Method and device for improving the stability of submarine cable monitoring based on improved DZI

Abstract

This invention discloses a method and apparatus for improving the stability of submarine cable monitoring based on an improved DMZI (Digital Microwave Interferometer). The apparatus includes a symmetrical Mach-Zeder interferometer, a phase modulator, a first polarization controller, and a second polarization controller. The phase modulator is used to input a triangular wave into the interferometer arm during the adjustment phase. The first polarization controller is used to change the polarization state of the first optical path during the adjustment phase, maximizing the peak-to-peak value of the interference signal obtained by the first optical path. The second polarization controller is used to change the polarization state of the second optical path during the adjustment phase, maximizing the similarity between the interference signals of the first and second optical paths. By implementing this invention, inputting a triangular wave using the phase modulator is equivalent to applying an external vibration; adjusting the first and second polarization controllers maximizes the similarity between the two interference signals. Therefore, when using this apparatus for submarine cable monitoring, the location of the vibration can be accurately calculated, making the apparatus most sensitive to external vibrations.

Description

Technical Field

[0001] This invention relates to the field of fiber optic sensing and measurement technology, specifically to a method and apparatus for improving the stability of submarine cable monitoring based on an improved DMZI. Background Technology

[0002] Optical fibers are sensitive to acoustic vibrations in the surrounding environment and have advantages such as small size, light weight, flexibility, low loss, resistance to electromagnetic interference, and good radiation resistance. Utilizing the existing optical fiber resources in submarine fiber optic composite cables (hereinafter referred to as submarine cables) to build an optical interferometry system can significantly improve the cable's sensitivity to acoustic vibrations in the surrounding environment and its frequency response range. This allows for precise location and early warning of events such as anchoring of ships or dragging of fishing nets near the cable, reducing the risk of external damage to the cable, improving power supply reliability, and ultimately enabling the prediction and assessment of large-scale dangerous events in nearby waters.

[0003] Currently, based on the principle of the Dual Mach-Zehnder Interferometer (DMZI), it is possible to monitor and provide early warning of acoustic information from submarine cables. The main principle of this technology is based on the different arrival times of the upper and lower light beams at the location of external vibrations. By calculating the time difference between the detection of interference signals by the two detection units, the location of the vibration can be accurately pinpointed, thus achieving the localization of external vibrations. However, existing technologies have the following two main problems:

[0004] 1. Since optical fibers are laid on the seabed, they are affected by environmental factors such as temperature. When the temperature rises, the tension on the fiber core decreases, the difference in refractive index between the slow axis and the fast axis (i.e., birefringence) decreases, and the polarization state changes.

[0005] 2. The submarine cable of the DMZI interferometer is used to detect acoustic vibrations in the seabed environment, such as vibration signals from ship engines, anchor winches, and net haulers. However, vibration signals not only change the phase of the light transmitted in the optical fiber, but also its polarization.

[0006] Due to the influence of polarization, the intensity of interference light in the upper and lower light paths will decrease, which may lead to vibration detection failure or result in poor accuracy of the detected vibration position. Summary of the Invention

[0007] In view of this, embodiments of the present invention provide a method and apparatus for improving the stability of submarine cable monitoring based on an improved DMZI, so as to solve the technical problems of vibration detection failure or low vibration detection accuracy in the prior art.

[0008] The technical solutions provided by the embodiments of the present invention are as follows:

[0009] A first aspect of this invention provides a device for improving the stability of submarine cable monitoring based on an improved DMZI, comprising: a symmetrical Mach-Zeder interferometer, a phase modulator, a first polarization controller, and a second polarization controller; the symmetrical Mach-Zeder interferometer includes a first optical path and a second optical path, the first optical path and the second optical path including a common portion, the common portion including a first interferometer arm and a second interferometer arm; the first polarization controller is disposed in the first optical path, the second polarization controller is disposed in the second optical path, and the phase modulator is disposed in either the first interferometer arm or the second interferometer arm; the phase modulator is used to input a triangular wave into the interferometer arm during the adjustment phase; the first polarization controller is used to change the polarization state of the first optical path during the adjustment phase, so that the peak-to-peak value of the interference signal obtained by the first optical path is maximized; the second polarization controller is used to change the polarization state of the second optical path during the adjustment phase, so that the similarity between the interference signals of the first optical path and the second optical path is maximized.

