A Robust Enhanced Fiber Optic Current Sensor and Its Control Method

Abstract

The present invention provides a robust enhanced high-precision fiber optic current sensor and its control method. By controlling the die of the light source to operate at a set working temperature and drive current, the problems of output optical power attenuation and unstable average wavelength of the light source can be solved, ensuring constant power and constant wavelength control of the light source. By controlling the integrated waveplate device to operate at a set target temperature, the errors caused by temperature changes and temperature-induced stress of the existing λ / 4 waveplate can be reduced, so as to achieve long-term stability of the waveplate phase delay angle and optimal adaptation of the waveplate phase delay angle to the sensor system parameters. Aiming at the problem of optical path average wavelength drift, by introducing a spectral acquisition module, the optical path average wavelength is monitored in real time, and the wavelength-related errors are corrected twice. Through the above three levels of improvement, the proposed solution of the present application can suppress the long-term drift error of the FOCS measurement accuracy.

Description

Technical Field

[0001] This application relates to the technical field of fiber optic sensing measurement devices, and specifically, to a robust enhanced high-precision fiber optic current sensor and its control method. Background Art

[0002] Fiber Optical Current Sensor (FOCS for short) has the advantages of high measurement accuracy, wide frequency response range, large dynamic range, good insulation performance, etc., and has currently become a key device for the construction of intelligent substations.

[0003] FOCS can be divided into an optical path part and a detection circuit part. The optical path part consists of a light source, a fiber coupler / fiber circulator, a fiber polarizer, a phase modulator, a photodetector, a polarization-maintaining fiber delay loop, a polarization-maintaining transmission fiber, a λ / 4 wave plate, and a sensing fiber. The detection circuit part consists of a light source control circuit and a signal processing unit. Due to the use of a large number of semiconductor devices and fiber materials, during long-term use, the measurement accuracy of FOCS is affected by both internal and external factors. Among them, the internal factors mainly include the attenuation of the output optical power of the light source, the drift of the center wavelength of the optical path, and the change of the optical path loss, etc. The external factors mainly include the change of the refractive index distribution of the fiber caused by external actions such as environmental temperature change and vibration shock, which in turn affects the performance of the key components in the optical path. As a key optical component of FOCS, the λ / 4 wave plate will be affected by both the average wavelength drift and temperature change during long-term operation. Among them, the long-term drift of the average wavelength will change the propagation constant of the wave plate fiber, causing its phase delay angle to change, which is the result of the action of internal factors; the temperature change not only changes the propagation constant of the wave plate fiber, but also transfers a part of the temperature-induced stress to the wave plate fiber through the wave plate packaging material, causing its phase delay angle to change, which is the result of the superposition of internal and external factors.

[0004] In summary, the mechanism of the long-term drift phenomenon of FOCS measurement accuracy is complex. The existing error compensation technologies do not consider the measurement errors caused by the performance degradation of key optical components during long-term use, and it is difficult to meet the correction requirements for the additional errors brought by long-term use. Summary of the Invention

[0005] The technical problem to be solved by the present invention is that the existing FOCS has long-term drift in measurement accuracy and low reliability, and thus provides a robust enhanced high-precision fiber optic current sensor and its control method.

[0006] In a first aspect, the present invention provides a robust enhanced high-precision fiber optic current sensor, comprising:

[0007] An optical path module, comprising, connected in sequence: a light source, an optical fiber coupler, an optical fiber polarizer, a spectral acquisition module, a phase modulator, an integrated wave plate device, and a photodetector; wherein, the integrated wave plate device includes a λ / 4 wave plate, a thermistor, a quartz substrate, a semiconductor cooler, a heat sink, and a housing; the light emitted by the light source enters the optical fiber coupler, one output end of the optical fiber coupler is connected to the optical fiber polarizer, the other output end of the optical fiber coupler is connected to the spectral acquisition module, and the spectral acquisition module acquires the spectral information at the output end of the optical fiber coupler;

[0008] An optical fiber sensing loop, comprising a sensing optical fiber and a mirror, one end of the sensing optical fiber is connected to the integrated wave plate device, and the other end of the sensing optical fiber is provided with the mirror; the sensing optical fiber surrounds the outside of a current-carrying wire, and the current-carrying wire transmits a measured current;

[0009] A circuit module, comprising a first control unit and a second control unit, wherein:

[0010] The first control unit is connected to the photodetector, receives the electrical signal output by the photodetector and analyzes it to obtain the current value of the current-carrying conductor and the optical power value received by the photodetector, and the optical power value is used to determine the modulation signal of the phase modulator;

[0011] The second control unit includes:

[0012] A light source control circuit, which controls the die of the light source to work at a set operating temperature and drive current, so that the average wavelength of the light source remains at a set average wavelength, and the output optical power of the light source is constant at a preset power;

[0013] An integrated wave plate device control circuit, which determines the actual temperature of the integrated wave plate device according to the resistance value of the thermistor, and controls the operating temperature of the semiconductor cooler so that the integrated wave plate device works at a target temperature;

[0014] A sensing optical fiber temperature acquisition circuit, which acquires the temperature value of the sensing optical fiber;

[0015] The spectral acquisition digital output signal conversion module receives the spectral information acquired by the spectral acquisition module and analyzes it to obtain spectral data;

[0016] A second signal processing sub-unit, which obtains a corrected demodulated current value according to the current value of the current-carrying conductor, the temperature value of the sensing optical fiber, the spectral data, and the optical power value, in combination with a preset data correspondence list therein; the data correspondence is the correspondence between the current value of the current-carrying conductor, the temperature value of the sensing optical fiber, the optical power value, and the demodulated current value obtained according to a calibration test.

[0017] The robust enhanced high-precision fiber optic current sensor described in some solutions further includes a polarization-maintaining fiber delay loop:

[0018] The output fiber of the phase modulator is connected to the input fiber of the polarization-maintaining fiber delay loop with a 0° axis alignment, and the output fiber of the polarization-maintaining fiber delay loop is connected to the input fiber of the integrated waveplate device with a 0° axis alignment.

[0019] For the robust enhanced high-precision fiber optic current sensor described in some solutions, the output fiber of the fiber polarizer is connected to the input fiber of the phase modulator with a 45° axis alignment.

[0020] For the robust enhanced high-precision fiber optic current sensor described in some solutions, the output fiber of the integrated waveplate device is connected to the sensing fiber with a 0° axis alignment.

[0021] The robust enhanced high-precision fiber optic current sensor described in some solutions further includes:

[0022] A temperature sensor, which is used to detect the temperature value of the sensing fiber and send it to the sensing fiber temperature acquisition circuit.

