Fibre optic device for high-speed measurement of electric current

Abstract

FIELD: fibre optics; fibre optic electric current sensors.SUBSTANCE: fibre optic device for measuring electric current contains an electronic signal processing module and a fibre optic circuit. In it, the radiation source is connected via a circulator to a photodiode connected to an electronic module, and to a series-connected linear polarizer, Faraday rotator, magnetically sensitive optical fibre, and mirror. The device is equipped with a second fibre-optic circuit with a second electronic signal processing module and an electronic calibration unit. The radiation is fed to the second circuit through a coupler installed between the radiation source and the circulator of the first circuit. The second circuit includes a circulator, the input of which is connected to a coupler, the reverse output of which is connected to a photodiode connected to a second signal processing module, and the forward output is connected to a series-connected linear polarizer, a fibre delay line made of polarization-maintaining optical fibre having a piezoceramic or integrated-optical phase modulator at the beginning, a phase plate, a magnetosensitive optical fibre, and a mirror. The magnetically sensitive fibres of both circuits are placed around a single current-carrying conductor. The outputs of both signal processing modules are connected to a calibration unit, configured to periodically calibrate the output signal of the first circuit based on the signal of the second circuit to compensate for the drift of the polarimetric circuit.EFFECT: increase in the accuracy of a polarimetric fibre-optic current sensor by periodic calibration using an interferometric sensor while maintaining the response speed of the polarimetric circuit and compensating for the influence of external mechanical and temperature effects.4 cl, 2 dwg

Description

[0001] The invention relates to fiber optics, in particular to fiber optic electric current sensors.

[0002] The operating principle of well-known fiber-optic current sensors (FOCS) is based on the magneto-optical Faraday effect. According to this effect, when two circularly polarized light waves propagate through a magnetic field induced by an electric current, a phase difference arises between the waves, directly proportional to the magnetic field strength. A FOCS is a device that measures this phase shift, using which the current is calculated. These sensors offer a wide dynamic range, high accuracy, resistance to external electromagnetic interference, and ease of installation, making them popular in the energy industry.

[0003] The relevance of this invention is determined by the active dissemination of high-voltage direct current (HVDC) power transmission technology and the development of highly intelligent systems for in-depth diagnostics and protection of high-voltage equipment, including those based on wave principles, which require extremely fast measurement data output times and high measurement stability over long periods. These requirements are virtually unattainable using existing measurement methods.

[0004] The closest approach to the proposed invention is a polarimetric method for measuring electric current and magnetic field with a reflective circuit and introducing a constant phase shift using a Faraday rotator (US20100253320, IPC G01R31 / 00, 07.10.2010). The device implementing this method includes a series-connected source of low-coherence optical radiation, a circulator, a polarizer, a Faraday rotator, a magnetically sensitive optical fiber, and a mirror. The return output of the circulator is connected to a photodiode, the signal from which is sent to the processing unit. In this device, the light from the source, after passing through the circulator, hits the polarizer, at the output of which the radiation has linear polarization. After passing through the rotator, the plane of polarization rotates through a certain angle, and then the light hits the magnetically sensitive fiber wound around the conductor with the measured current.As light passes through the fiber, the Faraday effect rotates the plane of polarization by an angle proportional to the measured current. The light then reflects off a mirror, travels the optical path in the opposite direction, and is directed by a circulator to a photodiode. Due to the nonreciprocity of the Faraday effect, as light passes in the opposite direction, the plane of polarization in the magnetically sensitive fiber and rotator rotates in the same direction. Continuously adjusting the phase shift using the Faraday rotator is necessary to shift the operating point to the region of maximum sensitivity.

[0005] This device has a drawback that manifests itself when used in a wide range of ambient temperatures and when exposed to external mechanical stress and vibration on the optical fiber. The Faraday rotator's polarization rotation angle depends on temperature in a complex manner, due to the temperature dependence of the rotator crystal's Verdet constant and the temperature influence on the adhesive bond between the fiber and the rotator for input / output of the light. These effects significantly reduce the accuracy of current measurement and make it impossible to use the described method for measuring current with a high accuracy of ~0.2%.

