the specific implementation process of the above method, please refer to the positioning type optical fiber intrusion detection system provided in Example 1, which will not be repeated here.

[0055] Based on the aforementioned scheme, in some implementations of the present application, when the oscillator unit is turned on, it includes turning on the oscillator unit within a first time period (15ms); when the oscillator unit is stopped, it includes a second time period (20s) when the oscillator unit stops working.

[0056] Based on the above scheme, in some implementations of the present application, a 3×3 coupler is used to split the interference light signal at the output position of the counterclockwise transmission loop of the bidirectional Mach-Zehnder interferometer structure into three ports, so that the interference light signals of the three ports and the clockwise interference light signal are sent to the control unit. Figure 2As shown, the control unit turns on the oscillator unit in the first time period (15ms), and the steps of monitoring and adjusting the polarization state of the optical signal of the clockwise transmission loop and the counterclockwise transmission loop are as follows: the polarization states of the three ports are detected in turn to see if they are qualified, wherein if at least one port is qualified, it is recorded as the polarization state is normal, and the oscillator unit is turned off in the second time period to continue positioning detection (20s); if all three ports are unqualified, the polarization state adjustment driver is started to adjust the polarization state of the clockwise transmission loop or the counterclockwise transmission loop.

[0057] In the above implementation, the 3×3 coupler distributes the interference light signal output by the counterclockwise transmission loop to three different output ports to form three port signals. These three port signals are then sent to the control unit to be analyzed and processed together with other interference light signals (such as the signal of the clockwise transmission loop) received by the control unit.

[0058] The oscillator unit is turned on in the first time period, and the control unit performs the following polarization state monitoring and adjustment process:

[0059] Port signal detection: The control unit receives and detects the three port signals in sequence and analyzes whether their polarization states are qualified.

[0060] Polarization state judgment: 1) At least one port is qualified: If the polarization state of at least one port is judged to be qualified, the control unit will regard the polarization state as normal as a whole. At this time, the system will continue with the subsequent positioning detection operation, that is, enter the second time period, and prepare to receive and analyze the interference light signal when the oscillator unit stops. 2) All three ports are unqualified: If the polarization state of all three ports is unqualified, the control unit will start the polarization state adjustment driver. This controller will adjust the polarization state of the clockwise transmission loop or the counterclockwise transmission loop (or both at the same time) to correct the current polarization state problem.

[0061] Adjustment and re-testing: After the polarization adjustment driver performs the adjustment, the control unit will re-test the polarization states of the three ports to confirm whether the adjustment is effective. If it is still unqualified, further adjustment or other remedial measures may be required.

[0062] It will be apparent to those skilled in the art that the present application is not limited to the details of the exemplary embodiments described above, and that the present application can be implemented in other specific forms without departing from the spirit or essential features of the present application. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the present application is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims be included in the present application. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

Claims

1. A positioning optical fiber intrusion detection system, characterized in that: include: The fiber optic sensor unit adopts a bidirectional Mach-Zehnder interferometer structure; An oscillator unit is provided on two interference arms of a bidirectional Mach-Zehnder interferometer structure and is used to generate an intermittent oscillation signal to obtain low-frequency interference fringes; A polarization state adjustment driver unit is provided between the laser unit and the optical fiber sensor unit; A laser unit is used to generate an optical signal and split the generated optical signal into two optical signals, wherein one optical signal is sent to a clockwise transmission loop of a bidirectional Mach-Zehnder interferometer structure, and the other optical signal is sent to a counterclockwise transmission loop of the bidirectional Mach-Zehnder interferometer structure; The control unit is used to control the oscillator unit to generate an intermittent oscillation signal. When the oscillator unit is turned on, the polarization state of the optical signal of the clockwise transmission loop and the counterclockwise transmission loop is monitored and adjusted; when the oscillator unit is stopped, the two interference optical signals output from the clockwise transmission loop and the counterclockwise transmission loop of the bidirectional Mach-Zehnder interferometer structure are received and detected, and the position of the disturbance on the bidirectional Mach-Zehnder interferometer structure is determined by using the optical path difference in the clockwise and counterclockwise directions.

2. A positioning optical fiber intrusion detection system according to claim 1, characterized in that: A circulator is also provided between the polarization state adjustment driver unit and the optical fiber sensor unit for isolating reflection and reducing light attenuation.

3. A positioning optical fiber intrusion detection system according to claim 1, characterized in that: The system further comprises: The coupler unit is used to split the optical signal on the clockwise transmission loop or the counterclockwise transmission loop of the bidirectional Mach-Zehnder interferometer structure, or to combine two optical signals to form interference.

4. A positioning optical fiber intrusion detection system according to claim 3, characterized in that: The coupler unit includes a 3×3 coupler for splitting the interference light signal at the output position of the counterclockwise transmission loop of the bidirectional Mach-Zehnder interferometer structure into three ports, and the phase difference of the light signals of the three ports is 120 degrees.

5. A positioning optical fiber intrusion detection system according to claim 4, characterized in that: The control unit is further used to start the oscillator unit in a first time period according to the interference light signals of the three ports received and the clockwise interference light signal, monitor and adjust the polarization states of the optical signals of the clockwise transmission loop and the counterclockwise transmission loop: sequentially detect whether the polarization states of the three ports are qualified, wherein if at least one port is qualified, it is recorded as the polarization state is normal, and the oscillator unit is turned off in a second time period to continue positioning detection; if all three ports are unqualified, the polarization state adjustment driver is started to adjust the polarization state of the clockwise transmission loop or the counterclockwise transmission loop.

6. A positioning optical fiber intrusion detection method, characterized in that: The optical fiber sensor part adopts a bidirectional Mach-Zehnder interferometer structure. A polarization state adjustment driver unit is provided between the light source and the optical fiber sensor. The two interference arms of the bidirectional Mach-Zehnder interferometer structure are provided with an oscillator unit, which is used to generate an intermittent oscillation signal to obtain low-frequency interference fringes. The method comprises the following steps: Controlling the oscillator unit to generate an intermittent oscillation signal, so as to monitor and adjust the polarization states of the optical signals of the clockwise transmission loop and the counterclockwise transmission loop when the oscillator unit is turned on; When the oscillator unit stops, two interference light signals output from the clockwise transmission loop and the counterclockwise transmission loop of the bidirectional Mach-Zehnder interferometer structure are received and detected, and the position of the disturbance on the bidirectional Mach-Zehnder interferometer structure is determined by using the optical path difference in the clockwise and counterclockwise directions.

7. A positioning optical fiber intrusion detection method according to claim 6, characterized in that: When the oscillator unit is turned on, it includes turning on the oscillator unit within a first time period; when the oscillator unit is stopped, it includes stopping the oscillator unit within a second time period.

8. A positioning optical fiber intrusion detection method according to claim 7, characterized in that: The method comprises using a 3×3 coupler to split the interference light signal at the output position of the counterclockwise transmission loop of the bidirectional Mach-Zehnder interferometer structure into three ports, so as to send the interference light signals of the three ports and the clockwise interference light signal to a control unit; The control unit turns on the oscillator unit in a first time period, monitors and adjusts the polarization states of the optical signals in the clockwise transmission loop and the counterclockwise transmission loop: detects in turn whether the polarization states of the three ports are qualified, wherein if at least one port is qualified, it is recorded as the polarization state is normal, and turns off the oscillator unit in a second time period to continue positioning detection; if all three ports are unqualified, the polarization state adjustment driver is started to adjust the polarization state of the clockwise transmission loop or the counterclockwise transmission loop.

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