Multi-path underground power optical cable multi-parameter detection equipment based on single-core distributed optical fiber synchronous measurement

Abstract

The utility model discloses multi-path underground power optical cable multi-parameter detection equipment based on single-core distributed optical fiber synchronous measurement, relates to the technical field of optical fiber sensing, and solves the problems that the existing equipment for collecting multiple single-core optical cables is influenced by multiple external factors, the structure is complicated, the construction cost is high, and the cost is low. And meanwhile, the existing distributed optical fiber sensing equipment can only measure a single optical fiber and a single parameter. According to the utility model, the time division multiplexing technology is adopted, multi-parameter measurement is carried out on a plurality of single-core optical cables in a polling mode, Rayleigh scattering light capable of reflecting vibration information is generated based on the Rayleigh scattering effect, and temperature and strain information can be reflected by Brillouin frequency shift generated based on the Brillouin scattering effect. And the central controller can control the high-speed optical switch to switch the optical cable channels according to a set polling sequence, the optical cable condition can be judged according to the threshold module, and if the optical cable condition is not within a threshold range, alarm processing can be carried out, so that the fusion type optical fiber sensing equipment capable of synchronously measuring multiple parameters through multiple channels is realized.

Description

Technical Field

[0001] This utility model relates to the field of optical fiber sensing technology, specifically to a multi-parameter detection device for multi-channel underground power optical cables based on synchronous measurement of single-core distributed optical fiber. Background Technology

[0002] Underground optical cables are an important component of the "nerve center" of urban underground power communication networks. Compared with overhead optical cables, underground optical cables are mainly laid in the form of ducts, tunnels, and underground veins. Due to the wide coverage area and complex laying environment of underground optical cables, they are characterized by high construction difficulty, difficult inspection, and high maintenance costs. Furthermore, in power communication networks, sites are often connected to multiple other sites, and several or even a dozen sites communicate with each other. If problems occur in underground optical cables, it will lead to excessively high maintenance costs and great difficulty in troubleshooting.

[0003] Traditionally, single-parameter testing equipment is used to monitor for faults in single-core optical cables. For applications requiring testing multiple single-core cables, this often necessitates either rotating a single device or using multiple devices simultaneously. Furthermore, abnormalities caused by external factors or issues arising from the cable's age and excessive aging require manual inspection and repair, significantly increasing time and labor costs and complexity. A new approach would address this by simultaneously monitoring multiple parameters (vibration, temperature, strain, etc.) in multiple single-core optical cables using a single device. This new device could adaptively schedule polling based on the cable's length, eliminating the need for additional fiber optic sensing cores and using the cable cores directly as the sensing medium. This alleviates the scarcity of fiber core resources, facilitates integrated management, and provides timely warnings based on the condition of each single-core cable, ultimately reducing maintenance and labor costs.

[0004] Therefore, based on existing research and inspired by the principles of fiber optic sensing technology, researching multi-channel synchronous measurement of multiple parameters using fiber optic sensing is an urgent problem for engineers in this field. Utility Model Content

[0005] This invention addresses the limitations of simultaneously measuring changes in multiple single-core optical cables caused by external factors, which requires sequential testing of each cable using monitoring equipment, resulting in high time and setup costs. Furthermore, existing fiber optic sensing equipment can only measure single parameters of a single cable. This invention provides a multi-parameter detection device for multiple underground power optical cables based on synchronous measurement of single-core distributed optical fibers. This device can utilize most optical components and achieve multi-parameter monitoring of multiple single-core optical cables. By demodulating Brillouin shift and Rayleigh scattering signals, it synchronously acquires temperature, stress, and vibration information for multiple single-core optical cables.

[0006] The application discloses a multi-path underground power optical cable multi-parameter detection equipment based on single-core distributed optical fiber synchronous measurement, which comprises a collection unit and an information processing unit.

[0007] The collection unit comprises four optical fiber couplers, a depolarizer, an acousto-optic modulator, a high-speed optical switch, an optical cable module, a circulator module, a multi-channel low-pass filter, a mixer, two demodulation modules, a PD detector, an APD detector and a signal generator.

