A current sensor and detection method based on a fiber loop structure

Abstract

The application discloses a current sensor and a current detection method based on a fiber circulation structure, and belongs to the technical field of fiber current sensing. The current sensor obtains circulating light by light intensity modulation on initial light, and then the circulating light is converted into linearly polarized light by entering a fiber circulation structure. When the linearly polarized light passes through a sensing fiber ring, the polarization plane is angularly deflected under the action of a magnetic field corresponding to a current to be measured. The linearly polarized light is then transmitted to a polarizer for polarization direction selection, and then coupled by an optical path adjustment module to obtain updated circulating light and probe light. The updated circulating light is transmitted into the fiber circulation structure to repeat the above operation to obtain updated circulating light and probe light. Finally, multiple target lights obtained through multiple cycles are photoelectrically converted and feature extracted to obtain a measurement value of the current to be measured. In the application, the fiber circulation structure makes the circulating light modulated by the initial light pass through the sensing fiber ring multiple times to interact with the magnetic field generated by the current, thereby improving the sensitivity of the current sensor.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of optical fiber current sensor, more particularly, to a kind of current sensor and current detection method based on optical fiber circulation structure. BACKGROUND

[0002] Power system is related to the economic lifeline of the country, plays a pivotal role in promoting the process of national modernization, with the continuous development of power system, the main power grid of the country has entered the era of intelligent grid, it is of great significance to ensure the safe and stable operation of power system, and the importance of current sensor as the real-time monitoring equipment of power equipment is also more and more obvious. Traditional coil type current sensor has the disadvantages of large size and heavy, poor electrical insulation performance, low response, magnetic saturation and the like, and a new type of current sensor is urgently needed to meet the needs of the development of intelligent power grid.

[0003] Optical fiber current sensor uses optical fiber as sensitive medium, has the advantages of small size, light weight, anti-electromagnetic interference, large dynamic range, high safety and the like. Its basic principle is Faraday optical rotation effect, when linearly polarized light passes through medium in magnetic field, the polarization plane of linearly polarized light will produce a certain angle of deflection, and the deflection degree is proportional to the size of magnetic field, recorded as Faraday rotation angle: θ=VNI, wherein, θ is the rotation angle of polarized light, V is the Verdet constant of sensing fiber ring, N is the number of turns of sensing fiber ring, and I is the size of current to be measured. According to the above principle, the size of current can be obtained by detecting the angle of polarization plane turned before and after linearly polarized light is affected by magnetic field. Although there are many problems in optical fiber current sensing technology, such as low current sensitivity of optical fiber material, high sensitivity to temperature, vibration and other external influences, high manufacturing cost, which greatly affects the practicality and promotion process of optical fiber current sensor.

[0004] For the above problems, the current solutions are: 1) using more turns of sensing fiber ring or special doped fiber; 2) using low birefringence fiber including annealed fiber, rotating birefringence fiber and the like to reduce the influence of environmental factors; 3) using a circulating light path structure to let the optical signal pass through the sensing fiber ring multiple times to amplify the Faraday rotation angle. The above solutions solve the problems of low sensitivity and poor stability to some extent, but there are still some problems: increasing the number of turns of sensing fiber ring will increase the volume and mass of sensing unit, and also amplify the influence of temperature and vibration on the system. And using doped special fiber and specially treated fiber is difficult to manufacture, which greatly increases the cost. In addition, the existing reflective optical fiber current sensor has high requirements for the polarization state stability of light, which makes the system sensitive to external vibration and temperature, and the interference is more, which affects the stability of the system. SUMMARY

[0005] To address the aforementioned deficiencies or improvement needs of existing technologies, this invention provides a current sensor and detection method based on an optical fiber loop structure. The purpose is to incorporate an optical fiber loop structure within the current sensor, including an optical path adjustment module, a polarizer, a sensing fiber ring, and an analyzer. Combined with modulation and demodulation techniques, the modulated loop light is transformed into a series of probe lights with gradually decreasing intensity. Photoelectric conversion of these multiple probe lights achieves high-sensitivity optical fiber current detection, thereby solving the technical problem of low sensitivity in optical fiber current sensors.

