Underwater tunnel monitoring system based on optical fiber sensor and visual monitoring method

Abstract

This invention relates to the field of tunnel monitoring technology, and discloses an underwater tunnel monitoring system and visualization monitoring method based on fiber optic sensors. A pulse signal generating unit generates a pulse signal of a certain frequency, which is converted into a light wave of the corresponding frequency by a laser and then incident on the fiber optic sensor. The fiber optic sensor is installed inside the tunnel. A fiber optic data analyzer converts the received reflected light wave into an electrical pulse of the corresponding frequency and transmits the electrical pulse signal to a pulse signal receiving unit. The pulse signal receiving unit counts the pulses, and a data processing unit calculates the pulse frequency reflected by each fiber optic segment based on the number of pulses counted. The strain value is calculated based on the pulse frequency for monitoring. Furthermore, the three-dimensional visualization monitoring allows for timely observation of alarm points, elimination of potential hazards, significantly reduced workload during manual inspections, and improved response efficiency. An interactive interface facilitates comprehensive and multi-angle viewing of the tunnel's condition.

Description

TECHNICAL FIELD

[0001] The application relates to underwater tunnel detection, in particular to an underwater tunnel monitoring system based on a fiber sensor and a visual monitoring method, and belongs to the technical field of tunnel monitoring. BACKGROUND

[0002] With the development of social economy and the improvement of people's living standards, people's demand for electric energy is increasing, and nuclear power generation as clean energy is also being paid more and more attention. In a nuclear power plant, flowing cooling water is used to ensure that the temperature of the nuclear power plant is controllable, so it is very important to ensure the normal operation of the water intake tunnel of the nuclear power plant. However, due to the influence of the surrounding environment of the tunnel and the aging of the structural materials, the tunnel structure will deform in different forms over time, which will threaten the safe operation of the tunnel when it exceeds a certain threshold. In order to protect the structural safety of the water intake tunnel, it is necessary to automatically monitor the deformation of the water intake tunnel during operation, and to monitor the specific conditions of the water intake tunnel in real time. At present, optical fibers are used for monitoring.

[0003] Publication No. CN114184137A discloses a tunnel deformation monitoring system and method based on long-gauge optical fiber sensing technology, which comprises an optical fiber sensor system, a data processing system, a deformation calculation system and a warning system. The optical fiber sensor system is used to arrange sensors and collect sensor data. The data processing system is used to obtain one-way strain data according to the sensor data. The deformation calculation system is used to obtain deformation data according to the one-way strain data. The warning system is used to issue a deformation warning based on the deformation data. However, when the monitoring reaches the threshold value, an alarm will occur, but it is not convenient to display the position of the detection point intuitively, it is not convenient to interactively monitor, and it is not convenient to quickly locate the deformation position.

[0004] Therefore, the present application can monitor the temperature and strain of each position of the target tunnel, and when the preset value is exceeded due to external factors, an alarm will be issued, and the alarm point can be displayed in three dimensions, so that problems can be found in time and tunnel safety hazards can be effectively eliminated. SUMMARY

[0005] In order to solve the above-mentioned technical problems, the purpose of the present application is to provide an underwater tunnel monitoring system based on a fiber sensor and a visual monitoring method. The fiber sensor is used in the whole tunnel, and after big data cloud computing, the actual situation of each position can be accurately calculated. When the preset value is exceeded, an alarm is issued, and the alarm point is quickly and intuitively prompted.

[0006] The application achieves the above-mentioned purposes through the following technical solutions:

[0007] An underwater tunnel monitoring system and visual monitoring method based on an optical fiber sensor, a pulse signal generation unit generates a pulse signal of a certain frequency, a laser converts it into an optical wave of a corresponding frequency, and the optical wave is injected into an optical fiber sensor, the optical fiber sensor is arranged in a tunnel, a fiber data analyzer converts the received reflected light wave into an electrical pulse of a corresponding frequency, and transmits the electrical pulse signal to a pulse signal receiving unit, the pulse signal receiving unit counts the pulses, a data processing unit calculates the pulse frequency reflected by each section of the optical fiber according to the number of counted pulses, a strain value is calculated according to the pulse frequency, and the strain value P is calculated according to the strain calculation formula:

[0008]

[0009] Wherein, K is a strain coefficient, V is a strain sensing measured frequency value, V t is a temperature sensing measured frequency value, V0 is an initial frequency value after installation of the strain sensing, V t0 is an initial frequency value after installation of the temperature sensing, K T is a temperature coefficient, K t is a temperature compensation coefficient.

