A distributed optical fiber sensor array, measurement system and method

Abstract

The present application provides a distributed optical fiber sensor array, measurement system and method, wherein multiple optical fiber current sensing units are cascaded on the same optical path to form a distributed optical fiber sensor array, and a time division multiplexing working mechanism is used for each optical fiber current sensing unit. The distributed current of each measuring point is calculated by adopting a fully digital closed-loop modulation and demodulation method, thereby solving the problem of measuring distributed current, especially the problem of measuring large current in a complex electromagnetic environment. The matrix optical fiber current measurement system and method based on wavelength division multiplexing and space division multiplexing based on the distributed optical fiber sensor array further improves the capacity of the optical fiber current sensing network and greatly reduces the system measurement cost of distributed current.

Description

Technical Field

[0001] The present application relates to the field of optical fiber sensing technology, and in particular, to a distributed optical fiber sensing array, a measurement system and a method. Background Art

[0002] Distributed current measurement is a technology that uses distributed sensor networks to monitor current distribution and changes. It is widely used in power systems, electrolysis industries, and energy management. In the field of power systems, distributed current measurement can be used to monitor the current distribution in the power grid in real time; by real-time monitoring of current data, it helps power companies optimize power grid operation, timely discover current anomalies in the power grid, and early warn and handle potential faults and problems, thereby improving power supply reliability and safety. In the metallurgical industry, distributed current measurement can help metallurgical manufacturers monitor the dynamic changes of the electrolysis process in real time; through accurate monitoring and analysis of data such as the cathode current, anode current, and series current of the electrolytic cell, it can discover and locate faults and problems in the electrolysis process, adjust production parameters in time, improve production quality and production efficiency, and optimize energy utilization, save energy, and reduce emissions. In the field of energy management, distributed current measurement can be used to monitor and manage distributed energy generation systems, such as solar and wind power generation systems; by accurately measuring current distribution, it can understand the stability and performance of new energy systems, optimize power generation efficiency, and adapt to large-scale new energy networking.

[0003] For the measurement of distributed current, traditional current measuring devices, such as Rogowski coil current measuring devices, Hall current sensors, shunts, etc., are difficult to overcome technical defects such as electromagnetic interference and insulation. Even if corresponding protection measures are taken, not only the weight and volume of the device are seriously increased, but also when measuring distributed current, the system cost increases sharply with the increase of measuring points. Summary of the invention

[0004] The technical problem to be solved by the present application is that the distributed current measurement solutions in the prior art are either difficult to overcome technical defects such as electromagnetic interference and insulation, or the devices are too heavy or too large and the cost is high.

[0005] To solve the above problems, in the first aspect, the technical solution of the present application provides a distributed optical fiber sensing array, comprising a plurality of optical fiber current sensing units, and the plurality of optical fiber current sensing units are cascaded on the same optical path, each of the optical fiber current sensing units receives an optical signal from a photoelectric collection unit and sends an interference optical signal carrying current information to be measured to the photoelectric collection unit;

[0006] The fiber optic current sensing unit comprises a polarization-maintaining delay optical fiber, a polarization-maintaining optical fiber coupler and an optical fiber sensing ring, wherein the optical fiber sensing ring comprises a 1 / 4 optical fiber wave plate, a sensing optical fiber and a reflector, and the optical fiber sensing ring is arranged around a measuring point to sense the current to be measured transmitted in the measuring point; after the optical fiber current sensing unit receives the optical signal emitted by the photoelectric collection unit, the optical signal passes through the polarization-maintaining delay optical fiber, and the polarization-maintaining optical fiber coupler sends a part of the optical signal to the optical fiber sensing ring in the same unit, and sends the other part of the optical signal to the next optical fiber current sensing unit, and then passes through multiple optical fiber current sensing units in sequence;

[0007] In each of the fiber optic current sensing units, after the current to be measured acts on the optical signal transmitted by the fiber optic sensing ring to form a Faraday phase difference, the optical signal in the fiber optic sensing ring carries the information of the current to be measured, and after being reflected by the reflector, returns along the original path, and the generated Faraday phase difference is doubled; the optical signal carrying the information of the current to be measured is modulated and polarized by the photoelectric collection unit again to form an interference optical signal; the interference optical signal is converted into an electrical signal in the photoelectric collection unit and then transmitted to the signal processing unit for the signal processing unit to perform signal sampling and numerical demodulation to calculate the current to be measured.

[0008] In some embodiments of the distributed optical fiber sensing array, in the optical fiber current sensing unit:

[0009] The polarization-maintaining time-delay optical fiber is a linear polarization-maintaining optical fiber or a linear polarization-maintaining optical cable, and the polarization-maintaining time-delay optical fiber and the polarization-maintaining optical fiber coupler are 0° axially fused;

[0010] The 1 / 4 fiber wave plate is a linear polarization-maintaining fiber, and its length is 1 / 4 or 3 / 4 of the linear polarization-maintaining fiber beat length. The 1 / 4 fiber wave plate and the output pigtail of the polarization-maintaining fiber coupler are 45° axially fused;

[0011] The sensing optical fiber is a circular polarization preserving optical fiber, a photonic crystal optical fiber, a low birefringence optical fiber or a single-mode optical fiber.

[0012] In some embodiments of the distributed optical fiber sensing array, in the optical fiber current sensing unit:

[0013] If the fiber optic current sensing unit is the last fiber optic current sensing unit, the polarization-maintaining delay optical fiber and the 1 / 4 fiber wave plate are fused at 45°.

[0014] In some embodiments of the distributed optical fiber sensing array, in each of the optical fiber current sensing units:

[0015] It is determined according to the distance between the measuring points: the polarization-maintaining time-delay optical fiber is a linear polarization-maintaining optical fiber and is packaged with the polarization-maintaining optical fiber coupler, or the polarization-maintaining time-delay optical fiber is laid as a linear polarization-maintaining optical cable.

[0016] In some embodiments of the distributed optical fiber sensing array, in each of the optical fiber current sensing units:

[0017] The length of the optical fiber loop formed by the optical fiber current sensing unit is twice the length of the optical fiber loop formed by the previous optical fiber current sensing unit.

[0018] In some embodiments of the distributed optical fiber sensing array, in each of the optical fiber current sensing units:

[0019] The splitting ratio of each polarization-maintaining optical fiber coupler is not completely the same.

[0020] In some embodiments of the distributed optical fiber sensing array, in each optical fiber current sensing unit: the number of winding turns of the optical fiber sensing loop is adjusted and set according to the magnitude of the current to be measured.

[0021] In a second aspect, the technical solution of the present application provides a measurement system, comprising the distributed optical fiber sensor array according to any one of the first aspects, and further comprising a photoelectric acquisition unit, a signal processing unit, a distributed sensor array and a data display unit, wherein:

[0022] The photoelectric collection unit includes an optical transceiver component, a polarizer and a phase modulator, and the optical transceiver component includes a light source, a detector and a coupler;

[0023] The signal processing unit includes a driving circuit, a modulation circuit and a sampling and demodulation circuit; the optical transceiver assembly generates an optical signal through the light source and receives an optical signal through the detector under the action of the driving circuit, and transmits the optical signal through the coupler, and the optical signal is polarized by the polarizer and then output to the phase modulator; the phase modulator performs phase modulation on the input optical signal under the action of the modulation circuit and then outputs the phase modulator to the distributed optical fiber sensor array;

[0024] The data display unit receives and displays the current to be measured output by the sampling and demodulation circuit.

