A fiber optic current transformer based on optical path hybrid integration

Abstract

The embodiment of the present disclosure provides a fiber optic current transformer based on optical path hybrid integration, including: an integrated optical transceiver assembly, a phase modulator, a polarization-maintaining coupler, a polarization-maintaining delay fiber, a λ / 4 wave plate, a sensor head, and a signal processing unit respectively connected to the integrated optical transceiver assembly and the phase modulator; wherein the sensor head includes: a sensing optical fiber and a fiber optic reflector, and the sensing optical fiber is wound around the energized conductor to be measured. The optical transceiver assembly and the optical modulation assembly of the present disclosure integrate the receiving, modulating and transmitting functions of optical signals, reducing the size of the device; the fiber optic current transformer device adopts an all-optical fiber connection to avoid electromagnetic interference; the design scheme ensures the stability of the received and transmitted signals in the optical detection, optical transmission and photoelectric conversion functions with a lightweight and small structure, and is highly adapted to the subsequent modules of the fiber optic current sensor.

Description

Technical Field

[0001] The present disclosure relates to the technical field of current transformers, and in particular to an optical fiber current transformer based on optical path hybrid integration. Background Art

[0002] Current transformer (CT) is an important measuring device in the power system, widely used in relay protection, current measurement, and power system analysis. At present, the standard of the domestic main power grid transmission line is 500KV, and even ultra-high voltage 1200V is used for power transmission. With the substantial increase in voltage levels and the continuous increase in transmission power, the traditional electromagnetic effect current transformer has gradually exposed its limitations due to its working principle, such as: potential risk of sudden failure, large size, high cost, extremely bulky equipment, poor response characteristics to high-frequency signals, the high voltage generated will cause harm to the distribution equipment and even endanger personal safety, and easy to cause interference.

[0003] With the improvement of modern optical material processing technology, the continuous progress of integrated optical technology and the increasing application of computers in power systems, there is a huge space for the development of optical current transformers (OCT). Existing optical current transformers still have defects such as large size, insufficient stability of signal reception and transmission, and low compatibility with subsequent modules of optical current sensors.

[0004] Therefore, how to design a lightweight and small-volume structure to improve the stability of signal transmission and the adaptability of the fiber optic current sensor is a key issue. Summary of the invention

[0005] The present disclosure provides a fiber optic current transformer based on optical path hybrid integration, which solves the technical problems of large size of traditional fiber optic current transformers, insufficient stability of signal reception and transmission, and low compatibility with subsequent modules of fiber optic current sensors. The optical transceiver assembly and optical modulation assembly of the present disclosure integrate the functions of receiving, modulating and sending optical signals, reducing the size of the device; the fiber optic current transformer device adopts all-optical fiber connection to avoid electromagnetic interference; the design scheme ensures the stability of receiving and transmitting signals in optical detection, optical transmission and photoelectric conversion functions with a lightweight and small structure, and is highly compatible with subsequent modules of fiber optic current sensors.

[0006] According to a first aspect of the present disclosure, a fiber-optic current transformer based on optical path hybrid integration is provided, comprising: an integrated optical transceiver assembly, a phase modulator, a polarization-maintaining coupler, a polarization-maintaining delay optical fiber, a λ / 4 wave plate, a sensor head, and a signal processing unit respectively connected to the integrated optical transceiver assembly and the phase modulator; wherein the sensor head comprises: a sensing optical fiber and a fiber-optic reflector, and the sensing optical fiber is wound around a conductor to be tested;

[0007] A part of the light beam emitted by the integrated optical transceiver assembly is polarized by the phase modulator to form linear polarized light, and is decomposed into X-axis polarized light and Y-axis polarized light by 45° deflection. The X-axis polarized light and the Y-axis polarized light are respectively transmitted into the polarization-maintaining delay fiber, the λ / 4 wave plate and the sensing fiber in an orthogonal mode after passing through the polarization-maintaining coupler, and a phase difference is generated in the sensing fiber under the action of the Faraday magneto-optical effect. Then, after being reflected by the optical fiber reflector, the two light signals carrying the phase information return to the integrated optical transceiver assembly along the original path, interfere with another part of the light beam of the integrated optical transceiver assembly, and are coupled into the photodetector in the integrated optical transceiver assembly and linearly converted into a light intensity voltage signal;

[0008] The signal processing unit is used to control the phase modulator to realize phase modulation, receive the light intensity voltage signal output by the integrated optical transceiver component, and obtain the current value in the wire by measuring two coherent light beams.