[0010] The strain value of the pulse frequency is obtained, saved through an SQL Server database, system parameters are adjusted, the strain value and the temperature are calculated, displayed through an icon UI, and a waveform diagram is drawn to display the parameters, and an alarm signal is generated to alarm when the threshold is exceeded.

[0011] Further, the pulse signal generation unit includes an SPI input module, a multiplier module, a time sequence generation module, a RAM read-write module, and an encoding output module, data is transmitted to the SPI input module through the SPI protocol, the encoding period N p of the data is extracted, the pulse delay N d , the number of encoding bits N bit , the pulse width N T , the number of zeros inserted after a single pulse N0, the pulse accumulation number N, and the code are sent to the multiplier module and the time sequence generation module, and the code is written into the data processing unit, and multiplication processing is performed in the multiplier module: (N0+1)*N T *N bit, the length of the encoding envelope of the system is obtained, and the data is transmitted into the timing generation module, in which the trigger envelope, the encoding envelope, the encoding output clock, the read data processing unit clock and the zero insertion signal are generated and used to read the encoding in the data processing unit, and the encoding pulse signal is output in the encoding output module, the pulse signal receiving unit includes an input data processing module, an adder module, a DDR3 read and write data processing module and a DDR3 module, the electrical pulse signal enters the input data processing module to process the data transmitted by the analog-digital conversion system, the addition processing of the data at the same position is performed in each pulse period, the two addends of the addition are the data in the input data processing module and the data in the DDR3 read data processing module, respectively, the added data is stored in the DRR3 module through the DDR3 write data processing module, and one cycle is realized, when the cycle number is equal to the set cycle number, the data is output to the PS end of the pulse signal receiving unit, after the corresponding frequency fb is obtained through calculation at the PS end, the data is uploaded to the host computer database, when the P value is calculated, the Brillouin time domain reflection principle is used, the Brillouin optical time domain reflection technology is a distributed Brillouin sensing technology using the technology of detecting self-luminous Brillouin scattering, by injecting pulse light with a frequency of f at one end of the optical fiber, a backscattered spBS signal with a central frequency of f-fB can be obtained, wherein fB is the Brillouin frequency shift, after detecting and processing the weak signal, the temperature or strain distribution can be sensed through the frequency shift or intensity of the spBS, when the hardware unit is erected, the detection points are detected according to one point every 10 meters, and each point is displayed and set with a detection animation, when in use, the FPGA sends the pulse signal with a frequency of f to the laser, the laser emits laser pulse f to the optical fiber cable, the optical fiber cable reflects laser pulse fb to the optical fiber data analyzer, the optical fiber data analyzer feeds back the pulse signal with a frequency of fb to the FPGE, data transmission is performed between the FPGE and the ARM, the ARM transmits f and fb to the host display for display, the host display transmits the inspection signal to the ARM, and the data is transmitted to the FPGA through the ARM, the monitoring cycle is completed, and the client can operate conveniently, in the FPGA, the pulse signal generation architecture is that the external data is transmitted to the FPGA chip through the SPI protocol, the data includes the encoding period N p , the pulse delay N d , the number of encoding bits Nbit, the pulse width NT, the number of zero insertion after a single pulse N0, the pulse accumulation number N and the specific encoding code, the data is transmitted according to the SPI protocol rule, the data is extracted after the same processing in the FPGA, the data is sent to the multiplier module and the timing generation module, and the specific encoding is written into the RAM, in the multiplier module, (N0+1)*N T *N bitThe multiplication processing obtains the encoding envelope length of the system, and transmits the data into the timing generation module, in which the trigger envelope, the encoding envelope, the encoding output clock, the reading RAM clock and the zero insertion signal are generated, the encoding in the RAM is read, and the encoding pulse signal is output in the encoding output module, the characteristics of the signal are consistent with the input data, and the signal can be changed according to the change of the input data, the pulse signal generated by the system is an electrical signal, is loaded on the laser power supply to perform electro-optical conversion, and the forward pumping optical pulse of the BOTDR optical fiber sensor is generated, however, the tunnel of the system is more than 4000 meters long, so that the power is large enough, the optical fiber amplifier is used to increase the optical signal power, and the optical fiber cable is shot again.