[0010] Optionally, the first interferometer arm includes a first optical fiber, the second interferometer arm includes a second optical fiber, and the common part further includes a laser, a first coupler, a first circulator, a second coupler, a third coupler, a third optical fiber, and a second circulator. The first optical path further includes a first photodetector, and the second optical path further includes a second photodetector. The first polarization controller is disposed between the first circulator and the second coupler, and the second polarization controller is disposed between the third optical fiber and the second circulator. The laser beam output from the laser is split into two beams after passing through the first coupler. The first beam passes through the first circulator and the first polarization controller. After being split by the first coupler, the light beams are split into two beams by the second coupler. The two beams are transmitted through the first optical fiber and the second optical fiber, respectively, and are then combined by the third coupler. After passing through the third optical fiber, the second polarization controller, and the second circulator, the light beams enter the second photodetector. The transmission path of the first beam constitutes the first optical path. The second beam obtained by splitting by the first coupler is transmitted through the second circulator, the second polarization controller, and the third optical fiber. After being split into two beams by the third coupler, the two beams are transmitted through the first optical fiber and the second optical fiber, respectively, and are then combined by the second coupler. After passing through the first polarization controller and the first circulator, the second beam enters the first photodetector. The transmission path of the second beam constitutes the second optical path.

[0011] Optionally, the device for improving the stability of submarine cable monitoring based on the improved DMZI further includes a drive circuit for providing an analog voltage to drive the phase modulator.

[0012] Optionally, the device for improving the stability of submarine cable monitoring based on the improved DMZI further includes: a data acquisition card, which is used to acquire the detection results of the first optical path to obtain the corresponding interference signal, and the data acquisition card is also used to acquire the detection results of the second optical path and compare them with the detection results of the first optical path.

[0013] Optionally, the peak-to-peak value of the triangular wave is greater than 2π.

[0014] This invention also provides a method for improving the stability of submarine cable monitoring based on an improved DMZI, applicable to the apparatus for improving the stability of submarine cable monitoring based on an improved DMZI according to the first aspect of this invention and any one of the first aspects. The method includes: adjusting a first polarization controller and using a phase modulator to input a triangular wave to the interferometer arm until the peak-to-peak value of the first optical path interference signal is maximized, thereby obtaining a first state of the first polarization controller; maintaining the first state of the first polarization controller, adjusting a second polarization controller and using a phase modulator to input a triangular wave to the interferometer arm until the similarity between the first optical path interference signal and the second optical path interference signal is highest, thereby obtaining a second state of the second polarization controller.

[0015] Optionally, the method for improving the stability of submarine cable monitoring based on the improved DMZI further includes: turning off the phase modulator, maintaining the first state of the first polarization controller and the second state of the second polarization controller, and using the device to perform submarine cable monitoring.

[0016] Optionally, the highest similarity between the first optical path interference signal and the second optical path interference signal is determined by the following method: shifting either interference signal by a preset time delay, calculating the Euclidean distance between the two interference signals, and the highest similarity is achieved when the Euclidean distance is minimized.

[0017] Optionally, adjusting the first polarization controller includes: traversing all states of the first polarization controller; adjusting the second polarization controller includes: traversing all states of the second polarization controller.

[0018] Optionally, before adjusting the first polarization controller, the process includes fixing the second polarization controller to a preset state.

[0019] The technical solution of this invention has the following advantages:

[0020] The device for improving the stability of submarine cable monitoring based on an improved DMZI provided in this invention uses a phase modulator, a first polarization controller, and a second polarization controller in the optical path of a symmetrical Mach-Zeder interferometer. During the adjustment phase, a triangular wave is input into the phase modulator, effectively applying an external vibration. Simultaneously, the states of the first and second polarization controllers are adjusted to maximize the similarity between the two interference signals. Therefore, when using this device for submarine cable monitoring, the location of the vibration can be accurately calculated, making the device highly sensitive to external vibrations. This improves the stability of the device and the vibration positioning accuracy, achieving meter-level accuracy in field tests.