[0009] Furthermore, the sequentially connected integrated optical transceiver assembly, phase modulator, polarization-maintaining coupler, polarization-maintaining delay fiber, λ / 4 wave plate, and sensor head include:

[0010] The pigtail of the integrated optical transceiver assembly is fused with the input fiber of the phase modulator;

[0011] Two pigtails of the phase modulator are connected to one end of the polarization-maintaining coupler;

[0012] The other end of the polarization-maintaining coupler is connected to one end of the polarization-maintaining delay optical cable;

[0013] The other end of the polarization-maintaining delay optical cable is connected to the λ / 4 wave plate;

[0014] The other end of the λ / 4 wave plate is fused to the sensing optical fiber of the sensing head.

[0015] Furthermore, the light intensity voltage signal output terminal of the integrated optical transceiver assembly is connected to a signal processing unit, and the signal processing unit outputs a superposition signal of a square wave and a step wave and transmits it back to the phase modulator;

[0016] The phase difference of light in the phase modulator satisfies sin4(V·N·I)≈4VNI, and 4V·N·I≤0.5°~1°, V represents the Verdet constant, N represents the number of optical fiber turns wrapped around the wire, and I represents the current value in the wire.

[0017] Furthermore, the integrated optical transceiver assembly (1) comprises a light source, a circulator and a photodetector.

[0018] Further, wherein the circulator comprises: a fiber collimator, a polarization beam splitter, a 90° Faraday rotator, a converging lens and a collimator for collimating the light beam output by the light source;

[0019] The optical path of the integrated optical transceiver assembly adopts a parallel light structure as a whole, and the optical transceiver path is separated by changing the polarization state. Of the collimated P polarized light emitted from the optical fiber collimator, a part of the light passes through the polarization beam splitter and the 90° Faraday rotator and is received by the collimator; the other part of the light is rotated 90° in polarization direction through the 90° Faraday rotator to become S light, which is folded 90° by the polarization beam splitter and hits the photosensitive surface of the photodetector through the converging lens.

[0020] Furthermore, the light source is a super luminescent diode (SLD).

[0021] Furthermore, the phase modulator is a Y-waveguide, which is used to polarize, split and phase modulate the optical signal output by the light source.

[0022] Furthermore, the λ / 4 wave plate is a full optical wave plate for converting linear polarization into circular polarization.

[0023] Furthermore, the sensing optical fiber of the sensor head is a single-mode optical fiber or a circular birefringence optical fiber or a low birefringence optical fiber.

[0024] Furthermore, the connection between the two ends of the polarization-maintaining delay optical fiber and the polarization-maintaining coupler and the λ / 4 wave plate is by jumper connection or fusion splicing.

[0025] Compared with the prior art, the above one or more technical solutions disclosed in the present invention have at least the following beneficial effects:

[0026] The present invention adopts a hybrid integrated optical circuit optical current transformer solution, in which the optical transceiver and optical modulation component integrates the receiving, modulating and sending functions of optical signals, reducing the size of the device; the device adopts all-optical fiber connection to avoid electromagnetic interference. The design scheme ensures the stability of receiving and transmitting signals in optical detection, optical transmission and photoelectric conversion functions with a lightweight and small structure, and is highly adapted to the subsequent modules of the optical fiber current sensor.

[0027] It should be understood that the contents described in the summary of the invention are not intended to limit the key or important features of the embodiments of the present disclosure, nor are they intended to limit the scope of the present disclosure. Other features of the present disclosure will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] 1. Integrated optical transceiver assembly; 11. Light source; 12. Circulator; 121. Fiber collimator; 122. Polarization beam splitter (PBS); 123. 90° Faraday rotator; 124. Converging lens; 125. Collimator; 13. Photodetector; 2. Phase modulator; 3. Polarization-maintaining coupler; 4. Polarization-maintaining delay fiber; 5. λ / 4 wave plate; 6. Sensor head; 61. Sensing fiber; 62. Fiber reflector; 7. Signal processing unit.