[0025] In a third aspect, the technical solution of the present application provides a measurement method using the measurement system described in the second aspect, comprising:

[0026] S110: Obtaining the light rate P of the interference light signal returned by the i-th optical fiber current sensing unit received by the detector in the distributed optical fiber current measurement system outi , the number of optical fiber current sensing units in the distributed optical fiber current measurement system is m, i=1, 2, 3, ...m;

[0027]

[0028] α i=A / 100;

[0029]

[0030] The П operator represents the multiplication of multiple consecutive data. in Represents the optical signal power output by the light source, α i and α j They respectively represent the loss coefficients of the optical fiber sensing loop transmitted to the same unit and introduced by the splitting ratio of the polarization-maintaining optical fiber coupler in the i-th and j-th optical fiber current sensing units; A represents the splitting ratio of the polarization-maintaining optical fiber coupler; Indicates the bias modulation phase of the modulation signal generated by the square wave bias modulation signal, represents the feedback modulation phase generated by the step wave feedback modulation signal; represents the Faraday phase difference formed in the i-th optical fiber sensing loop; N i is the number of turns of the i-th sensing optical fiber ring, I i is the current value to be measured at the corresponding measuring point of the i-th sensing optical fiber ring, and V is the Verdet constant of the sensing optical fiber;

[0031] S120: According to the time division multiplexing working mechanism, the feedback modulation period of the step wave is set to T i , in the previous cycle T of the feedback modulation cycle i+ Within the period, the interference light signal returned by the first 1 to i optical fiber current sensing units has a complete cycle. The interference light signal returned by the first 1 to i optical fiber current sensing units is sampled and superimposed to obtain P outi+ for:

[0032]

[0033] In the next cycle of the feedback modulation cycle T i- The interference light signals returned by the first 1 to i optical fiber current sensing units also have a complete cycle. The interference light signals returned by the first 1 to i optical fiber current sensing units are sampled and superimposed to obtain P outi- for:

[0034]

[0035] Among them, the step wave feedback modulation period T in the modulation signal i Determined by: i =2nl i / c, where c is the speed of light in a vacuum and n is the effective refractive index of the optical fiber; l i is the length of the optical fiber loop formed by the i-th optical fiber current sensing unit; the length of the optical fiber loop formed by the first optical fiber current sensing unit: l1 = l d1 +l s1, the square wave bias modulation period in the modulation signal is 2T1, that is, 4nl1 / c;

[0036] S130: At any time t, the interference light signal received by the detector is divided into time periods T i+ and T i- Demodulate and obtain the P of each optical fiber current sensing unit. outi+ and P outi- , according to ΔP i =(P outi+ -P outi- ) Demodulate and calculate the current to be measured I i (t).

[0037] In a fourth aspect, the technical solution of the present application provides a measurement system, including a multi-band photoelectric acquisition unit, a multi-channel signal processing unit, a sensor matrix composed of the distributed optical fiber sensor array according to any one of the first aspects, and a data display unit; wherein:

[0038] The multi-band optoelectronic collection unit includes a plurality of optical transceiver components of different bands, a first wavelength division multiplexer, a polarizer, a phase modulator and a second wavelength division multiplexer, and the optical signal working bands of the first wavelength division multiplexer, the second wavelength division multiplexer, the polarizer and the phase modulator cover the optical signals of different bands output by all optical transceiver components;

[0039] The multi-channel signal processing unit includes a multi-channel driving circuit, a multi-channel sampling demodulation circuit and a modulation circuit;

[0040] The sensing matrix includes a plurality of distributed optical fiber sensing arrays, and the optical signal working band of each distributed optical fiber sensing array should at least cover the optical signal bands corresponding to different optical transceiver components;

[0041] The plurality of optical transceiver components generate and receive optical signals of different bands under the action of the multi-channel driving circuit. The optical signals of different bands are output to the polarizer through the first wavelength division multiplexer for polarization, and then enter the phase modulator for phase modulation under the action of the modulation circuit, and then output to each distributed optical fiber sensor array of the corresponding band in the sensor matrix through the second wavelength division multiplexer, and each optical fiber current sensor unit senses the current information to be measured at each measuring point; based on the principle of reversibility of the optical path, the returned interference optical signal is converted into an electrical signal by the optical transceiver component of the corresponding band, and the signal is sampled and numerically demodulated by the multi-channel sampling and demodulation circuit, and the current to be measured at each measuring point in the sensor matrix of a specific band is calculated; the current to be measured is output to the data display unit for display.

[0042] In a fifth aspect, the technical solution of the present application provides a measurement method using the measurement system described in the fourth aspect, comprising:

[0043] S210: For optical transceiver components and distributed optical fiber sensor arrays with p optical signal bands, the average wavelength of the optical signal band transmitted in each optical transceiver component and the corresponding distributed optical fiber sensor array is k = 1, 2, 3, ..., p; with the working band optical signal Form a closed-loop system, where mid∈[1, 2, 3, …, p];

[0044] S220: For The current measurement in the optical signal band uses the time division multiplexing working mechanism to demodulate and calculate the current value to be measured at each measuring point of the distributed optical fiber sensor array in this band. For other optical signal bands Current measurement, where k≠mid, the power of the interference light signal returned by each optical fiber current sensing unit received by the detector in the optical transceiver component is:

[0045]

[0046] S230: Based on a specific optical signal band Step wave feedback cycle Corresponding to other optical signal bands In the previous cycle and the next cycle After internal sampling, we get and

[0047] S240: According to Demodulation calculation to obtain other optical signal bands Corresponding to the current to be measured of the distributed optical fiber sensor array

[0048] In a sixth aspect, the present application provides a measurement system, comprising a multi-channel photoelectric acquisition unit, a signal processing control unit, an optical fiber sensor matrix composed of the distributed optical fiber sensor array according to any one of the first aspects, and a data display unit, wherein the optical signal working band of each distributed optical fiber sensor array in the sensor matrix is ​​consistent with the optical signal band of the optical transceiver component; wherein:

[0049] The multi-channel photoelectric acquisition unit includes an optical transceiver component, a polarizer, a phase modulator and a multi-channel optical switch, and the optical transceiver component includes a light source, a detector and a coupler;

[0050] The signal processing control unit includes a control circuit, a drive circuit, a sampling and demodulation circuit and a modulation circuit; the control circuit is used to control the channel switching of the multi-channel optical switch, realize the optical path disconnection and positioning of each distributed optical fiber sensor array, and upload the positioning signal to the sampling and demodulation circuit, and obtain the current to be measured at each measuring point in the distributed optical fiber sensor array through modulation and demodulation calculation.

[0051] In a seventh aspect, the technical solution of the present application provides a measurement method using the measurement system described in the sixth aspect, comprising:

[0052] S310: For a multi-channel optical switch and a distributed optical fiber sensor array with q channels, the step wave feedback modulation period in each channel is T gi =2nl gi / c, g=1, 2, 3,..., q;

[0053] S320: The control circuit controls the multi-channel optical switch to be connected to the g-th channel distributed optical fiber sensor array, respectively in the period T before the feedback modulation period. gi+ and the next cycle T gi- After the inner sampling is superimposed, P is obtained outgi+ and P outgi- ;

[0054] S330: Divide the interference light signal received by the detector into time periods T gi+ and T gi- Demodulation, according to ΔP gi =(P outgi+ -P outgi- ) Demodulate and calculate the current to be measured I gi (t).

[0055] The above technical solution has the following beneficial effects:

[0056] In the solution provided by this application, multiple fiber optic current sensing units are cascaded on the same optical path to form a distributed fiber optic sensing array. For each fiber optic current sensing unit, a time division multiplexing working mechanism is used to calculate the distributed current of each measuring point by adopting a fully digital closed-loop modulation and demodulation method, thereby solving the problem of measuring distributed current, especially the problem of measuring large currents in complex electromagnetic environments. The matrix fiber optic current measurement system and method based on wavelength division multiplexing and space division multiplexing based on the distributed fiber optic sensing array further improves the capacity of the fiber optic current sensing network and greatly reduces the system measurement cost of distributed current. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 This is a schematic diagram of the structure of a distributed optical fiber sensor array in one embodiment of the present application;

[0058] Figure 2 This is a schematic diagram of the structure of a fiber optic current measurement system in one embodiment of the present application;

[0059] Figure 3 This is a schematic diagram of the structure of a matrix optical fiber current measurement system based on wavelength division multiplexing in one embodiment of the present application;

[0060] Figure 4 This is a structural schematic diagram of a matrix optical fiber current measurement system based on space division multiplexing in one embodiment of the present application;

[0061] Figure 5 Schematic diagram of the bias modulation phase and step modulation phase waveforms of the optical fiber current measurement system described in this application. DETAILED DESCRIPTION

[0062] The specific implementation of the present application is further described below with reference to the accompanying drawings.