[0006] To achieve the above objectives, according to one aspect of the present invention, a current sensor based on an optical fiber loop structure is provided, comprising:

[0007] A light source, used to provide initial light;

[0008] An intensity modulator, connected to a light source, is used to modulate the intensity of the initial light to obtain circulating light;

[0009] The fiber optic loop structure includes: an optical path adjustment module, a polarizer, a sensing fiber loop, and an analyzer; the sensing fiber loop is wound around the cable under test; the loop light enters the fiber optic loop structure from the optical path adjustment module, and is converted into first linearly polarized light by the polarizer. When the first linearly polarized light passes through the sensing fiber loop, its polarization plane is deflected under the influence of the magnetic field corresponding to the current under test in the cable under test. It is then transmitted to the analyzer for polarization direction selection to obtain second linearly polarized light. The second linearly polarized light is coupled into two beams by the optical path adjustment module. The higher-power beam is the updated loop light, and the other is the probe light. The updated loop light is transmitted back into the input side of the fiber optic loop structure after the optical path adjustment module changes its optical path, and a new cycle is performed to obtain updated loop light and probe light. This cycle is performed multiple times until the intensity of the probe light output in the final cycle is lower than the threshold.

[0010] A photodetector, connected to an optical fiber loop structure, is used to convert the probe light in each loop into a photoelectric signal to obtain the target electrical signal.

[0011] The signal processor, along with the photodetector and intensity modulator, is used to extract phase features from all target electrical signals and obtain the measured value of the current to be measured based on the circulating light output by the intensity modulator.

[0012] In one embodiment, the fiber optic loop structure is a fiber optic ring loop structure, wherein the optical path adjustment module includes:

[0013] The first coupler is located on the input side of the fiber optic ring structure. It is used to receive the circulating light through the input end and send it to the polarizer through the output end, so that the circulating light is converted into first linearly polarized light, and then outputs second linearly polarized light through the sensing fiber ring and the analyzer.

[0014] The second coupler, with its input end connected to the analyzer and its output end connected to the input end of the first coupler and the photodetector, is used to couple the second linearly polarized light into a newer circulating light and a probe light. The newer circulating light is transmitted to the input side of the fiber optic loop structure and enters the first coupler for cyclic transmission, while the probe light is transmitted to the photodetector.

[0015] In one embodiment, the fiber optic loop structure is a linear fiber optic loop structure, wherein the optical path adjustment module includes:

[0016] An optical fiber circulator, located on the input side of a linear optical fiber loop structure, is used to receive circulating light and output probe light.

[0017] The first reflecting mirror is placed in the output optical path of the circulating light to reflect the circulating light;

[0018] An optical fiber coupler is set in the reflected light path of the circulating light. It has a first end, a second end and a third end. The first end receives the circulating light and couples it to the polarizer through the second end, so that the polarizer converts the circulating light into first linearly polarized light, and then outputs second linearly polarized light through the sensing fiber ring and the analyzer.

[0019] The second reflector is positioned in the output optical path of the second linearly polarized light to reflect the second linearly polarized light to the second end of the fiber coupler, so that the second linearly polarized light is coupled into a newer circulating light and a probe light. The newer circulating light is transmitted from the third end of the fiber coupler to the first reflector, reflected into the fiber coupler, and transmitted to the polarizer for subsequent circulation. The probe light is transmitted from the first end of the fiber coupler to the fiber circulator, and then from the fiber circulator to the photodetector.

[0020] In one embodiment, the transmittance of the fiber optic loop structure is expressed as: α=α0·α(θ)∈[0,1]; where α0 is the initial transmittance of the fiber optic loop structure when no current is applied, and α(θ) is the transmittance corresponding to the polarization plane change angle θ caused by the polarizer.

