Power cable monitoring system and method based on single-core optical fiber multi-parameter sensing

Abstract

The invention discloses a power cable monitoring system and method based on single-core optical fiber multi-parameter sensing. The monitoring system comprises a laser, a first optical fiber coupler, an acousto-optic modulation unit, an optical fiber circulator, a distributed sensing optical fiber, a power cable, a wavelength division multiplexer, a second optical fiber coupler and a data acquisition monitoring unit. When the power cable to be detected is subjected to temperature change and vibration change, the temperature value of the power cable can be obtained by demodulating Raman scattering light data in backscattering light of the distributed sensing optical fiber, and Rayleigh scattering light in the backscattering light and local laser are subjected to interference frequency mixing to obtain a beat frequency signal; and the beat frequency signal is demodulated to obtain a vibration signal of the power cable. Based on the Raman scattering effect and the Rayleigh scattering effect, the temperature and vibration signals of the power cable can be detected at the same time only through one single-core optical fiber, and the method has the advantages of being high in signal-to-noise ratio, low in cost, easy and convenient to operate and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of power cable detection, and in particular relates to a power cable detection system and method based on single-core optical fiber multi-parameter sensing. Background Art

[0002] With the continuous promotion of urbanization, high-voltage transmission towers are no longer applicable, and power cables are becoming the main way to transmit electricity. However, since power cables are under the surface for a long time and the laying environment is extremely harsh, they are prone to damage, corrosion, temperature abnormalities and other problems during use, which pose a threat to the safety of the power system. In order to ensure the normal use of electricity for urban residents, it is very important to detect power cables and discover these problems in time.

[0003] As a cutting-edge sensing technology that develops in parallel with optical fiber and optical fiber communication technology, optical fiber sensing technology is gaining increasing attention. This sensor has the characteristics of corrosion resistance, electromagnetic interference resistance, high temperature resistance and good electrical insulation, which enables it to play an important role in a variety of harsh environments. Light propagating in optical fiber will undergo a variety of scattering, reflection and transmission processes, and its optical parameters such as wavelength, phase, intensity and polarization state are susceptible to changes due to external environmental factors such as temperature and vibration. Therefore, by analyzing the characteristics of scattered light, reflected light or transmitted light of the optical fiber built into the power cable, accurate perception of various parameters of the power cable can be achieved.

[0004] At present, optical fiber sensing technology has been applied to multi-parameter detection of power cables.

[0005] For example, Patent Application 1 with Publication No. CN117309050A discloses "a high-voltage cable multi-parameter detection system", including: laser, modulator, erbium-doped fiber amplifier, circulator, vibration fiber sensor, temperature fiber sensor, strain fiber sensor, fiber spectrometer, photoelectric detector, signal processing module and upper monitoring machine. Although this technical method can detect the vibration value, temperature value and strain value of the power cable, it requires the use of multiple optical fibers at the same time, which is complicated to operate and high in cost, making it unfavorable for promotion.

[0006] For another example, Patent Application 2 with the publication number CN219608263U discloses "a multi-parameter fusion type distributed optical fiber detection system", including a light source, a first optical fiber coupler, a detection light synthesis unit, a first optical fiber circulator, a sensing optical fiber, a second optical fiber circulator, a second modulator, a continuous light EDFA, a second optical fiber coupler, a demodulation unit, and a data acquisition and processing unit. This technical solution can use optical fiber to simultaneously measure parameters such as temperature and vibration, but it has the disadvantages of a small measurement range and being greatly affected by the state of the optical fiber itself.

[0007] Therefore, it is necessary to improve the existing power cable monitoring system and method based on optical fiber sensing. Summary of the invention

[0008] In order to solve the deficiencies in the prior art, the purpose of the present invention is to provide a power cable monitoring system and method based on single-core optical fiber multi-parameter sensing, which can simultaneously measure the static temperature parameters and dynamic vibration parameters of the power cable using only one optical fiber, and has the advantages of low cost, wide measurement range, and high signal-to-noise ratio.