[0021] The method for improving the stability of submarine cable monitoring based on an improved DMZI provided in this invention uses a phase modulator to input a triangular wave, which can simulate external vibrations. By changing the state of two polarization controllers, the arbitrary polarization state of the transmitted beam can be adjusted, so that the similarity of the two interference signals obtained is the highest. Thus, the state of the polarization controller corresponding to the highest similarity is used for submarine cable monitoring, so that the influence of polarization on interference is minimized, thereby making the improved DMZI most sensitive to external vibrations. Attached Figure Description

[0022] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0023] Figure 1 This is a structural block diagram of the device for improving the stability of submarine cable monitoring based on an improved DMZI in an embodiment of the present invention;

[0024] Figure 2 This is a block diagram of a symmetrical Mach-Zeder interferometer in related technologies;

[0025] Figure 3 This is a flowchart illustrating a method for improving submarine cable monitoring stability based on an improved DMZI in an embodiment of the present invention.

[0026] Figure 4 This is a flowchart of a method for improving the stability of submarine cable monitoring based on an improved DMZI in another embodiment of the present invention. Detailed Implementation

[0027] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0029] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can also refer to the internal connection of two components; and they can refer to a wireless connection or a wired connection. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0030] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0031] This invention provides a device for improving the stability of submarine cable monitoring based on an improved DMZI, such as... Figure 1 As shown, the system includes: a symmetrical Mach-Zeder interferometer, a phase modulator 12, a first polarization controller 10, and a second polarization controller 20. The symmetrical Mach-Zeder interferometer includes a first optical path and a second optical path, which share a common portion comprising a first interferometer arm and a second interferometer arm. The first polarization controller 10 is disposed in the first optical path, and the second polarization controller 20 is disposed in the second optical path. The phase modulator 12 is disposed in either the first or second interferometer arm. The phase modulator 12 is used to input a triangular wave into the interferometer arm during the adjustment phase. The first polarization controller 10 is used to change the polarization state of the first optical path during the adjustment phase, maximizing the peak-to-peak value of the interference signal obtained by the first optical path. The second polarization controller 20 is used to change the polarization state of the second optical path during the adjustment phase, maximizing the similarity between the interference signals of the first and second optical paths.

[0032] Specifically, such as Figure 1As shown, the first interferometer arm includes a first optical fiber A, the second interferometer arm includes a second optical fiber B, and the common part further includes a laser LD, a first coupler 30, a first circulator 60, a second coupler 40, a third coupler, a third optical fiber C, and a second circulator 70. The first optical path further includes a first photodetector, and the second optical path further includes a second photodetector. The first polarization controller 10 is disposed between the first circulator 60 and the second coupler 40, and the second polarization controller 20 is disposed between the third optical fiber C and the second circulator 70. The beam output from the laser LD is split into two beams after passing through the first coupler 30. The first beam passes through the first circulator 60 and the first polarization controller 10, and is then split into two beams by the second coupler 40. The two beams enter the first optical fiber A and the second optical fiber B respectively for transmission, are combined by the third coupler, and then pass sequentially through the third optical fiber C. C. After passing through the second polarization controller 20 and the second circulator 70, the light enters the second photodetector 90. The transmission path of the first beam constitutes the first optical path. The second beam obtained by splitting the beam by the first coupler 30 passes through the second circulator 70, the second polarization controller 20, and the third fiber C. After passing through the third coupler, the second beam is split into two beams. The two beams enter the first fiber A and the second fiber B respectively for transmission. After being combined by the second coupler 40, they pass through the first polarization controller 10 and the first circulator 60 and enter the first photodetector 80. The transmission path of the second beam constitutes the second optical path.