[0063] It is easy to understand that according to the technical solution of the present application, without changing the essential spirit of the present application, a variety of structural modes and implementation modes that can be replaced by those skilled in the art can be replaced with each other. Therefore, the following specific implementation modes and drawings are only exemplary descriptions of the technical solution of the present application, and should not be regarded as the entirety of the present application or as a limitation or restriction on the technical solution of the application.

[0064] The directional terms such as up, down, left, right, front, back, front, back, top, bottom, etc. mentioned or may be mentioned in this specification are defined relative to the structures shown in the drawings. They are relative concepts and may change accordingly according to different positions and different usage conditions. Therefore, these or other directional terms should not be interpreted as restrictive terms.

[0065] In recent years, with the development of fiber optic sensing technology and the improvement of the performance of optoelectronic devices, fiber optic current sensors based on the Faraday magneto-optical effect have been maturely applied in power systems, especially ultra-high voltage / ultra-high voltage direct current transmission systems. Since fiber optic current sensors have technical characteristics such as high measurement accuracy, large dynamic range, and wide measurement bandwidth, and use optical fiber as a signal transmission medium, they not only have strong anti-electromagnetic interference capabilities and can work stably in complex electromagnetic environments, but also have small transmission losses, which greatly improves the measurement accuracy and overall performance of the system. The following scheme of this application is implemented using a fiber optic current sensor based on the Faraday magneto-optical effect.

[0066] This embodiment provides a distributed optical fiber sensor array, such as Figure 1As shown, it includes multiple fiber optic current sensing units (three fiber optic current sensing units are used as an example in the figure) and multiple fiber optic current sensing units are cascaded on the same optical path. Each fiber optic current sensing unit receives the optical signal from the photoelectric collection unit and sends the interference optical signal carrying the current information to be measured to the photoelectric collection unit. The fiber optic current sensing unit includes a polarization-maintaining delay optical fiber 111, a polarization-maintaining optical fiber coupler and a fiber optic sensing ring 112. The fiber optic sensing ring 112 includes a 1 / 4 optical fiber wave plate 1121, a sensing optical fiber 1122 and a reflector 1123. The fiber optic sensing ring 112 is arranged around the measuring point to sense the current to be measured transmitted in the measuring point. After the fiber optic current sensing unit receives the optical signal from the photoelectric collection unit, it passes through the polarization-maintaining delay optical fiber 111, and the polarization-maintaining optical fiber coupler sends a part of the optical signal to the fiber optic sensing ring 112 in the same unit, and sends the other part of the optical signal to the next fiber optic current sensing unit and then passes through multiple fiber optic current sensing units in sequence. In each of the fiber optic current sensing units, after the current to be measured acts on the optical signal transmitted by the fiber optic sensing ring 112 to form a Faraday phase difference, the optical signal in the fiber optic sensing ring carries the information of the current to be measured, and after being reflected by the reflector 1123, it returns along the original path, and the generated Faraday phase difference is doubled; the optical signal carrying the information of the current to be measured is modulated and polarized by the photoelectric collection unit again to form an interference optical signal; the interference optical signal is converted into an electrical signal in the photoelectric collection unit and then transmitted to the signal processing unit for the signal processing unit to perform signal sampling and numerical demodulation to calculate the current to be measured. In the above scheme, in each fiber optic current sensing unit, based on the Faraday magneto-optical effect and Ampere's loop theorem, the current to be measured acts on the transmitted optical signal to form a Faraday phase difference, carrying the information of the current to be measured. After being reflected by the reflector 1123, the optical signal returns along the original path, so that the generated Faraday phase difference is doubled; since each polarization-maintaining delay optical fiber 111 is connected in series on the same optical path, the optical signal returned by each fiber optic current sensing unit is distinguished in the time domain; the photoelectric collection unit can calculate the modulation signal and the current signal to be measured by demodulating the Faraday phase difference.

[0067] In the above scheme, each fiber optic current sensing unit in the distributed fiber optic sensor array uses the same optical path to transmit the same band optical signal. A time division multiplexing working mechanism is used for each fiber optic current sensing unit. The distributed current of each measuring point is calculated by adopting a fully digital closed-loop modulation and demodulation method, thereby solving the problem of measuring distributed current, especially the problem of measuring large current in complex electromagnetic environments.

[0068] Preferably, in the above scheme, the polarization-maintaining delay optical fiber 111 in each fiber optic current sensing unit can be determined according to the distance between the measuring points: the polarization-maintaining delay optical fiber 111 is a linear polarization-maintaining optical fiber and is packaged with the polarization-maintaining optical fiber coupler, or the polarization-maintaining delay optical fiber 111 is laid with a linear polarization-maintaining optical cable. That is, the implementation method of the polarization-maintaining delay optical fiber 111 is selected according to the distance between each measuring point. When the distance between the measuring points is short, the packaging method of the linear polarization-maintaining optical fiber and the polarization-maintaining optical fiber coupler can be selected, and when the distance between the measuring points is far, the laying method of the linear polarization-maintaining optical cable can be selected. Specifically, a critical distance value can be determined through experiments, and when the distance between the measuring points exceeds the critical distance value, it is considered that the distance is far, otherwise it is considered that the distance is close.

[0069] In specific implementation, the solution in the present application can adjust the length of each polarization-maintaining delay optical fiber 111 so that the length of the optical fiber loop formed by each optical fiber current sensing unit is twice the length of the optical fiber loop of the previous unit, thereby making the time difference between the optical signals transmitted by each optical fiber current sensing unit more obvious, thereby being able to more accurately distinguish the optical signals carrying the current information to be measured at each measuring point in the time domain.

[0070] Furthermore, the splitting ratio of each polarization-maintaining fiber coupler is not exactly the same, and the optimal solution can be designed according to the actual application requirements. Specifically, for the last fiber optic current sensing unit, the polarization-maintaining coupler can be omitted, and the splitting ratio A is 100 at this time, while the previous fiber optic current sensing unit needs to split the optical signal to the next fiber optic current sensing unit, and the splitting ratio can be selected in the range of 0 to 100. That is, in the previous fiber optic current sensing units, when the polarization-maintaining delay fiber 111 is a linear polarization-maintaining fiber, the polarization-maintaining delay fiber 111 and the polarization-maintaining fiber coupler are 0° axially fused, the 1 / 4 fiber wave plate 1121 is a linear polarization-maintaining fiber, and the length is 1 / 4 or 3 / 4 of the length of the linear polarization-maintaining fiber, and the 1 / 4 fiber wave plate 1121 and the output pigtail of the polarization-maintaining fiber coupler are 45° axially fused. If the fiber optic current sensing unit is the last fiber optic current sensing unit, since there is no next-stage fiber optic current sensing unit that needs to split, the polarization-maintaining fiber coupler can be omitted, and the polarization-maintaining delay fiber 111 and the 1 / 4 fiber wave plate 1121 can be directly 45° axially welded.