[0009] The present invention adopts the following technical solution.

[0010] According to a first aspect of the present invention, a power cable detection system based on single-core optical fiber multi-parameter sensing is provided. The system comprises: a laser, a first optical fiber coupler, an acousto-optic modulation unit, an optical fiber circulator, a distributed sensing optical fiber, a power cable, a wavelength division multiplexer, a second optical fiber coupler and a data acquisition and monitoring unit;

[0011] The first optical fiber coupler is used to divide the laser light emitted by the laser into a first branch laser light and a second branch laser light;

[0012] The acousto-optic modulation unit is used to modulate the first branch laser into pulse light;

[0013] Distributed sensing optical fiber is built into the power cable to sense the temperature and vibration changes of the power cable;

[0014] The optical fiber circulator is respectively connected to the acousto-optic modulation unit, the distributed sensing optical fiber and the wavelength division multiplexer, and is used to pass the pulse light into the distributed sensing optical fiber, and pass the backscattered light returned by the distributed sensing optical fiber into the wavelength division multiplexer;

[0015] The wavelength division multiplexer is used to separate the returned backscattered light into Rayleigh backscattered light, Raman Stokes light and Raman anti-Stokes light;

[0016] The second optical fiber coupler is used to perform interference mixing on the Rayleigh backscattered light and the second branch laser to obtain a beat frequency signal;

[0017] The data acquisition and monitoring unit is used to monitor the beat frequency signal, Raman Stokes light and Raman anti-Stokes light, and then demodulate and extract the vibration signal and temperature value of the power cable.

[0018] Preferably, the first optical fiber coupler is a 90:10 optical fiber coupler; the ratio of the first laser branch to the second laser branch in the laser light emitted by the laser is 90:10.

[0019] Preferably, the second optical fiber coupler is a 50:50 optical fiber coupler.

[0020] Preferably, the acousto-optic modulation unit comprises an acousto-optic modulator, a pulse generator and an erbium-doped fiber amplifier;

[0021] The acousto-optic modulator is used to convert laser light into initial pulse light;

[0022] The pulse generator is connected to the AOM and is used to control the pulse width and frequency of the initial pulse light via the AOM;

[0023] The erbium-doped fiber amplifier is used to amplify the optical power of the initial pulse light as the output of the acousto-optic modulation unit.

[0024] Preferably, the data acquisition monitoring unit comprises a balanced photodetector, an avalanche photodiode, a data acquisition card and a processor;

[0025] The avalanche photodiode is used to convert the Raman Stokes light and the Raman anti-Stokes light into a first electrical signal and a second electrical signal respectively;

[0026] The balanced photodetector is used to convert the beat frequency signal into a third electrical signal;

[0027] The data acquisition card acquires the first, second and third electrical signals and transmits them to the processor;

[0028] The processor demodulates the first and second electrical signals to extract temperature values, and demodulates the third electrical signal to extract vibration values.

[0029] According to a second aspect of the present invention, there is provided a power cable monitoring method based on single-core optical fiber multi-parameter sensing implemented by using the system described in the first aspect of the present invention. The method comprises the following steps:

[0030] Splitting the laser light emitted by the laser into a first branch laser light and a second branch laser light through a first optical fiber coupler;

[0031] Modulating the first branch laser into pulse light by an acousto-optic modulation unit;

[0032] Distributed sensing optical fiber is built into the power cable;

[0033] The pulse light is passed into the distributed sensing optical fiber through the optical fiber circulator, and the backscattered light returned by the distributed sensing optical fiber is passed into the wavelength division multiplexer;

[0034] The returned backscattered light is separated into Rayleigh backscattered light, Raman Stokes light and Raman anti-Stokes light by a wavelength division multiplexer;

[0035] The Rayleigh backscattered light is interfered and mixed with the second branch laser through the second optical fiber coupler to obtain a beat frequency signal;

[0036] The beat frequency signal, Raman Stokes light and Raman anti-Stokes light are monitored by a data acquisition monitoring unit, and then the vibration signal and temperature value of the power cable are obtained by demodulation and extraction.