[0006] A device is also known (US5644397, IPC G01R33 / 032, 01.07.1997), implementing an interferometric method for optical current measurement based on the Faraday effect. The device consists of a series-connected source of low-coherence optical radiation, a circulator, a polarizer, the output of which is connected to a long section of optical fiber with built-in linear birefringence (PM fiber / polarization state-maintaining fiber) - a delay line, wherein the angle between the transmission axis of the polarizer and the birefringence axes of the fiber is 45º. A piezoceramic or integrated-optical phase modulator is located at the initial section of the delay line fiber. At the other end of the delay line fiber, a fiber quarter-wave phase plate is located, connected to a magnetosensitive fiber with a mirror at its opposite end.The device operates based on the fact that after passing through a polarizer, linearly polarized light is split into two light waves polarized along the fiber's birefringence axes upon entering the PM fiber of the delay line. After passing through the delay line fiber, the wave polarizations are converted into circular polarizations by a quarter-wavelength phase plate. The waves then enter the magnetically sensitive fiber, where, as they propagate, an additional phase shift occurs between them due to the Faraday effect. Upon reflection from the mirror, the wave polarizations are converted into orthogonal polarizations. The light then passes through the device's optical path in the opposite direction and is directed by a circulator to the photodiode.The modulator in this circuit modulates the phase shift between light waves harmonically, allowing the interferometer's operating point to be shifted to the region of maximum sensitivity, reducing the sensor's output noise, and using a synchronous detection method for precise phase shift measurement. This device eliminates the need for temperature-unstable components. However, the modulation detection method in this technical solution limits the frequency band of the measured currents to the modulation frequency.

[0007] The technical objective of the invention is to create a high-speed fiber-optic current sensor that satisfies metrological requirements for a measurement accuracy of 0.2%, which makes it possible to analyze the quality of electrical energy in a wide frequency band and to perform high-precision measurements of non-harmonic currents.

[0008] The technical result of the invention is to increase the accuracy of a polarimetric fiber-optic current sensor by periodic calibration using an interferometric sensor, while maintaining the speed of the polarimetric circuit and compensating for the influence of external mechanical and temperature effects.

[0009] The specified technical result is achieved in that the fiber-optic device for measuring electric current includes a first fiber-optic circuit together with a first electronic signal processing module, in which the optical radiation source is connected to the input of the circulator, the reverse output of the circulator is connected to a photodiode connected to the electronic signal processing module, and the direct output of the circulator is connected to a series-connected linear polarizer, Faraday rotator, magnetically sensitive optical fiber and mirror.The device is provided with a second fiber-optic circuit with a second electronic signal processing module and an electronic calibration unit, wherein optical radiation is supplied to the second fiber-optic circuit by means of a coupler installed between the radiation source and the circulator of the first fiber-optic circuit, and the second fiber-optic circuit includes a circulator, the radiation to the input of which is supplied from the said coupler, the reverse output of the circulator is connected to a photodiode connected to the second electronic signal processing module, and the forward output of the circulator is connected to a series-connected linear polarizer, a fiber delay line made of polarization-maintaining optical fiber and having at its beginning a piezoceramic or integrated-optical phase modulator, a phase plate, a magnetosensitive optical fiber and a mirror.Moreover, the magnetosensitive optical fibers of the first and second circuits are arranged around a single conductor carrying the measured current. The output signals of both electronic signal processing modules are connected to an electronic calibration unit, which is capable of periodically calibrating the output signal of the first optical circuit at a specified time interval using the output signal of the second optical circuit to compensate for polarimetric circuit drift.

[0010] The output signals of both circuits are input into the electronic unit for digitalization, synchronization, and correction of the current measurement by the polarimetric circuit based on the measurement results of the interferometric circuit. The results of the electric current measurement by the polarimetric method, which has a high speed and high-frequency sampling rate, are calibrated at a specified period by the current measurement results performed by the slow-response interferometric method with a low sampling rate.