[0071] Further preferably, the number of winding turns of the optical fiber sensing ring 112 in each optical fiber current sensing unit is adjusted accordingly according to the magnitude of the current to be measured at each measuring point, and the Faraday phase difference formed in each optical fiber sensing ring is related to the number of winding turns of the sensing optical fiber ring and the value of the current to be measured at the corresponding measuring point of the sensing optical fiber ring. Therefore, by adjusting the number of winding turns of the sensing optical fiber ring according to the magnitude of the current to be measured at the measuring point, the Faraday phase difference can be adjusted within an appropriate range.

[0072] The present application also provides a fiber optic current measurement system, such as Figure 2 As shown, it includes the distributed optical fiber sensor array described in the above embodiments, and also includes an optoelectronic collection unit, a signal processing unit and a data display unit. Wherein, the optoelectronic collection unit includes an optical transceiver component, a polarizer and a phase modulator, and the optical transceiver component includes a light source, a detector and a coupler, and the light source, the detector and the coupler are packaged as a device or integrated as a chip. The signal processing unit includes a driving circuit, a modulation circuit and a sampling and demodulation circuit. Under the action of the driving circuit, the optical transceiver component generates an optical signal of a fixed band by the light source and / or receives an optical signal by the detector, and transmits it through the coupler, and then polarizes the optical signal through the polarizer and outputs it to the phase modulator. The phase modulator phase-modulates the input optical signal under the action of the modulation circuit, and then outputs it to the distributed optical fiber sensor array. In combination with the scheme in the aforementioned embodiment, in the distributed optical fiber sensing array, when the optical signal is input to each optical fiber current sensing unit, after passing through each polarization-maintaining delay optical fiber, a part of the optical signal is sent to the optical fiber sensing ring in the same unit by the polarization-maintaining optical fiber coupler, and another part of the optical signal is sent to the next optical fiber current sensing unit, and passes through multiple optical fiber current sensing units in sequence; in each optical fiber current sensing unit, based on the Faraday magneto-optical effect and Ampere's loop theorem, the current to be measured acts on the transmitted optical signal to form a Faraday phase difference, carrying the current information to be measured, and after being reflected by the reflector, the optical signal returns along the original path, so that the generated Faraday phase difference is generated. The phase difference is doubled; since each polarization-maintaining time-delay optical fiber is connected in series on the same optical path, the optical signal returned by each optical fiber current sensing unit is distinguished in the time domain; after the output optical signal is modulated by the phase modulator again, it is polarized by the polarizer to form an interference optical signal, and then returned to the detector of the optical transceiver component, and the detector converts the interference optical signal into an electrical signal; the sampling and demodulation circuit performs signal sampling and numerical demodulation, and the modulated signal and the current signal to be measured are calculated by demodulating the Faraday phase difference, and the modulated signal is sent to the phase modulator via the modulation circuit to form a closed-loop system, and the current signal to be measured is output to the data display unit.

[0073] Furthermore, the present application also provides a distributed optical fiber current measurement method using the above-mentioned distributed optical fiber current measurement system, specifically, a method of calculating the distributed current using a fully digital closed-loop modulation and demodulation method combining square wave bias modulation and step wave feedback modulation, and a method of calculating the distributed current using a time division multiplexing working mechanism, the method comprising:

[0074] S110: Obtaining the light rate P of the interference light signal returned by the i-th optical fiber current sensing unit received by the detector in the distributed optical fiber current measurement system outi The number of fiber optic current sensing units in the distributed fiber optic current measurement system is m, i=1, 2, 3, ... m, wherein the splitting ratio of each polarization-maintaining fiber coupler is A:(100-A), and the length of each fiber optic sensing loop is l si(i=1, 2, 3, ..., m);

[0075]

[0076] α i =A / 100;

[0077]

[0078] The П operator represents the multiplication of multiple consecutive data. in Represents the optical signal power output by the light source, α i and α j They represent the loss coefficient of the optical fiber sensing ring transmitted to the same unit introduced by the splitting ratio of the polarization-maintaining optical fiber coupler in the i-th and j-th optical fiber current sensing units, that is, the loss coefficient of the optical fiber sensing ring transmitted to the same unit is α i =A / 100, the loss coefficient transmitted to the next unit is (1-α i ), A represents the splitting ratio of the polarization-maintaining fiber coupler. For the last fiber current sensing unit, if its polarization-maintaining coupler is omitted, the splitting ratio A is 100; Indicates the bias modulation phase of the modulation signal generated by the square wave bias modulation signal, represents the feedback modulation phase generated by the step wave feedback modulation signal; represents the Faraday phase difference formed in the i-th optical fiber sensing loop; N i is the number of turns of the i-th sensing optical fiber ring, I i is the current value to be measured at the measuring point corresponding to the i-th sensing optical fiber ring, and V is the Verdet constant of the sensing optical fiber.

[0079] S120: According to the time division multiplexing working mechanism, the feedback modulation period of the step wave is set to T i , in the previous cycle T of the feedback modulation cycle i+ Within the period, the interference light signal returned by the first 1 to i optical fiber current sensing units has a complete cycle. The interference light signal returned by the first 1 to i optical fiber current sensing units is sampled and superimposed to obtain P outi+ for:

[0080]

[0081] In the next cycle of the feedback modulation cycle T i- The interference light signals returned by the first 1 to i optical fiber current sensing units also have a complete cycle. The interference light signals returned by the first 1 to i optical fiber current sensing units are sampled and superimposed to obtain P outi- for:

[0082]

[0083] Among them, the step wave feedback modulation period T in the modulation signal i Determined by: i =2nl i / c, where c is the speed of light in a vacuum and n is the effective refractive index of the optical fiber; l i is the length of the optical fiber loop formed by the i-th optical fiber current sensing unit; the length of the optical fiber loop formed by the first optical fiber current sensing unit: l1 = l d1 +l s1 , the square wave bias modulation period in the modulation signal is 2T1, that is, 4nl1 / c; for the optical fiber loop formed by the i-th optical fiber current sensing unit, the length of the optical fiber loop is:

[0084]

[0085] Correspondingly, the length of the optical fiber loop formed by the i-th optical fiber current sensing unit is l i ≈2l i-1 .

[0086] S130: At any time t, the interference light signal received by the detector is divided into time periods T i+ and T i- Demodulate and obtain the P of each optical fiber current sensing unit. outi+ and P outi- , according to ΔP i =(P outi+ -P outi- ) Demodulate and calculate the current to be measured I i (t).

[0087] Furthermore, the interference light signal received by the detector is divided into time periods T i+ and T i- Demodulate and obtain the P of each optical fiber current sensing unit. outi+ and P outi- , based on the fully digital closed-loop modulation and demodulation method, according to ΔP i =(P outi+ -P outi- ) can be demodulated and calculated to obtain the current value I to be measured i (t), and the feedback modulation phase of the next modulation cycle Thus, a fully digital closed-loop solution is formed.

[0088] In some schemes, such as Figure 3As shown, a matrix optical fiber current measurement system based on wavelength division multiplexing is provided, including a multi-band optoelectronic acquisition unit, a multi-channel signal processing unit, a sensor matrix and a data display unit. The sensor matrix includes a plurality of distributed optical fiber sensor arrays in the aforementioned embodiments, and the optical signal working band of each distributed optical fiber sensor array should at least cover the optical signal band of the corresponding different optical transceiver components, such as the optical signal working band of the first row of distributed optical fiber sensor arrays at least covers the output optical signal band of the first optical transceiver component. The multi-band optoelectronic acquisition unit includes a plurality of optical transceiver components of different bands, a first wavelength division multiplexer, a polarizer, a phase modulator and a second wavelength division multiplexer, and the optical signal working bands of the first wavelength division multiplexer, the second wavelength division multiplexer, the polarizer and the phase modulator can cover the optical signals of different bands output by all optical transceiver components. The multi-channel signal processing unit includes a multi-channel driving circuit, a multi-channel sampling demodulation circuit and a modulation circuit.