[0029] The above and other features, advantages and aspects of the embodiments of the present disclosure will become more apparent with reference to the following detailed description in conjunction with the accompanying drawings. The accompanying drawings are used to better understand the present solution and do not constitute a limitation of the present disclosure. In the accompanying drawings, the same or similar reference numerals represent the same or similar elements, among which:

[0030] Figure 1 A schematic diagram of a fiber optic current transformer based on optical path hybrid integration according to an embodiment of the present disclosure is shown;

[0031] Figure 2 A schematic diagram of a circulator in an integrated optical transceiver assembly of an optical fiber current transformer based on optical path hybrid integration according to an embodiment of the present disclosure is shown. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solution and advantages of the embodiments of the present disclosure clearer, the technical solution in the embodiments of the present disclosure will be clearly and completely described below in conjunction with the drawings in the embodiments of the present disclosure. Obviously, the described embodiments are part of the embodiments of the present disclosure, not all of the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present disclosure.

[0033] In addition, the term "and / or" in this article is only a description of the association relationship between the associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0034] In the present disclosure, the essence of the fiber optic current transformer with an all-fiber structure is measured by the principle of interference of two beams of light; the magnetic field is generated in the sensing fiber due to the transmission current. When a beam of circularly polarized light passes through the sensing fiber, the phase of the circularly polarized light changes due to the Faraday effect. By measuring the two coherent beams of light, the current value in the conductor can be indirectly measured; and the present disclosure reduces the size of the device by adopting a hybrid integrated optical circuit fiber optic current transformer solution; the device adopts an all-fiber connection to avoid electromagnetic interference. The design scheme ensures the stability of receiving and transmitting signals in optical detection, optical transmission and photoelectric conversion functions with a lightweight and small structure, and is highly adapted to the subsequent modules of the fiber optic current sensor.

[0035] Figure 1 FIG. 1 is a schematic diagram of an optical fiber current transformer based on optical path hybrid integration according to an embodiment of the present disclosure. Figure 1 As shown, an optical fiber current transformer based on optical path hybrid integration includes: an integrated optical transceiver assembly 1, a phase modulator 2, a polarization-maintaining coupler 3, a polarization-maintaining delay optical fiber 4, a λ / 4 wave plate 5, a sensor head 6, and a signal processing unit 7 respectively connected to the integrated optical transceiver assembly 1 and the phase modulator 2; wherein the sensor head 6 includes: a sensing optical fiber 61 and an optical fiber reflector 62 (including an optical fiber reflective film), and the sensing optical fiber 61 is wound around the current-carrying conductor to be measured;

[0036] A portion of the light beam emitted by the integrated optical transceiver assembly 1 is polarized by the phase modulator 2 to form linear polarized light, and is decomposed into X-axis polarized light and Y-axis polarized light by 45° deflection, and then phase biased. The X-axis polarized light and the Y-axis polarized light are respectively transmitted through the polarization-maintaining coupler 3 in an orthogonal mode into the polarization-maintaining delay fiber 4, the λ / 4 wave plate 5 and the sensing fiber 61, wherein the X-axis polarized light and the Y-axis polarized light are respectively transformed into right-handed circularly polarized light and left-handed circularly polarized light after passing through the λ / 4 wave plate 5 and enter the sensing fiber 61, and are acted on by the Faraday magneto-optical effect in the sensing fiber 61 to generate a phase difference Δθ=2V·N·I, and then, after being reflected by the optical fiber reflective film of the optical fiber reflector 62, the right-handed circularly polarized light is transformed into left-handed circularly polarized light, and the left-handed circularly polarized light is transformed into right-handed circularly polarized light, and the two light signals carrying phase information return along the original path, and the two transformed light beams are again acted on by the Faraday magneto-optical effect through the sensing fiber 61 to generate a doubled phase difference After the conversion, the right-handed circularly polarized light and the left-handed circularly polarized light pass through the λ / 4 wave plate 5 again, and then are restored to the X-axis polarized light and the Y-axis polarized light, and are transmitted to the integrated optical transceiver assembly 1 to interfere with another part of the light beam of the integrated optical transceiver assembly 1. Finally, the light carrying the phase information is coupled into the photodetector in the integrated optical transceiver assembly 1 and is linearly converted into a light intensity voltage signal.