[0011] Due to the presence of two schemes, polarimetric and interferometric, with a common source of low-coherence optical radiation, simultaneous measurement of the same current by two different methods is ensured.

[0012] The polarimetric circuit has a high response speed, therefore it allows the use of high-frequency measurement sampling, but at the same time it has an output signal drift due to noise, the influence of external mechanical and temperature effects on the optical elements of the circuit, therefore its use without output signal calibration does not provide the required measurement accuracy.

[0013] The interferometric circuit contains a PM fiber delay line and a phase modulator, which ensures high stability and accuracy, but limits the frequency bandwidth of the output signal.

[0014] Periodic calibration of the first circuit by the second one allows it to transfer high accuracy and stability of current measurement, allowing for both high-speed and accurate measurement.

[0015] The 45° angle between the polarizer and the delay line maximizes the contrast of the interferometric circuit and, consequently, the signal-to-noise ratio, which is necessary to ensure high accuracy.

[0016] A fiber coupler between the radiation source and the first circuit eliminates the need for an additional radiation source, simplifying the design. Furthermore, this eliminates the influence of source noise on measurement results.

[0017] The electronic calibration unit connected to the outputs of both modules implements the correction algorithm.

[0018] The claimed invention is explained by drawings, which show:

[0019] Fig. 1 shows a diagram of a fiber-optic device for high-speed measurement of electric current (an embodiment without an additional coupler with preservation of polarization in the polarimetric circuit).

[0020] Fig. 2 shows a diagram of a fiber-optic device (an embodiment with a polarization-maintaining fiber coupler and an additional photodiode in the polarimetric circuit).

[0021] In Fig. 1 and Fig. 2 the following positions are indicated:

[0022] 1 - low coherence optical source;

[0023] 2 - branch;

[0024] 3 - interferometric circuit circulator;

[0025] 4 - polarizer;

[0026] 5 - phase modulator (piezoceramic or integrated-optical);

[0027] 6 - delay line (PM fiber);

[0028] 7 - phase plate;

[0029] 8 - magnetically sensitive fiber;

[0030] 9 - interferometric circuit mirror;

[0031] 10 - photodiode;

[0032] 11 - interferometric channel calculator block;

[0033] 12 - reference generator;

[0034] 13 - frequency grid generator;

[0035] 14 - synchronized measurement pipeline of the interferometric channel;

[0036] 15 - synchronous correction calculator;

[0037] 16 - high-speed calculator;

[0038] 17 - output signal generator;

[0039] 18 - input and / or output phase plate;

[0040] 19 - magnetically sensitive fiber;

[0041] 20 - polarimetric mirror;

[0042] 21 - conductor with measurable electric current;

[0043] 22 - synchronized measurement pipeline of the polarimetric channel;

[0044] 23 - photodiode;

[0045] 24 - polarimetric channel calculator block;

[0046] 25 - circulator;

[0047] 26 - polarizer;

[0048] 27 - Faraday rotator;

[0049] 28 - synchronization source;

[0050] 29 - the first electronic signal processing module (interferometric circuit);

[0051] 30 - the second electronic signal processing module (polarimetric circuit);

[0052] 31 - electronic calibration unit;

[0053] 32 - branch;

[0054] 33 - photodiode;

[0055] 34 - phase plate;

[0056] 35 - sensitive elements of polarimetric and interferometric circuits.

[0057] The claimed fiber-optic device for measuring electric current (Fig. 1, Fig. 2) consists of two optical circuits - polarimetric and interferometric, consisting of electron-optical units 30 and 29, respectively, and a block of sensitive elements 35 of the polarimetric and interferometric circuits and an electronic calibration unit 31. In this case, the sensitive elements of the polarimetric circuit consist of a phase plate 18, a magnetosensitive optical fiber 19 and a mirror 20, and the sensitive elements of the interferometric circuit consist of a phase plate 7 and / or 34, a magnetosensitive optical fiber 8, a mirror 9 and are located on the bus with the measured current.