[0008] The optical wave signal is divided into two paths through the first optical fiber coupler, one path of the optical signal passes through the depolarizer to change the polarization state of the optical signal and enters the third optical fiber coupler as reference light, and the other path of the optical signal enters the acousto-optic modulator and is modulated into periodic pulse light, which enters the circulator module and the optical cable module in turn through the optical cable channel pointed by the high-speed optical switch, and the scattered light reflected by the optical cable module enters the multi-channel low-pass filter and the second optical fiber coupler in turn through the circulator module, and the scattered light is divided into two paths through the second optical fiber coupler, one path of the scattered light enters the third optical fiber coupler, and the other path of the scattered light enters the fourth optical fiber coupler.

[0009] The third optical fiber coupler divides the scattered light and the reference light into two paths after fusion, one path of the light beam enters the APD detector to convert the optical signal into an electric signal, the electric signal is mixed with the microwave local signal generated by the signal generator in the mixer, and the signal after mixing is input into the information processing unit; the other path of the light beam is demodulated into a digital signal by the first demodulation module and then input into the information processing unit.

[0010] The fourth optical fiber coupler divides the scattered light into two paths, one path of the scattered light is demodulated into a digital signal by the second demodulation module and then input into the information processing unit, and the other path of the scattered light is converted into an electric signal by the PD detector and then input into the information processing unit.

[0011] The embedded data acquisition card in the information processing unit respectively collects the frequency shift information in the signal output by the mixer and the vibration information in the electric signal output by the PD detector.

[0012] The central controller in the information processing unit processes the temperature and strain information of the single-core optical cable for the digital signal input by the first demodulation module, processes the vibration information of the single-core optical cable for the digital signal input by the second demodulation module, and switches to the next optical cable channel through the high-speed optical switch.

[0013] The application has the following beneficial effects:

[0014] The detection equipment disclosed by the new type can detect multiple parameters of multiple single-core optical cables synchronously, can detect the multiple single-core optical cables through polling by using time division multiplexing technology through a high-speed optical switch, and can compare thresholds in a demodulation module and a central controller to determine whether the current optical cable state and external influences on the optical cable will cause the optical cable to be abnormal and to timely make an alarm notification.

[0015] The new type can amplify and denoise the scattered light reflected by the optical cable in a series of optical devices in the demodulation module, such as a photodetector, a preamplifier, a low-pass filter, an analog-to-digital converter and an interface circuit, convert the scattered light into a digital signal, and interact information with a central controller in an information processing unit through the interface circuit to obtain specific information transmitted by each optical cable, so that changes can be made in time to avoid system analysis of false information.

[0016] The new type can set a vibration threshold module, a temperature threshold module, a strain threshold module, an alarm module, a channel switching time table and an automatic switching module in the central controller in the information processing unit to realize multi-channel and multi-parameter fusion type distributed sensing by switching different optical cable channels through the high-speed optical switch, can determine whether the optical cable itself has a problem or is greatly affected by external factors through the threshold module, can alarm if the threshold is exceeded or is lower than the threshold range, and can switch to the next single-core optical cable according to the time set by the channel switching time table and the polling function of the automatic switching module if the threshold is within the threshold range. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 The structure diagram of the multi-path underground power optical cable multi-parameter detection equipment based on single-core distributed optical fiber synchronous measurement.

[0018] Figure 2 The integrated diagram of the circulator module, the amplifier module and the optical cable module (the number of optical cables N=16).

[0019] Figure 3 The principle block diagram of the central controller module.

[0020] Figure 4 This is a block diagram illustrating the principle of the demodulation module.

[0021] In the diagram: 1. Narrow linewidth laser; 2. First fiber optic coupler; 3. Circulator module; 4. Amplifier module; 5. Optical cable module (number of fibers N=16); 6. First demodulation module; 7. Second demodulation module; 8. Central controller; 801. Vibration threshold module; 802. Temperature threshold module; 803. Strain threshold module; 804. Alarm module; 805. Channel switching schedule; 806. Automatic switching module; 9. Acousto-optic modulator; 10. Bandpass filter; 11. High-speed optical switch; 12. Polarizer; 13. Multi-channel low-pass filter; 14. Second fiber optic coupler; 15. Third fiber optic coupler; 16. Fourth fiber optic coupler; 17. APD detector; 18. Mixer; 19. Signal generator; 20. PD detector; 21. Embedded data acquisition card. Detailed Implementation

[0022] Combination Figures 1 to 4 This embodiment describes a multi-parameter detection device for underground power optical cables based on synchronous measurement using a single-core distributed optical fiber. The detection device includes a narrow-linewidth laser 1, a first optical fiber coupler 2, a circulator module 3, an optical cable module (number of optical cables N=16) 5, a first demodulation module 6, a second demodulation module 7, a central controller 8, an acousto-optic modulator 9, a high-speed optical switch 11, a polarization scrambler 12, a multi-channel low-pass filter 13, a second optical fiber coupler 14, a third optical fiber coupler 15, a fourth optical fiber coupler 16, an APD detector 17, a mixer 18, a signal generator 19, a PD detector 20, and an embedded data acquisition card 21.

