A true random code modulation optical fiber sensing perimeter security system for wooden ancient buildings

Abstract

The present invention relates to the field of optical fiber sensing technology, and specifically to a wooden ancient building optical fiber sensing perimeter security system with true random code modulation. The system comprises a narrow line width laser, a first optical fiber coupler connected to the narrow line width laser, the first optical fiber coupler divides the laser into a detection light and a local oscillator light, the local oscillator light is output to a fourth optical fiber coupler, the detection light is output to an acousto-optic modulator, the acousto-optic modulator receives a driving pulse provided by a true random code generator and modulates the continuous light into a coded pulse light; the acousto-optic modulator outputs the coded pulse light and connects it to the a input end of a circulator through an optical pulse signal amplifying device; the b input end of the circulator is connected to a sensing optical fiber arranged in a protective wall, the end of the sensing optical fiber is connected to a third optical isolator, the c port of the circulator is connected to a fourth optical fiber coupler, the Rayleigh backscattered light generated by the detection pulse light in the circulator beats with the local oscillator light to generate a beat signal light, and the beat signal light is output to a demodulation device for demodulation.

Description

Technical Field

[0001] The invention relates to the technical field of optical fiber sensing, in particular to an optical fiber sensing perimeter security system for ancient wooden buildings modulated by true random codes. Background Art

[0002] As a carrier of historical culture, wooden ancient buildings are precious treasures for studying ancient society and have extremely high artistic and archaeological value. Traditional security warning systems often have certain limitations when monitoring thefts in wooden ancient buildings. For example, manual patrols cannot detect thefts that enter wooden ancient buildings from underground; video camera monitoring, infrared alarms, etc. will affect the overall appearance of the ancient buildings, and there are fire hazards because they require power supply.

[0003] Since the non-stationary vibration signals generated by underground digging and ground climbing of wooden ancient buildings have the characteristics of wide range, small target and wide frequency band, higher requirements are put forward for the high-resolution vibration positioning capability of the security warning system. In recent years, the distributed optical fiber vibration sensing technology has developed rapidly, which has the characteristics of wide sensing range, high spatial resolution and fast response speed. In addition, optical fiber has the significant advantages of easy laying, low price and strong anti-interference ability. When using optical signals as detection signals, there is no need to worry about causing fires, so it has become an effective means of security warning for wooden ancient buildings.

[0004] Phase-sensitive optical time-domain reflectometry (Φ-OTDR) is a typical distributed fiber vibration sensing technology that can realize the function of multi-point positioning of vibration signals by monitoring the laser phase changes caused by vibration signals. In order to improve the spatial resolution of Φ-OTDR, researchers often use laser pulse coding technology to optimize the resolution of vibration signals by compressing the width of a single code element. However, traditional pulse coding methods require multiple sets of codes for decoding, and generally have problems such as increasing decoding storage space, reducing system response bandwidth, and limiting transient effects, making them difficult to be applied in the field of security warning for ancient wooden buildings. Summary of the invention

[0005] In order to solve the above problems, the present invention provides a true random code modulated optical fiber sensing perimeter security system for ancient wooden buildings.

[0006] The present invention adopts the following technical scheme: a true random code modulated optical fiber sensing perimeter security system for wooden ancient buildings, comprising a narrow line width laser, a first optical fiber coupler connected to the narrow line width laser, the first optical fiber coupler divides the laser into a detection light and a local oscillator light, the local oscillator light is output to a fourth optical fiber coupler, the detection light is output to an acousto-optic modulator, the acousto-optic modulator receives a driving pulse provided by a true random code generator and modulates the continuous light into a coded pulse light; the acousto-optic modulator outputs the coded pulse light and connects it to the a input end of a circulator through an optical pulse signal amplifying device; the b input end of the circulator is connected to a sensing optical fiber arranged in a protective wall, the end of the sensing optical fiber is connected to a third optical isolator, the c port of the circulator is connected to a fourth optical fiber coupler, the Rayleigh backscattered light generated by the detection pulse light in the circulator beats with the local oscillator light to generate a beat signal light, and the beat signal light is output to a demodulation device for demodulation.