[0089] Among them, multiple optical transceiver components generate and receive optical signals of different bands under the action of a multi-channel driving circuit, and the optical signals of different bands are output to the polarizer through a first wavelength division multiplexer for polarization, and then enter the phase modulator for phase modulation under the action of a modulation circuit, and then output to each distributed optical fiber sensor array of the corresponding band in the sensing matrix through a second wavelength division multiplexer, and each optical fiber current sensing unit senses the current to be measured at each measuring point; combined with the working principle of the aforementioned distributed optical fiber sensor array, based on the principle of reversibility of the optical path, the returned interference optical signal is converted into an electrical signal by the optical transceiver component of the corresponding band, and is sampled and numerically demodulated by a multi-channel sampling and demodulation circuit, and the modulation signal of the specific band and the current signal to be measured at each measuring point in the sensing matrix are calculated by demodulating the Faraday phase difference; the modulated signal is sent to the phase modulator via the modulation circuit to form a closed-loop system for the specific band, and the current to be measured is output to the data display unit. In this embodiment, each distributed optical fiber sensor array in the sensor matrix uses optical signals of different wavelength bands, and utilizes the working mechanism of wavelength division multiplexing to achieve synchronous measurement of distributed optical fiber sensor arrays of different wavelength bands. This embodiment improves the capacity of the optical fiber current sensing network and significantly reduces the system measurement cost of distributed current. Further preferably, in the above scheme, the number of optical fiber current sensing units in each distributed optical fiber sensor array is the same, or the number of optical fiber current sensing units in the distributed sensor array corresponding to the specific wavelength band forming the closed-loop system is kept at the maximum.

[0090] Furthermore, in combination with the detection method for the measuring point current in the distributed optical fiber sensor array, the present application also provides a current measurement method implemented by a matrix optical fiber current measurement system based on wavelength division multiplexing, using square wave bias modulation and step wave feedback modulation schemes, combined with full digital closed-loop modulation and demodulation and open-loop modulation and demodulation methods, and using the working mechanism of time division multiplexing and wavelength division multiplexing to calculate the matrix distributed current, the method includes the following steps:

[0091] S210: For optical transceiver components and distributed optical fiber sensor arrays with p optical signal bands, the average wavelength of the optical signal band transmitted in each optical transceiver component and the corresponding distributed optical fiber sensor array is (k = 1, 2, 3, ..., p), since the modulation coefficients of the phase modulator for different optical signal wavelengths are different, that is, the modulation voltage is the same but the resulting modulation phase is different, so the optical signal of the working band with the corresponding modulation coefficient in the middle is selected Form a closed-loop system, where mid∈[1, 2, 3, …, p];

[0092] S220: For The current measurement system in the optical signal band uses the time division multiplexing working mechanism and is based on the full digital closed-loop modulation and demodulation method to demodulate and calculate the current to be measured at each measuring point of the distributed optical fiber sensor array in this band. and the feedback modulation phase of the next modulation cycle

[0093] S230: For other optical signal bands Where k≠mid) is a distributed current measurement, the interference light signal returned by each optical fiber current sensing unit received by the detector in the optical transceiver component is:

[0094]

[0095] The meanings of the parameters in the formulas of this embodiment can refer to the meanings of the parameters in the formulas in steps S110 to S130, except that due to the use of the wavelength division multiplexing mechanism, a band identifier is added for each parameter.

[0096] S240: Using the time division multiplexing mechanism, according to the specific optical signal band The step wave feedback cycle is Corresponding to other optical signal bands Where k≠mid) in the previous and next cycles respectively and After internal sampling, we get and Based on the open-loop modulation and demodulation method, Other optical signal bands can be obtained by demodulation and calculation Corresponding to the current value to be measured of the distributed sensor array and the feedback modulation phase of the next modulation cycle The solution of this embodiment improves the capacity of the optical fiber current sensing network and significantly reduces the system measurement cost of distributed current.

[0097] The matrix optical fiber current measurement system and method based on wavelength division multiplexing proposed in the above scheme of the present application are based on the wide spectrum width characteristics of optical fiber transmission, and use the wavelength division multiplexing mechanism to send optical signals of different bands to the corresponding distributed optical fiber sensor arrays respectively. By selecting a specific optical signal band for closed-loop feedback control, the time division multiplexing working mechanism is used to demodulate and calculate the current value to be measured at each measuring point in the distributed sensor array in this band, and combined with the full digital closed-loop modulation and demodulation and open-loop modulation and demodulation methods, the distributed current of the distributed sensor array corresponding to other bands is demodulated and calculated at the same time, thereby realizing the synchronous measurement of matrix distributed current and further improving the capacity of the sensor network.

[0098] In some embodiments of the present application, a matrix optical fiber current measurement system based on space division multiplexing is provided, such as Figure 4 As shown, it includes a multi-channel photoelectric acquisition unit, a signal processing control unit, a sensor matrix and a data display unit. The sensor matrix is ​​composed of multiple distributed optical fiber sensor arrays in the above-mentioned embodiments. The optical signal working band of each distributed sensor array is consistent with the optical signal band of the optical transceiver component. The multi-channel photoelectric acquisition unit includes an optical transceiver component, a polarizer, a phase modulator and a multi-channel optical switch. The optical transceiver component includes a light source, a detector and a coupler. The light source, the detector and the coupler are packaged or chip integrated. The signal processing control unit includes a control circuit, a drive circuit, a sampling and demodulation circuit and a modulation circuit. The control circuit is used to control the channel switching of the multi-channel optical switch to achieve the optical path disconnection and positioning of each distributed optical fiber sensor array, and upload the positioning signal to the sampling and demodulation circuit. The current to be measured at each measuring point in the distributed optical fiber sensor array is obtained through modulation and demodulation calculation. The light source of the optical transceiver assembly generates and receives a fixed-band optical signal under the action of the driving circuit and sends it to the polarizer for polarization through the coupler, and then enters the phase modulator for phase modulation under the action of the modulation circuit. The optical signal is sent to the sensor matrix through the control circuit when passing through the multi-channel optical switch; using the working mechanism of space division multiplexing, each distributed optical fiber sensor array senses the current to be measured at each measuring point in turn; similar to the current detection principle of the optical fiber sensor array in the aforementioned embodiment, based on the reversible principle of the optical path, the detector converts the returned interference light signal into an electrical signal, and performs signal sampling and numerical demodulation through the sampling and demodulation circuit; the modulation signal and the current signal to be measured of each distributed sensor array are calculated by demodulating the Faraday phase difference; the modulation signal is sent to the phase modulator through the modulation circuit to form a closed-loop system, and the positioning corresponding to the current to be measured and the control circuit signal is output to the data display unit.

[0099] Furthermore, the embodiment of the present application also provides a matrix optical fiber current measurement method based on space division multiplexing, which adopts a fully digital closed-loop modulation and demodulation method combining square wave bias modulation and step wave feedback modulation, and uses the working mechanism of time division multiplexing and space division multiplexing to calculate the matrix distributed current. The method includes the following steps:

[0100] S310: For a multi-channel optical switch and a distributed optical fiber sensor array with q channels, the step wave feedback modulation period in each channel is T gi =2nl gi / c(g=1,2,3,…,q);

[0101] S320: Using the working mechanism of space division multiplexing, the multi-channel optical switch is controlled by the control circuit to connect with the distributed sensor array of the g-th channel, and the feedback modulation cycle is performed in the first and last cycles T gi+ and T gi- After sampling, they are superimposed to obtain P outgi+ and P outgi- , where g = 1, 2, 3, ..., q;

[0102] S330: Using the time division multiplexing mechanism, the interference light signal received by the detector is divided into time periods T gi+ and T gi- Demodulate and obtain the P of each optical fiber current sensing unit. outgi+ and P outgi- , based on the fully digital closed-loop modulation and demodulation method, according to ΔP gi =(P outgi+ -P outgi- ) can be demodulated and calculated to obtain the current value to be measured I gi (t), and the feedback modulation phase of the next modulation cycle

[0103] The meaning of each parameter in the formula of this embodiment can refer to the meaning of the parameters in each formula in steps S110 to S130, except that due to the use of the space division multiplexing mechanism, a channel identifier is added for each parameter. This embodiment improves the capacity of the optical fiber current sensing network and greatly reduces the system measurement cost of distributed current.