[0012] The application further discloses an underwater tunnel visual monitoring method based on the optical fiber sensor.

[0013] Step S01: a virtual scene and a tunnel model are constructed, and the length and the detected position of the tunnel model are visually displayed through a coordinate ruler;

[0014] Step S02: data obtained by the underwater tunnel monitoring system based on the optical fiber sensor is acquired, saved through an SQL Server database, adjusted system parameters, calculated strain values and temperatures, and displayed through an icon UI;

[0015] Step S03: real-time change conditions of each parameter are displayed through a waveform diagram, and if the parameter exceeds a corresponding threshold value, alarm is performed.

[0016] Further, the step S03 also includes performing inspection by setting the type of the inspection target, when performing the inspection operation, the view angle follows the cursor for inspection and advances along the water intake tunnel, reads the corresponding data in the database and displays, the step S03 displays a UI sign above the corresponding monitoring point of the tunnel to indicate whether the inspection parameter meets the requirement, if the monitored parameter exceeds the preset range, the UI sign will display red, and a red alarm frame will flash at the bottom of the whole interface, if it is within the required range, it will display gray, after the inspection is completed, an inspection end window will automatically pop up, and the number of normal points and alarm points in the inspection process is displayed, in the step S03, the data icon analysis interface is entered through point screening, the corresponding tunnel position is positioned according to the quick positioning bar, the data acquisition point is selected, the parameter change of the data acquisition point in the inspection process is displayed, and all historical data of the point are obtained, in the step S01, an equal ratio three-dimensional model is constructed, including terrain, seawater, plant, tunnel and optical cable, when making the terrain, sandstone and grassland maps are added on the basis of adding grassland and tree models, and a selectable display hidden coordinate ruler is used to visually display the length of the tunnel and the detected position, when it is needed to be viewed, the scale ruler switch is clicked on the left console to open, if it is not needed, it is closed again, the parameters obtained by inspection are visually displayed by the line chart at the end of the inspection, and the three-dimensional model also includes a view module and a zoom module, and the roaming module is used to move in the simulation view in the first person view, and the user can control the mouse to view the tunnel from different angles, and the zoom module is used for zooming in and out in the simulation view, and the macro layout or local details in the scene can be understood by using different zoom ratios.

[0017] Technical effects and advantages of the present application:

[0018] Based on the Brillouin time domain reflection technology, the FPGA is used to generate and count frequency pulses, and the photoelectric pulse is output through the converter, the frequency of the photoelectric pulse is calculated twice, the stress and temperature change of the tunnel are measured according to the corresponding formula, so that the long-distance tunnel monitoring can be realized, on this basis, the data is transmitted to the host, the unity3D virtual reality technology is used to build a 1:1 virtual scene, the system parameters can be adjusted, the strain value and temperature are calculated, and the icon UI is displayed. And set up a variety of UI interfaces, the system man-machine interaction is good, the operator can use the system according to his own style. When an alarm occurs, the three-dimensional model can be used for quick positioning, the alarm point can be observed in time, the reaction can be carried out in time, the hidden danger can be eliminated, the intensity during manual inspection can be greatly reduced, the reaction efficiency can be improved, and the tunnel condition can be viewed from all directions and multiple angles through the interactive interface.