[0023] In this embodiment, a bandpass filter 10 is disposed between the acousto-optic modulator 9 and the high-speed optical switch 11, and an amplifier module 4 is disposed between the circulator module 13 and the optical cable module 5.

[0024] The pulsed light modulated by the acousto-optic modulator 9 passes through the bandpass filter 10 and then through the high-speed optical switch 11 into the circulator module 13; after passing through the circulator module 13, it enters the amplifier module 4 to increase the intensity of the pulsed light, and then enters the single-core optical cable of the corresponding channel of the optical cable module 5.

[0025] like Figure 1 and Figure 2As shown, in the present embodiment, a narrow linewidth laser 1 is used as the light source, the light wave emitted by the laser is divided into two paths by the first fiber coupler 2, one path enters the perturber 12, the perturber quickly and randomly changes the polarization state of the light signal and serves as the reference light, then the reference light enters the third fiber coupler 15 for merging with the backscattered Brillouin light; the other path is modulated into periodic pulse light by the acousto-optic modulator 9, then enters the band-pass filter 10, enters the optical cable channel pointed by the high-speed optical switch 11, enters the circulator module 3 (multiple optical circulators 301-3016) in turn, the intensity of the pulse light is improved by the amplifier module 4 (multiple erbium-doped fiber amplifiers 401-4016), enters the optical cable module 5 (the number of optical cables N=16 (multiple single-core optical cables 501-5016)), and the scattered light reflected back by the optical cable module 5 enters the multi-channel low-pass filter 13 through the circulator module 3, then enters the second fiber coupler 14.

[0026] In the present embodiment, the circulator in the optical cable channel enters the erbium-doped fiber amplifier, then enters the single-core optical cable in the channel, the Rayleigh scattering light based on the Rayleigh scattering effect and the Brillouin scattering light based on the Brillouin scattering effect are generated by the scattering of the single-core optical cable, the scattered light enters the multi-channel low-pass filter through the circulator in the channel, then enters the second fiber coupler 14; after entering the second fiber coupler 14, it is divided into two beams.

[0027] A bundle of light into the third optical fiber coupler 15, the reference light and backscattered Brillouin light is combined into two ways, one way into the APD detector 17 for photoelectric conversion, in this process, because there is a frequency difference between the Brillouin scattering light and the reference light, that is, the Brillouin frequency shift, so the output of the APD detector 17 is an electrical signal carrying the frequency shift information, which is mixed with the microwave local signal generated by the signal generator 19 in the mixer 18, which can help further extract the accurate Brillouin frequency shift information, and finally the information is input into the embedded data acquisition card 21 to obtain the Brillouin frequency shift and convert it into a digital signal for analysis and processing, and further obtain the temperature and strain information; The other way of scattering light enters the first demodulation module 6, and through the photoelectric detector, preamplifier, low pass filter, analog to digital converter, the signal is amplified and noise is filtered and converted into a digital signal, then through the interface circuit connected to the central controller 8 in the information processing unit, the temperature threshold module 802 and the strain threshold module 803 are used to compare the threshold values of temperature and strain, to determine whether the single-core optical cable is affected by external parameters within the threshold range or whether the optical cable itself is broken, loose connection or other abnormal conditions, if not within the threshold range, the alarm module (buzzer) 804 is used for alarm processing, and the automatic switching module 806 is used to switch to the next optical cable channel to achieve the polling effect, if within the threshold range, the shortest time interval defined by the channel switching time table 805 and the automatic switching module 806 are used to control the high-speed optical switch 11 to switch the optical cable channel;