[0023] For the robust enhanced high-precision fiber optic current sensor described in some solutions, the first control unit further includes:

[0024] A preamplification circuit, whose input end receives the electrical signal output by the photodetector and amplifies it into a voltage signal;

[0025] An A / D conversion circuit, which converts the voltage signal into a digital signal;

[0026] A first signal processing sub-unit, which receives the digital signal and resolves the current value of the current-carrying conductor and the optical power value, and at the same time generates a digital quantity value corresponding to the phase feedback signal; the first signal processing sub-unit outputs the current value of the current-carrying conductor;

[0027] A D / A conversion circuit, which receives the digital quantity value corresponding to the phase feedback signal and converts it into an analog signal, and the analog signal is applied to the phase modulator as a modulation signal.

[0028] In a second aspect, the technical solution of the present application provides a control method for the robust enhanced high-precision fiber optic current sensor according to any one of the technical solutions in the first aspect, including:

[0029] Controlling the die temperature and drive current of the light source to ensure that the average wavelength of the light source remains at the set average wavelength and the output optical power of the light source is constant at the preset power;

[0030] Control the temperature of the integrated waveplate device at a target temperature, where the target temperature makes the measurement error of the integrated waveplate device at the temperature equal in magnitude and opposite in sign to the measurement error of the sensing optical fiber at the same temperature;

[0031] Perform error compensation and correction on the wavelength drift of the integrated waveplate device and the wavelength drift of the sensing optical fiber.

[0032] In some embodiments, the control method of the robust enhanced high-precision fiber optic current sensor, which controls the die temperature and drive current of the control light source to ensure that the average wavelength of the light source remains at a set average wavelength and the output optical power of the light source is constant at a preset power, includes:

[0033] Establish a light source control model, where the light source control model includes the corresponding relationship between the output optical power of the light source, the average wavelength, and the die temperature and drive current;

[0034] According to the light source control model, by controlling the die temperature and drive current of the light source, make the average wavelength output by the light source constant at the set average wavelength, and the output optical power of the light source constant at the preset power.

[0035] In some embodiments, the control method of the robust enhanced high-precision fiber optic current sensor, which controls the die temperature and drive current of the control light source to ensure that the average wavelength of the light source remains at a set average wavelength and the output optical power of the light source is constant at a preset power, further includes:

[0036] Obtain the measured wavelength of the light source according to the spectral data collected by the spectral acquisition module;

[0037] Obtain the difference between the measured wavelength and the set average wavelength;

[0038] Combined with a preset multi-dimensional parameter model and the difference, adjust the die temperature and drive current of the light source to make the average wavelength output by the light source constant at the set average wavelength, and the output optical power of the light source constant at the preset power output optical power; where the multi-dimensional parameter model is used to record the corresponding relationship between the output optical power of the light source, the average wavelength of the light source, and the die temperature and drive current.

[0039] In some embodiments, the control method of the robust enhanced high-precision fiber optic current sensor, which controls the temperature of the integrated waveplate device at a target temperature, where the target temperature makes the measurement error of the integrated waveplate device equal in magnitude and opposite in sign to the measurement error of the sensing optical fiber, includes:

[0040] Model the measurement error of the integrated waveplate device at different temperatures to obtain an integrated waveplate device measurement error model;

[0041] Model the measurement error of the sensing optical fiber at different temperatures to obtain the measurement error model of the sensing optical fiber at different temperatures;

[0042] Based on the measured temperature of the sensing optical fiber, obtain the corresponding sensing optical fiber error value according to the measurement error model of the sensing optical fiber;

[0043] Take the opposite of the sensing optical fiber error value as the target error value of the integrated waveplate device;

[0044] Based on the target error value of the integrated waveplate device and the integrated waveplate measurement error model, obtain the target temperature of the integrated waveplate device, and control the operating temperature of the semiconductor cooler so that the operating temperature of the integrated waveplate device is the target temperature.

[0045] In some embodiments, the control method of the robust enhanced high-precision fiber optic current sensor, the error compensation and correction of the wavelength drift of the integrated waveplate device and the wavelength drift of the sensing optical fiber includes:

[0046] Model the wavelength drift of the integrated waveplate device, including: changing the average wavelength of the light source input to the integrated waveplate device at different constant temperatures and testing the measurement errors caused by different average wavelengths of the light source; or, changing the average wavelength of the light source input to the integrated waveplate device at different constant temperatures and testing the change in the phase delay angle of the integrated waveplate device caused by different average wavelengths of the light source, and determining the measurement error according to the change in the phase delay angle; model according to the measurement results to obtain the wavelength drift error model of the integrated waveplate device at different constant temperatures;

[0047] Obtain the measured average wavelength of the light source according to the spectral data collected by the spectral acquisition module;

[0048] According to the wavelength drift error model of the integrated waveplate device corresponding to the target temperature, combined with the measured average wavelength of the light source, obtain the error compensation coefficient of the integrated waveplate device;

[0049] Send the error compensation coefficient of the integrated waveplate device to the second control unit for the second signal processing sub-unit to correct the demodulated current value.

[0050] In some embodiments, the control method of the robust enhanced high-precision fiber optic current sensor, the error compensation and correction of the wavelength drift of the integrated waveplate device and the wavelength drift of the sensing optical fiber further includes:

[0051] Obtain the corresponding relationship between the average wavelength of the light source, the Verdet constant of the optical fiber and the measurement error: where V is the Verdet constant of the optical fiber, λ c is the average wavelength of the light source, is the phase difference, and ε is the measurement error;

[0052] Obtain the wavelength drift of the sensing optical fiber according to the corresponding relationship and the actually measured wavelength of the light source;

[0053] Obtain the error compensation coefficient of the sensitivity of the sensing optical fiber according to the wavelength drift of the sensing optical fiber; the error compensation coefficient of the sensitivity of the sensing optical fiber is sent to the second control unit for the second signal processing sub-unit to correct the demodulation current value.

[0054] In a third aspect, the technical solution of the present application provides a packaging process for an integrated wave plate device in a robust enhanced high-precision fiber optic current sensor according to any one of the technical solutions in the first aspect, including:

[0055] Groove on the quartz substrate;

[0056] Place the λ / 4 wave plate and the optical fibers at both ends thereof in the groove opened on the quartz substrate and fix them;

[0057] Place the quartz substrate on the heat sink, and arrange a thermistor on at least one side of the quartz substrate, and the size of the heat sink is larger than the size of the quartz substrate;

[0058] Place the heat sink on the thermoelectric cooler, and the size of the thermoelectric cooler is larger than or equal to the size of the heat sink;

[0059] The thermoelectric cooler is arranged in the housing, and the optical fibers at both ends are respectively led out and fixed from the fiber outlet holes at both ends of the housing;

[0060] Cover the upper cover of the housing and seal it by welding or sealant.