[0019] Instant inspection and timing inspection can be carried out, the system will automatically save the recent inspection data in the history record, when the inspection result value reaches the preset yellow line and red line, the system will make different responses, which is convenient for more accurate mastering of the real-time situation inside the tunnel. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 The figure is the system overall design framework in the embodiment;

[0021] Figure 2 The figure is the system hardware connection running diagram in the embodiment;

[0022] Figure 3 The figure is the FPGA architecture diagram in the embodiment;

[0023] Figure 4 The figure is the underwater tunnel visualization monitoring method flow chart based on the optical fiber sensor in the embodiment;

[0024] Figure 5 The figure is the view module schematic diagram in the embodiment;

[0025] Figure 6 The figure is the interface diagram of the rapid inspection in the embodiment;

[0026] Figure 7 The figure is the total use case diagram in the embodiment;

[0027] Figure 8 The figure is the rapid inspection example diagram in the embodiment;

[0028] Figure 9 The figure is the system main function sequence diagram in the embodiment;

[0029] Figure 10 The figure is the interface diagram in the rapid inspection in the embodiment;

[0030] Figure 11 The figure is the data visualization display diagram in the embodiment. DETAILED DESCRIPTION

[0031] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0032] Please refer to Figure 1 , 2As shown in the figure, a kind of underwater tunnel monitoring system based on optical fiber sensor, by pulse signal generating unit generates a certain frequency of pulse signal, by laser conversion corresponding frequency light wave, into optical fiber sensor, optical fiber sensor is set in tunnel, by optical fiber data analyzer the received reflected light wave is converted into corresponding frequency electric pulse, and the electric pulse signal is given to pulse signal receiving unit, pulse signal receiving unit counts the pulse, by data processing unit according to the number of pulse counting calculation each section of optical fiber reflected pulse frequency, by pulse frequency calculation strain value, strain value P through strain calculation formula:

[0033]

[0034] Wherein, K is strain coefficient, V is strain sensing measured frequency value, V t Temperature sensing measured frequency value, V0 is the initial frequency value after strain sensing installation, V t0 Temperature sensing installation initial frequency value, K T Temperature coefficient, K t Temperature compensation coefficient.

[0035] Pulse frequency strain value, through SQL Server database is saved, adjust system parameters, calculate strain value and temperature, through icon UI display, and draw waveform diagram, display parameters, when exceeding threshold, alarm signal is generated, alarm.

[0036] Specifically, pulse signal generating unit and pulse signal receiving unit can use FPGA, data processing unit can adopt ARM.

[0037] Preferably, in combination Figure 3 As shown in the figure, pulse signal generating unit includes SPI input module, multiplier module, time sequence generating module, RAM read-write module and encoding output module, data is transmitted to SPI input module by SPI protocol, processing extraction obtains the encoding period N p Pulse delay N d Encoding bit number N bit Pulse width N T Single pulse zero number N0 after insertion, pulse accumulation number N and code, data is sent to multiplier module and time sequence generating module, and the encoding is written into data processing unit, multiplication processing is carried out in multiplier module: (N0+1)*N T *N bitThe length of the encoding envelope of the system is obtained, and the data is transmitted into the timing generation module, in which the trigger envelope, the encoding envelope, the encoding output clock, the read data processing unit clock and the zero insertion signal are generated and used to read the encoding in the data processing unit, and the encoding pulse signal is output in the encoding output module.

[0038] The pulse signal receiving unit comprises an input data processing module, an adder module, a DDR3 read and write data processing module and a DDR3 module. The electric pulse signal enters the input data processing module to process the data output by the analog-digital conversion system. In each pulse period, the data at the same position is added. The two addends of the addition are the data in the input data processing module and the data in the DDR3 read data processing module. The added data is stored in the DRR3 module through the DDR3 write data processing module, and one cycle is realized. When the cycle number is equal to the set cycle number, the data is output to the PS end of the pulse signal receiving unit. After the corresponding frequency fb is obtained through calculation at the PS end, the frequency is uploaded to the host computer database.

[0039] In the calculation of P value, the Brillouin time domain reflection principle is used. The Brillouin optical time domain reflection technology is a sensing Brillouin distributed sensing technology using the technology of detecting self-Brillouin scattering. By injecting pulse light with a frequency of f at one end of the optical fiber, a backscattered spBS signal with a central frequency of f-fB can be obtained, wherein fB is the Brillouin frequency shift. After detecting and processing the weak signal, the temperature or strain distribution can be sensed through the frequency shift or intensity of the spBS.