[0028] Another bundle of scattered light enters the fourth optical fiber coupler 16, which is divided into two ways in the fourth optical fiber coupler 16, one way enters the PD detector 20 to convert the Rayleigh scattering light into an electrical signal, and then the embedded data acquisition card 21 obtains the vibration information, the other way enters the second demodulation module 7, which is converted into a digital signal through the photoelectric detector, preamplifier, low pass filter, analog to digital converter, and then input into the central controller 8 in the information processing unit through the interface circuit, according to the vibration threshold module of the central controller 8, to determine whether the vibration information is within the threshold range or the optical cable is broken, loose connection or other conditions, if it exceeds or is below the threshold, the alarm module (buzzer) 804 issues a warning, and the automatic switching module 806 controls the high-speed optical switch 11 to switch the optical cable channel, if within the threshold range, the channel switching time table 805 and the automatic switching module 806 are used to control the high-speed optical switch 11 to switch to the next optical cable channel, thereby achieving the polling effect.

[0029] In the embodiment, the high-speed optical switch 11 is a device for quickly switching the path of optical signals, which is controlled by the channel switching time table 805 and the automatic switching module 806 in the central controller 8. The shortest time interval required by each optical cable is obtained according to the length of the optical fiber and the information processing time, and the shortest time interval is set by the channel switching time table 805 and the optical cable channel is switched by the automatic switching module 806. The central controller is connected with the high-speed optical switch 11 through the four-wire structure (SCK, MOSI, MISO, CS) of SPI, and sends control instructions to the high-speed optical switch 11 through the SPI interface to perform channel switching operation. These instructions contain channel selection information and other control parameters, so that the periodic pulsed light can be transmitted in different optical cable channels.

[0030] In the embodiment, the number N of optical cables in the optical cable module 5 can be added according to the experimental requirements. In the embodiment, the number N of optical cables is 16.

[0031] As shown in Figure 3 In the embodiment, the central controller 8 in the information processing unit has six parts, which are vibration threshold module 801, temperature threshold module 802, strain threshold module 803, alarm module 804, channel switching time table 805 and automatic switching module 806. The definition of the shortest time interval of the channel switching time table 805 is used in the embodiment with 16 identical single-core optical cables. The frame period is set to 1 millisecond, and each time slot length is 62.5 microseconds. Each single-core optical cable is allocated a time slot, so that all optical fibers are polled once in a frame. At the beginning of each time slot, the central controller 8 sends a switching command to the high-speed optical switch 11 to select the corresponding optical cable path, waits for a period of time for the light source to send pulsed light and propagate through the selected optical cable, then receives the reflected signal, repeats the above operation until the end of a frame, and then enters the next frame to continue the cycle. If the required optical cable length is different, the channel switching time table 805 with different time intervals can be dynamically set according to the different lengths of the optical cables. The time t required for light to travel back and forth in the optical fiber is calculated according to the formula min : t min = 2*L*n / c; where t minL is the length of the sensing optical cable connected by the high-speed optical switch 11, c is the speed of light in vacuum, and n is the refractive index of the optical fiber material. In this embodiment, 16 single-core optical cables of the same length are used, and each optical cable is given a time interval by dividing the time of one frame into 16 parts. It should be noted that additional time is required, partly because the information processing unit needs time to process information from the optical fiber scattered light when the high-speed optical switch 11 switches to a new optical cable each time, and partly because although the switching speed of the high-speed optical switch is fast, there is still a certain mechanical or electrical delay. If the channel switching time table 805 is too tight, it may cause task scheduling conflicts or resource contention. The channel switching time table in the central controller can be implemented using SQLite database technology. SQLite is a lightweight relational database management system suitable for embedded systems, does not require a separate server process, can be directly integrated into the firmware of the central controller, and only requires a few hundred KB of memory. By creating a SQLite database and defining a table to store information for each optical cable channel, including channel ID, monitoring duration, and last switch timestamp, and providing add, delete, modify, and query functions through the host computer interface, the updated plan can be sent to the central controller by sending relevant data through an HTTP request. When the shortest time interval of a certain channel needs to be dynamically adjusted, it can be updated through an SQL statement, providing persistent storage capabilities and supporting flexible data management and query operations.