[0061] In some of the described packaging processes for the integrated wave plate device in the robust enhanced high-precision fiber optic current sensor, placing the λ / 4 wave plate and the optical fibers at both ends thereof in the groove opened on the quartz and fixing them: the λ / 4 wave plate and the optical fibers at both ends thereof are fixed by using UV glue in a point-by-point fixing manner;

[0062] The thermoelectric cooler is arranged in the housing, and the optical fibers at both ends are respectively led out and fixed from the fiber outlet holes at both ends of the housing: use silicone rubber to fix the optical fibers at the fiber outlet holes at both ends of the housing.

[0063] The above technical solutions provided by the present invention have the following technical effects:

[0064] The robust enhanced high-precision fiber optic current sensor and its control method provided by the present invention control the light source to operate at a set working temperature and drive current, which can solve the problems of output optical power attenuation and wavelength instability of the light source, ensuring constant power and constant wavelength control of the light source; controlling the integrated wave plate device to operate at a set target temperature can reduce the errors caused by temperature changes and temperature-induced stress of the existing λ / 4 wave plate, so as to achieve long-term stability of the wave plate phase delay angle and optimal adaptation of the wave plate phase delay angle to the sensor system parameters. Aiming at the problem of average optical path wavelength drift, by introducing a spectral acquisition module, the average optical path wavelength is monitored in real time, and the wavelength-related errors are corrected twice. Through the above three levels of improvement, the solution of this application can suppress the long-term drift error of the FOCS measurement accuracy and output optical power measurement error. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] Figure 1 It is a schematic structural diagram of the robust enhanced high-precision fiber optic current sensor described in the embodiment of the present invention;

[0066] Figure 2 It is a schematic circuit layout diagram of the first control unit and the second control unit described in the embodiment of the present invention;

[0067] Figure 3 It is a flowchart of the control method of the robust enhanced high-precision fiber optic current sensor described in the embodiment of the present invention;

[0068] Figure 4 It is a schematic diagram of the processing process steps of the integrated wave plate device described in the embodiment of the present invention;

[0069] Figure 5 It is a schematic internal structure diagram of the integrated wave plate device described in the embodiment of the present invention;

[0070] Figure 6 It is a perspective view of the packaging structure of the integrated wave plate device described in the embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0071] The following further describes the specific embodiments of the present application with reference to the drawings.

[0072] It is easy to understand that according to the technical solution of the present application, without changing the essence of the present application, there are various structural ways and implementation ways that can be mutually replaced by those of ordinary skill in the art. Therefore, the following specific embodiments and the drawings are only exemplary descriptions of the technical solution of the present application, and should not be regarded as all of the present application or as a limitation or restriction on the technical solution of the application.

[0073] In this specification, the orientation terms such as up, down, left, right, front, back, front side, back side, top, bottom, etc., which are mentioned or may be mentioned, are defined with respect to the structures shown in the respective drawings. They are relative concepts and may accordingly change depending on their different positions and usage states. Therefore, these or other orientation terms should not be construed as restrictive terms.

[0074] This embodiment provides a robust enhanced high-precision fiber optic current sensor, as Figure 1 and Figure 2 shown, including an optical path module, a fiber optic sensing loop, and a circuit module, where:

[0075] The optical path module includes, connected in sequence: a light source 1, an optical fiber coupler 2, an optical fiber polarizer 31, a spectral acquisition module 13, a phase modulator 32, an integrated wave plate device 6, and a photodetector 9; wherein, the integrated wave plate device 6 includes a thermistor, a temperature maintaining component, and a λ / 4 wave plate. The λ / 4 wave plate can be either an optical fiber wave plate or a crystal wave plate; the temperature maintaining component includes a semiconductor refrigerator and a heat sink. The semiconductor refrigerator can operate at a certain temperature, and the heat sink is a material with high heat conductivity. The light emitted by the light source 1 enters the optical fiber coupler 2. One output end of the optical fiber coupler 2 is connected to the optical fiber polarizer 31, and the other output end of the optical fiber coupler 2 is connected to the spectral acquisition module 13. The spectral acquisition module 13 acquires the spectral information at the output end of the optical fiber coupler 2.

[0076] The fiber optic sensing loop includes a sensing optical fiber 7 and a mirror 8. One end of the sensing optical fiber is connected to the integrated wave plate device 6, and the other end of the sensing optical fiber 7 is provided with the mirror 8; the sensing optical fiber 7 surrounds the outside of the current-carrying conductor 10, and the current-carrying conductor 10 transmits the measured current.

[0077] Combined with Figure 2 shown, the circuit module includes a first control unit 14 and a second control unit 12, where:

[0078] The first control unit 14 is connected to the photodetector 9, receives the electrical signal output by the photodetector 9, and analyzes it to obtain the current value of the current-carrying conductor and the optical power value received by the photodetector. The current value of the current-carrying conductor is used to determine the modulation signal of the phase modulator 32.

[0079] The second control unit 12 includes:

[0080] A light source control circuit that controls the die of the light source 1 to operate at a set working temperature and drive current; keeps the average wavelength of the light source at a set average wavelength, and the output optical power of the light source is constant at a preset power.

[0081] An integrated waveplate device control circuit determines the actual temperature of the integrated waveplate device 6 according to the resistance value of the thermistor, and controls the operating temperature of the semiconductor cooler so that the integrated waveplate device 6 operates at a target temperature.

[0082] A sensing optical fiber temperature acquisition circuit acquires the temperature value of the sensing optical fiber 7.

[0083] The spectral acquisition digital output signal conversion module receives the spectral information acquired by the spectral acquisition module 13 and analyzes it to obtain spectral data.

[0084] The second signal processing sub-unit 12 obtains a corrected demodulation current value according to the current value of the current-carrying conductor, the temperature value of the sensing optical fiber, the spectral data, and the optical power value, in combination with a pre-set data correspondence list therein; the data correspondence is the correspondence between the current value of the current-carrying conductor, the temperature value of the sensing optical fiber, the optical power value, and the demodulation current value obtained according to a calibration test.

[0085] In the solution of the above embodiment, the optical fiber coupler 2 can be a 2×2 coupler. The integrated waveplate device 6 includes an input end pigtail and an output end pigtail, wherein the optical fiber type of the input end pigtail is polarization-maintaining fiber, and the optical fiber types of the output end pigtail are circular polarization-maintaining fiber, single-mode fiber, low-birefringence fiber, or photonic crystal fiber. The type of the sensing optical fiber is: circular polarization-maintaining fiber, single-mode fiber, low-birefringence fiber, photonic crystal fiber. The type of the mirror 8 can be: coated fiber mirror, metal patch fiber mirror, Faraday rotatory mirror.