[0037] Preferably, the beat frequency signal, Raman Stokes light and Raman anti-Stokes light are monitored by a data acquisition monitoring unit, and then demodulated and extracted to obtain the vibration signal and temperature value of the power cable, including the following steps:

[0038] Determine a power ratio of the anti-Stokes light to the Stokes light at a reference temperature value T0 as a first ratio;

[0039] Determine the power ratio of the anti-Stokes light to the Stokes light at the temperature value T to be measured as the second ratio;

[0040] According to the first ratio and the second ratio, a temperature value T to be measured of the power cable is obtained.

[0041] Preferably, obtaining the temperature value T to be measured of the power cable according to the first ratio and the second ratio comprises calculating the temperature value T to be measured by the following formula:

[0042]

[0043] In the formula,

[0044] R(T0) is the first ratio,

[0045] R(T) is the second ratio;

[0046] h is Planck's constant,

[0047] Δv is the frequency shift of Raman scattering,

[0048] k is the Boltzmann constant,

[0049] T0 is the thermodynamic temperature.

[0050] Preferably, the beat frequency signal, Raman Stokes light and Raman anti-Stokes light are monitored by a data acquisition monitoring unit, and then demodulated and extracted to obtain the vibration signal and temperature value of the power cable, including:

[0051] According to the waveform diagram of the beat frequency signal, the amplitude and phase of the beat frequency signal are obtained by demodulation;

[0052] According to the amplitude and phase of the beat frequency signal and combined with the beat frequency signal synthesis mechanism, the vibration signal of the power cable is obtained.

[0053] Preferably, according to the waveform diagram of the beat frequency signal, demodulating to obtain the amplitude and phase of the beat frequency signal includes: expressing the beat frequency signal P as:

[0054]

[0055] in,

[0056] E L is the second branch laser input into the second fiber coupler, i.e., the local light.

[0057] E R is the interference light field of Rayleigh scattered light,

[0058] is the phase angle of the local light,

[0059] is the phase angle of Rayleigh scattered light,

[0060] W L is the angular frequency of the local light,

[0061] W R is the angular frequency of the Rayleigh scattered light,

[0062] t is the time variable.

[0063] Preferably, the vibration signal of the power cable is obtained according to the amplitude and phase of the beat frequency signal in combination with the beat frequency signal synthesis mechanism, including:

[0064] The vibration signal Z of the power cable is expressed as:

[0065]

[0066] The beneficial effect of the present invention is that, compared with the prior art, based on the Rayleigh scattering effect and the Raman scattering effect, only one single-core optical fiber can be used to simultaneously measure the temperature and vibration values ​​of the power cable, and the temperature measurement range is large and the cost is low. Specifically, on the one hand, the present invention divides the laser light emitted by the laser into a first branch laser and a second branch laser through a first optical fiber coupler, converts the first branch laser into pulse light and then introduces it into the distributed sensing optical fiber, and interferes and mixes the Raman Rayleigh backscattered light separated from the optical signal fed back by the distributed sensing optical fiber with the second branch laser to obtain a beat frequency signal, and then demodulates the beat frequency signal to obtain a vibration signal. Compared with the conventional The optical time-domain reflectometer (OTD) structure has a higher signal-to-noise ratio and can more fully restore the vibration signal of the power cable. On the other hand, the present invention measures the temperature value of the power cable based on the Raman scattering effect. By increasing the laser energy and EDFA amplification energy, it effectively solves the problem of inaccurate temperature measurement caused by insufficient Raman scattering effect energy in single-mode optical fiber. Compared with the Brillouin scattering effect temperature measurement technology used in the background technology patent application 2, it has a higher temperature measurement range and lower cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] Figure 1 It is a structural diagram of a power cable monitoring system based on single-core optical fiber multi-parameter sensing of the present invention;

[0068] Figure 2 It is a flow chart of the power cable monitoring method based on single-core optical fiber multi-parameter sensing of the present invention.