[0021] In one embodiment, the light intensity of the probe light received by the photodetector for the nth cycle is expressed as: Where I0 is the output light intensity of light source 1, γ≤1 is the modulation depth of the intensity modulator, and ω m ω is the modulation angular frequency of the intensity modulator; L is the length traveled by the cyclic light as it passes through the fiber optic loop once; n is the number of loops; and v is the propagation speed of the first linearly polarized light in the sensing fiber optic loop. α represents the phase of the probe light in the first cycle, α represents the transmittance of the optical fiber loop structure in a single pass, and t1 represents the propagation time of the loop light in the optical fiber loop structure.

[0022] In one embodiment, the light intensity of the circulating light output by the intensity modulator is expressed as:

[0023] I in =I0[1+γsin(ω) m t0)]; where I0 is the output light intensity of light source 1, γ≤1 is the modulation depth, ω m The modulation angular frequency is t0, and the propagation time of the cyclic light within the intensity modulator is t0.

[0024] In one embodiment, the signal processor is further configured to extract the phase of the superposition of all target electrical signals and demodulate the phase change to obtain the measured value of the current to be measured.

[0025] The phase change is expressed as: α represents the transmittance of the fiber optic loop structure; β characterizes the inherent phase shift of the fiber optic loop structure.

[0026] The present invention also provides a current detection method, applied to a current sensor based on an optical fiber loop structure, comprising:

[0027] S1: Modulate the intensity of the initial light to obtain cyclic light;

[0028] S2: Convert the circulating light into the first linearly polarized light. The first linearly polarized light undergoes a deflection of its polarization plane under the influence of the magnetic field corresponding to the current to be measured. Then, the second linearly polarized light is obtained by selecting the polarization direction. The second linearly polarized light is then coupled into two beams. The beam with higher power is the updated circulating light, and the other beam is the probe light.

[0029] S3: Execute S2 on the updated loop light to obtain the updated loop light and probe light corresponding to this loop; then execute S2 on the updated loop light of this loop again, repeating multiple times until the light intensity of the probe light output in the final loop is lower than the threshold.

[0030] S4: The probe light output in each cycle is converted into a target electrical signal by photoelectric conversion;

[0031] S4: Extract the phase features of all target electrical signals to obtain the measured value of the current to be measured.

[0032] In summary, compared with the prior art, the above-described technical solutions conceived by this invention can achieve the following beneficial effects:

[0033] (1) The current sensor provided by this invention modulates the intensity of the initial light to obtain circulating light. The circulating light enters the fiber optic loop structure from the optical path adjustment module, is converted into linearly polarized light by the polarizer, and undergoes an angle deflection of the polarization plane under the action of the magnetic field corresponding to the current to be measured in the cable under test when passing through the sensing fiber ring. It is then transmitted to the analyzer for polarization direction selection, and coupled through the optical path adjustment module to obtain updated circulating light and probe light. The updated circulating light is transmitted into the input side of the fiber optic loop structure to perform a new round of looping to obtain updated circulating light and probe light. Finally, multiple target lights obtained from multiple loops are photoelectrically converted and feature extracted to obtain the measured value of the current to be measured. Unlike the existing fiber optic loop structure based on time-domain pulse detection, the fiber optic loop structure of this invention combines modulation and demodulation technology to pass the circulating light modulated by the initial light through the sensing fiber ring multiple times to interact with the magnetic field generated by the current to be measured, amplifying the length of the interaction between the circulating light and the magnetic field, thereby improving the sensitivity of the current sensor. In addition, this invention has a simple structure, fewer components, less interference, and strong system stability.