[0086] The robust enhanced high-precision optical fiber current sensor in the above solution can solve the problems of output optical power attenuation and wavelength instability of the light source by controlling the core of the light source 1 to operate at a set operating temperature and drive current, ensuring constant power and constant wavelength control of the light source 1; by controlling the integrated waveplate device 6 to operate at a set target temperature, it can reduce the errors caused by temperature changes and temperature-induced stress of the existing λ / 4 waveplate, so as to achieve long-term stability of the waveplate phase delay angle and optimal adaptation of the waveplate phase delay angle to the sensor system parameters. Aiming at the drift problem of the average wavelength in the optical path, by introducing the spectral acquisition module 13, the average wavelength of the optical path is monitored in real time, and the wavelength-related errors are corrected twice. The above solution can suppress the errors of long-term drift of the FOCS measurement accuracy.

[0087] Further, as shown in the figure, in the above-mentioned robust enhanced high-precision fiber optic current sensor, a polarization-maintaining fiber delay loop 4 is further included, which is connected to the phase modulator 32 and the integrated waveplate device 6 through a polarization-maintaining transmission fiber 5. Specifically, the output fiber of the phase modulator 32 and the input fiber of the polarization-maintaining fiber delay loop 4 are connected with 0° axis alignment, and the output fiber of the polarization-maintaining fiber delay loop 4 and the input fiber of the integrated waveplate device 6 are connected with 0° axis alignment. By setting the polarization-maintaining fiber delay loop 4, the polarization state of light can be effectively maintained.

[0088] Preferably, in specific implementation, the output fiber of the fiber polarizer 31 and the input fiber of the phase modulator 32 are connected with 45° axis alignment. The output fiber of the integrated waveplate device 6 and the sensing fiber 7 are connected with 0° axis alignment.

[0089] In the above solution, the temperature value of the sensing fiber 7 can be detected by the temperature sensor 11. Specifically, the temperature sensor 11 is used to detect the temperature value of the sensing fiber 7 and send it to the sensing fiber temperature acquisition circuit, thereby realizing real-time and accurate detection of the temperature value of the sensing fiber.

[0090] In the solution of this application, the first control unit 14 further includes:

[0091] A preamplification circuit, whose input end receives the electrical signal output by the photodetector 9 and amplifies it into a voltage signal; an A / D conversion circuit, which converts the voltage signal into a digital signal; a first signal processing sub-unit, which receives the digital signal and analyzes the current value of the current-carrying conductor and the optical power value, and simultaneously generates a digital quantity value corresponding to the phase feedback signal; the first signal processing sub-unit outputs the current value of the current-carrying conductor; a D / A conversion circuit, which receives the digital quantity value corresponding to the phase feedback signal and converts it into an analog signal, and the analog signal is applied to the phase modulator 32 as a modulation signal. As shown in the figure, there is a connection relationship between the first control unit 14 and the second control unit 12. Therefore, the first control unit 14 can send the current value of the current-carrying conductor and the optical power value to the second control unit 12. The second control unit 12 uses the spectral data transmitted by the spectral acquisition digital output signal conversion module, the current value of the current-carrying conductor and the optical power value transmitted by the first signal processing sub-unit, and the temperature data transmitted by the temperature sensor 11 to calculate the corrected demodulated current value and output it through the output data line 15.

[0092] Based on the cooperation of the spectral acquisition module, the spectral acquisition digital output signal conversion module, the light source control circuit, the integrated wave plate device control circuit, and the sensing optical fiber temperature acquisition circuit, the above solution of the present application corrects the wavelength drift error of the light source and the integrated wave plate device, and suppresses the error generated by the long-term drift of the FOCS measurement accuracy.

[0093] An embodiment of the present invention further provides a control method for the robust enhanced high-precision optical fiber current sensor described in any one of the above solutions, as Figure 3 shown, including the following steps:

[0094] S10: Control the die temperature and drive current of the light source to ensure that the average wavelength of the light source remains at the set average wavelength, and the output optical power of the light source is constant at the preset power.

[0095] S20: Control the temperature of the integrated wave plate device at the target temperature, where the target temperature makes the measurement error of the integrated wave plate device at the temperature equal in magnitude and opposite in sign to the measurement error of the sensing optical fiber at the same temperature.

[0096] S30: Perform error compensation and correction on the wavelength drift of the integrated wave plate device and the wavelength drift of the sensing optical fiber.

[0097] The present invention proposes the above control method. Aiming at the problem of the attenuation of the output optical power of the light source, the light source is controlled with constant power and constant wavelength; aiming at the temperature change and temperature-induced stress error of the λ / 4 wave plate, the temperature of the integrated wave plate device is controlled to be constant to achieve the long-term stability of the wave plate phase delay angle and the optimal adaptation of the wave plate phase delay angle to the sensor system parameters. Aiming at the problem of the average wavelength drift of the optical path, by introducing a spectral acquisition module, the average wavelength of the optical path is monitored in real time, and the wavelength-related error is corrected twice, where the wavelength-related error also includes the additional error generated by the short-term measurement error with the wavelength drift.

[0098] Specifically, controlling the die temperature and drive current of the light source in step S10 to ensure that the average wavelength of the light source remains at the set average wavelength and the output optical power of the light source is constant at the preset power can be achieved in the following two ways:

[0099] Method 1: Direct control of the output wavelength of the light source

[0100] S101: Establish a light source control model, where the light source control model includes the corresponding relationship between the output optical power, average wavelength of the light source, and die temperature and drive current output optical power.

[0101] The main reason for the change in the average wavelength in the optical path is the change in the average wavelength of the light source. The average wavelength λ of the light source c is mainly affected by the die temperature T of the light source SLD and the drive current ISLD The influence, therefore, the average wavelength λ of the light source c can be written as the die temperature T SLD and the drive current I SLD calculation model of:

[0102] λ c = f(T SLD , I SLD )(1)

[0103] Meanwhile, the output optical power P of the light source SLD is also affected by the die temperature T of the light source SLD and the drive current I SLD Therefore, the output optical power P of the light source SLD can be written as the die temperature T SLD and the drive current I SLD calculation model of:

[0104] P SLD = g(T SLD , I SLD )(2)

[0105] S102: According to the light source control model, by controlling the die temperature T of the light source SLD and the drive current I SLD , so that the average wavelength λ output by the light source c is kept constant at the set average wavelength, and the output optical power P of the light source SLD is kept constant at the preset power output optical power.

[0106] Based on the calculation model (1) of the light source wavelength and the calculation model (2) of the output optical power of the light source, through matching calculations, the die temperature T c required to increase the output optical power P of the light source SLD is obtained on the premise that the average wavelength λ of the light source remains unchanged SLD and the drive current I SLD , and constant temperature and constant drive current control are performed to achieve constant wavelength control under the premise of increasing the output optical power of the light source.