[0104] The matrix fiber optic current measurement system and measurement method based on space division multiplexing proposed in the present application adopt the same optical transceiver component to connect each distributed sensor array in sequence, and utilize the working mechanism of time division multiplexing and space division multiplexing. Based on the fully digital closed-loop modulation and demodulation method combining square wave bias modulation and step wave feedback modulation, the matrix distributed current is obtained, which greatly reduces the system measurement cost.

[0105] The following is an explanation of the above three measurement schemes with specific examples:

[0106] Specific example 1: Measurement principle of distributed optical fiber current measurement system

[0107] like Figure 2 The length of the optical fiber loop formed by each of the three optical fiber current sensing units shown is twice the length of the optical fiber loop of the previous unit. Ignoring the optical fiber length at the output end of the photoelectric collection unit, the square wave bias modulation period corresponding to the optical fiber loop formed by the first row of optical fiber current sensing units is 2τ=2T1=4nl1 / c, and the step wave feedback modulation period is τ. The step wave feedback modulation period of the optical fiber current sensing units in the second row is 2τ, and the step wave feedback modulation period of the optical fiber current sensing units in the third row is 4τ. Figure 5 As shown in Figure 2, τ is the transit time of the optical signal traveling back and forth to the modulator during transmission.

[0108] The splitting ratios of the polarization-maintaining fiber couplers of the three fiber current sensing units are 33:67, 50:50, and 100:0, respectively. That is, if the polarization-maintaining fiber coupler in the last fiber current sensing unit is omitted, the loss coefficients transmitted to each fiber sensing ring are: α1=0.33, α2=0.5, and α3=0.5, respectively.

[0109] Based on the Faraday effect, if the Faraday phase difference generated by each row of optical fiber current sensing units is and The bias modulation phase generated by the square wave bias modulation signal is The feedback modulation phases generated by the step wave feedback modulation signal are and Ignoring the optical path loss introduced by the photoelectric collection unit, the interference light signal returned by each optical fiber current sensing unit received by the detector is:

[0110]

[0111] Using the time division multiplexing working mechanism, when the distributed optical fiber current measurement system forms a closed loop system, there are and right Figure 5 The demodulation calculation is performed on the sampled data of the step wave feedback modulation period 1τ~8τ, and the step wave feedback modulation period T of each optical fiber current sensing unit is calculated according to the step wave feedback modulation period T of each optical fiber current sensing unit. i It can be determined that:

[0112] (1.1) For the optical fiber loop formed by the first row of optical fiber current sensing units, within the interval of 1τ to 2τ before and after the feedback modulation period T1, after sampling and superposition, we can obtain:

[0113]

[0114] Based on the all-digital closed-loop modulation and demodulation method, according to ΔP1=(P out1+ -P out1- ) is calculated to obtain the measured current value I1(t). Since the interference light signals returned by the second row fiber optic current sensing units and the third row fiber optic current sensing units in the feedback modulation period 1τ~2τ are P out2 (1τ) = P out2 (2τ) and P out3 (1τ) = P out3 (2τ), so its influence in the demodulation calculation process can be ignored. Similarly, the demodulation calculation of the sampling data in the feedback modulation period 1τ~2τ, 3τ~4τ, 5τ~6τ and 7τ~8τ has the same effect.

[0115] (1.2) For the optical fiber loop formed by the second row of optical fiber current sensing units, in the interval (1τ+2τ) to (3τ+4τ) before and after the feedback modulation period T2, after sampling and superposition, we obtain:

[0116]

[0117] Based on the all-digital closed-loop modulation and demodulation method, according to ΔP2=(P out2+ -P out2- ) is used to calculate the measured current value I2(t). Since in the feedback modulation period (1τ+2τ) to (3τ+4τ), the interference light signal P returned by the first row of optical fiber current sensing units is out1 (1τ+2τ)=P out1 (3τ+4τ), and the interference light signal P returned by the third row of optical fiber current sensing units out3 (1τ+2τ)=P out3 (3τ+4τ), so its influence in the demodulation calculation process can be ignored. Similarly, demodulation calculation of the sampling data in the feedback modulation period (5τ+6τ) to (7τ+8τ) has the same effect.

[0118] (1.3) For the optical fiber loop formed by the third row of optical fiber current sensing units, in the interval (1τ+2τ+3τ+4τ) to (5τ+6τ+7τ+8τ) before and after the feedback modulation period T3, after sampling and superposition, the result is:

[0119]

[0120] Based on the all-digital closed-loop modulation and demodulation method, according to ΔP3=(P out3+ -P out3-) is used to calculate the measured current value I3(t). In the feedback modulation period (1τ+2τ+3τ+4τ) to (5τ+6τ+7τ+8τ), the interference light signals returned by the first row of optical fiber current sensing units and the second row of optical fiber current sensing units are P out1 (1τ+2τ+3τ+4τ)=P out1 (5τ+6τ+7τ+8τ) and P out2 (1τ+2τ+3τ+4τ)=P out2 (5τ+6τ+7τ+8τ), so its influence in the demodulation calculation process can be ignored.

[0121] Since the total interference optical signal formed by the three optical fiber current sensing units repeats with a period of 8τ, the sampling data of subsequent periods can be demodulated and calculated by referring to the above processing process.

[0122] Specific example 2: Measurement principle of matrix optical fiber current measurement system based on wavelength division multiplexing

[0123] Figure 3 This application proposes a matrix-type fiber optic current measurement system based on wavelength division multiplexing. In this example, the multi-band photoelectric acquisition unit is composed of optical transceiver components of three different bands, a first wavelength division multiplexer, a polarizer, a phase modulator and a second wavelength division multiplexer. The sensing matrix is ​​composed of three distributed fiber optic sensor arrays. The multi-channel photoelectric acquisition unit is optically connected to each distributed sensor array through the second wavelength division multiplexer. Working by using the wavelength division multiplexing mechanism, the first wavelength division multiplexer and the second wavelength division multiplexer distinguish the optical signals of different bands for sending, receiving and sensing the current signals to be measured in the three distributed fiber optic sensor arrays, so that the optical signals of different bands do not interfere with each other when transmitted in the formed optical fiber loop, thereby forming a sensing matrix. The optical fiber loops formed by the optical fiber current sensing units at corresponding positions in the three distributed optical fiber sensor arrays are equal in length, and the optical fiber loop length formed by the optical fiber current sensing unit at each position is twice that of the previous position. Since the modulation coefficient of the phase modulator is equal to the average wavelength of the optical signal band, (k=1, 2, 3) correlation, select the working band optical signal with the corresponding modulation coefficient in the middle Form a closed-loop system.