[0007] In some embodiments, the optical pulse signal amplifying device includes a first optical isolator, the first optical isolator is connected to the a input end of the wavelength division multiplexer, the b input end of the wavelength division multiplexer is connected to the output end of the pump source, and the c output end of the wavelength division multiplexer is connected to the erbium-doped optical fiber and the second optical isolator in sequence.

[0008] In some embodiments, the optical pulse signal amplifying device also includes a real-time dynamic adjustment device for real-time dynamic adjustment of the output power of the pump source, the real-time dynamic adjustment device includes a second fiber coupler connected between the c output end of the acousto-optic modulator and the first optical isolator and a third fiber coupler connected to the output end of the second optical isolator, the second fiber coupler divides the coded pulse light into a detection pulse light and a reference pulse light, the reference pulse light enters the second radio frequency signal power amplifier after being converted into an electrical signal by the second photodetector and is amplified and then output to the second analog-to-digital converter, and the detection pulse light is input to the first optical isolator; the a input end of the third fiber coupler is connected to the second optical isolator, the b output end of the third fiber coupler is connected to the a input end of the circulator, and the c output end of the third fiber coupler is sequentially connected to the first photoelectric converter, the first radio frequency signal power amplifier, the first analog-to-digital converter and the a input end of the subtractor; the c output end of the subtractor is connected to the a input end of the threshold comparator, the b port of the threshold comparator is connected to the a input end of the pump source driver, and the pump source driver outputs a driving signal to the pump source.

[0009] In some embodiments, the real-time dynamic adjustment device also includes a double rate synchronous dynamic random access memory, the a input terminal of the double rate synchronous dynamic random access memory is connected to the c output terminal of the threshold comparator, the b input terminal of the double rate synchronous dynamic random access memory is connected to the b output terminal of the true random code generator, and the c output terminal of the double rate synchronous dynamic random access memory is connected to the b input terminal of the pump source driver.

[0010] In some embodiments, the demodulation device includes a balanced photodetector, and the c output end and d output end of the fourth optical fiber coupler are output to the a input end and b input end of the balanced photodetector. The balanced photodetector converts the optical signal into an electrical signal and outputs it from the c port to the bandpass filter. The bandpass filter filters out the noise of the system beat frequency signal and sends the filtered result to the high-speed data acquisition card. The high-speed acquisition card converts the beat frequency signal into a digital signal and outputs it to the host computer. The host computer displays the required information on the screen after demodulating the data accordingly.

[0011] In some embodiments, the host computer is connected to an audible and visual alarm.

[0012] In some embodiments, the protective wall surrounds the ancient wooden building at a central position, and the protective wall includes an above-ground protective wall and an underground protective wall, and a door is provided in the middle part of the above-ground protective wall.

[0013] In some embodiments, the protective wall is composed of hollow bricks, and adjacent hollow bricks are interconnected. The sensing optical fiber is laid in the gaps between the hollow bricks of the wall, and the sensing optical fiber is laid around the door.

[0014] In some embodiments, the protective wall is provided with multiple sides, the sensing optical fibers in adjacent protective walls are connected via optical fiber connectors, and the end sensing optical fibers are connected to the third optical isolator.

[0015] In the present invention, an anti-theft outer wall composed of hollow bricks is constructed around the ancient building, and a sensing optical fiber is laid in the hollow bricks. The Φ-OTDR system is used to monitor and locate the non-stationary vibration signals generated by underground digging and ground climbing of thieves in wooden ancient buildings, thereby achieving sensitive perception of underground digging theft and ground climbing theft while playing a physical anti-theft role. In order to solve the defects of the traditional pulse encoding method, the present invention utilizes the advantages of single-group encoding for decoding of true random code, realizes vibration positioning with high spatial resolution on the basis of reducing decoding storage space and maintaining system response bandwidth, and adopts a combination of static control and dynamic control to dynamically adjust the output power of the pump laser in real time, eliminating the transient effect faced by the power amplification of the true random code pulse sequence.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] 1. The present invention adopts distributed optical fiber vibration sensing technology to monitor the intrusion and theft of ancient wooden buildings. It can monitor and locate the non-stationary vibration signals generated by thieves' underground digging and ground climbing. The system has significant advantages such as wide monitoring range, adaptability to various scenarios, intrinsic safety, high sensitivity, easy laying and installation, strong anti-interference ability and low price, and there is no risk of causing fire.