[0069] The accompanying drawings are marked as follows:

[0070] 1-Laser, 2-First fiber coupler, 3-Acousto-optic modulator, 4-Pulse generator, 5-Erbium-doped fiber amplifier, 6-Fiber circulator, 7-Distributed sensing fiber, 8-Power cable, 9-Wavelength division multiplexer, 10-Second fiber coupler, 11-Balanced photodetector, 12-Avalanche photodiode, 13-Data acquisition card, 14-Computer host computer. DETAILED DESCRIPTION

[0071] In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. The embodiments described in this application are only part of the embodiments of the present invention, not all of them. Based on the spirit of the present invention, other embodiments obtained by ordinary technicians in this field without creative work are all within the scope of protection of the present invention.

[0072] Example 1

[0073] This embodiment provides a power cable monitoring system based on single-core optical fiber multi-parameter sensing. Figure 1 As shown, the monitoring system includes: a laser 1, a first fiber coupler 2, an acousto-optic modulation unit, a fiber circulator 6, a distributed sensing fiber 7, a power cable 8, a wavelength division multiplexer 9, a second fiber coupler 10 and a data acquisition monitoring unit.

[0074] The laser 1 is used to emit laser light. In this embodiment, preferably, the laser 1 is a 1550 nm laser.

[0075] The first fiber coupler 2 is used to divide the laser light emitted by the laser into a first branch laser light and a second branch laser light. In this embodiment, preferably, the first fiber coupler 2 is a 90:10 fiber coupler, which enables the continuous laser light output by the laser 1 to be divided into a first branch laser light with a ratio of 90 and a second branch laser light with a ratio of 10. Selecting a 90:10 fiber coupler can ensure that enough energy enters the distributed sensing fiber 7, so that there is enough Raman scattering effect energy to ensure the accuracy of temperature measurement.

[0076] The acousto-optic modulation unit is used to modulate the first branch laser into pulse light. In this embodiment, preferably, the pulse generating unit generates a pulse signal with a pulse width of 100ns and a repetition frequency of 5khz. Specifically, the acousto-optic modulation unit includes an acousto-optic modulator 3, a pulse generator 4 and an erbium-doped fiber amplifier 5. The acousto-optic modulator 3 is used to convert the laser into an initial pulse light. The pulse generator 4 is connected to the acousto-optic modulator, and is used to control the pulse width and frequency of the initial pulse light via the acousto-optic modulator 3. The erbium-doped fiber amplifier 5 is used to amplify the optical power of the initial pulse light as the output of the acousto-optic modulation unit. By controlling the pulse and frequency generated by the acousto-optic modulator through the pulse generator, and amplifying the pulse signal generated by the pulse generator through the erbium-doped fiber amplifier, it can be ensured that the entire monitoring system obtains a higher single-measurement signal-to-noise ratio.

[0077] The optical fiber circulator 6 is respectively connected to the acousto-optic modulation unit, the distributed sensing optical fiber 7 and the wavelength division multiplexer 9 for passing the pulse light into the distributed sensing optical fiber 7 and passing the backscattered light returned by the distributed sensing optical fiber 7 into the wavelength division multiplexer 9 .

[0078] The distributed sensing optical fiber 7 is built into the power cable 8 to sense its temperature and vibration changes.

[0079] The wavelength division multiplexer 9 separates the returned backscattered light into Rayleigh backscattered light, Raman Stokes light and Raman anti-Stokes light.

[0080] The second fiber coupler 10 is used to perform interference mixing on the Rayleigh backscattered light and the second branch laser output by the first fiber coupler to obtain a beat frequency signal. In this embodiment, preferably, the second fiber coupler 10 is a 50:50 fiber coupler, that is, the 50:50 fiber coupler performs interference mixing on the input Rayleigh backscattered light and the second branch laser in a ratio of 50:50.