[0124] The demodulation calculation process for each distributed optical fiber sensor array in the sensor matrix is ​​as follows:

[0125] (2.1) For the optical signal in the working band The corresponding distributed optical fiber sensor array, referring to the data processing process based on the full digital closed-loop modulation and demodulation method in "Specific Example 1", can demodulate and calculate the current to be measured at each measuring point

[0126] (2.2) For the working band optical signal and The corresponding distributed sensor array uses a square wave bias modulation phase modulator to generate a phase modulator due to the difference in the optical signal in the working band. and step wave feedback modulation phase The Faraday phase difference with the current to be measured There is a fixed deviation between them, and a closed loop cannot be formed. Using the working mechanism of time division multiplexing, the modulation cycle is modulated according to the step wave feedback. For working band optical signal and After sampling in the previous and next cycles respectively, we can get the following result:

[0127]

[0128]

[0129] Since in the feedback modulation cycle Within the range, the working band optical signal and The interference optical signals returned by each fiber current sensing unit in the corresponding distributed sensing array do not affect each other, so based on the open-loop modulation and demodulation method, according to The optical signals in the working band can be demodulated and calculated separately and Corresponding to the current value to be measured of the distributed sensor array and

[0130] Specific example 3: Measurement principle of matrix optical fiber current measurement system based on space division multiplexing

[0131] Figure 4 This application proposes a matrix optical fiber current measurement system based on space division multiplexing. The sensing matrix consists of three distributed optical fiber sensor arrays. The multi-channel photoelectric acquisition unit is optically connected to each distributed optical fiber sensor array in turn through a multi-channel optical switch. The length of the optical fiber loop formed by each optical fiber current sensing unit of each distributed optical fiber sensor array in the sensing matrix is ​​twice the length of the optical fiber loop of the previous unit. The demodulation calculation process of each distributed optical fiber sensor array in the sensing matrix is ​​as follows:

[0132] (3.1) Using the working mechanism of space division multiplexing, the multi-channel optical switch is controlled by the control circuit to connect to each distributed sensor array respectively;

[0133] (3.2) For the three distributed sensor arrays, the step wave feedback modulation period corresponding to each distributed sensor array is T 1i , T 2i and T3i ;

[0134] (3.3) By using the time division multiplexing working mechanism, when each distributed optical fiber current measurement system forms a closed-loop system, referring to the data processing process based on the full digital closed-loop modulation and demodulation method in "Specific Example 1", the current I to be measured at each measuring point in the sensor matrix can be obtained by demodulation and calculation. gi (t).

[0135] As needed, the above technical solutions can be combined to achieve the best technical effect.

[0136] The above are only the principles and preferred embodiments of the present application. It should be noted that, for ordinary technicians in this field, on the basis of the principles of the present application, several other modifications can be made, which should also be considered as the protection scope of the present application.

Claims

1. A distributed optical fiber sensor array, characterized in that: It comprises a plurality of optical fiber current sensing units which are cascaded on the same optical path, each of which receives an optical signal from a photoelectric collection unit and sends an interference optical signal carrying information of the current to be measured to the photoelectric collection unit; The fiber optic current sensing unit comprises a polarization-maintaining delay optical fiber, a polarization-maintaining optical fiber coupler and an optical fiber sensing ring, wherein the optical fiber sensing ring comprises a 1 / 4 optical fiber wave plate, a sensing optical fiber and a reflector, and the optical fiber sensing ring is arranged around a measuring point to sense the current to be measured transmitted in the measuring point; after the optical fiber current sensing unit receives the optical signal emitted by the photoelectric collection unit, the optical signal passes through the polarization-maintaining delay optical fiber, and the polarization-maintaining optical fiber coupler sends a part of the optical signal to the optical fiber sensing ring in the same unit, and sends the other part of the optical signal to the next optical fiber current sensing unit, and then passes through multiple optical fiber current sensing units in sequence; In each of the fiber optic current sensing units, after the current to be measured acts on the optical signal transmitted by the fiber optic sensing ring to form a Faraday phase difference, the optical signal in the fiber optic sensing ring carries the information of the current to be measured, and after being reflected by the reflector, returns along the original path, and the generated Faraday phase difference is doubled; The optical signal carrying the current information to be measured is modulated and polarized by the photoelectric acquisition unit again to form an interference optical signal; the interference optical signal is converted into an electrical signal in the photoelectric acquisition unit and then transmitted to the signal processing unit for the signal processing unit to perform signal sampling and numerical demodulation to calculate the current to be measured; including: obtaining the optical power P of the interference optical signal returned by the i-th optical fiber current sensor unit received by the detector in the distributed optical fiber sensor array measurement system outi The number of optical fiber current sensing units in the distributed optical fiber sensing array measurement system is m, i = 1, 2, 3, ... m; according to the time division multiplexing working mechanism, the feedback modulation period of the step wave is T i , in the previous cycle T of the feedback modulation cycle i+ Within the period, the interference light signal returned by the first 1 to i optical fiber current sensing units has a complete cycle. The interference light signal returned by the first 1 to i optical fiber current sensing units is sampled and superimposed to obtain P outi+ for: In the next cycle of the feedback modulation cycle T i- The interference light signals returned by the first 1 to i optical fiber current sensing units also have a complete cycle. The interference light signals returned by the first 1 to i optical fiber current sensing units are sampled and superimposed to obtain P outi- for: At any time t, the interference light signal received by the detector is divided into time periods T i+ and T i- Demodulate and obtain the P of each optical fiber current sensing unit. outi+ and P outi- , according to ΔP i =(P outi+ -P outi- ) Demodulate and calculate the current to be measured I i (t).

2. The distributed optical fiber sensor array according to claim 1, characterized in that: In the fiber optic current sensing unit: The polarization-maintaining time-delay optical fiber is a linear polarization-maintaining optical fiber or a linear polarization-maintaining optical cable, and the polarization-maintaining time-delay optical fiber and the polarization-maintaining optical fiber coupler are 0° axially fused; The 1 / 4 fiber wave plate is a linear polarization-maintaining fiber, and its length is 1 / 4 or 3 / 4 of the linear polarization-maintaining fiber beat length. The 1 / 4 fiber wave plate and the output pigtail of the polarization-maintaining fiber coupler are 45° axially fused; The sensing optical fiber is a circular polarization preserving optical fiber, a photonic crystal optical fiber, a low birefringence optical fiber or a single-mode optical fiber.

3. The distributed optical fiber sensor array according to claim 1, characterized in that: In the fiber optic current sensing unit: If the fiber optic current sensing unit is the last fiber optic current sensing unit, the polarization-maintaining delay optical fiber and the 1 / 4 fiber wave plate are fused at 45°.

4. The distributed optical fiber sensor array according to claim 1, characterized in that: In each of the fiber optic current sensing units: It is determined according to the distance between the measuring points: the polarization-maintaining time-delay optical fiber is a linear polarization-maintaining optical fiber and is packaged with the polarization-maintaining optical fiber coupler, or the polarization-maintaining time-delay optical fiber is laid as a linear polarization-maintaining optical cable.

5. The distributed optical fiber sensor array according to claim 4, characterized in that: In each of the fiber optic current sensing units: The length of the optical fiber loop formed by the optical fiber current sensing unit is twice the length of the optical fiber loop formed by the previous optical fiber current sensing unit.

6. The distributed optical fiber sensor array according to claim 4, characterized in that: In each of the fiber optic current sensing units: The splitting ratio of each polarization-maintaining optical fiber coupler is not completely the same.

7. The distributed optical fiber sensor array according to claim 4, characterized in that: In each of the fiber optic current sensing units: The number of winding turns of the optical fiber sensing ring is adjusted and set according to the magnitude of the current to be measured.

8. A distributed optical fiber sensor array measurement system, characterized in that: The distributed optical fiber sensor array according to any one of claims 1 to 7 further comprises a photoelectric acquisition unit, a signal processing unit, a distributed sensor array and a data display unit, wherein: The photoelectric collection unit includes an optical transceiver component, a polarizer and a phase modulator, and the optical transceiver component includes a light source, a detector and a coupler; The signal processing unit includes a driving circuit, a modulation circuit and a sampling and demodulation circuit; the optical transceiver assembly generates an optical signal through the light source and receives an optical signal through the detector under the action of the driving circuit, and transmits the optical signal through the coupler, and the optical signal is polarized by the polarizer and then output to the phase modulator; the phase modulator performs phase modulation on the input optical signal under the action of the modulation circuit and then outputs the phase modulator to the distributed optical fiber sensor array; The data display unit receives and displays the current to be measured output by the sampling and demodulation circuit.