[0033] The structural principle diagram of the symmetrical Mach-Zeder interferometer is shown below. Figure 2 As shown. The symmetrical Mach-Zeder interferometer monitors external vibrations by monitoring changes in the interference signals in the first photodetector 80 and the second photodetector 90. Specifically, if a phase modulator, a first polarization controller, and a second polarization controller are not included in the optical path, the AC component I of the interference signal output by the first photodetector 80 and the second photodetector 90 will... 上 and I 下 They are represented as follows:

[0034]

[0035]

[0036] Where A1, A2, A′1, and A′2 are the amplitudes of E1, E2, E′1, and E′2, respectively. The phase change is due to vibration, and τ is the signal delay related to the vibration position. η1(t) can be considered as the polarization angle between the E1 and E2 components. Due to the influence of external environment and vibration, η1(t) changes with time. When the polarizations of the E1 and E2 components are consistent, η1(t) is zero, and the AC component is strongest; when the polarizations of the E1 and E2 components are perpendicular, η1(t) is 90°, the AC component is zero, and this will cause a decrease in the intensity of the interference light. η2(t) is related to I 下 The effect is the same as the principle described above. μ1(t) and μ2(t) can be considered as additional phases caused by polarization. Due to the influence of external environment and vibration, μ1(t) and μ2(t) change with time. When μ1(t) = μ2(t), I 上 and I 下 It has a fixed time delay of τ. The I in equations (1) and (2) 上 and I 下 By performing cross-correlation and finding the peak point of the cross-correlation function, the signal delay τ can be mapped, thereby allowing the location of external disturbances to be calculated.

[0037] Due to the influence of polarization in the actual environment, as can be seen from equations (1) and (2), η will cause the interference light intensity to decrease, the signal-to-noise ratio of the interference signal to drop, or even be submerged in noise, which may lead to the failure of sensor vibration detection. At the same time, μ in the equation will cause the signal phase to drift, the similarity between the two signals will decrease, the time delay will change, and the vibration positioning error of the system will increase. Therefore, in order to obtain the interference signal caused only by the phase change caused by vibration and to correctly demodulate the time delay, polarization must be controlled so that I 上 and I 下 They are similar in shape and are most sensitive to vibration.

[0038] Therefore, by setting up a phase modulator, a first polarization controller, and a second polarization controller in the optical path of a symmetrical Mach-Zeder interferometer, a triangular wave is input through the phase modulator during the adjustment phase, which is equivalent to applying an external vibration. Simultaneously, the states of the first and second polarization controllers are adjusted to achieve the highest similarity between the two interference signals. The adjustment phase refers to the state before using the device for submarine cable monitoring. Specifically, before monitoring, the first and second polarization controllers are adjusted to obtain the states of the two polarization controllers corresponding to the highest similarity of the interference signals. These states are then maintained during monitoring, resulting in the highest similarity of the interference signals obtained during submarine cable monitoring, thus allowing for accurate determination of the vibration location.

[0039] It should be noted that when the similarity between the two interference signals is highest, then I... 上 and I 下The waveform consistency is best, and at this time we can assume that cos[η1(t)]=cos[η2(t)]≈1, μ1(t)=μ2(t)=μ, then formulas (1) and (2) can be simplified to:

[0040]

[0041]

[0042] At this point, it can be assumed that the phase change of the two interference signals is caused only by external vibration, and can be determined through I. 上 and I 下 The cross-correlation is used to calculate the signal delay, thereby deducing the accurate location of the vibration.

[0043] The device for improving the stability of submarine cable monitoring based on an improved DMZI provided in this invention uses a phase modulator, a first polarization controller, and a second polarization controller in the optical path of a symmetrical Mach-Zeder interferometer. During the adjustment phase, a triangular wave is input into the phase modulator, effectively applying an external vibration. Simultaneously, the states of the first and second polarization controllers are adjusted to maximize the similarity between the two interference signals. Therefore, when using this device for submarine cable monitoring, the location of the vibration can be accurately calculated, making the device highly sensitive to external vibrations. This improves the stability of the device and the vibration positioning accuracy, achieving meter-level accuracy in field tests.

[0044] In one implementation, such as Figure 1 As shown, the device for improving the stability of submarine cable monitoring based on the improved DMZI further includes: a driving circuit 13 and a data acquisition card 11. The driving circuit 13 is used to provide an analog voltage to drive the phase modulator 12. The data acquisition card 11 is used to acquire the detection results of the first optical path to obtain the corresponding interference signal. The data acquisition card 11 is also used to acquire the detection results of the second optical path and compare them with the detection results of the first optical path.