[0081] The data acquisition and monitoring unit is used to monitor the beat frequency signal, Raman Stokes light and Raman anti-Stokes light, and obtain the vibration signal and temperature value of the power cable by demodulation and extraction. In this embodiment, preferably, the data acquisition and monitoring unit includes a balanced photodetector 11, an avalanche photodiode 12, a data acquisition card 13 and a processor 14. The avalanche photodiode 12 is used to respectively receive the Stokes light and the anti-Stokes light separated by the wavelength division multiplexer 9, and convert the two optical signals into a first electrical signal and a second electrical signal respectively. The balanced photodetector 11 is used to receive the beat frequency signal after interference mixing by the second optical fiber coupler 10, and process and convert it into a third electrical signal. The data acquisition card 13 is used to collect the first, second and third electrical signals converted by the balanced photodetector 11 and the avalanche photodiode 12. The processor 14 receives the digital electrical signal after analog-to-digital conversion from the data acquisition card 13, and demodulates and extracts the Raman and Rayleigh scattering data to obtain the temperature value and the vibration value.

[0082] When the detected power cable fails, the internal current increases sharply and the temperature rises abnormally, and the system collects Raman scattered light information with temperature changes. At this time, the electrical information converted from optical information is obtained through the avalanche photodiode and data acquisition card, and the data is solved on the computer host.

[0083] At this time, the computer host computer demodulates the Raman scattering data from the avalanche photodiode to obtain the temperature value of the power cable. The power ratio R(T0) of anti-Stokes light and Stokes light at the reference temperature T0 can be expressed as:

[0084]

[0085] In the formula,

[0086] R(T0) is the power ratio of anti-Stokes light to Stokes light at reference temperature T0,

[0087] P as (T0) is the anti-Stokes optical power value at reference temperature T0,

[0088] P s (T0) is the Stokes optical power value at reference temperature T0,

[0089] K as is the scattering coefficient of anti-Stokes light,

[0090] K s is the scattering coefficient of Stokes light,

[0091] v as is the frequency of the anti-Stokes light,

[0092] v s is the frequency of Stokes light,

[0093] h is Planck's constant,

[0094] Δν is the frequency shift of Raman scattering,

[0095] k is the Boltzmann constant,

[0096] T0 is the thermodynamic temperature,

[0097] a as is the attenuation coefficient of anti-Stokes light in the optical fiber,

[0098] a s is the attenuation coefficient of Stokes light in the optical fiber,

[0099] L is the length of the optical fiber to be tested.

[0100] When the temperature of the optical fiber to be tested changes, the following formula can be obtained:

[0101]

[0102] Further solving gives:

[0103]

[0104] The temperature value of the power cable can be obtained based on the reference temperature T0 and the ratio of anti-Stokes light to Stokes light at T under the measurement condition.

[0105] When the power cable under test is hit or collided from the surrounding environment and mechanical vibration occurs, the system will demodulate the collected Rayleigh scattering data to obtain the vibration value.

[0106] At this time, the computer host computer demodulates the optical signal with vibration information after being converted by the balanced photoelectric detector and the data acquisition card to obtain the vibration value of the power cable. The calculation process is as follows:

[0107]

[0108] In the formula,

[0109] E R (t) is the interference light field of Rayleigh scattered light,

[0110] E R0 is the amplitude of the scattered light,

[0111] ω is the optical frequency shift introduced by the AOM,

[0112] Δω is the light field frequency,

[0113] is the phase of the Rayleigh scattered light,

[0114] E L (t) is the branch laser with a ratio of 10 input into the 50:50 fiber coupler, i.e., the local light.

[0115] E L0 is the amplitude of the local light,

[0116] is the initial phase of the local light.