[0032] The automatic switching module 806 in the central controller 8 in this embodiment determines that a certain optical cable has failed or that the threshold value received is not within the specified range, and the central controller 8 should immediately stop querying the optical cable and jump to the next available optical cable path according to the predefined polling order. The automatic switching module 806 has a recovery strategy that can periodically reconnect the optical cable marked as faulty to check if it has returned to normal, and if it has, it can be reclassified into the normal polling cycle. By using the transitions library in Python, a state machine model can be defined to simulate switching between different optical cable channels, and state transitions can be triggered according to preset time intervals or specific events, and the current state can be sent to the central controller through an HTTP request. The central controller runs an HTTP server to listen for commands from the host computer, and after receiving a command, it parses the command and controls the high-speed optical switch through the SPI interface according to the command content to select the corresponding optical fiber channel for detection, effectively implementing the function of the automatic switching module in the central controller, thereby controlling the high-speed optical switch and achieving switching between different optical cable channels.

[0033] The vibration threshold module 801, the temperature threshold module 802, and the strain threshold module 803 in the central controller 8 in this embodiment are used to detect whether the scattered light returned by the optical cable is above or below the threshold range. If it is not within the threshold range, an alarm is sent through the alarm module 804, and the automatic switching module 806 is notified to switch to the next optical cable. The vibration threshold can be set within the range of -7dB to -10dB, the temperature threshold can be set within the range of 15°C to 65°C, and the strain threshold can be set within the range of -500με to 1500με. Considering environmental factors such as temperature changes, humidity, etc. that may affect signal strength, the threshold can be updated regularly or adjusted using an adaptive algorithm according to actual conditions. The threshold can be set by connecting the central controller 8 in the information processing unit to the upper computer through an external device. The specific operation of the threshold or the adaptive algorithm of the threshold is performed in the upper computer. The lower limit of the threshold represents the case of signal loss or significant weakening (such as optical fiber breakage, loose connection, etc.), and the upper limit of the threshold represents the case of abnormal reflection, interference, or other conditions that may cause the signal to be too strong.

[0034] In this embodiment, a multi-channel low-pass filter 13 is used, each channel has independent input and output lines, and each channel independently low-pass filters the input signal and suppresses high-frequency components above the cutoff frequency while retaining low-frequency components below the cutoff frequency.

[0035] In this embodiment, a narrow linewidth laser 1 emitting at 1.5 microns is used, with an output wavelength of 1550 nm. In this wavelength band, the transmission loss of the optical cable is minimal, and it has high coherence, allowing for long-distance optical signal transmission.

[0036] In this embodiment, the first optical fiber coupler 2 is used to divide the laser into two paths with a coupling split ratio of 90:10, of which 90% is input into the acousto-optic modulator 9, and 10% is input into the depolarizer 12 as reference light; the second optical fiber coupler 14 is used to divide the scattered light into two paths with a coupling split ratio of 50:50, of which 50% of the scattered light enters the third optical fiber coupler 15, and 50% of the scattered light enters the fourth optical fiber coupler 16. The third optical fiber coupler 15 has a coupling split ratio of 50:50, and the fourth optical fiber coupler 16 has a coupling split ratio of 50:50.

[0037] In this embodiment, the depolarizer 12 changes the polarization state of the light by passing the divided reference light through it. The depolarizer quickly and randomly changes the polarization state of the optical signal. This eliminates signal fluctuations caused by fixed polarization states and ensures that the device is not sensitive to changes in different polarization states.

[0038] In this embodiment, the signal generator 19 can generate a stable, tunable microwave local oscillator signal for mixing with the electrical signal output by the APD detector 17, which helps to shift the Brillouin frequency shift to a more easily processed intermediate frequency range, which makes subsequent signal processing easier, resulting in a more accurate Brillouin frequency shift. According to the known Brillouin frequency shift range, the signal generator is set to a fixed frequency of 10.8 GHz. The specific value of the Brillouin frequency shift can also be accurately measured using a spectrum analyzer to set the initial frequency of the signal generator. When the ambient temperature or strain changes significantly, the Brillouin frequency shift value is re-measured using a spectrum analyzer to set the signal transmission frequency of the signal generator.

[0039] In this embodiment, the photodetector in the first demodulation module 6 receives scattered light from the optical cable and converts it into a corresponding electrical signal. Because the electrical signal output by the photodetector can be very weak, it is usually necessary to enhance the signal strength by using a preamplifier, which not only amplifies the signal but also filters out some unnecessary noise. A low-pass filter is used to remove high-frequency noise. The amplified analog signal is then sent to an analog-to-digital converter, which converts the continuously varying analog signal into a discrete digital signal. In order to enable smooth communication between the analog-to-digital converter and the central controller 8, an interface circuit is required.