[0045] Specifically, to extract the peak-to-peak value of the interference signal, the phase modulation needs to traverse from 0 to 2π. Therefore, the driving circuit needs to send a set of triangular waves with a peak-to-peak value greater than 2π to the phase modulator. Simultaneously, the phase modulator is located at the beginning of the first or second optical fiber, which is equivalent to applying an external vibration at the starting end. Without considering the influence of polarization, the two output signals have a fixed time delay τ = 2L / c, where L is the length of the optical fiber. The acquisition card compares the detection results of the two optical paths, i.e., compares whether the similarity of the interference signals of the two optical paths is the highest. When it is the highest, there is only a fixed time delay τ between the two signals. Therefore, when judging the similarity, one of the signals can be shifted by τ, and the Euclidean distance between the two interference signals can be calculated. When the Euclidean distance is the smallest, the similarity is judged to be the smallest.

[0046] The device for improving the stability of submarine cable monitoring based on an improved DMZI provided in this embodiment of the invention addresses the problem that the polarization state of DMZI is easily interfered with when used for submarine cable vibration monitoring. It proposes an improved DMZI structure that adds two polarization controllers and a phase modulator to the traditional structure, thereby realizing real-time adjustment of the polarization state of the first and second optical paths.

[0047] This invention also provides a method for improving the stability of submarine cable monitoring based on an improved DMZI, applicable to the apparatus for improving the stability of submarine cable monitoring based on an improved DMZI described in the above embodiments, such as... Figure 3 As shown, the method includes the following steps:

[0048] Step S101: Adjust the first polarization controller and input a triangular wave to the interferometer arm using a phase modulator until the peak-to-peak value of the first optical path interference signal is maximized, thus obtaining the first state of the first polarization controller. Specifically, adjusting the first polarization controller can change the polarization state of the beam passing through it. During adjustment, a triangular wave with a peak-to-peak value greater than 2π needs to be input to the interferometer arm using a phase modulator. During the adjustment process, the peak-to-peak value of the first optical path interference signal, i.e., the difference between the highest and lowest values ​​of the signal within one period, is recorded to determine whether it has reached its maximum.

[0049] Before adjusting the first polarization controller, the process includes fixing the second polarization controller to a preset state. This preset state can be any state of the first polarization controller; that is, while adjusting the first polarization controller, the state of the second polarization controller remains fixed.

[0050] Step S102: Maintain the first state of the first polarization controller, adjust the second polarization controller, and input a triangular wave into the interferometer arm using a phase modulator until the similarity between the first and second optical path interference signals is highest, thus obtaining the second state of the second polarization controller. Specifically, control the first polarization controller to be in the state corresponding to the maximum peak-to-peak value; then adjust the second polarization controller to change the polarization state of the beam passing through it. During adjustment, a triangular wave with a peak-to-peak value greater than 2π needs to be input into the interferometer arm using a phase modulator; during the adjustment process, record the first and second optical path interference signals, determine whether their similarity is highest, and determine the state of the second polarization controller corresponding to the highest similarity.

[0051] The method for improving the stability of submarine cable monitoring based on an improved DMZI provided in this invention uses a phase modulator to input a triangular wave, which can simulate external vibrations. By changing the state of two polarization controllers, the arbitrary polarization state of the transmitted beam can be adjusted, so that the similarity of the two interference signals obtained is the highest. Thus, the state of the polarization controller corresponding to the highest similarity is used for submarine cable monitoring, so that the influence of polarization on interference is minimized, thereby making the improved DMZI most sensitive to external vibrations.

[0052] In one embodiment, the method for improving the stability of submarine cable monitoring based on the improved DMZI further includes: turning off the phase modulator, maintaining the first state of the first polarization controller and the second state of the second polarization controller, and using the device for submarine cable monitoring. Specifically, the phase modulator is used to simulate external vibrations during the adjustment phase. Once the highest similarity is determined, the phase modulator is turned off, maintaining the corresponding states of the first and second polarization controllers. Submarine cable monitoring is performed in this state, thereby suppressing the interference light intensity fading and phase drift caused by polarization changes due to the environment, vibration, etc., during the monitoring process, ensuring the highest interference efficiency, and improving stability and vibration positioning accuracy.