[0107] As mentioned above, the chips of different light sources have different light-emitting mechanisms. Therefore, based on the measured output optical power of the light source, the average wavelength of the light source, and the corresponding die temperature T SLD of the light source and the drive current I SLD , a mathematical model is established to achieve constant power and constant wavelength control. The specific modeling method is as follows:

[0108] When the drive current of the light source is constant, adjust the die temperature T SLD of the light source, and measure the output optical power of the light source and the average wavelength of the light source and the die temperature TSLD Based on the value of SLD to establish the die temperature T SLD and the output optical power P c and the average wavelength λ of the light source SLD to obtain a multi-dimensional parameter model of "temperature-power-average wavelength" of the light source. That is, when the drive current I

[0109]

[0110] T SLD1n is the die temperature of the light source, n = 1, 2, 3, 4... n; P 1m is the output optical power of the light source, m = 1, 2, 3, 4... m, λ 1s is the average wavelength of the light source, s = 1, 2, 3, 4... s.

[0111] When the die temperature T of the light source SLD is constant, adjust the drive current I of the light source SLD and measure the output optical power P of the light source SLD and the average wavelength λ of the light source c and the value of the drive current I SLD to establish an array of the drive current I SLD and the output optical power P of the light source SLD and the average wavelength λ of the light source c to obtain a multi-dimensional parameter model of "drive current-power-average wavelength" of the light source. That is, when the die temperature T of the light source SLD is constant, the following array is measured:

[0112]

[0113] I sld2j is the die temperature of the light source, j = 1, 2, 3, 4... j; P 2i is the output optical power of the light source, i = 1, 2, 3, 4... i, λ 2k is the average wavelength of the light source, k = 1, 2, 3, 4... k.

[0114] Fit the relationship model of the die temperature T of the light source SLD and the drive current I of the light source SLD and the output optical power P of the light source SLD and the average wavelength λ of the light source c as the light source control model. Based on the light source control model, the average wavelength of the light source can be kept at the set average wavelength.

[0115] Method 2: Feedback control based on the average wavelength of the optical path by the spectral acquisition module

[0116] In this solution, a spectral acquisition module is used to monitor and feedback the average wavelength of the light source in real time, and a photodetector is used to monitor and feedback the optical power output of the optical path in real time. The methods for controlling the average wavelength of the light source include:

[0117] S111: Obtain the measured wavelength of the light source according to the spectral data collected by the spectral acquisition module.

[0118] S112: Obtain the difference between the measured wavelength and the preset wavelength.

[0119] S113: Adjust the die temperature T SLD and drive current I SLD of the light source by combining the adjustment of the preset multi-dimensional parameter model and the difference, so that the average wavelength λ c of the light source is kept constant at the set average wavelength, and the output optical power P SLD of the light source is kept constant at the preset power; where the multi-dimensional parameter model is used to record the corresponding relationship between the output optical power of the light source, the average wavelength of the light source, and the die temperature and drive current. Among them, the multi-dimensional parameter model can adopt the "temperature-power-wavelength" multi-dimensional parameter model obtained in Method 1. Based on the difference obtained in S112 and the above model, the average wavelength λ c of the light source is feedback-adjusted, and the die temperature T SLD and the drive current I SLD of the light source are adjusted, so that the measured average wavelength of the light source is consistent with the set average wavelength. At this time, a certain deviation in the output optical power of the light source is allowed.

[0120] Further preferably, in step S20, controlling the temperature of the integrated waveplate device at the target temperature, where the target temperature makes the measurement error of the integrated waveplate device at the temperature equal in magnitude and opposite in sign to the measurement error of the sensing optical fiber at the same temperature, includes:

[0121] S201: Model the measurement error of the integrated waveplate device at different temperatures to obtain an integrated waveplate device measurement error model.

[0122] The measurement error (i.e., specific difference) of FOCS can be expressed as a function of the ambient temperature T, the average wavelength λ c of the light source, and the waveplate phase delay angle δ. The waveplate phase delay angle δ can in turn be expressed as a function of the ambient temperature T, the average wavelength λ c of the light source, and the stress σ, as shown in the following equations (5) and (6):

[0123] ε = f(T, λ c , δ) (5)

[0124] δ = f1(T, λ c , σ) (6)

[0125] where T is the ambient temperature, λ c is the average wavelength of the light source, σ is the external stress applied to the wave plate, δ is the phase retardation angle of the wave plate, and ε is the measurement error of the FOCS. Therefore, changes in the internal physical parameters (such as temperature, wavelength, and stress) of the integrated wave plate device will directly result in measurement errors of the FOCS. In this application, through the internal packaging process of the integrated wave plate device, the influence of external stress on the λ / 4 wave plate can be isolated, so the influence of stress on the λ / 4 wave plate in the above formula can be basically ignored. At the same time, the Verdet constant of the sensing optical fiber is also affected by temperature changes, resulting in measurement errors of the FOCS. The Verdet constant is related to the material of the sensing optical fiber and the frequency of light. In practical applications, since the material of the sensing optical fiber changes with temperature, the Verdet constant is also temperature-related. The typical temperature characteristics of the sensing optical fiber are expressed as:

[0126]

[0127] where V0 is the Verdet constant at room temperature, V is the Verdet constant, and T is the ambient temperature.

[0128] According to the above formula, it can be seen that V0 has an obvious influence on the temperature characteristics of the measurement error of the FOCS. Therefore, in this solution, the measurement error of the integrated wave plate device is used to self-compensate the measurement error of the Verdet constant of the sensing optical fiber in the FOCS.

[0129] S202: Model the measurement errors of the sensing optical fiber at different temperatures to obtain a sensing optical fiber measurement error model at different temperatures.

[0130] Specifically, during implementation, the error measurement of the sensing optical fiber at different temperatures can be pre-conducted by means of a calibration test. After obtaining a series of values, a model is established to record the corresponding relationship between the measurement error and the temperature of the sensing optical fiber.

[0131] S203: Based on the measured temperature of the sensing optical fiber, obtain the corresponding sensing optical fiber error value according to the sensing optical fiber measurement error model.

[0132] Substitute the measured temperature of the sensing optical fiber into the sensing optical fiber measurement error model to obtain the FOCS measurement error caused by the measured temperature of the sensing optical fiber.

[0133] S204: Take the opposite value of the sensing optical fiber error value as the target error value of the integrated wave plate device.

[0134] S205: Based on the target error value of the integrated wave plate device and the integrated wave plate measurement error model, obtain the target temperature of the integrated wave plate device, and control the operating temperature of the semiconductor cooler so that the operating temperature of the integrated wave plate device is the target temperature.

[0135] Thus, the target error value of the integrated waveplate device can be made to cancel out the error value of the sensing optical fiber, thereby compensating for the measurement error of the sensing optical fiber point by point and improving the measurement accuracy of the current sensor.