[0040] In this embodiment, the circulator module 3 has 16 optical circulators, each connected to an erbium-doped fiber amplifier on each fiber channel, for outputting the optical pulse signal received by the No. 1 port to the erbium-doped fiber amplifier via the No. 2 port, and then inputting it into a single-core optical cable. The backscattering Rayleigh scattering and backscattering Brillouin scattering generated by the single-core optical cable are input back into the optical circulator via the No. 2 port and output to the multi-channel low-pass filter 13 via the No. 3 port. The circulator is a three-port optical circulator, and its optical characteristics are that the light input from the No. 1 port can only be output from the No. 2 port, and the light input from the No. 2 port can only be output from the No. 3 port.

[0041] In this embodiment, the APD detector 17 is used to detect the signal from the third coupler 15 and convert it into an electrical signal, has high gain, is suitable for low light intensity signal detection, and also has high response speed and high sensitivity.

[0042] In this embodiment, the PD detector 20 is used to detect the Rayleigh scattering signal, receives the Rayleigh scattering signal, and converts it into an electrical signal.

[0043] In the embodiment, the embedded data acquisition card 19 is used for receiving the electrical signals from the mixer 18 and the PD detector 20, converting the analog electrical signals into digital signals, and performing high-speed sampling and storage, and performing preliminary information processing on the signals, and then the information in the embedded data acquisition card can be processed by the external host computer to obtain specific vibration, temperature and strain information.

[0044] The embodiment is based on B-OTDR technology and Φ-OTDR technology, and demodulates the back Rayleigh scattering signals and Brillouin scattering signals in the synchronous processing of multiple single-core optical cables, so as to complete the synchronous acquisition of the temperature, stress and vibration information of the single-core optical cables, control the high-speed optical switch by using a central controller to achieve the function of polling the optical cables, and set an alarm module to timely inform when the optical cable has a problem. Compared with the traditional single-parameter distributed optical fiber sensing device, the system has a simple structure, can independently complete the experimental effect of multiple single-parameter devices, has low laying difficulty and cost, can realize the multi-parameter monitoring of the distributed synchronous measurement of multiple single-core optical cables, and has high economic value and social value.

[0045] The technical features of the above-described embodiments can be combined arbitrarily, and to make the description concise, all possible combinations of the technical features in the above-described embodiments are not described, however, as long as the combinations of the technical features do not contradict, they should be considered as the scope of the present disclosure.

[0046] The above-described embodiments only express several implementation manners of the present application, the description is relatively specific and detailed, but it should not be understood as the limitation of the scope of the new patent. It should be pointed out that for ordinary skilled persons in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which all belong to the protection scope of the present application. Therefore, the protection scope of the present application patent should be subject to the appended claims.

Claims

1. A multi-path underground power optical cable multi-parameter detection device based on single-core distributed optical fiber synchronous measurement, characterized in that: The detection device comprises a collecting unit and an information processing unit; The collecting unit comprises four optical fiber couplers, a depolarizer, an acousto-optic modulator, a high-speed optical switch, an optical cable module, a circulator module, a multi-channel low-pass filter, a frequency mixer, two demodulation modules, a PD detector, an APD detector and a signal generator; The optical wave signal is divided into two paths by the first optical fiber coupler, one path of the optical signal passes through the depolarizer to change the polarization state of the optical signal and enters the third optical fiber coupler as reference light, and the other path of the optical signal enters the acousto-optic modulator to be modulated into periodic pulse light, which enters the circulator module and the optical cable module in turn through the optical cable channel pointed by the high-speed optical switch, the scattered light reflected by the optical cable module enters the multi-channel low-pass filter and the second optical fiber coupler in turn through the circulator module, the scattered light is divided into two paths by the second optical fiber coupler, one path of the scattered light enters the third optical fiber coupler, and the other path of the scattered light enters the fourth optical fiber coupler; The third optical fiber coupler divides the scattered light and the reference light into two paths after fusion, one path of the light beam enters the APD detector for photoelectric signal conversion, the converted electrical signal is mixed with the microwave local signal generated by the signal generator in the frequency mixer, and the mixed signal is input to the information processing unit; the other path of the light beam is demodulated into a digital signal by the first demodulation module and then input to the information processing unit; The fourth optical fiber coupler divides the scattered light into two paths, one path of the scattered light is demodulated into a digital signal by the second demodulation module and then input to the information processing unit; the other path of the scattered light is converted into an electrical signal by the PD detector and then input to the information processing unit; The embedded data acquisition card in the information processing unit respectively collects frequency shift information in the signal output by the frequency mixer and vibration information in the electrical signal output by the PD detector; The central controller in the information processing unit processes single-core optical cable temperature and strain information of the digital signal input by the first demodulation module and processes single-core optical cable vibration information of the digital signal input by the second demodulation module; And the high-speed optical switch is switched to the next optical cable channel.