[0018] 2. The present invention introduces true random code pulse coding into distributed optical fiber vibration sensing technology, which can achieve high spatial resolution vibration positioning on the basis of reducing decoding storage space and maintaining system response bandwidth.

[0019] 3. The present invention uses a combination of static control and dynamic control to dynamically adjust the pump laser output power in real time to eliminate the transient effects faced by true random code pulse sequence power amplification.

[0020] 4. The present invention constructs a hollow brick through-combination structure for protecting the wall of a wooden ancient building, and lays sensing optical fibers around the periphery of the door of the ground protective wall and directly penetrates other positions to achieve sensitive perception of ground climbing theft and underground digging theft. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The present invention provides a true random code modulated optical fiber sensing perimeter security system for wooden ancient buildings;

[0022] Figure 2 A partial schematic diagram of the fiber optic cable layout for the protection wall of an ancient wooden building;

[0023] Figure 3 Schematic diagram of the wall structure for protecting wooden ancient buildings;

[0024] Wherein: 1- narrow linewidth laser, 2- first fiber coupler, 3- acousto-optic modulator, 4- true random code generator, 5- second fiber coupler, 6- first optical isolator, 7- wavelength division multiplexer, 8- erbium-doped fiber, 9- second optical isolator, 10- third fiber coupler, 11- first photodetector, 12- first RF signal power amplifier, 13- first analog-to-digital converter, 14- second photodetector, 15- second RF signal amplifier, 16- second analog-to-digital converter, 17- subtractor, 18 -Threshold comparator, 19-double rate synchronous dynamic random access memory, 20-pump source driver, 21-pump source, 22-circulator, 23-sensing optical fiber, 24-third optical isolator, 25-fourth optical fiber coupler, 26-balanced photodetector, 27-bandpass filter, 28-high-speed acquisition card, 29-host computer, 30-sound and light alarm, 101-wooden ancient building, 102-ground protection wall, 103-underground protection wall 104-optical fiber connector, 105-ground 106-door. DETAILED DESCRIPTION

[0025] like Figure 1As shown, a true random code modulated optical fiber sensing perimeter security system for wooden ancient buildings comprises a narrow linewidth laser 1 and a first optical fiber coupler 2 connected to the narrow linewidth laser 1. The narrow linewidth laser 1 emits a continuous narrow linewidth laser with a central wavelength of 1550nm to the a input end of the first optical fiber coupler 2; the first optical fiber coupler 2 divides the continuous light into two parts, 99% and 1%, 99% of the laser light is output from the b port of the first optical fiber coupler 2 as detection light to the a input end of the acousto-optic modulator 3, and 1% of the laser light is output from the c port of the first optical fiber coupler 2 as local oscillation light to the b input end of the fourth optical fiber coupler 25; a true random code generator 4 generates two true random code encoding sequences, one of which is output to the b input end of the acousto-optic modulator 3 through the a output end and provides a driving pulse for it, and the other is output to the b input end of the double rate synchronous dynamic random access memory 19 through the b output end.

[0026] The coded pulse light output by the acousto-optic modulator 3 is connected to the a input terminal of the circulator 22 through the optical pulse signal amplifying device.

[0027] In some embodiments, the optical pulse signal amplifying device includes a first optical isolator 6, the first optical isolator 6 is connected to the a input end of the wavelength division multiplexer 7, the b input end of the wavelength division multiplexer 7 is connected to the output end of the pump source 21, and the c output end of the wavelength division multiplexer 7 is connected to the erbium-doped optical fiber 8 and the second optical isolator 9 in sequence.