[0053] In one embodiment, the highest similarity between the first and second optical path interference signals is determined as follows: either interference signal is shifted by a preset time delay, and the Euclidean distance between the two interference signals is calculated. The highest similarity is achieved when the Euclidean distance is minimized. Specifically, when the phase modulator inputs a triangular wave to its interferometer arm, it is equivalent to applying an external vibration at the starting end. Without considering the effects of polarization, the two output signals have a fixed time delay τ = 2L / c. Therefore, the two interference signals have a fixed time delay τ when the similarity is highest. Thus, the similarity can be determined by shifting one interference signal by τ and calculating the Euclidean distance between the two interference signals; the highest similarity is achieved when the Euclidean distance is minimized.

[0054] In one embodiment, adjusting the first polarization controller includes: traversing all states of the first polarization controller; adjusting the second polarization controller includes: traversing all states of the second polarization controller. Specifically, to determine whether the peak-to-peak value of the interference signal has reached its maximum, all states of the first polarization controller can be traversed, and then the peak-to-peak values ​​recorded in all states can be compared. The state corresponding to the maximum peak-to-peak value is selected as the first state of the first polarization controller. Similarly, when performing similarity judgment, all states of the second polarization controller also need to be traversed, and the state corresponding to the highest similarity is selected as the second state of the second polarization controller. When the first polarization controller is in the first state and the second polarization controller is in the second state, the device is in its optimal operating state.

[0055] The method for improving the stability of submarine cable monitoring based on an improved DMZI provided in this embodiment of the invention iterates through the states of two polarization controllers and optimizes them with the maximum peak-to-peak value and the highest similarity of the interference signal as the targets. This simultaneously suppresses the intensity fading and phase drift of the interference light caused by polarization changes due to the environment, vibration, etc., and improves the vibration monitoring and positioning performance of DMZI when applied to submarine cable monitoring.

[0056] In one implementation, such as Figure 4 As shown, the method for improving the stability of submarine cable monitoring based on the improved DMZI adopts the following process: keeping the state of the second polarization controller unchanged, adjusting the first polarization controller, and sending a triangular wave to the phase modulator using a drive circuit; the acquisition card acquires and records the peak-to-peak value of the interference signal of the second photodetector; it is determined whether all states of the first variable array controller have been traversed; if so, the state corresponding to the maximum peak-to-peak value is selected to set the state of the first polarization controller; the second polarization controller is adjusted, and a triangular wave is sent to the phase modulator using a drive circuit; the acquisition card acquires the two interference signals of the first and second photodetectors, calculates the Euclidean distance after shifting either signal by a time delay τ, and records it; it is determined whether all states of the second polarization controller have been traversed; if so, the state corresponding to the minimum Euclidean distance and the highest similarity is selected to set the state of the second polarization controller; after the first and second polarization controllers are set, the DZMI is in the optimal working state and can be used for subsequent submarine cable monitoring.

[0057] While exemplary embodiments and their advantages have been described in detail, those skilled in the art can make various changes, substitutions, and modifications to these embodiments without departing from the spirit of the invention and the scope of protection defined by the appended claims. Such modifications and variations all fall within the scope defined by the appended claims. For other examples, those skilled in the art should readily understand that the order of process steps can be changed while remaining within the scope of the invention.

[0058] Furthermore, the scope of this invention is not limited to the processes, mechanisms, manufacturing methods, material compositions, means, methods, and steps of the specific embodiments described in the specification. From the disclosure of this invention, those skilled in the art will readily understand that any existing or future processes, mechanisms, manufacturing methods, material compositions, means, methods, or steps that perform substantially the same function or obtain substantially the same results as the corresponding embodiments described in this invention can be applied according to this invention. Therefore, the appended claims are intended to include these processes, mechanisms, manufacturing methods, material compositions, means, methods, or steps within their scope of protection.