[0136] In the above solution of this embodiment, the measurement errors of the integrated waveplate device and the sensing optical fiber are respectively modeled. According to the measured temperature of the sensing optical fiber, the error value of the sensing optical fiber at this time is obtained based on the measurement error model of the sensing optical fiber. The opposite of this sensing optical fiber error value is taken to obtain the target error value of the integrated waveplate device. Based on the target error value of the integrated waveplate device and the measurement error model of the integrated waveplate device, the target temperature value is obtained. By adjusting the control parameters of the thermoelectric cooler in the integrated waveplate device, the operating temperature of the integrated waveplate device is made the target temperature value to compensate for the measurement error of the sensing optical fiber.

[0137] In actual applications, according to the usage scenarios of fiber optic current sensors, the requirements for measurement accuracy are different. When a fiber optic current sensor requires high-precision accuracy at room temperature, the phase delay angle of the integrated waveplate device can be made 90°. However, due to reasons such as manufacturing processes and measurement errors of measuring tools, there are certain deviations in the phase delay angle of the actually manufactured integrated waveplate device. This deviation is random and cannot be designed. At this time, the phase delay angle can be adjusted to 90° by adjusting the operating temperature of the integrated waveplate device. Therefore, if the initial phase delay angle of the integrated waveplate device is inaccurate due to reasons such as manufacturing processes and measurement errors of measuring tools, there is no need to remanufacture the integrated waveplate device, and the phase delay angle can be adjusted by adjusting the preset temperature.

[0138] The model of the phase delay angle of the integrated waveplate device is as shown in the aforementioned formula (6), and there is a functional relationship between the sensitivity of the sensing optical fiber and the ambient temperature and the average wavelength of the light source as shown in formula (8):

[0139] S = f(T, λ c )(8)

[0140] where S is the sensitivity of the sensing optical fiber, T is the ambient temperature, and λ c is the average wavelength of the optical path.

[0141] As the FOCS operates for a long time, its average light source wavelength cannot remain constant. Therefore, after achieving constant light source wavelength control and constant temperature control of the integrated waveplate device, it is still necessary to perform secondary compensation for the wavelength drift error. The compensation methods include:

[0142] S301: Model the wavelength drift of the integrated waveplate device, including: changing the average wavelength of the light source input to the integrated waveplate device at different constant temperatures and testing the measurement errors caused by different average wavelengths of the light source; or, changing the average wavelength of the light source input to the integrated waveplate device at different constant temperatures and testing the change in the phase delay angle of the integrated waveplate device caused by different average wavelengths of the light source, and determining the measurement error based on the change in the phase delay angle; modeling based on the measurement results to obtain the wavelength drift error model of the integrated waveplate device at different constant temperatures.

[0143] S302: Obtain the measured average wavelength of the light source according to the spectral data collected by the spectral acquisition module;

[0144] S303: Obtain the error compensation coefficient of the integrated waveplate device based on the wavelength drift error model of the integrated waveplate device corresponding to the target temperature and in combination with the measured average wavelength of the light source;

[0145] S304: Send the error compensation coefficient of the integrated waveplate device to the second control unit for the second signal processing subunit to correct the demodulation current value.

[0146] Using the integrated waveplate measurement error calculation model shown in the foregoing formula (6), conduct modeling of the measured data to obtain the wavelength drift error model of the integrated waveplate device, calculate the wavelength drift amount based on the measured average wavelength of the light source collected by the spectral acquisition module, calculate the error compensation coefficient of the FOCS according to the wavelength drift error model of the integrated waveplate device, and perform secondary correction on the measurement output value of the FOCS.

[0147] S305: The correspondence between the average wavelength of the light source, the Verdet constant of the optical fiber, and the measurement error is as follows: where V is the Verdet constant of the optical fiber, λ c is the average wavelength of the light source, is the phase difference, and ε is the FOCS measurement error;

[0148] S306: Obtain the wavelength drift amount of the sensing optical fiber according to the correspondence and the measured wavelength of the light source;

[0149] S307: Obtain the error compensation coefficient of the sensitivity of the sensing optical fiber according to the wavelength drift amount of the sensing optical fiber

[0150] S308: Send the error compensation coefficient of the sensitivity of the sensing optical fiber to the second control unit for the second signal processing subunit to correct the demodulation current value.

[0151] Combining the error compensation coefficient of the integrated waveplate device and the error compensation coefficient of the sensitivity of the sensing optical fiber, the measurement error of the FOCS is compensated twice together to further improve the measurement accuracy of the FOCS.

[0152] Some embodiments of the present application also provide a packaging process for the integrated waveplate device in the above-mentioned robust enhanced high-precision optical fiber current sensor, combining Figure 4 and Figure 5 As shown, it includes:

[0153] S100: Groove the quartz substrate.

[0154] Specifically, the λ / 4 waveplate in the integrated waveplate device can be an optical fiber waveplate or a crystal waveplate. The size of the quartz substrate 601 and the size of the grooved can be selected according to the type of the λ / 4 waveplate and other actual requirements. For example, when the λ / 4 waveplate is an optical fiber waveplate, the width of the quartz substrate 601 is 5 mm, the length is 50 mm, the thickness is 1 mm, and the diameter of the groove is 300 μm. When the λ / 4 waveplate is a crystal waveplate, the size of the quartz substrate 601 and the size of the grooved can be determined according to the crystal waveplate and the sizes of the input and output end collimators.

[0155] S200: Place the λ / 4 waveplate 602 and the optical fibers at both ends thereof in the groove opened on the quartz substrate 601 and fix them. The optical fibers at both ends include an input optical fiber 607 and an output optical fiber 608. The input optical fiber 607 is a linearly polarized maintaining optical fiber, and the output optical fiber 608 is a circularly polarized maintaining optical fiber. The λ / 4 waveplate 602 can be fabricated in advance using a fusion splicer with high fusion splicing accuracy and a tool for measuring length with high precision.

[0156] Preferably, the λ / 4 waveplate 602 and the optical fibers at both ends are fixed using a low-stress UV glue. The UV glue is fixed in a point-by-point manner to reduce the influence of the tensile force, torsional force or temperature stress on the λ / 4 waveplate 602 during the use of the pigtail.

[0157] S300: Place the quartz substrate 601 on the heat sink 604, and arrange a thermistor 605 on at least one side of the quartz substrate 601. The size of the heat sink is larger than the size of the substrate.

[0158] The thermistor 605 is connected to the resistor pin 6052 through the resistor lead 6051. The heat sink 604 is fixed to the substrate 601 and the thermistor 605 by welding or bonding using a high thermal conductivity material.