[0028] The acousto-optic modulator 3 modulates the continuous light into a coded pulse light signal under the drive of the true random code generator 4, and generates a 200MHz shift frequency; the modulated coded pulse light signal is output from the c output end of the acousto-optic modulator 3 to the a input end of the second optical fiber coupler 5; the second optical fiber coupler 5 divides the coded pulse light into two parts, 99% and 1%, 99% of the coded pulse light is output from the c output end of the second optical fiber coupler 5 as the detection pulse light, the detection pulse light enters the a input end of the wavelength division multiplexer 7 through the first optical isolator 6, and 1% of the coded pulse light is output from the b output end of the second optical fiber coupler 5 as the reference pulse light. The output is converted into an electrical signal by the second photodetector 14, and then enters the second RF signal power amplifier 15 and is amplified and output to the second analog-to-digital converter 16. The second analog-to-digital converter 16 converts the input signal into a digital signal and outputs it to the b input terminal of the subtractor 17; the pump source 21 outputs 980nm pump light to the b input terminal of the wavelength division multiplexer 7; the wavelength division multiplexer 7 combines the detection pulse light and the pump light into one beam and outputs it from the c output terminal to the input terminal of the erbium-doped optical fiber 8; the 980nm pump light excites the electrons in the erbium-doped optical fiber 8 to transition to the pump energy level, thereby amplifying the optical pulse signal.

[0029] In some embodiments, the optical pulse signal amplifying device also includes a real-time dynamic adjustment device for real-time dynamic adjustment of the output power of the pump source 21, wherein the real-time dynamic adjustment device includes a second optical fiber coupler 5 connected between the c output end of the acousto-optic modulator 3 and the first optical isolator 6 and a third optical fiber coupler 10 connected to the output end of the second optical isolator 9.

[0030] The second optical fiber coupler 5 divides the coded pulse light into a detection pulse light and a reference pulse light. The reference pulse light output is converted into an electrical signal by the second photodetector 14 and then enters the second RF signal power amplifier 15 and is amplified and then output to the second analog-to-digital converter 16. The detection pulse light is input to the first optical isolator 6.

[0031] The a input end of the third optical fiber coupler 10 is connected to the second optical isolator 9, the b output end of the third optical fiber coupler 10 is connected to the a input end of the circulator 22, and the c output end of the third optical fiber coupler 10 is connected to the first photoelectric converter 11, the first RF signal power amplifier 12, the first analog-to-digital converter 13 and the a input end of the subtractor 17 in sequence.

[0032] The c output terminal of the subtractor 17 is connected to the a input terminal of the threshold comparator 18 , and the b port of the threshold comparator 18 is connected to the a input terminal of the pump source driver 20 . The pump source driver 20 outputs a driving signal to the pump source 21 .

[0033] The amplified optical pulse signal is output from the output end of the erbium-doped optical fiber 8 and input to the a input end of the third optical fiber coupler 10 through the second optical isolator 9; the third optical fiber coupler 10 divides the amplified optical pulse signal into two parts, 99% and 1%, and the 99% amplified optical pulse signal is output from the b output end of the third optical fiber coupler 10 to the a input end of the circulator 22 as a detection coding pulse light signal, and the 1% amplified optical pulse signal is output from the c output end of the third optical fiber coupler 10 to the first photoelectric converter 11 as a correction pulse light; the first photoelectric converter 11 converts the input optical signal into an electrical signal and outputs it to the first radio frequency signal power amplifier 12, and the first radio frequency signal power amplifier 12 is used to generate an electrical signal. The amplifier 12 amplifies the electrical signal and outputs it to the first analog-to-digital converter 13. The first analog-to-digital converter 13 converts the input signal into a digital signal and outputs it to the a input terminal of the subtractor 17. The subtractor 17 subtracts the digital signals input from the a input terminal and the b input terminal, quantifies the difference between the two, and outputs the difference from the c output terminal of the subtractor 17 to the a input terminal of the threshold comparator 18. When the difference input to the threshold comparator 18 is less than the minimum set threshold or greater than the maximum set threshold, the threshold comparator 18 outputs the corresponding dynamic gain coefficient from the b port to the a input terminal of the pump source driver 20, thereby dynamically controlling the size of the drive signal output by the pump source driver 20.