[0117] Specifically, after 50:50 interferometric mixing by the fiber coupler, the beat frequency signal detected by the balanced photodetector is:

[0118] After the balanced photoelectric detector, the first two items can be removed, and the final beat frequency signal input into the computer host is:

[0119]

[0120] According to the waveform diagram displayed in the computer host computer, the amplitude and phase demodulation of the beat frequency signal can be performed. L The amplitude, angular frequency and phase of (t) (i.e., the second branch laser with a ratio of 10) are known, so the vibration signal Z of the power cable is obtained by further using the fiber interference mechanism and phase unwrapping algorithm, which is expressed as:

[0121]

[0122] In this embodiment, based on the Rayleigh scattering effect and the Raman scattering effect, only one single-core optical fiber can be used to simultaneously measure the temperature and vibration values ​​of the power cable, and the temperature measurement range is large and the cost is low. Specifically, on the one hand, this embodiment uses a first optical fiber coupler to divide the laser light emitted by the laser into a first branch laser and a second branch laser, converts the first branch laser into pulse light and then introduces it into the distributed sensing optical fiber, and interferes and mixes the Raman Rayleigh backscattered light separated from the optical signal fed back by the distributed sensing optical fiber with the second branch laser to obtain a beat frequency signal, and then demodulates the beat frequency signal to obtain a vibration signal. Compared with the conventional The optical time-domain reflectometer (OTD) structure has a higher signal-to-noise ratio and can more fully restore the vibration signal of the power cable. On the other hand, this embodiment measures the temperature value of the power cable based on the Raman scattering effect. By increasing the laser energy and EDFA amplification energy, it effectively solves the problem of inaccurate temperature measurement caused by insufficient Raman scattering effect energy in single-mode optical fiber. Compared with the Brillouin scattering effect temperature measurement technology used in the prior art, it has a higher temperature measurement range and lower cost.

[0123] Example 2

[0124] This embodiment provides a method for monitoring a power cable based on single-core optical fiber multi-parameter sensing. The method utilizes the power cable monitoring system based on single-core optical fiber multi-parameter sensing of embodiment 1.

[0125] Specifically, Figure 2 , the method of this embodiment may include the following steps:

[0126] Step 1: split the laser light emitted by the laser into a first branch laser light and a second branch laser light through a first optical fiber coupler.

[0127] The first optical fiber coupler is preferably a 90:10 optical fiber coupler, and the ratio of the first laser branch to the second laser branch in the laser light emitted by the laser is 90:10.

[0128] Step 2: modulate the first branch laser into pulse light through an acousto-optic modulation unit.

[0129] Step 3: embed the distributed sensing optical fiber into the power cable.

[0130] Step 4: Pass the pulse light into the distributed sensing optical fiber through the optical fiber circulator, and pass the backscattered light returned by the distributed sensing optical fiber into the wavelength division multiplexer.

[0131] Step 5: Separate the returned backscattered light into Rayleigh backscattered light, Raman Stokes light and Raman anti-Stokes light through a wavelength division multiplexer.

[0132] Step 6: Perform interference mixing on the Rayleigh backscattered light and the second branch laser through a second optical fiber coupler to obtain a beat frequency signal.

[0133] The second optical fiber coupler is preferably a 50:50 optical fiber coupler.

[0134] Step 7: monitor the beat frequency signal, Raman Stokes light and Raman anti-Stokes light through a data acquisition monitoring unit, and then demodulate and extract the vibration signal and temperature value of the power cable.

[0135] The temperature value of the power cable can be obtained by demodulating and extracting the Raman Stokes light and the Raman anti-Stokes light, which specifically includes the following steps:

[0136] Step A1, determining a power ratio of anti-Stokes light to Stokes light at a reference temperature value T0 as a first ratio;

[0137] Step A2, determining the power ratio of the anti-Stokes light to the Stokes light at the temperature value T to be measured as the second ratio;

[0138] Step A3: Obtain the temperature value T to be measured of the power cable according to the first ratio and the second ratio:

[0139]

[0140] Further, the vibration signal of the power cable is obtained by demodulating and extracting the beat frequency signal, which specifically includes the following steps:

[0141] Step B1: demodulate the beat frequency signal to obtain the amplitude and phase of the beat frequency signal according to the waveform diagram of the beat frequency signal.

[0142] The beat frequency signal P is expressed as:

[0143]

[0144] Step B2: Obtain a vibration signal of the power cable according to the amplitude and phase of the beat frequency signal.