[0058] The device operates as follows.

[0059] The radiation from low-coherence optical source 1 is divided into two or more parts using coupler 2. The two coupler outputs are connected to two optical current measurement circuits.

[0060] The first circuit is a polarimetric fiber-optic current sensor with a reflective configuration. In this circuit, radiation from a low-coherence optical source 1, emitted from one of the output fibers of coupler 2, is directed into circulator 25 and incident on fiber polarizer 26, after which the radiation acquires linear polarization. After the polarizer, the light is fed directly (diagram in Fig. 1) or through a fiber coupler 32 with polarization maintenance (diagram in Fig. 2), the return output of which is connected to a photodiode 33, into a Faraday rotator 27, which rotates the plane of polarization by an angle of 22.5º, at which the maximum sensitivity of the polarimetric circuit with a linear response is achieved, as well as the maximum efficiency of the sensor, and then enters a sensitive element 35, consisting of an input and / or output phase plate 18 and a magnetically sensitive fiber 19 (spun fiber), wound around a conductor with electric current 21.In a magnetically sensitive optical fiber, the plane of polarization rotates due to the Faraday effect. If the sensitive fiber circuit forms an integral number of turns, then when light passes through it, according to the Faraday effect, the magnetic field of the current induces a rotation of the plane of polarization by an angle φ.

[0061] , (1)

[0062] where V is the Verdet constant of the fiber material, S is the relative magneto-optical sensitivity of the fiber, N is the number of fiber turns, and I is the measured current. When light propagates in the opposite direction, due to the nonreciprocity of the Faraday effect, the plane rotates by the same angle (1). In this case, only that portion of the optical radiation whose polarization component is parallel to the transmission axis of the polarizer will pass through the polarizer. The light is then directed to photodiode 23 using a circulator, the output signal I1 of which will be

[0063] , (2)

[0064] where I0 is the intensity of the radiation source.

[0065] The second optical circuit is an interferometric fiber-optic current sensor with a reflective configuration. In this circuit, the low-coherence light from the source, emitted from one of the output fibers of coupler 2, passes through circulator 3 and hits polarizer 4, resulting in linear polarization of the light. The output PM fiber of the polarizer is connected via a spliced ​​joint to fiber delay line 6, made of PM fiber, with the angle between the birefringence axes of both fibers in the joint being 45º. At this joint, the light is divided into two linear orthogonally polarized waves, the polarizations of which are oriented along the birefringence axes of the fiber of delay line 6. At the beginning of the delay line, an integrated optical or piezoceramic phase modulator 5 is located, which modulates the phase shift between the waves according to the harmonic law.

[0066] The highest efficiency of the modulator is achieved with a delay line length L=c / (4nf), where c is the speed of light, n is the refractive index of the fiber, and f is the modulation frequency.

[0067] At the end of delay line fiber 6 is a sensitive element 35 consisting of a fiber phase plate 7 that converts the polarization of each wave from linear to circular or elliptical. Light then enters the spun fiber through a spun joint, where, as it propagates, an additional phase shift occurs between the waves due to the Faraday effect. A second phase plate 34 is installed at the end of the magnetically sensitive fiber, between which and mirror 9 (the radiation reflector), to convert elliptical polarization to circular polarization. Upon reflection from mirror 9, located at the end of the optical path, the wave polarizations are converted to orthogonal ones; therefore, during the reverse propagation of waves in the magnetically sensitive fiber, the Faraday phase shift doubles. Furthermore, magnetically sensitive fibers 19 and 8 are arranged around the same current-carrying conductor.The light then passes through the optical path in the opposite direction and is directed by the circulator to photodiode 10. The phase shift between the waves, caused by the birefringent structure of the optical path, is completely compensated for by reciprocity, while the remaining phase shift is due to the Faraday effect and phase modulation. As a result, the signal I2 at the sensor's photodiode output will have the form

[0068] (3)

[0069] where I0 is the intensity of the radiation source, aφ m (t) =Mcos(2πft) phase shift of the modulator, where M is the modulation depth, and f is the modulation frequency.