[0034] The real-time dynamic adjustment device also includes a double-rate synchronous dynamic random access memory 19, the a input terminal of the double-rate synchronous dynamic random access memory 19 is connected to the c output terminal of the threshold comparator 18, the b input terminal of the double-rate synchronous dynamic random access memory 19 is connected to the b output terminal of the true random code generator 4, and the c output terminal of the double-rate synchronous dynamic random access memory 19 is connected to the b input terminal of the pump source driver 20.

[0035] The threshold comparator 18 outputs the threshold judgment result from the c output terminal to the a input terminal of the double rate synchronous dynamic random access memory 19. When the result shows that the difference is greater than the maximum set threshold, the static gain coefficient stored in the corresponding storage space of the double rate synchronous dynamic random access memory 19 is reduced according to the value output by the true random code generator 4. When the result shows that the difference is less than the minimum set threshold, the static gain coefficient stored in the corresponding storage space of the double rate synchronous dynamic random access memory 19 is increased according to the value output by the true random code generator 4. When the true random code generator 4 outputs a high level to the double rate synchronous dynamic random access memory 19, the static gain coefficient stored in the corresponding storage space of the double rate synchronous dynamic random access memory 19 is increased. When the double rate synchronous dynamic random access memory 19 is used, the double rate synchronous dynamic random access memory 19 outputs the static gain coefficient stored in the corresponding storage space from the c output terminal to the b input terminal of the pump source driver 20, thereby statically controlling the size of the driving signal output by the pump source driver 20; under the joint action of dynamic control and static control, the pump source driver 20 outputs a 980nm pump source driving signal from the c output terminal to the input terminal of the pump source 21, thereby adjusting the amplification factor of the erbium-doped optical fiber 8, and finally achieving the purpose of eliminating the transient effect generated by EDFA amplification.

[0036] The b input end of the circulator 22 is connected to the sensing optical fiber 23 arranged in the protective wall, the end of the sensing optical fiber 23 is connected to the third optical isolator 24, and the c port of the circulator 22 is connected to the fourth optical fiber coupler 25. The Rayleigh backscattered light generated by the detection pulse light in the circulator 22 beats with the local oscillator light to generate a beat signal light, and the beat signal light is output to the demodulation device for demodulation.

[0037] The demodulation device includes a balanced photodetector 26. The c output terminal and d output terminal of the fourth optical fiber coupler 25 are output to the a input terminal and b input terminal of the balanced photodetector 26. The balanced photodetector 26 converts the optical signal into an electrical signal and outputs it from the c port to the bandpass filter 27. The bandpass filter 27 filters out the noise of the system beat frequency signal and sends the filtered result to the high-speed data acquisition card 28. The high-speed acquisition card 28 converts the beat frequency signal into a digital signal and outputs it to the host computer 29. The host computer 29 displays the required information on the screen after demodulating the data accordingly.

[0038] The host computer 29 is connected to the sound and light alarm 30 .

[0039] The detection coded pulse light signal input from the a input end of the circulator 22 is output from the b port of the circulator 22 and output to the third optical isolator 24 through the sensing optical fiber 23 to prevent the Fresnel reflection peak from appearing at the tail end of the optical fiber, which may cause misjudgment of the vibration signal at the tail end of the sensing optical fiber 23; the Rayleigh backscattered light generated by the detection coded pulse light signal enters from the b port of the circulator 22 and is output to the a input end of the fourth optical fiber coupler 25 through the c port of the circulator 22, and beats with the 1% local oscillation light output from the c output end of the first optical fiber coupler 2 to generate a beat signal light; the beat signal light is output from the c output end and the d output end of the fourth optical fiber coupler 25 to the a input end and the b input end of the balanced photodetector 26 respectively; the balanced photodetector 26 then converts the optical signal into an electrical signal and outputs it from port c to a bandpass filter 27; the bandpass filter 27 filters out the noise of the system beat frequency signal and sends the filtered result to a high-speed data acquisition card 28; the high-speed acquisition card 28 converts the beat frequency signal into a digital signal and outputs it to a host computer 29; the host computer 29 displays the required information on the screen after demodulating the data accordingly. When the host computer 29 detects an abnormal vibration signal, it first determines the number of sampling points included in the vibration position. If the number of sampling points included in the vibration position is greater than the set value, it is considered to be environmental noise, otherwise it is considered to be an invasion event of a wooden ancient building; when the host computer 29 determines that an invasion event of a wooden ancient building occurs, it outputs a driving signal to the sound and light alarm 30, and then drives the sound and light alarm 30 to alarm.