[0145] Among them, due to the local light E input to the second fiber coupler L The amplitude, angular frequency and phase of (t) (i.e. the second branch laser with a ratio of 10) are known, so the vibration signal Z of the power cable can be obtained as:

[0146]

[0147] The beneficial effect of the present invention is that, compared with the prior art, based on the Rayleigh scattering effect and the Raman scattering effect, only one single-core optical fiber can be used to simultaneously measure the temperature and vibration values ​​of the power cable, and the temperature measurement range is large and the cost is low. Specifically, on the one hand, the present invention divides the laser light emitted by the laser into a first branch laser and a second branch laser through a first optical fiber coupler, converts the first branch laser into pulse light and then introduces it into the distributed sensing optical fiber, and interferes and mixes the Raman Rayleigh backscattered light separated from the optical signal fed back by the distributed sensing optical fiber with the second branch laser to obtain a beat frequency signal, and then demodulates the beat frequency signal to obtain a vibration signal. Compared with the conventional The structure has a higher signal-to-noise ratio and can more fully restore the vibration signal of the power cable. On the other hand, the present invention measures the temperature value of the power cable based on the Raman scattering effect. By increasing the laser energy and EDFA amplification energy, it effectively solves the problem of inaccurate temperature measurement caused by insufficient Raman scattering effect energy in single-mode optical fiber. Compared with the Brillouin scattering effect temperature measurement technology used in the background technology patent application 2, it has a higher temperature measurement range and lower cost.

[0148] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents, and any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A power cable monitoring system based on single-core optical fiber multi-parameter sensing, characterized in that: include: A laser, a first optical fiber coupler, an acousto-optic modulation unit, an optical fiber circulator, a distributed sensing optical fiber, a power cable, a wavelength division multiplexer, a second optical fiber coupler, and a data acquisition and monitoring unit; The first optical fiber coupler is used to divide the laser light emitted by the laser into a first branch laser light and a second branch laser light; The acousto-optic modulation unit is used to modulate the first branch laser into pulse light; Distributed sensing optical fiber is built into the power cable to sense the temperature and vibration changes of the power cable; The optical fiber circulator is respectively connected to the acousto-optic modulation unit, the distributed sensing optical fiber and the wavelength division multiplexer, and is used to pass the pulse light into the distributed sensing optical fiber, and pass the backscattered light returned by the distributed sensing optical fiber into the wavelength division multiplexer; The wavelength division multiplexer is used to separate the returned backscattered light into Rayleigh backscattered light, Raman Stokes light and Raman anti-Stokes light; The second optical fiber coupler is used to perform interference mixing on the Rayleigh backscattered light and the second branch laser to obtain a beat frequency signal; The data acquisition and monitoring unit is used to monitor the beat frequency signal, Raman Stokes light and Raman anti-Stokes light, and then demodulate and extract the vibration signal and temperature value of the power cable.

2. The power cable monitoring system based on single-core optical fiber multi-parameter sensing according to claim 1 is characterized in that: The first fiber coupler is a 90:10 fiber coupler; the ratio of the first laser branch to the second laser branch in the laser light emitted by the laser is 90:10; and the second fiber coupler is a 50:50 fiber coupler.

3. The power cable monitoring system based on single-core optical fiber multi-parameter sensing according to claim 1 is characterized in that: The acousto-optic modulation unit includes an acousto-optic modulator, a pulse generator and an erbium-doped fiber amplifier; The acousto-optic modulator is used to convert laser light into initial pulse light; The pulse generator is connected to the AOM and is used to control the pulse width and frequency of the initial pulse light via the AOM; The erbium-doped fiber amplifier is used to amplify the optical power of the initial pulse light as the output of the acousto-optic modulation unit.