[0070] In practice, the modulation frequency is approximately 100 kHz. Therefore, the optical path length of the circuit for high phase modulator efficiency must be approximately 500 m, which introduces a current measurement delay of approximately 5 μs. Furthermore, the frequency band of the measured currents is limited by the modulation frequency. These factors limit the measurement speed of the interferometric circuit, as well as its range of application.

[0071] At the same time, the polarimetric circuit has a short optical path (several tens of meters), resulting in low optical signal latency. Therefore, the response time of this sensor is determined by the speed of the output signal digitization unit, and the use of fast analog-to-digital converters (ADCs) allows for current measurement over a sufficiently wide frequency band. However, the temperature-dependent optical elements of this circuit, particularly the Faraday rotator, and other factors described above prevent a measurement error of 0.2% with an adequate intertest interval required for industrial applications.

[0072] The proposed solution to this problem consists of measuring the current with two sensors simultaneously and periodically calibrating the readings of the high-speed polarimetric sensor with the readings of the accurate but slow-acting interferometric sensor, thereby providing the polarimetric sensor with high measurement accuracy under conditions of external temperature and mechanical influences on its components.

[0073] The output signal from photodiode 10 is fed to the input of the interference channel's computing unit 11, which generates a harmonic phase modulation signal, digitizes the photodiode signal, and calculates the phase delay. The measurement data stream is then transmitted to synchronized measurement pipeline 14 for data buffering and further processing.

[0074] The output signal of photodiode 23 is fed to the input of the calculator block 24 of the polarimetric channel, which digitizes the photodiode signal and calculates the phase delay, the measurement information about which is then fed to the synchronized measurement pipeline 22 for data buffering and further processing.

[0075] Based on the single time generated by the reference generator 12, the frequency grid generator 13 generates synchronous streams of time samples, from which synchronized measurement pipelines 14 and 22 generate two synchronous streams of current measurement data with a time shift equal to the light transit time in the interference and polarimetric optical circuits. Both streams are then fed to the synchronous correction calculator 15, which calculates the measured current values ​​in both channels at a single instant in time. Based on the measurement results in both circuits corresponding to the same instant in time, a correction is calculated for the measurement result of the polarimetric circuit for the measurement result of the interferometric circuit to compensate for the influence of external mechanical and temperature effects on the elements of the polarimetric circuit. The measurement data are then fed to the high-speed calculator 16, where the measurement readings of the polarimetric circuit are corrected.The data stream of corrected current measurements from the polarimetric circuit is then fed to output signal generator 17, which converts the current measurement results into digital and / or analog format for transmission to external receivers. To ensure that the measurements are referenced to a standardized time, a precise time stamp from a satellite or other synchronization source 28 can be added to the output data stream.

[0076] Achieving the required current measurement accuracy over a temperature range requires temperature compensation of the magneto-optical sensitivity of spun fiber, which is determined by the temperature dependence of the fiber's built-in linear birefringence and the fiber's Verdet constant [3]. To achieve this, in the proposed device, a fiber-optic temperature sensor is connected to one of the outputs of coupler 2, which is used to correct the temperature dependence.

[0077] Example of implementation

[0078] To implement the claimed device, a superluminescent radiation source 1 with an output power of 30 mW, a central wavelength of 1550 nm, and a spectral width of 20 nm was used. The source's radiation is directed via a 1x3 coupler to a polarimetric circuit, an interferometric circuit, and a fiber-optic temperature sensor.