[0040] Specifically, when the hardware unit is erected, the detection points are detected every 10 meters, and each point is displayed and set with a detection animation. When in use, the FPGA sends a pulse signal with a frequency of f to the laser, and the laser emits a laser pulse f to the optical fiber cable. The optical fiber cable reflects a laser pulse fb to the optical fiber data analyzer, and the optical fiber data analyzer feeds back a pulse signal with a frequency of fb to the FPGE. Data transmission is performed between the FPGE and the ARM, and the ARM transmits f and fb to the host display for display. The host display transmits a patrol signal to the ARM, which is transmitted to the FPGA through the ARM data transmission to complete the monitoring cycle. The client can easily operate the FPGA. In the FPGA, the pulse signal generation architecture is that external data is transmitted to the FPGA chip through the SPI protocol, and the encoded pulse signal is output. The characteristics of this signal match the input data, and can be changed according to the change of the input data. The pulse signal generated by this system is an electrical signal, which is loaded onto the laser power supply for electro-optical conversion, thereby generating a forward pumping photoelectric pulse of the BOTDR optical fiber sensor. However, since the tunnel is as long as 4000 meters, in order to make the power large enough, an EDFA optical fiber amplifier is used to increase the optical signal power, and then the optical fiber cable is injected.

[0041] In another embodiment, as shown in Figure 4 A method for visualizing monitoring of an underwater tunnel based on an optical fiber sensor, comprising the following steps:

[0042] S01: Construct a virtual scene and a tunnel model, and the length of the tunnel model and the detected position are visualized displayed through a coordinate ruler;

[0043] S02: The data obtained by the underwater tunnel monitoring system based on the optical fiber sensor is saved through the SQL Server database, the system parameters are adjusted, the strain value and the temperature are calculated, and the icon UI is displayed;

[0044] S03: The real-time change of each parameter is displayed through a waveform diagram, and an alarm is given if the parameter exceeds the corresponding threshold.

[0045] Specifically, the three-dimensional view part is developed using Unity3D 2019, dynamic UI and visual data display are used, and all visual parts are made through Unity3D. The three-dimensional model is modeled using Maya and 3dsMax software, and the three-dimensional model is restored to the appearance of the tunnel 1:1. Under the premise of not changing the model accuracy, the surface is optimized to ensure the smoothness of the system operation.

[0046] In the software, island, factory, road, living area simple model (island for schematic, factory with general factory model and satellite map instead, road according to the drawing, living area to place house simple model), waterway according to the general shape of the production (semi-transparent, concrete shape), water tunnel above the terrain simple model (80% transparent), put into seawater, the program overall display content according to the general map size design, according to the realistic style adjustment, in the general realistic style increase contrast and color saturation, enhance the picture color brightness and aesthetic sense.

[0047] As shown in Figure 5 , the setting view module contains tunnel appearance image display, tunnel model, virtual scene, and system UI. The overall virtual scene contains mountain terrain and simulated ocean scene. The scene is made by the terrain making module built in Unity3D, and on the basis of adding sandstone map and grassland map, grassland model, adjusting light and direction, the scene is more realistic, as shown in Figure 6 .

[0048] The tunnel model is designed and made by using 3DMax and loaded into Unity, and the program for tunnel appearance visualization is written by C#, so that users can choose the display style of the tunnel according to their own preferences.

[0049] System UI, namely functional UI, contains interface display, indication icon, control bar, inspection animation, etc.

[0050] The total use case diagram of the three-dimensional tunnel visualization real-time monitoring system is shown in Figure 7 . In the simulation view, move in the first person perspective, and let the user control the mouse to let the user view the tunnel from different angles. In the simulation view, zoom in and zoom out the view, understand the macro layout or local details in the scene through different zoom ratios.

[0051] Inspection is divided into timed inspection and timely inspection.