4. The power cable monitoring system based on single-core optical fiber multi-parameter sensing according to claim 1 is characterized in that: The data acquisition monitoring unit includes a balanced photodetector, an avalanche photodiode, a data acquisition card and a processor; The avalanche photodiode is used to convert the Raman Stokes light and the Raman anti-Stokes light into a first electrical signal and a second electrical signal respectively; The balanced photodetector is used to convert the beat frequency signal into a third electrical signal; The data acquisition card acquires the first, second and third electrical signals and transmits them to the processor; The processor demodulates the first and second electrical signals to extract temperature values, and demodulates the third electrical signal to extract vibration values.

5. A power cable monitoring method based on single-core optical fiber multi-parameter sensing implemented by using the system according to any one of claims 1 to 4, characterized in that: The following steps are involved: Splitting the laser light emitted by the laser into a first branch laser light and a second branch laser light through a first optical fiber coupler; Modulating the first branch laser into pulse light by an acousto-optic modulation unit; Distributed sensing optical fiber is built into the power cable; The pulse light is passed into the distributed sensing optical fiber through the optical fiber circulator, and the backscattered light returned by the distributed sensing optical fiber is passed into the wavelength division multiplexer; The returned backscattered light is separated into Rayleigh backscattered light, Raman Stokes light and Raman anti-Stokes light by a wavelength division multiplexer; The Rayleigh backscattered light is interfered and mixed with the second branch laser through the second optical fiber coupler to obtain a beat frequency signal; The beat frequency signal, Raman Stokes light and Raman anti-Stokes light are monitored by a data acquisition monitoring unit, and then the vibration signal and temperature value of the power cable are obtained by demodulation and extraction.

6. The power cable monitoring method based on single-core optical fiber multi-parameter sensing according to claim 5 is characterized in that: The beat frequency signal, Raman Stokes light and Raman anti-Stokes light are monitored by a data acquisition monitoring unit, and then demodulated and extracted to obtain the vibration signal and temperature value of the power cable, including the following steps: Determine a power ratio of the anti-Stokes light to the Stokes light at a reference temperature value T0 as a first ratio; Determine the power ratio of the anti-Stokes light to the Stokes light at the temperature value T to be measured as the second ratio; According to the first ratio and the second ratio, a temperature value T to be measured of the power cable is obtained.

7. The power cable monitoring method based on single-core optical fiber multi-parameter sensing according to claim 6 is characterized in that: According to the first ratio and the second ratio, a temperature value T to be measured of the power cable is obtained, including: The temperature value T to be measured is calculated by the following formula: In the formula, R(T0) is the first ratio, R(T) is the second ratio; h is Planck's constant, Δv is the frequency shift of Raman scattering, k is the Boltzmann constant, T0 is the thermodynamic temperature.

8. The power cable monitoring method based on single-core optical fiber multi-parameter sensing according to claim 5 is characterized in that: The beat frequency signal, Raman Stokes light and Raman anti-Stokes light are monitored by a data acquisition monitoring unit, and then demodulated and extracted to obtain the vibration signal and temperature value of the power cable, which also includes the following steps: According to the waveform diagram of the beat frequency signal, the amplitude and phase of the beat frequency signal are obtained by demodulation; According to the amplitude and phase of the beat frequency signal and combined with the beat frequency signal synthesis mechanism, the vibration signal of the power cable is obtained.

9. The power cable monitoring method based on single-core optical fiber multi-parameter sensing according to claim 8 is characterized in that: According to the waveform diagram of the beat frequency signal, the amplitude and phase of the beat frequency signal are obtained by demodulation, including: The beat frequency signal P is expressed as: in, E L is the second branch laser input into the second fiber coupler, i.e., the local light. E R is the interference light field of Rayleigh scattered light, is the phase angle of the local light, is the phase angle of Rayleigh scattered light, W L is the angular frequency of the local light, W R is the angular frequency of the Rayleigh scattered light, t is the time variable.

10. The power cable monitoring method based on single-core optical fiber multi-parameter sensing according to claim 9, characterized in that: According to the amplitude and phase of the beat frequency signal, combined with the beat frequency signal synthesis mechanism, the vibration signal of the power cable is obtained, including: The vibration signal Z of the power cable is expressed as:

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