[0079] In the polarimetric scheme, the radiation, after passing through the circulator 25, enters the fiber polarizer 26 with an extinction of at least 25 dB, then enters the polarization-maintaining 2x2 fiber coupler 32, the extinction coefficient of which is at least 20 dB. One of the output ports of the coupler is connected to the Faraday fiber rotator 27, which rotates the polarization by an angle of 22.5° (selected to ensure maximum sensitivity and linear response), and then the radiation is introduced into the spun fiber 19 of the sensitive element of the sensor 35. The spun fiber has a total length of 14 m, the beat length of the built-in linear birefringence of the fiber is 10 mm at a wavelength of 1550 nm, and the pitch length of the helical structure is 3 mm. At the end of the fiber, there is a mirror 20, made by sputtering a layer of gold on the end of the cleaved fiber.The second return output of fiber coupler 32 and the return output of circulator 25 are connected to photodiodes, the outputs of which are connected to polarimetric channel processing unit 24. In this unit, the output signal from circulator 25, which carries information about the measured current, is normalized by the signal from the return output of coupler 32, which does not carry information about the measured current, in order to eliminate the influence of variations in the radiation power of the source and losses in the optical path. The current value calculated in the processing unit as a digital signal with a sampling frequency of 1 MHz is the output for the polarimetric circuit. The maximum possible response time of this circuit is determined by the light propagation time along the optical path in the forward and reverse directions, the total length of which was 20 m, and is limited by a time constant of 190 ns, which determines the frequency band of the recorded currents of 5.3 MHz.

[0080] In the interferometric scheme, the radiation, having passed through the circulator 3, enters the fiber polarizer 4 with an extinction of at least 25 dB, the output fiber of which is fused with the PM fiber of the delay line 6, 800 m long. The fusion joint is made at an angle of 45° between the transmission axis of the polarizer and the birefringence axes of the delay line fiber.

[0081] At the beginning of the PM fiber, a piezoelectric phase modulator 5 is located. For this purpose, 8 m of the initial fiber section is wound onto a piezoelectric cylinder with a diameter of 2 cm, the resonant frequency of which is 67 kHz. When a harmonic voltage with an amplitude of 5 V and a frequency equal to the resonant frequency of the piezoelectric cylinder is applied to the cylinder, a modulation depth of 1.84 rad is achieved, ensuring the maximum value of the harmonics of the circuit output signal at frequencies multiples of the modulation frequency. At the end of the PM fiber of the delay line, a sensitive element 35 is located, consisting of a quarter-wave fiber phase plate 34, spun fiber, and mirror 9. The plate is manufactured by welding a section of PM fiber with an angle between the birefringence axes of 45°. The birefringence beat length of this fiber is 8 mm, and the length of the segment is chosen to be equal to a quarter of the beat length.The spun fiber is 14 m long, and its parameters are the same as those described above for the polarimetric scheme. The mirror is fabricated by sputtering a gold layer onto the end of the cleaved fiber. The return output of circulator 3 is connected to a photodiode, the output of which is connected to the processing unit of interferometric channel 11, which extracts the measured current value using synchronous detection and generates an output stream of measured data.

[0082] Spun fiber 19 and 8 of both circuits are wound on the same conductor with a measured current of 21. For testing, it was laid in a circle with a diameter of 20 cm, forming 30 turns, inside a solenoid wound from copper wire with 1200 turns. When a current of 3 A was passed through the solenoid, the equivalent current measured by sensing circuits 35 was 3.6 kA.

[0083] The third output of coupler 2 was directed to a fiber-optic temperature sensor consisting of a circulator, a polarizer, a PM fiber line, and a sensitive phase plate consisting of a section of another PM fiber, fused to the PM fiber at a 45° angle, the length of which is 1 / 8 of the birefringence beat length. This phase plate is located near the spun fibers of the measurement circuits. The return output of the circulator is connected to a photodiode, the signal from which is fed to a processing unit, which calculates the temperature in the spun fiber region. Digital temperature data is fed to the calculators of the polarimetric and interferometric channels, which compensate for the temperature deviation of the magneto-optical sensitivity of spun fibers, which is 0.013% / °C.