[0052] Alarm: the system judges according to the data fed back by the inspection and the preset alarm value, and reports yellow alarm when the preset value exceeds the yellow warning line. At this time, the alarm point will be yellow, and will always be displayed in the simulation tunnel and the left menu bar of the system. Clicking this alarm point can view the historical data of the alarm point; when the preset value exceeds the red warning line, report red alarm. The display content of red alarm is the same as that of yellow alarm, but the color is displayed in red, and the system will automatically send a message to the mobile phone retained by the system. (Can add sound alarm, alarm flashing, etc.).

[0053] The length of the tunnel and the detected position are visualized by a selectable display hidden coordinate ruler, which can be opened by clicking the ruler switch in the left console when needed, and closed by clicking again if not needed. The parameters obtained by the inspection are visualized by a line chart at the end of the inspection.

[0054] After entering the system, the left mouse button is held down to rotate the view angle, the mouse wheel is scrolled to zoom in and out, the mouse is moved to the left of the screen to open the control bar, and the corresponding function button is clicked to trigger the corresponding event, such as Figure 6 .

[0055] Quick positioning

[0056] Due to the length of the water intake tunnel, in order to facilitate the viewing of each position of the water intake tunnel, a quick positioning function is added. After clicking the quick positioning function in the left control bar, a draggable progress bar appears above to move to the specific position to be observed. The bottom also provides a button method for quick positioning. The operator can choose to use according to preference. After selecting the positioning location, the view angle will also move to the specified location for point detection.

[0057] Quick inspection

[0058] As shown in Figure 8 , before the inspection: after selecting the quick inspection in the left console, a parameter selection box appears on the interface, which can select the type of inspection target as temperature A, temperature B, strain force A, and strain force B. Click the quick inspection target on the right to start the inspection.

[0059] During the inspection: as shown in Figure 9 , the view angle will follow the cursor along the water intake tunnel, simulating the process of manual inspection. During the inspection, a UI signboard will be displayed above the corresponding monitoring point of the tunnel to indicate whether the inspection parameters meet the requirements. If the monitored parameters exceed the expected range, it may indicate a risk. The UI display board will display red, and there will be a red alarm box flashing at the bottom of the entire interface. If it is within the required range, it will display gray, as shown in Figure 10 .

[0060] After the inspection is completed, an inspection completion window will automatically pop up, summarizing the number of normal, yellow alarm, and red alarm during the inspection.

[0061] After understanding the overall inspection situation, click the point selection bar on the left control bar to enter the data icon analysis interface. Drag the quick positioning bar to the corresponding tunnel location on the top.

[0062] After finding the corresponding section of the problem point, through the left control bar, the data acquisition point is selected, and after the point is selected, the parameter change of the data acquisition point in the current inspection process is displayed (as shown in 11). And can drag the history positioning bar above the image to view all historical data of the point at the corresponding historical time, so as to know the reason of the alarm more clearly.

[0063] Through the history positioning bar, the history can be inquired from all data, the data group can be switched to switch A group and B group data, and the specific point can be clicked to display the point value.

[0064] It is apparent for those skilled in the art that the present application is not limited to the details of the above exemplary embodiments, and the present application can be implemented in other concrete forms without departing from the spirit or essential characteristics of the present application. Therefore, the embodiments should be considered in all aspects as illustrative and not restrictive, and the scope of the present application is defined by the appended claims rather than the above description, and it is intended to encompass all changes falling within the meaning and range of equivalents of the claims. Any reference signs in the claims should not be considered as limiting the claims to which they relate.

[0065] In addition, it should be understood that although the present specification is described in terms of embodiments, not every embodiment contains only one independent technical solution, and the description of the specification is only for the sake of clarity, and those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can be combined appropriately to form other embodiments that those skilled in the art can understand.