[0159] S400: Place the heat sink 604 on the thermoelectric cooler 603. The size of the thermoelectric cooler is larger than or equal to the size of the heat sink. The thermoelectric cooler 603 is connected through the cooler lead 6031 and the cooler pin 6032. The above leads and pins include a positive electrode and a negative electrode.

[0160] A high - thermal - conductivity material is used for welding or bonding to fix the semiconductor cooler 603 and the heat sink 604.

[0161] S500: The semiconductor cooler 603 is arranged inside the housing 606, and the optical fibers at both ends are respectively led out and fixed from the fiber - output holes at both ends of the housing.

[0162] A high - thermal - conductivity material is used to fix the semiconductor cooler 603 and the housing 606. Low - stress silicone rubber is used to fix the optical fibers at the fiber - output holes at both ends of the housing.

[0163] S600: Cover the upper cover of the housing and perform sealing by welding or using sealant.

[0164] The integrated waveplate device obtained by the above - mentioned process of this application is as Figure 5 and 6 shown. The integrated waveplate device includes an input - end collimator 6071, an output - end collimator 6081, a λ / 4 waveplate 602, a semiconductor cooler 603, cooler leads 6031, cooler pins 6032, a heat sink 604, a thermistor 605, resistor leads 6051, resistor pins 6052, a housing 606, and a fixing bracket 609. The input - end collimator 6071 consists of a collimator and an input optical fiber 607 inside it; the output - end collimator 6081 consists of a collimator and an output optical fiber 608 inside it. The input - end collimator 6071, the output - end collimator 6081, and the λ / 4 waveplate 602 are fixed on the heat sink 604 using the fixing bracket 609. The fixing bracket 609 and the heat sink 604 are designed as an integral structure. The thermistor 605 is fixed on the heat sink 604 using a high - thermal - conductivity adhesive respectively. The heat sink 604 is fixed on the semiconductor cooler 603, and the semiconductor cooler 603 is fixed in the metal housing 606. There are openings at both ends of the housing 606, and the input optical fiber and the output optical fiber are led out from the openings on both sides. The input optical fiber and the output optical fiber are fixed and sealed using low - stress silicone rubber. The top of the housing is sealed with a metal cover. The integrated waveplate device provided by this solution can manufacture, package, test, and use the "λ / 4 waveplate" individually, becoming an independent optical device, realizing batch production of waveplates, and solving the problem of customization of fiber - optic sensing rings. Combining with the solutions in the foregoing embodiments, the integrated waveplate device provided by this solution can realize pre - setting and adjustment of the phase - delay angle. In addition, the pigtail in the integrated waveplate device provided by this solution can be made in the form of a fiber optic jumper, which is convenient for docking with external optical fibers.

[0165] According to needs, the above - mentioned technical solutions can be combined to achieve the best technical effect.

[0166] The above are only the principles and preferred embodiments of this application. It should be noted that for those of ordinary skill in the art, based on the principles of this application, several other variations can also be made, which should also be regarded as the protection scope of this application.

Claims

1. A robust enhanced high-precision optical fiber current sensor, characterized in that, Comprising: An optical path module, including, connected in sequence: a light source, an optical fiber coupler, an optical fiber polarizer, a spectral acquisition module, a phase modulator, an integrated wave plate device, and a photodetector; wherein, the integrated wave plate device includes a λ / 4 wave plate, a thermistor, a quartz substrate, a semiconductor cooler, a heat sink, and a housing; the light emitted by the light source enters the optical fiber coupler, one output end of the optical fiber coupler is connected to the optical fiber polarizer, the other output end of the optical fiber coupler is connected to the spectral acquisition module, and the spectral acquisition module acquires the spectral information at the output end of the optical fiber coupler; An optical fiber sensing loop, including a sensing optical fiber and a mirror, one end of the sensing optical fiber is connected to the integrated wave plate device, and the other end of the sensing optical fiber is provided with the mirror; the sensing optical fiber surrounds the outside of a current-carrying conductor, and the current-carrying conductor transmits the current to be measured; A circuit module, including a first control unit and a second control unit, wherein: The first control unit is connected to the photodetector, receives the electrical signal output by the photodetector and analyzes it to obtain the current value of the current-carrying conductor and the optical power value received by the photodetector, and the optical power value is used to determine the modulation signal of the phase modulator; The second control unit includes: A light source control circuit, which controls the die of the light source to work at a set operating temperature and drive current, so that the average wavelength of the light source remains at a set average wavelength, and the output optical power of the light source is constant at a preset power; An integrated wave plate device control circuit, which determines the actual temperature of the integrated wave plate device according to the resistance value of the thermistor, and controls the operating temperature of the semiconductor cooler so that the integrated wave plate device works at a target temperature; A sensing optical fiber temperature acquisition circuit, which acquires the temperature value of the sensing optical fiber; A spectral acquisition digital output signal conversion module, which receives the spectral information acquired by the spectral acquisition module and analyzes it to obtain spectral data; A second signal processing sub-unit, which obtains a corrected demodulated current value according to the current value of the current-carrying conductor, the temperature value of the sensing optical fiber, the spectral data, and the optical power value, in combination with a pre-set data correspondence list therein; the data correspondence is the correspondence between the current value of the current-carrying conductor, the temperature value of the sensing optical fiber, the optical power value, and the demodulated current value obtained according to a calibration test.

2. The robust enhanced high-precision optical fiber current sensor according to claim 1, wherein It further includes a polarization-maintaining optical fiber delay loop: The output end optical fiber of the phase modulator is connected to the input end optical fiber of the polarization-maintaining optical fiber delay loop with 0° axis alignment, and the output end optical fiber of the polarization-maintaining optical fiber delay loop is connected to the input end optical fiber of the integrated wave plate device with 0° axis alignment.

3. The robust enhanced high-precision optical fiber current sensor according to claim 1, characterized in that: The output end optical fiber of the optical fiber polarizer is connected to the input end optical fiber of the phase modulator with 45° axis alignment.

4. The robust enhanced high-precision optical fiber current sensor according to claim 1, characterized in that: The output end optical fiber of the integrated wave plate device is connected to the sensing optical fiber with 0° axis alignment.

5. The robust enhanced high-precision optical fiber current sensor according to claim 1, wherein It further includes: A temperature sensor, which is used to detect the temperature value of the sensing optical fiber and send it to the sensing optical fiber temperature acquisition circuit.

6. The robust enhanced high-precision fiber optic current sensor according to any one of claims 1-5, characterized in that, The first control unit further includes: A preamplification circuit, whose input end receives the electrical signal output by the photodetector and amplifies it into a voltage signal; An A / D conversion circuit, which converts the voltage signal into a digital signal; A first signal processing sub-unit, which receives the digital signal and analyzes the current value of the current-carrying conductor and the optical power value, and simultaneously generates a digital quantity value corresponding to the phase feedback signal; the first signal processing sub-unit outputs the current value of the current-carrying conductor; A D / A conversion circuit, which receives the digital quantity value corresponding to the phase feedback signal and converts it into an analog signal, and the analog signal is applied to the phase modulator as a modulation signal.