[0084] The interferometric circuit's response time is determined by the phase modulation frequency and is limited by a time constant of 60 μs, which determines the frequency band of the recorded currents at 16 kHz. The current measurement delay is determined by the light travel time from the spun fiber of the sensing element to the photodiode and is 3.7 μs.

[0085] The electronic calibration unit, which receives digital data streams of measured current from the polarimetric and interferometric circuits, is implemented using data processing software on a personal computer. Calibration of the polarimetric circuit measurement results with the interferometric circuit measurement results was performed at a frequency of 100 Hz.

[0086] The results of measurements with the described device show that the deviation of current measurements by the polarimetric circuit under mechanical stress on the optical fiber, vibration, and temperature changes in the spun fiber and Faraday rotator in the range from -40°C to +60°C reaches 4%. Meanwhile, the deviation of current measurements by the interferometric circuit under the same conditions meets the metrological requirements of 0.2%. Moreover, the frequency band of the measured currents by the polarimetric circuit is limited by a sampling frequency of 1 MHz, which is 6500 times greater than the bandwidth for the interferometric circuit. However, the calibration of the polarimetric circuit measurements performed by the device allows for the output of current measurements in a 1 MHz bandwidth and a deviation from the measured current within metrological standards.

[0087] Bibliography:

[0088] [1] Laming RI, Payne DN, J. Lightwave Technology, 7, 2084 (1989).

[0089] [2] Frosio G., Dancliker R. “Reciprocal reflection interferometer for a fiber-optic Faraday current sensor”, Applied Optics, vol.33, no.25, 6111-6122 (1994).

[0090] [3] G. M. Müller, A. Frank, L. Yang, X. Gu and K. Bohnert, "Temperature Compensation of Interferometric and Polarimetric Fiber-Optic Current Sensors With Spun Highly Birefringent Fiber", in Journal of Lightwave Technology, vol. 37, no. 18, pp. 4507-4513, 15 Sept.15, 2019.

Claims

1. A fiber-optic device for measuring electric current, including a first fiber-optic circuit together with a first electronic signal processing module, in which the optical radiation source is connected to the input of a circulator, the reverse output of the circulator is connected to a photodiode connected to the electronic signal processing module, and the forward output of the circulator is connected to a series-connected linear polarizer, Faraday rotator, magnetically sensitive optical fiber and mirror, characterized in that said device is equipped with a second fiber-optic circuit with a second electronic signal processing module and an electronic calibration unit, wherein optical radiation is supplied to the second fiber-optic circuit using a coupler installed between the radiation source and the circulator of the first fiber-optic circuit, and the second fiber-optic circuit includes a circulator, the radiation to the input of which is supplied from the said coupler, the reverse output of the circulator is connected to a photodiode connected to the second electronic signal processing module, and the forward output of the circulator is connected to a series-connected linear polarizer, a fiber delay line made of polarization-maintaining optical fiber and having at its beginning a piezoceramic or integrated-optical phase modulator, a phase plate, a magnetosensitive optical fiber and a mirror; wherein the magnetically sensitive optical fibers of the first and second circuits are placed around one conductor with the measured current; the output signals of both electronic signal processing modules are connected to an electronic calibration unit, which is configured to perform periodic calibration at a specified time interval of the output signal of the first optical circuit based on the output signal of the second optical circuit to compensate for the drift of the polarimetric circuit.

2. A fiber-optic device according to claim 1, characterized in that in the first fiber-optic circuit, a polarization-maintaining coupler is installed between the linear polarizer and the Faraday rotator, the second return input of which is connected to the photodiode.

3. A fiber-optic device according to claim 1, characterized in that a second phase plate is installed between the magnetically sensitive optical fiber and the mirror of the second fiber-optic circuit.

4. A fiber-optic device according to paragraph 1, characterized in that a fiber-optic temperature sensor is connected to the third output of the coupler connected to the radiation source.

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