Claims

1. An optical fiber sensor based underwater tunnel monitoring system characterized by: The pulse signal generating unit generates a pulse signal of a certain frequency, which is converted into a light wave of a corresponding frequency by a laser, and is injected into an optical fiber sensor arranged in a tunnel. The optical fiber data analyzer converts the received reflected light wave into an electric pulse of a corresponding frequency, and transmits the electric pulse signal to the pulse signal receiving unit. The pulse signal receiving unit counts the pulses, and the data processing unit calculates the strain value according to the counted number of pulses. The pulse signal generating unit comprises an SPI input module, a multiplier module, a timing generating module, a RAM read-write module and an encoding output module, data is transmitted to the SPI input module through SPI protocol, the encoding period N p , pulse delay N d , encoding bit number N bit , pulse width N T , single pulse post-insert zero number N0, pulse accumulation number N and after encoding, the data is sent to the multiplier module and the timing generating module, and the encoding is written into the data processing unit, multiplication processing is carried out in the multiplier module: (N0+1)*N T *N bit , the encoding envelope length of the system is obtained, and the data is transmitted into the timing generating module, the trigger envelope, the encoding envelope, the encoding output clock, the read data processing unit clock and the insert zero signal are generated in the timing generating module, and are used to read the encoding in the data processing unit, and the encoding pulse signal is output in the encoding output module.

2. The optical fiber sensor based underwater tunnel monitoring system as claimed in claim 1, wherein: The pulse signal receiving unit includes an input data processing module, an adder module, a DDR3 read / write data processing module, and a DDR3 module. The electric pulse signal enters the input data processing module to process the data output by an analog-to-digital conversion system. In each pulse cycle, the data at the same position is added. The two addends of the addition are the data in the input data processing module and the data in the DDR3 read data processing module. The added data is stored in the DRR3 module through the DDR3 write data processing module, and one cycle is completed.

3. The optical fiber sensor based underwater tunnel monitoring system as claimed in claim 2, wherein: When the number of cycles is equal to the set number of cycles, the data is output to the PS end of the pulse signal receiving unit. After the corresponding frequency fb is calculated at the PS end, it is uploaded to the host computer database.

4. The optical fiber sensor based underwater tunnel monitoring system as claimed in claim 1, wherein: The strain value P is calculated by the strain calculation formula: ； wherein K is a coefficient of strain, V is a strain sensing measured frequency value, is a temperature sensing measured frequency value, is a strain sensing post-installation initial frequency value, is a temperature sensing post-installation initial frequency value, is a temperature coefficient, is a temperature compensation coefficient.

5. A method for visual monitoring of underwater tunnels based on fiber optic sensors, characterized by: The method comprises the following steps: Step S01: constructing a virtual scene and a tunnel model, the length and the detected position of the tunnel model being visually displayed through a coordinate ruler; Step S02: obtaining the data obtained by the underwater tunnel monitoring system based on the optical fiber sensor according to any one of claims 1-4, saving the data through an SQL Server database, adjusting system parameters, calculating strain values and temperatures, and displaying the parameters through an icon UI; Step S03: displaying the real-time changes of each parameter through a waveform diagram, and performing alarm if the parameter exceeds the corresponding threshold.

6. The optical fiber sensor based visualization monitoring method of underwater tunnels according to claim 5, characterized in that: In step S03, the type of the inspection target is set to perform inspection. When the inspection operation is performed, the visual angle follows the cursor along the water intake tunnel, and the corresponding data in the database is read and displayed.

7. The optical fiber sensor based visualization monitoring method of underwater tunnels according to claim 6, characterized in that: In step S03, a UI sign is displayed above the corresponding monitoring point of the tunnel to indicate whether the inspection parameter meets the requirements. If the monitored parameter exceeds the preset range, the UI sign displays red, and a red alarm frame flashes at the bottom of the entire interface. If the parameter is within the required range, the UI sign displays gray. After the inspection is completed, an inspection end window is automatically popped up, and the number of normal points and alarm points in the inspection process is displayed.

8. The optical fiber sensor based visualization monitoring method of underwater tunnels according to claim 6, characterized in that: In step S03, the data icon analysis interface is entered through point screening. The corresponding tunnel position is positioned according to the quick positioning bar, the data acquisition point is selected, the parameter change of the data acquisition point in the inspection process is displayed, and all historical data of the point are obtained.

9. The optical fiber sensor based visualization monitoring method of underwater tunnels according to claim 5, characterized in that: In step S01, an equal-ratio three-dimensional model is constructed, including terrain, seawater, plant, tunnel, and optical cable. When the terrain is made, sandstone and grassland maps are added, and grass and tree models are added.

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