2. The multi-parameter detection device for multi-path underground power optical cable based on single-core distributed synchronous measurement of optical fiber according to claim 1, characterized in that: A band-pass filter is arranged between the acousto-optic modulator and the high-speed optical switch, and an amplifier module is arranged between the circulator module and the optical cable module; The pulse light modulated by the acousto-optic modulator passes through the band-pass filter and then enters the circulator module through the high-speed optical switch; after passing through the circulator module, the pulse light enters the amplifier module to increase the intensity of the pulse light, and then enters the single-core optical cable of the corresponding channel of the optical cable module.

3. The multi-parameter detection device for multi-path underground power optical cable based on single-core distributed synchronous measurement of optical fiber according to claim 1, characterized in that: The first demodulation module and the second demodulation module have the same structure and are composed of a photodetector, a preamplifier, a low-pass filter, an analog-to-digital converter and an interface circuit; the scattered light enters the first demodulation module or the second demodulation module, and then passes through the photodetector, the preamplifier, the low-pass filter and the analog-to-digital converter in sequence to amplify the signal and filter the noise and convert the signal into a digital signal, and the digital signal is received by the central controller of the information processing unit through the interface circuit.

4. The multi-parameter detection device for multi-path underground power optical cable based on single-core distributed synchronous measurement of optical fiber according to claim 1, characterized in that: The central controller is composed of a temperature threshold module, a strain threshold module, a vibration threshold module, an alarm module, an automatic switching module and a channel switching time table. The digital signal inputted by the first demodulation module is judged by the temperature threshold module and the strain threshold module for temperature and strain, if not in the set threshold range, the alarm module is processed for alarm, and the automatic switching module is switched to the next optical cable channel, if in the threshold range, the shortest time interval defined by the channel switching time table and the automatic switching module control the high-speed optical switch to switch the optical cable channel; The digital signal inputted by the second demodulation module is judged by the vibration threshold module for vibration information threshold, if exceeds or is lower than the threshold, the information is sent to the alarm module for alarm, and the automatic switching module controls the high-speed optical switch to switch the optical cable channel, if in the threshold range, the high-speed optical switch is controlled according to the channel switching time table and the automatic switching module, and switched to the next optical cable channel.

5. The multi-parameter detection device based on single-core distributed optical fiber synchronous measurement of multi-path underground power optical cable according to claim 1, characterized in that: The number of the circulator module, the amplifier module and the optical cable module is the same.

6. The multi-parameter detection device based on single-core distributed optical fiber synchronous measurement of multi-path underground power optical cable according to claim 1, characterized in that: The circulator module is provided with 16 optical circulators, which are connected with the erbium-doped fiber amplifiers on each optical fiber channel, for outputting the optical pulse signal received by the first port to the erbium-doped fiber amplifier through the second port, and then inputting to the single-core optical cable; the back Rayleigh scattering and back Brillouin scattering generated by the single-core optical cable are inputted back to the optical circulator by the second port and outputted to the multi-channel low-pass filter by the third port.

7. The multi-parameter detection device based on single-core distributed optical fiber synchronous measurement of multi-path underground power optical cable according to claim 1, characterized in that: The first optical fiber coupler is used for splitting the laser into two paths, and the coupling splitting ratio is 90:10, wherein 90% of one path is inputted to the acousto-optic modulator, and 10% of one path is inputted to the depolarizer as reference light; the second optical fiber coupler is used for splitting the scattered light into two paths, and the coupling splitting ratio is 50:50, 50% of the scattered light enters the third optical fiber coupler, and 50% of the scattered light enters the fourth optical fiber coupler; the coupling splitting ratio of the third optical fiber coupler is 50:50; the coupling splitting ratio of the fourth optical fiber coupler is 50:50.

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