[0034] (2) The fiber optic loop structure of this invention utilizes two couplers as optical path adjustment modules to adjust the optical path of the looping light output in each cycle, so that most of the light enters the input side of the fiber optic loop structure for a new cycle, and a small portion of the output light is used for photoelectric detection. The structure is simple, requires no complex polarization control devices, and is easy to integrate;

[0035] (3) The fiber optic linear loop structure of this invention utilizes a fiber optic circulator, a fiber optic coupler, and two mirrors to adjust the optical path of the looping light output in each cycle, allowing most of the light to enter the input side of the fiber optic linear loop structure for a new cycle, and a small portion of the output light to be used for photoelectric detection. The structure is simple, does not require complex polarization control devices, and is easy to integrate.

[0036] (4) The signal processor in this application extracts the phase change amount through the phase demodulation algorithm to obtain the current value corresponding to the initial light, which reduces the influence of light source fluctuation and has high stability; it can also realize the measurement of extremely weak (microampere level) current, and achieves higher measurement accuracy compared with light intensity demodulation algorithm and differential demodulation algorithm.

[0037] (5) The devices in this application can be connected using single-mode optical fiber, which is low-cost and easy to maintain. By adding a delay fiber between the intensity modulator and the optical fiber loop structure, the intensity modulator position can be flexibly set on the wire where the current to be measured is located, which can realize remote current detection and support various current measurement scenarios. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the high-precision current sensor based on an optical fiber ring loop structure in an embodiment of the present invention.

[0039] Figure 2 This is a schematic diagram of the high-precision current sensor based on a fiber optic linear loop structure in an embodiment of the present invention.

[0040] Figure 3 This is a schematic diagram illustrating the effect of the optical fiber loop structure on the change of the polarization direction of the looping light in an embodiment of the present invention. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0042] Example 1

[0043] This embodiment provides a current transmitter based on a fiber optic loop structure, comprising: a power supply, an intensity modulator, a fiber optic loop structure, a photodetector, and a signal processor; a sensing fiber optic loop is wound around the cable under test; wherein, the intensity modulator is used to modulate the intensity of the initial light provided by the power supply to obtain looped light, thereby improving the efficiency of the initial light and facilitating the increase of subsequent loops; the fiber optic loop structure includes: an optical path adjustment module, a polarizer, a sensing fiber optic loop, and a polarization detector; the looped light enters the fiber optic loop structure from the optical path adjustment module, is converted into first linearly polarized light by the polarizer, and the first linearly polarized light is polarized under the influence of the magnetic field corresponding to the current under test when passing through the sensing fiber optic loop. The vibrating surface undergoes an angular deflection, and the light is then transmitted to an analyzer for polarization direction selection to obtain second linearly polarized light. This second linearly polarized light is coupled through an optical path adjustment module to obtain updated circulating light and probe light. The updated circulating light is then adjusted again by the optical path adjustment module and transmitted back to the input side of the fiber optic loop structure, performing a new cycle to obtain updated circulating light and probe light. This cycle is repeated multiple times until the intensity of the probe light output in the final cycle is below a threshold. A photodetector is used to perform photoelectric conversion on the probe light from each cycle to obtain the target electrical signal. A signal processor is used to extract the phase features of all target electrical signals to obtain the measured value of the current to be measured. The threshold is a performance parameter set based on the minimum intensity of the target light that the photodetector can recognize; its specific value is not limited.

[0044] Example 2

[0045] like Figure 1As shown, this embodiment provides a high-precision current sensor based on an optical fiber loop structure 3, including: a light source 1, an intensity modulator 2, a first coupler 311a, a second coupler 312a, a polarizer 32, an analyzer 34, a sensing fiber loop 33, a photodetector 4, and a signal processor 5. The light source 1 is connected to one port of the first coupler 311a via the intensity modulator 2. The first coupler 311a and the second coupler 312a are directly connected. One port of the second coupler 312a is connected to the first coupler 311a via the analyzer 34, the sensing fiber loop 33, and the polarizer 32. The second coupler 312a is connected to the photodetector 4. The signal processor 5 is connected to the intensity modulator 2 and the photodetector 4. In this embodiment, the optical path adjustment module 31 (not marked in the figure) in the optical fiber loop structure 3 includes the first coupler 311a and the second coupler 312a. The dashed box in the figure represents the optical fiber loop structure 3.