[0037] The signal processing unit 7 is used to control the phase modulator 2 to achieve phase modulation, and to receive the light intensity voltage signal output by the integrated optical transceiver component 1 and obtain the current value in the wire by measuring two coherent light beams.

[0038] According to this embodiment, by measuring two coherent beams of light, the current value in the conductor can be indirectly measured; and by adopting a hybrid integrated optical circuit optical current transformer solution, the device size is reduced; the optical current transformer device adopts an all-optical fiber connection to avoid electromagnetic interference. This design scheme ensures the stability of receiving and transmitting signals in optical detection, optical transmission and photoelectric conversion functions with a lightweight and small structure, and is highly adapted to the subsequent modules of the optical fiber current sensor.

[0039] Furthermore, the sequentially connected integrated optical transceiver assembly 1, phase modulator 2, polarization-maintaining coupler 3, polarization-maintaining delay fiber 4, λ / 4 wave plate 5, and sensor head 6 include:

[0040] The pigtail of the integrated optical transceiver assembly 1 is fused with the input fiber of the phase modulator 2;

[0041] The two pigtails of the phase modulator 2 are connected to one end of the polarization-maintaining coupler 3;

[0042] The other end of the polarization-maintaining coupler 3 is connected to one end of the polarization-maintaining delay optical cable 4;

[0043] The other end of the polarization-maintaining delay optical cable 4 is connected to the λ / 4 wave plate 5;

[0044] The other end of the λ / 4 wave plate 5 is fused to the sensing optical fiber 61 of the sensor head 6 .

[0045] Furthermore, the light intensity voltage signal output end of the integrated optical transceiver component 1 is connected to the signal processing unit 7, and the signal processing unit 7 outputs the superposition signal of the square wave and the step wave and then transmits it back to the phase modulator 2; optionally, the phase modulator 2 uses a lithium niobate multifunctional integrated optical device.

[0046] The phase difference of light in the phase modulator 2 satisfies sin4(V·N·I)≈4VNI, and 4V·N·I≤0.5°~1°, V represents the Verdet constant, N represents the number of turns of optical fiber wrapped around the wire, and I represents the current value in the wire.

[0047] Further, the integrated optical transceiver assembly 1 includes a light source 11, a circulator 12 and a photodetector 13. Preferably, the light source 11 adopts a superluminescent diode (SLD), which is a semiconductor light source between a laser diode (LD) and a light emitting diode (LED) and has a high output power to improve the accuracy and sensitivity of the optical fiber current transformer in testing the current size; the low coherence of the SLD, that is, the short coherence length, can avoid the influence of back reflection and scattering in the system.

[0048] Furthermore, Figure 2 A schematic diagram of a circulator in an integrated optical transceiver assembly of an optical fiber current transformer based on optical path hybrid integration according to an embodiment of the present disclosure is shown. Figure 2 As shown, the circulator 12 includes: a fiber collimator 121 for collimating the light beam output by the light source 11, a polarization beam splitter (PBS) 122, a 90° Faraday rotator 123, a converging lens 124 and a collimator 125;

[0049] The optical path of the integrated optical transceiver assembly 1 adopts a parallel light structure as a whole, and the optical transceiver path is separated by changing the polarization state. Of the collimated P polarized light emitted from the optical fiber collimator 121, a part of the light passes through the polarization beam splitter 122 and the 90° Faraday rotator 123 and is received by the collimator 125; the other part of the light is rotated 90° in polarization direction through the 90° Faraday rotator 123 to become S light, which is folded 90° by the polarization beam splitter (PBS) 122 and hits the photosensitive surface of the photodetector 13 through the converging lens 124.