7. A control method for the robust enhanced high-precision fiber optic current sensor according to any one of claims 1-6, characterized in that, It includes: Controlling the chip temperature and drive current of the light source to ensure that the average wavelength of the light source remains at a set average wavelength and the output optical power of the light source is constant at a preset power; Controlling the temperature of the integrated wave plate device at a target temperature, and the target temperature makes the measurement error of the integrated wave plate device at the temperature equal in magnitude and opposite in sign to the measurement error of the sensing optical fiber at the same temperature; Performing error compensation and correction on the wavelength drift of the integrated wave plate device and the wavelength drift of the sensing optical fiber.

8. The control method of the robust enhanced high-precision fiber optic current sensor according to claim 7, characterized in that The controlling the chip temperature and drive current of the light source to ensure that the average wavelength of the light source remains at a set average wavelength and the output optical power of the light source is constant at a preset power includes: Establishing a light source control model, which includes the corresponding relationship between the output optical power of the light source and the chip temperature and drive current, and the corresponding relationship between the average wavelength and the chip temperature and drive current; According to the light source control model, by controlling the chip temperature and drive current of the light source, the average wavelength output by the light source is made constant at the set average wavelength, and the output optical power of the light source is constant at the preset power.

9. The control method of the robust enhanced high-precision optical fiber current sensor according to claim 7, wherein The controlling the chip temperature and drive current of the light source to ensure that the average wavelength of the light source remains at a set average wavelength and the output optical power of the light source is constant at a preset power further includes: Obtaining the measured wavelength of the light source according to the spectral data collected by the spectral acquisition module; Obtaining the difference between the measured wavelength and the set average wavelength; Combining the preset multi-dimensional parameter model and the difference, adjusting the chip temperature and drive current of the light source, so that the average wavelength output by the light source is constant at the set average wavelength, and the output optical power of the light source is constant at the preset power output optical power; wherein, the multi-dimensional parameter model is used to record the corresponding relationship between the output optical power of the light source and the chip temperature and drive current, and the corresponding relationship between the average wavelength of the light source and the chip temperature and drive current.

10. The control method of the robust enhanced high-precision optical fiber current sensor according to claim 7, characterized in that, The controlling the temperature of the integrated wave plate device at a target temperature, and the target temperature makes the measurement error of the integrated wave plate device equal in magnitude and opposite in sign to the measurement error of the sensing optical fiber includes: Modeling the measurement errors of the integrated wave plate device at different temperatures to obtain an integrated wave plate device measurement error model; Model the measurement error of the sensing optical fiber at different temperatures to obtain the measurement error model of the sensing optical fiber at different temperatures; Based on the measured temperature of the sensing optical fiber, obtain the corresponding sensing optical fiber error value according to the measurement error model of the sensing optical fiber; Take the opposite number of the sensing optical fiber error value as the target error value of the integrated waveplate device; Based on the target error value of the integrated waveplate device and the measurement error model of the integrated waveplate device, obtain the target temperature of the integrated waveplate device, and control the operating temperature of the semiconductor cooler so that the operating temperature of the integrated waveplate device is the target temperature.

11. The control method of the robust enhanced high-precision optical fiber current sensor according to claim 7, characterized in that, The error compensation and correction for the wavelength drift of the integrated waveplate device and the wavelength drift of the sensing optical fiber include: Model the wavelength drift of the integrated waveplate device, including: changing the average wavelength of the light source input to the integrated waveplate device at different constant temperatures and testing the measurement error caused by different average wavelengths of the light source; or, changing the average wavelength of the light source input to the integrated waveplate device at different constant temperatures and testing the change in the phase delay angle of the integrated waveplate device caused by different average wavelengths of the light source, and determining the measurement error according to the change in the phase delay angle; modeling according to the measurement results to obtain the wavelength drift error model of the integrated waveplate device at different constant temperatures; Obtain the measured average wavelength of the light source according to the spectral data collected by the spectral acquisition module; Based on the wavelength drift error model of the integrated waveplate device corresponding to the target temperature, combined with the measured average wavelength of the light source, obtain the error compensation coefficient of the integrated waveplate device; the error compensation coefficient of the integrated waveplate device is sent to the second control unit for the second signal processing subunit to correct the demodulated current value.

12. The control method of the robust enhanced high-precision optical fiber current sensor according to claim 11, characterized in that The error compensation and correction for the wavelength drift of the integrated waveplate device and the wavelength drift of the sensing optical fiber further include: Obtain the corresponding relationship among the average wavelength of the light source, the Verdet constant of the optical fiber, and the measurement error: where V is the Verdet constant of the optical fiber, λ c is the average wavelength of the light source, is the phase difference, and ε is the measurement error; Obtain the wavelength drift amount of the sensing optical fiber according to the corresponding relationship and the measured average wavelength of the light source; Obtain the error compensation coefficient of the sensitivity of the sensing optical fiber according to the wavelength drift amount of the sensing optical fiber; the error compensation coefficient of the sensitivity of the sensing optical fiber is sent to the second control unit for the second signal processing subunit to correct the demodulated current value.

13. The packaging process of the integrated waveplate device in the robust enhanced high-precision fiber optic current sensor according to any one of claims 1-6, characterized in that, Include: Groove on the quartz substrate; Place the λ / 4 waveplate and the optical fibers at both ends thereof in the groove opened on the quartz substrate and fix them; Place the quartz substrate on the heat sink, and arrange a thermistor on at least one side of the quartz substrate, and the size of the heat sink is larger than the size of the quartz substrate; Place the heat sink on the semiconductor cooler, and the size of the semiconductor cooler is larger than or equal to the size of the heat sink; The semiconductor cooler is arranged in the housing, and the optical fibers at both ends are respectively led out and fixed from the fiber outlet holes at both ends of the housing; Cover the upper cover of the housing and seal it by soldering or sealant.

14. The packaging process of the integrated waveplate device in the robust enhanced high-precision optical fiber current sensor according to claim 13, characterized in that: The λ / 4 wave plate and the optical fibers at both ends thereof are placed in the groove opened on the quartz substrate and fixed: The λ / 4 wave plate and the optical fibers at both ends thereof are fixed by using UV glue in a point-by-point fixing manner; The semiconductor refrigerator is arranged in the housing, and the optical fibers at both ends are respectively led out from the fiber outlet holes at both ends of the housing and fixed: Silicone rubber is used to fix the optical fibers at the fiber outlet holes at both ends of the housing.

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