[0046] Example 3

[0047] like Figure 2 As shown, this embodiment provides a current sensor based on a linear fiber optic loop structure 3, including: a light source 1, an intensity modulator 2, a fiber optic circulator 311b, a fiber optic coupler 313b, a polarizer 32, an analyzer 34, a sensing fiber optic loop 33, a first reflector 312b (fiber optic reflector), a photodetector 4, and a signal processor 5; the light source 1 is connected to the input port of the fiber optic circulator 311b via the intensity modulator 2, the fiber optic circulator 311b and the fiber optic coupler 313b are directly connected, one port of the fiber optic coupler 313b is connected to the fiber optic coupler 313b via the polarizer 32, the sensing fiber optic loop 33, the analyzer 34 and the second reflector 314b in sequence, the other port of the fiber optic coupler 313b is connected to the first reflector 312b, the output port of the fiber optic circulator 311b is connected to the photodetector 4, and the signal processor 5 is connected to the intensity modulator 2 and the photodetector 4. In this embodiment, the optical path adjustment module 31 (not marked in the figure) in the optical fiber linear circulation structure 3 includes an optical fiber circulator 311b, a first reflector 312b, an optical fiber coupler 313b, and a second reflector 314b. The area within the dashed box in the figure represents the optical fiber linear circulation structure 3.

[0048] Example 4

[0049] The initial light emitted by light source 1 enters intensity modulator 2 through the connecting optical fiber. After being modulated by intensity modulator 2, it can be expressed as: I in =I0[1+γsin(ω) m t0)]; where I0 is the output light intensity of light source 1, γ≤1 is the modulation depth, ω mFor the modulation angular frequency, t0 is the time it takes for the cyclic light to be output from the intensity modulator. In one embodiment, the initial light emitted by the light source 1 is a broadband continuous light signal, or it can be low-coherence continuous light. This invention restricts the initial light.

[0050] Example 5

[0051] The circulating light cycles multiple times within the sensing structure. In each cycle, a portion of the target light enters photodetector 4, which receives a series of modulated optical signals whose intensity continuously decreases. The optical signal entering the detector after n cycles can be represented as: Where L is the length traveled by the optical signal through one optical fiber loop structure 3, n is the number of times the optical signal propagates through the sensing optical fiber loop 33, and v is the propagation speed of the optical signal in the sensing optical fiber loop 33. α is the initial phase accumulated when the optical signal first arrives at the detector, α is the transmittance of the fiber optic loop structure 3 during a single pass, and t1 is the transmission time of the optical signal in the fiber optic loop structure.

[0052] Example 6

[0053] like Figure 3 As shown, the optical signal passes through polarizer 32 and sensing fiber loop 33 in each cycle. The Faraday effect caused by the current under test will cause the polarization plane of the light to deflect by an angle θ. Then, under the polarization analysis of analyzer 34, according to Malus's law, the light intensity will change. Therefore, the transmittance of fiber loop structure 3 can be further expressed as: α=α0·α I =α0·α(θ)∈[0,1]; where α0 is the initial transmittance of the fiber loop structure 3 when no current is applied, and α(θ) is the transmittance introduced by the Faraday rotation angle generated by the current. Then the light finally received by the detector can be expressed as the sum of n loop signals: Through mathematical derivation, the above formula can be written as: Where k is a parameter related to the fiber loop structure 3, is the modulation depth attenuation factor, and b is a coefficient related to the light intensity of light source 1, called the light intensity attenuation factor. Defined as the inherent phase shift of fiber optic loop structure 3.