[0040] like Figure 2 FIG. 1 is a partial schematic diagram of the optical fiber layout of the wooden ancient building protection wall provided by the present invention, as shown in FIG. Figure 3 The figure shows a schematic diagram of the structure of the wooden ancient building protection wall provided by the present invention, which includes a wooden ancient building 101, an above-ground protection wall 102, an underground protection wall 103, an optical fiber connector 104, a ground 105 and a door 106.

[0041] The wooden ancient building 101 is located in the center of the protective wall. The protective wall has a total of six sides, each of which is composed of an above-ground protective wall 102 and an underground protective wall 103. The above-ground protective wall 102 is used to monitor and prevent thieves from climbing over the ground, and the underground protective wall 103 is used to monitor and prevent thieves from digging underground. The middle part of the above-ground protective wall 102 of the six protective walls has a door 106 for tourists to enter and exit during daily open visits. After the visit, the door 106 is closed to cooperate with the above-ground protective wall 102 and the underground protective wall 103 for physical anti-theft. The protective wall is composed of hollow bricks, which are cubes. There are two penetration modes, one is front and back penetration, and the other is adjacent two-side penetration. When the sensing optical fiber 23 needs to be laid in a turn, the hollow bricks penetrating the adjacent two sides are used, and when the sensing optical fiber 23 needs to be laid directly through, the front and back penetration is used. Hollow bricks; the sensing optical fiber 23 is laid in the gap in the middle of the hollow bricks of the wall, and the sensing optical fiber 23 is laid around the door 106, and can be directly passed through other places; the detection coded pulse light is output to the next section of the sensing optical fiber 23 through the sensing optical fiber 23 and the optical fiber connector 104; the Rayleigh backscattered light signal of the subsequent sensing optical fiber 23 is input into the sensing optical fiber 23 through the optical fiber connector 104, and then output to the previous section of the sensing optical fiber 23 through the optical fiber connector 104 of the previous section of the protective wall; each protective wall has an optical fiber connector 104 to facilitate the optical path connection between the walls; the sensing optical fiber 23 of the first protective wall is connected to the b port of the circulator 22 of the monitoring room, and the optical fiber connector 104 of the last protective wall is connected to the third optical isolator 24 to prevent the Fresnel reflection peak from appearing at the tail end of the optical fiber, resulting in misjudgment of the vibration signal at the tail end of the sensing optical fiber 23.