9. A measurement method using the distributed optical fiber sensor array measurement system according to claim 8, characterized in that: include: S110: Obtaining the optical power P of the interference optical signal returned by the i-th optical fiber current sensing unit received by the detector in the distributed optical fiber sensing array measurement system outi , the number of optical fiber current sensing units in the distributed optical fiber sensing array measurement system is m, i=1, 2, 3, ...m; α i ＝A / 100； The П operator represents the multiplication of multiple consecutive data. in Represents the optical signal power output by the light source, α i and α j They respectively represent the loss coefficients of the optical fiber sensing loop transmitted to the same unit and introduced by the splitting ratio of the polarization-maintaining optical fiber coupler in the i-th and j-th optical fiber current sensing units; A represents the splitting ratio of the polarization-maintaining optical fiber coupler; represents the bias modulation phase generated by the square wave bias modulation signal in the modulation signal, represents the feedback modulation phase generated by the step wave feedback modulation signal; represents the Faraday phase difference formed in the i-th optical fiber sensing loop; N i is the number of turns of the i-th sensing optical fiber ring, I i is the current value to be measured at the corresponding measuring point of the i-th sensing optical fiber ring, and V is the Verdet constant of the sensing optical fiber; S120: According to the time division multiplexing working mechanism, the feedback modulation period of the step wave is set to T i , in the previous cycle T of the feedback modulation cycle i+ Within the period, the interference light signal returned by the first 1 to i optical fiber current sensing units has a complete cycle. The interference light signal returned by the first 1 to i optical fiber current sensing units is sampled and superimposed to obtain P outi+ for: In the next cycle of the feedback modulation cycle T i- The interference light signals returned by the first 1 to i optical fiber current sensing units also have a complete cycle. The interference light signals returned by the first 1 to i optical fiber current sensing units are sampled and superimposed to obtain P outi- for: Among them, the step wave feedback modulation period T in the modulation signal i Determined by: i =2nl i / c, where c is the speed of light in a vacuum and n is the effective refractive index of the optical fiber; l i is the length of the optical fiber loop formed by the i-th optical fiber current sensing unit; the length of the optical fiber loop formed by the first optical fiber current sensing unit: l1 = l d1 +l s1 , the square wave bias modulation period in the modulation signal is 2T1, that is, 4nl1 / c; S130: At any time t, the interference light signal received by the detector is divided into time periods T i+ and T i- Demodulate and obtain the P of each optical fiber current sensing unit. outi+ and P outi- , according to ΔP i =(P outi+ -P outi- ) Demodulate and calculate the current to be measured I i (t).

10. A distributed optical fiber sensor array measurement system, characterized in that: It comprises a multi-band photoelectric acquisition unit, a multi-channel signal processing unit, a sensing matrix composed of a distributed optical fiber sensor array according to any one of claims 1 to 7, and a data display unit; wherein: The multi-band optoelectronic collection unit includes a plurality of optical transceiver components of different bands, a first wavelength division multiplexer, a polarizer, a phase modulator and a second wavelength division multiplexer, and the optical signal working bands of the first wavelength division multiplexer, the second wavelength division multiplexer, the polarizer and the phase modulator cover the optical signals of different bands output by all optical transceiver components; The multi-channel signal processing unit includes a multi-channel driving circuit, a multi-channel sampling demodulation circuit and a modulation circuit; The sensing matrix includes a plurality of distributed optical fiber sensing arrays, and the optical signal working band of each distributed optical fiber sensing array should at least cover the optical signal bands corresponding to different optical transceiver components; The plurality of optical transceiver components generate and receive optical signals of different bands under the action of the multi-channel driving circuit. The optical signals of different bands are output to the polarizer through the first wavelength division multiplexer for polarization, and then enter the phase modulator for phase modulation under the action of the modulation circuit, and then output to each distributed optical fiber sensor array of the corresponding band in the sensor matrix through the second wavelength division multiplexer, and each optical fiber current sensor unit senses the current information to be measured at each measuring point; based on the principle of reversibility of the optical path, the returned interference optical signal is converted into an electrical signal by the optical transceiver component of the corresponding band, and the signal is sampled and numerically demodulated by the multi-channel sampling and demodulation circuit, and the current to be measured at each measuring point in the sensor matrix of the working band is calculated; the current to be measured is output to the data display unit for display.

11. A measurement method using the distributed optical fiber sensor array measurement system according to claim 10, characterized in that: include: S210: For optical transceiver components and distributed optical fiber sensor arrays with p optical signal bands, the average wavelength of the optical signal band transmitted in each optical transceiver component and the corresponding distributed optical fiber sensor array is w=1,2,3,…,p; Working band optical signal Form a closed-loop system, where mid∈[1, 2, 3, …, p]; S220: For working band optical signals The current measurement of the distributed optical fiber sensor array in this band is obtained by demodulating and calculating the current value to be measured at each measuring point using the time division multiplexing working mechanism. For other optical signal bands Current measurement, where k≠mid, the power of the interference light signal returned by each optical fiber current sensing unit received by the detector in the optical transceiver component is: Among them, P in Represents the optical signal power output by the light source, α i and α j They represent the loss coefficients of the optical fiber sensing loop transmitted to the same unit introduced by the splitting ratio of the polarization-maintaining optical fiber coupler in the i-th and j-th optical fiber current sensing units, respectively; represents the bias modulation phase generated by the square wave bias modulation signal in the modulation signal, represents the feedback modulation phase generated by the step wave feedback modulation signal; represents the Faraday phase difference formed in the i-th optical fiber sensing loop; S230: According to the working band optical signal Step wave feedback cycle Corresponding to other optical signal bands In the previous cycle and the next cycle After internal sampling, we get and S240: According to Demodulation calculation to obtain other optical signal bands Corresponding to the current to be measured of the distributed optical fiber sensor array 12. A distributed optical fiber sensor array measurement system, characterized in that: It comprises a multi-channel photoelectric acquisition unit, a signal processing control unit, an optical fiber sensor matrix composed of a distributed optical fiber sensor array according to any one of claims 1 to 7, and a data sensing unit, wherein the optical signal working band of each distributed optical fiber sensor array in the sensor matrix is ​​consistent with the optical signal band of the optical transceiver component; wherein: The multi-channel photoelectric acquisition unit includes an optical transceiver component, a polarizer, a phase modulator and a multi-channel optical switch, and the optical transceiver component includes a light source, a detector and a coupler; The signal processing control unit includes a control circuit, a drive circuit, a sampling and demodulation circuit and a modulation circuit; the control circuit is used to control the channel switching of the multi-channel optical switch, realize the optical path disconnection and positioning of each distributed optical fiber sensor array, and upload the positioning signal to the sampling and demodulation circuit, and obtain the current to be measured at each measuring point in the distributed optical fiber sensor array through modulation and demodulation calculation.

13. A measurement method using the distributed optical fiber sensor array measurement system according to claim 12, characterized in that: include: S310: For a multi-channel optical switch and a distributed optical fiber sensor array with q channels, the step wave feedback modulation period in each channel is T gi =2nl gi / c, g=1, 2, 3,..., q; Where c is the speed of light in a vacuum, n is the effective refractive index of the optical fiber; l gi is the length of the i-th optical fiber loop under the space division multiplexing mechanism; S320: The control circuit controls the multi-channel optical switch to be connected to the g-th channel distributed optical fiber sensor array, respectively in the period T before the feedback modulation period. gi+ and the next cycle T gi- After the inner sampling is superimposed, P is obtained outgi+ and P outgi- ; S330: Divide the interference light signal received by the detector into time periods T gi+ and T gi- Demodulation, according to ΔP gi =(P outgi+ -P outgi- ) Demodulate and calculate the current to be measured I gi (t).

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