Claims

1. A device for improving the stability of submarine cable monitoring based on an improved DMZI, characterized in that, include: Symmetrical Mach-Zeder interferometer, phase modulator, first polarization controller and second polarization controller; The symmetrical Mach-Zeder interferometer includes a first optical path and a second optical path, the first optical path and the second optical path include a common part, the common part includes a first interferometer arm and a second interferometer arm; The first polarization controller is disposed in the first optical path, the second polarization controller is disposed in the second optical path, and the phase modulator is disposed in the first interferometer or the second interferometer. The phase modulator is used to input a triangular wave into the interferometer arm during the adjustment phase; The first polarization controller is used to change the polarization state of the first optical path during the adjustment phase, so that the peak-to-peak value of the interference signal obtained by the first optical path is maximized. The second polarization controller is used to change the polarization state of the second optical path during the adjustment phase, so that the similarity of the interference signals of the first and second optical paths is the highest.

2. The device for improving submarine cable monitoring stability based on improved DMZI according to claim 1, characterized in that, The first interferometer arm includes a first optical fiber, the second interferometer arm includes a second optical fiber, and the common part further includes a laser, a first coupler, a first circulator, a second coupler, a third coupler, a third optical fiber, and a second circulator. The first optical path further includes a first photodetector, the second optical path further includes a second photodetector, the first polarization controller is disposed between the first circulator and the second coupler, and the second polarization controller is disposed between the third optical fiber and the second circulator. The laser beam output by the laser is split into two beams after passing through the first coupler. The first beam passes through the first circulator and the first polarization controller, and then is split into two beams by the second coupler. The two beams enter the first optical fiber and the second optical fiber respectively for transmission. After being combined by the third coupler, they pass through the third optical fiber, the second polarization controller, and the second circulator in sequence before entering the second photodetector. The transmission optical path of the first beam constitutes the first optical path. The second beam obtained by the first coupler passes through the second circulator, the second polarization controller, and the third optical fiber, and is then split into two beams by the third coupler. The two beams enter the first optical fiber and the second optical fiber respectively for transmission, and are then combined by the second coupler. After passing through the first polarization controller and the first circulator, they enter the first photodetector. The transmission optical path of the second beam constitutes the second optical path.

3. The device for improving submarine cable monitoring stability based on improved DZI according to claim 1, characterized in that, Also includes: A driving circuit is provided to provide an analog voltage to drive the phase modulator.

4. The device for improving submarine cable monitoring stability based on improved DMZI according to claim 1, characterized in that, Also includes: The acquisition card is used to acquire the detection results of the first optical path to obtain the corresponding interference signal. The acquisition card is also used to acquire the detection results of the second optical path and compare them with the detection results of the first optical path.

5. The device for improving submarine cable monitoring stability based on improved DMZI according to claim 1, characterized in that, The peak-to-peak value of the triangular wave is greater than 2π.

6. A method for improving the stability of submarine cable monitoring based on an improved DMZI, characterized in that, The method for using the apparatus according to any one of claims 1-5, which enhances the stability of submarine cable monitoring based on an improved DMZI, comprises: The first polarization controller is adjusted and a triangular wave is input to the interferometer arm using a phase modulator until the peak-to-peak value of the first optical path interference signal is maximized, thus obtaining the first state of the first polarization controller. Maintain the first state of the first polarization controller, adjust the second polarization controller and use a phase modulator to input a triangular wave into the interferometer arm until the similarity between the first optical path interference signal and the second optical path interference signal is the highest, thus obtaining the second state of the second polarization controller.

7. The method for improving submarine cable monitoring stability based on improved DMZI according to claim 6, characterized in that, Also includes: The phase modulator is turned off, the first polarization controller is kept in the first state, and the second polarization controller is kept in the second state. The device is used to monitor the submarine cable.

8. The method for improving submarine cable monitoring stability based on improved DMZI according to claim 6, characterized in that, The highest similarity between the first optical path interference signal and the second optical path interference signal is determined using the following method: Shift any one of the interference signals by a preset time delay, calculate the Euclidean distance between the two interference signals, and the similarity is highest when the Euclidean distance is minimized.

9. The method for improving submarine cable monitoring stability based on improved DMZI according to claim 6, characterized in that, Adjusting the first polarization controller includes: traversing all states of the first polarization controller; Adjusting the second polarization controller involves iterating through all states of the second polarization controller.

10. The method for improving submarine cable monitoring stability based on improved DMZI according to claim 6, characterized in that, Before adjusting the first polarization controller, the process includes fixing the second polarization controller to a preset state.

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