Claims

1. A true random code modulated optical fiber sensing perimeter security system for wooden ancient buildings, characterized by: The invention comprises a narrow linewidth laser (1), a first optical fiber coupler (2) connected to the narrow linewidth laser (1), The first optical fiber coupler (2) divides the laser light into a detection light and a local oscillator light, the local oscillator light is output to the fourth optical fiber coupler (25), the detection light is output to the acousto-optic modulator (3), and the acousto-optic modulator (3) receives a driving pulse provided by a true random code generator (4) to modulate the continuous light into a coded pulse light; The coded pulse light output by the acousto-optic modulator (3) is connected to the input terminal a of the circulator (22) through the optical pulse signal amplifying device; The b input end of the circulator (22) is connected to a sensing optical fiber (23) arranged in the protective wall, the end of the sensing optical fiber (23) is connected to a third optical isolator (24), and the c port of the circulator (22) is connected to a fourth optical fiber coupler (25). Rayleigh backscattered light generated by the detection pulse light in the circulator (22) beats with the local oscillator light to generate beat signal light, and the beat signal light is output to a demodulation device for demodulation; The optical pulse signal amplifying device comprises a first optical isolator (6), the first optical isolator (6) is connected to the a input end of the wavelength division multiplexer (7), the b input end of the wavelength division multiplexer (7) is connected to the pump source (21) from the b output end, and the c output end of the wavelength division multiplexer (7) is connected to the erbium-doped optical fiber (8) and the second optical isolator (9) in sequence; The optical pulse signal amplifying device further comprises a real-time dynamic adjustment device for real-time dynamic adjustment of the output power of the pump source (21), the real-time dynamic adjustment device comprising a second optical fiber coupler (5) connected between the C output end of the acousto-optic modulator (3) and the first optical isolator (6), and a third optical fiber coupler (10) connected to the output end of the second optical isolator (9). The second optical fiber coupler (5) divides the coded pulse light into a detection pulse light and a reference pulse light. The reference pulse light output is converted into an electrical signal by a second photoelectric detector (14) and then enters a second radio frequency signal power amplifier (15) and is amplified and then output to a second analog-to-digital converter (16). The detection pulse light is input to the second optical fiber coupler (6); The a input end of the third optical fiber coupler (10) is connected to the second optical isolator (9), the b output end of the third optical fiber coupler (10) is connected to the a input end of the circulator (22), the c output end of the third optical fiber coupler (10) is connected in sequence to the a input end of the first photoelectric converter (11), the first radio frequency signal power amplifier (12), the first analog-to-digital converter (13), and the a input end of the subtractor (17), and the output end of the second analog-to-digital converter (16) is connected to the b input end of the subtractor (17); The c output terminal of the subtractor (17) is connected to the a input terminal of the threshold comparator (18), the b port of the threshold comparator (18) is connected to the a input terminal of the pump source driver (20), and the pump source driver (20) outputs the magnitude of the driving signal to the pump source (21); The protective wall is composed of hollow bricks, adjacent hollow bricks are interconnected, and the sensing optical fiber (23) is laid in the gap between the hollow bricks of the wall.

2. The true random code modulated wooden ancient building optical fiber sensing perimeter security system according to claim 1 is characterized by: The real-time dynamic adjustment device also includes a double rate synchronous dynamic random access memory (19), the a input end of the double rate synchronous dynamic random access memory (19) is connected to the c output end of the threshold comparator (18), the b input end of the double rate synchronous dynamic random access memory (19) is connected to the b output end of the true random code generator (4), and the c output end of the double rate synchronous dynamic random access memory (19) is connected to the b input end of the pump source driver (20).

3. The true random code modulated wooden ancient building optical fiber sensing perimeter security system according to claim 1 or 2, characterized in that: The demodulation device comprises a balanced photoelectric detector (26); the c output end and the d output end of the fourth optical fiber coupler (25) are output to the a input end and the b input end of the balanced photoelectric detector (26) respectively; the balanced photoelectric detector (26) converts the optical signal into an electrical signal and outputs the electrical signal from the c port to the bandpass filter (27); the bandpass filter (27) filters out the noise of the system beat frequency signal and sends the filtered result to the high-speed data acquisition card (28); the high-speed acquisition card (28) converts the beat frequency signal into a digital signal and outputs the digital signal to the host computer (29); the host computer (29) displays the required information on the screen after performing corresponding demodulation on the data.

4. The true random code modulated wooden ancient building optical fiber sensing perimeter security system according to claim 3 is characterized by: The host computer (29) is connected to the sound and light alarm (30).

5. The true random code modulated wooden ancient building optical fiber sensing perimeter security system according to claim 1 or 4, characterized in that: The protective wall includes a wooden ancient building (101) surrounding the central position, and the protective wall includes an above-ground protective wall (102) and an underground protective wall (103). The middle part of the above-ground protective wall (102) is provided with a door (106).

6. The true random code modulated wooden ancient building optical fiber sensing perimeter security system according to claim 5, characterized in that: A sensing optical fiber (23) is laid around the door (106).

7. The true random code modulation wooden ancient building optical fiber sensing perimeter security system according to claim 6 is characterized by: The protective wall (102) is provided with multiple faces, the sensing optical fibers (23) in adjacent protective walls (102) are connected via optical fiber connectors (104), and the sensing optical fibers (23) at the ends are connected to the third optical isolator (24).

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