[0050] The optical path of the integrated optical transceiver assembly 1 adopts a parallel light structure as a whole, and the optical transceiver path is separated by changing the polarization state. Of the collimated P polarized light emitted from the optical fiber collimator 121, a part of the light is received by the collimator through the polarization beam splitter (PBS) 122 and the rotator 123; the other part of the light is rotated 90° in polarization direction through the 90° Faraday rotator 123 to become S light, which is folded 90° by the polarization beam splitter (PBS) 122 and hits the photosensitive surface of the photodetector 13 through the converging lens 124.

[0051] In this embodiment, the circulator 12 receives the optical signal from the light source 11 and divides an input light beam into two or more ports for output, and the optical signal passing through optical devices such as the λ / 4 wave plate 5 and the phase modulator is linearly converted into a light intensity voltage signal by the integrated optical transceiver component 1 for output.

[0052] Furthermore, the phase modulator 2 is a Y-waveguide, which is used to polarize, split and phase modulate the optical signal output by the light source 11.

[0053] In this embodiment, the phase modulator 2 integrates the functions of polarizer and phase modulation. Since the polarization characteristics of the light working in the fiber optic current transformer are most ideally polarized light, the light from the light source after passing through the polarizer is required to be ideal linearly polarized light. However, the polarization degree of the light emitted by the integrated optical transceiver assembly generally cannot meet the requirements. In order to obtain a higher polarization degree, a polarizer should be used as a polarizer to produce linearly polarized light. This system uses an integrated optical waveguide polarizer as a polarizer; the function of phase modulation is that in the detection system, the circuit can realize square wave modulation and superimpose non-reciprocal phase difference on the phase of the light wave. This modulation method has a large bandwidth and low modulation voltage, and can also realize dynamic closed-loop detection.

[0054] Furthermore, the λ / 4 wave plate 5 is a full optical wave plate for converting linear polarization into circular polarization.

[0055] In this embodiment, the λ / 4 wave plate 5 converts linear polarization into circular polarization; this is achieved by causing two mutually perpendicular linear polarizations of the polarized light to produce a relative λ / 4 wave plate 5 phase delay; an all-fiber wave plate is used, which is made by cutting an appropriate length of polarization-maintaining fiber and fusing two sections of polarization-maintaining fiber at a suitable axis angle.

[0056] Furthermore, the sensing optical fiber 61 of the sensing head 6 is a single-mode optical fiber or a circular birefringence optical fiber or a low birefringence optical fiber.

[0057] Furthermore, the connection between the two ends of the polarization-maintaining delay optical fiber 4 and the polarization-maintaining coupler 3 and the λ / 4 wave plate 5 is performed by jumper connection or fusion splicing.

[0058] Optionally, in some embodiments, the polarization-maintaining delay fiber 4 uses a single-mode fiber whose polarization state remains unchanged along the length of the fiber, achieving an intrinsic birefringence that is much greater than the internal and external perturbation birefringence used, thereby making the polarization state of the transmitted light insensitive to external disturbances, thereby maintaining the stability of the polarization state.

[0059] It should be understood that the various forms of processes shown above can be used to reorder, add or delete steps. For example, the steps recorded in this disclosure can be executed in parallel, sequentially or in different orders, as long as the desired results of the technical solutions disclosed in this disclosure can be achieved, and this document does not limit this.

[0060] The above specific implementations do not constitute a limitation on the protection scope of the present disclosure. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present disclosure shall be included in the protection scope of the present disclosure.