[0054] Example 7

[0055] By using relevant detection algorithms and extracting the phase information of the output signal by a signal processor, we can obtain: in, It is the initial phase of the system. The phase change is introduced by the current. By measuring the change in the output phase through a lock-in amplifier, the magnitude of the current to be measured can be further demodulated.

[0056] Example 8

[0057] This embodiment adds a delay fiber between the intensity modulator and the fiber optic loop structure. The intensity modulator position can be flexibly set as long as the fiber optic loop structure is on the conductor where the current to be measured is located, enabling remote current detection and supporting various current measurement scenarios.

[0058] Example 9

[0059] This invention provides a current detection method applied to the aforementioned current sensor based on the fiber optic loop structure 3, comprising:

[0060] S1: The intensity of the initial light is sinusoidally modulated to obtain the circulating light;

[0061] S2: Convert the circulating light into the first linearly polarized light. The first linearly polarized light undergoes a deflection of its polarization plane under the influence of the magnetic field corresponding to the current to be measured. Then, the second linearly polarized light is obtained by selecting the polarization direction. The second linearly polarized light is then coupled into two beams. The beam with higher power is the updated circulating light, and the other beam is the probe light.

[0062] S3: Execute S2 on the updated loop light to obtain the updated loop light and probe light corresponding to this loop; then execute S2 on the updated loop light of this loop again, repeating multiple times until the light intensity of the probe light output in the final loop is lower than the threshold.

[0063] S4: The probe light output in each cycle is converted into a target electrical signal by photoelectric conversion;

[0064] S4: Extract phase features from all target electrical signals and obtain the measured value of the current to be measured based on the initial circulating light.

[0065] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A current sensor based on an optical fiber loop structure, characterized in that, include: A light source, used to provide initial light; An intensity modulator, connected to a light source, is used to sinusoidally modulate the intensity of the initial light to obtain circulating light. The fiber optic loop structure includes: an optical path adjustment module, a polarizer, a sensing fiber loop, and an analyzer; the sensing fiber loop is wound around the cable under test; the loop light enters the fiber optic loop structure from the optical path adjustment module, and is converted into first linearly polarized light by the polarizer. When the first linearly polarized light passes through the sensing fiber loop, its polarization plane is deflected under the influence of the magnetic field corresponding to the current under test in the cable under test. It is then transmitted to the analyzer for polarization direction selection to obtain second linearly polarized light. The second linearly polarized light is coupled into two beams by the optical path adjustment module. The higher-power beam is the updated loop light, and the other is the probe light. The updated loop light is transmitted back into the input side of the fiber optic loop structure after the optical path adjustment module changes its optical path, and a new cycle is performed to obtain updated loop light and probe light. This cycle is performed multiple times until the intensity of the probe light output in the final cycle is lower than the threshold. A photodetector, connected to an optical fiber loop structure, is used to convert the probe light in each loop into a photoelectric signal to obtain the target electrical signal. The signal processor, along with the photodetector and intensity modulator, is used to extract the phase features of all target electrical signals and obtain the measured value of the current to be measured based on the circulating light output by the intensity modulator. In each cycle, the optical signal passes through a polarizer and then through the sensing fiber loop. The Faraday effect caused by the current under test will cause the polarization plane of the light to change by an angle of θ. After deflection, the light intensity will change under the polarization analysis of the analyzer. Therefore, the transmittance of the fiber optic loop structure is expressed as: ; It is the initial transmittance of the fiber optic loop structure when no current is applied. The transmittance is introduced by the Faraday rotation angle generated by the current; the light ultimately received by the photodetector is expressed as... Accumulation of signals in each cycle , The output light intensity of the light source. The modulation depth of the intensity modulator. The modulation angular frequency of the intensity modulator; This is the length that the circulating light travels when passing through the fiber optic loop structure once. The number of loops. Let be the propagation speed of the first linearly polarized light in the sensing fiber optic loop. The phase of the probe light in the first loop. The transmittance through a single fiber optic loop structure. Let be the propagation time of the cyclic light in the fiber optic cyclic structure; the derivation is as follows: ; b is the modulation depth attenuation factor, and b is the light intensity attenuation factor. This is due to the inherent phase shift of the fiber optic loop structure. The phase information of the output signal is extracted by a signal processor through relevant detection algorithms. ; The phase change is introduced by the current; the change in output phase is measured by a lock-in amplifier, and the magnitude of the current to be measured is obtained by further demodulation.