Claims

1. An optical fiber current transformer based on optical path hybrid integration, characterized in that it includes: An integrated optical transceiver assembly (1), a phase modulator (2), a polarization-maintaining coupler (3), a polarization-maintaining delay optical fiber (4), a λ / 4 wave plate (5), a sensor head (6), and a signal processing unit (7) respectively connected to the integrated optical transceiver assembly (1) and the phase modulator (2); wherein the sensor head (6) comprises a sensing optical fiber (61) and an optical fiber reflector (62), and the sensing optical fiber (61) is wound around a conductor to be tested; A portion of the light beam emitted by the integrated optical transceiver assembly (1) is polarized by the phase modulator (2) to form linear polarized light, and is decomposed into X-axis polarized light and Y-axis polarized light after being deflected by 45 degrees. The X-axis polarized light and the Y-axis polarized light are respectively transmitted through the polarization-maintaining coupler (3) in sequence in an orthogonal mode into the polarization-maintaining delay fiber (4), the λ / 4 wave plate (5) and the sensing fiber (61). A phase difference is generated in the sensing fiber (61) due to the Faraday magneto-optical effect. After being reflected by the optical fiber reflector (62), the two light signals carrying the phase information return to the integrated optical transceiver assembly (1) along the original path, interfere with another portion of the light beam of the integrated optical transceiver assembly (1), and are coupled into the photodetector in the integrated optical transceiver assembly (1) and are linearly converted into a light intensity voltage signal. The signal processing unit (7) is used to control the phase modulator (2) to realize phase modulation, and to receive the light intensity voltage signal output by the integrated optical transceiver component (1) and obtain the current value in the wire by measuring two coherent light beams; The integrated optical transceiver assembly (1) comprises a light source (11), a circulator (12) and a photodetector (13); wherein the circulator (12) comprises: a fiber collimator (121) for collimating the light beam output by the light source, a polarization beam splitter (122), a 90° Faraday rotator (123), a converging lens (124) and a collimator (125); The optical path of the integrated optical transceiver assembly (1) adopts a parallel light structure as a whole, and the optical transceiver path is separated by changing the polarization state. Of the collimated P polarized light emitted from the optical fiber collimator (121), a portion of the light passes through the polarization beam splitter (122) and the 90° Faraday rotator (123) and is received by the collimator (125); the other portion of the light passes through the 90° Faraday rotator (123) and is rotated 90° in polarization direction to become S light, which is folded 90° by the polarization beam splitter (122) and hits the photosensitive surface of the photodetector (13) through the converging lens (124).

2. The optical fiber current transformer according to claim 1, wherein: The sequentially connected integrated optical transceiver assembly (1), phase modulator (2), polarization-maintaining coupler (3), polarization-maintaining delay optical fiber (4), λ / 4 wave plate (5), and sensor head (6) include: The pigtail of the integrated optical transceiver assembly (1) is fused with the input fiber of the phase modulator (2); The two pigtail fibers of the phase modulator (2) are connected to one end of the polarization-maintaining coupler (3); The other end of the polarization-maintaining coupler (3) is connected to one end of the polarization-maintaining delay optical fiber (4); The other end of the polarization-maintaining delay optical fiber (4) is connected to the λ / 4 wave plate (5); The other end of the λ / 4 wave plate (5) is fused to the sensing optical fiber (61) of the sensing head (6).

3. The optical fiber current transformer according to claim 1, wherein: The light intensity voltage signal output end of the integrated optical transceiver assembly (1) is connected to a signal processing unit (7), and the signal processing unit (7) outputs a superimposed signal of a square wave and a step wave and transmits it back to the phase modulator (2); The phase difference of light in the phase modulator (2) satisfies sin4(V·N·I)≈4VNI, and 4 V·N·I≤0.5°~1°, V represents the Verdet constant, N represents the number of turns of the optical fiber wound around the wire, and I represents the current value in the wire.

4. The optical fiber current transformer according to claim 1, wherein: The light source is a super luminescent diode (SLD).

5. The optical fiber current transformer according to claim 1, wherein: The phase modulator (2) is a Y-waveguide, and is used to realize polarization, light splitting and phase modulation of the optical signal output by the light source.

6. The optical fiber current transformer according to claim 1, wherein: The λ / 4 wave plate (5) is a full optical wave plate used for converting linear polarization into circular polarization.

7. The optical fiber current transformer according to claim 1, wherein: The sensing optical fiber (61) of the sensing head (6) is a single-mode optical fiber or a circular birefringence optical fiber or a low birefringence optical fiber.

8. The optical fiber current transformer according to claim 1, wherein: The connection between the two ends of the polarization-maintaining delay optical fiber (4) and the polarization-maintaining coupler (3) and the λ / 4 wave plate (5) is achieved by jumper connection or fusion splicing.

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