2. The current sensor based on an optical fiber loop structure as described in claim 1, characterized in that, The fiber optic loop structure is a fiber optic ring loop structure, in which the optical path adjustment module includes: The first coupler is located on the input side of the fiber optic ring structure. It is used to receive the circulating light through the input end and send it to the polarizer through the output end, so that the circulating light is converted into first linearly polarized light, and then outputs second linearly polarized light through the sensing fiber ring and the analyzer. The second coupler, with its input end connected to the analyzer and its output end connected to the input end of the first coupler and the photodetector, is used to couple the second linearly polarized light into a newer circulating light and a probe light. The newer circulating light is transmitted to the input side of the fiber optic loop structure and enters the first coupler for cyclic transmission, while the probe light is transmitted to the photodetector.

3. The current sensor based on an optical fiber loop structure as described in claim 1, characterized in that, The fiber optic loop structure is a linear fiber optic loop structure, and the optical path adjustment module includes: An optical fiber circulator, located on the input side of a linear optical fiber loop structure, is used to receive circulating light and output probe light. The first reflecting mirror is placed in the output optical path of the circulating light to reflect the circulating light; An optical fiber coupler is set in the reflected light path of the circulating light. It has a first end, a second end and a third end. The first end receives the circulating light and couples it to the polarizer through the second end, so that the polarizer converts the circulating light into first linearly polarized light, and then outputs second linearly polarized light through the sensing fiber ring and the analyzer. The second reflector is positioned in the output optical path of the second linearly polarized light to reflect the second linearly polarized light to the second end of the fiber coupler, so that the second linearly polarized light is coupled into a newer circulating light and a probe light. The newer circulating light is transmitted from the third end of the fiber coupler to the first reflector, reflected into the fiber coupler, and transmitted to the polarizer for subsequent circulation. The probe light is transmitted from the first end of the fiber coupler to the fiber circulator, and then from the fiber circulator to the photodetector.

4. The current sensor based on an optical fiber loop structure as described in claim 1, characterized in that, The light intensity of the output circulating light from the intensity modulator is expressed as: ; This is the propagation time of the circulating light within the intensity modulator.

5. The current sensor based on an optical fiber loop structure as described in any one of claims 1-4, characterized in that, Also includes: An extension fiber is placed between the intensity modulator and the fiber optic loop structure to extend the transmission path of the circulating light between the intensity modulator and the fiber optic loop structure.

6. A current detection method, characterized in that, The current sensor based on the fiber optic loop structure according to any one of claims 1-5 comprises: S1: The intensity of the initial light is sinusoidally modulated to obtain the circulating light; S2: Convert the circulating light into the first linearly polarized light. The first linearly polarized light undergoes a deflection of its polarization plane under the influence of the magnetic field corresponding to the current to be measured. Then, the second linearly polarized light is obtained by selecting the polarization direction. The second linearly polarized light is then coupled into two beams. The beam with higher power is the updated circulating light, and the other beam is the probe light. S3: Execute S2 on the updated loop light to obtain the updated loop light and probe light corresponding to this loop; execute S2 on the updated loop light of this loop, repeating multiple times until the light intensity of the probe light output in the final loop is lower than the threshold. S4: The probe light output in each cycle is converted into a target electrical signal by photoelectric conversion; S4: Extract phase features from all target electrical signals and obtain the measured value of the current to be measured based on the initial circulating light.

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