High-sensitivity reciprocal optical voltage sensor capable of resisting environmental interference

Abstract

The invention relates to a high-sensitivity reciprocal optical voltage sensor resistant to environmental interference. A wide-spectrum light source, a polarizer, a circulator, a 45-degree fusion welding point and a sensing head are connected in sequence, and the circulator is connected with a photoelectric detector; natural light emitted by the wide-spectrum light source emits an optical signal to the polarizer, the optical signal is changed into single polarized light after passing through the polarizer, and the single polarized light is transmitted to the 45-degree fusion welding point after passing through the circulator and then is divided into two beams of polarized light which are perpendicular to each other and enters the sensing head; when voltage is applied to the outside, two beams of polarized light cause a phase difference between two light beams in the sensing head due to the Pockels effect, the phase difference passes through the sensing head after being reflected by the reflecting film of the sensing head, the sensing head realizes orthogonal line polarized light mode interchange, and light path reciprocity is formed; the reflected light returns to the circulator along the original light path and enters the photoelectric detector through the circulator, and voltage measurement is achieved by establishing the linear relation between the optical phase difference change and the voltage change. According to the invention, interference of environmental factors such as temperature, magnetic field, vibration and the like is resisted, and the sensitivity of the sensor is improved.

Description

Technical Field

[0001] This invention belongs to the field of optical voltage sensing technology, and in particular relates to a high-sensitivity reciprocal optical voltage sensor that is resistant to environmental interference and suitable for complex environments such as ship systems. Background Technology

[0002] With the increasing automation of relay protection and electrical equipment in large power systems (such as ships, power grids, and railways), and the improvement of power system insulation levels, traditional electromagnetic voltage sensors, due to their inherent limitations, can no longer meet the needs of power system development and are gradually being replaced by optical voltage sensors. Optical voltage sensors use electro-optic crystals as sensing elements and have high sensitivity. Based on different optical path structures, electro-optic crystal sensing heads can be divided into two types: transmissive and reflective. Transmissive sensors typically have a polarizer and photodetector at the output end of the probe. However, transmissive structures have poor resistance to environmental interference, and the detection of light intensity is easily affected by fluctuations in the light source. In practical applications, such as in marine environments, temperature, magnetic fields, vibration, and shock are unavoidable. Furthermore, the launch of future high-energy weapons (such as electromagnetic guns, high-energy microwaves, and laser systems) will generate short-term, ultra-high-power impact pulses and magnetic fields, significantly affecting the sensor output and making it impossible to meet the high stability requirements of the industry.

[0003] Currently, to improve the sensitivity of the system's voltage measurement and enhance the sensor's anti-interference capability and long-term stability, most research focuses on adding optical devices and then employing algorithmic compensation. However, these solutions are structurally complex, costly, and have limited effectiveness, failing to completely eliminate errors caused by environmental factors. Furthermore, while reflective structures increase sensitivity, the current prevalence of structured light devices increases system complexity and is detrimental to the long-term stability of the sensor.

[0004] In existing technologies, such as the quasi-reciprocal reflective structures disclosed in patent documents CN103197113A and WO2014127654A1, mode interchange is achieved through two polarization-maintaining circulators. However, a single electro-optic crystal is still used, and errors introduced by the non-Paukles effect cannot be canceled, limiting anti-interference capabilities. Furthermore, the introduction of circulators increases structural complexity. Patent document CN103176159A focuses on a test device for reciprocal reflective sensing units. Although its sensing unit achieves mode interchange through a Faraday rotator, the single-crystal structure still cannot solve the phase difference problem caused by environmental interference. Summary of the Invention

[0005] To address the problems existing in the prior art and further promote the application of optical voltage sensors in power systems, this invention proposes a high-sensitivity, dual-crystal reciprocal optical voltage sensor that can resist interference from environmental factors such as temperature, magnetic field, and vibration. This improves the sensor's sensitivity and resistance to environmental interference, and expands the sensor's application range.

[0006] To achieve the above objectives, the technical solution of this invention is: a high-sensitivity reciprocal optical voltage sensor resistant to environmental interference, comprising a broadband light source, a polarizer, a circulator, a 45° fusion point, a sensing head, and a photodetector. The broadband light source, polarizer, circulator, 45° fusion point, and sensing head are connected sequentially, and the circulator is connected to the photodetector. The natural light emitted by the broadband light source sends an optical signal to the polarizer, which converts it into single-polarized light. After passing through the circulator, it is transmitted to the 45° fusion point and splits into two mutually perpendicular polarized beams, which then enter the sensing head. When an external voltage is applied, the two polarized beams generate a phase difference in the sensing head due to the Paulclaw effect. After being reflected by the reflective film of the sensing head, the phase difference is multiplied, the sensitivity is amplified, and the sensing head achieves mode interchange of orthogonally linearly polarized light, forming optical path reciprocity. The reflected light returns to the circulator along the original optical path and enters the photodetector. By establishing a linear relationship between the change in optical phase difference and the change in voltage, voltage measurement is finally achieved.

[0007] Furthermore, the sensing head includes a Faraday rotator, a first LiNbO3 crystal, a second LiNbO3 crystal, a metal electrode, and a reflective film; one end of the Faraday rotator is a fiber optic pigtail, and the other end is connected to the light-transmitting surface of the first LiNbO3 crystal; the second LiNbO3 crystal is parallel to the first LiNbO3 crystal along the x-axis and arranged at 90° along the yz-axis.

[0008] Furthermore, a reflective film is provided at the end of the second LiNbO3 crystal; a metal electrode is provided on the xy plane of the first LiNbO3 crystal.

[0009] Furthermore, the reflective film has a reflectivity of 100%.

[0010] Furthermore, the first LiNbO3 crystal and the second LiNbO3 crystal are crystals grown, cut, and processed in the same batch and are in the same temperature environment, so the phase difference introduced by the non-Paukles effect is consistent.

[0011] Furthermore, the dimensions of both the first LiNbO3 crystal and the second LiNbO3 crystal are 10mm×5mm×5mm, and the light-transmitting surfaces are polished.

[0012] Furthermore, the Faraday rotator can rotate the polarization direction of polarized light propagating along the fast and slow axes of the polarization-maintaining fiber by 45°; then, it enters the first LiNbO3 crystal, with vibration directions along the y and z axes respectively. After the signal light enters the second LiNbO3 crystal, the two principal axes of induction rotate by 90°. After the two beams of polarized light are acted upon twice by the Faraday rotator, their polarization directions rotate by a total of 90°, realizing mode interchange along the fast and slow axes of the polarization-maintaining fiber and forming a reciprocal optical path structure.

[0013] Furthermore, ordinary light in the first LiNbO3 crystal directly becomes extraordinary light when it enters the second LiNbO3 crystal, and extraordinary light in the first LiNbO3 crystal directly becomes ordinary light when it enters the second LiNbO3 crystal.

[0014] Furthermore, after the two polarized beams reflected by the reflective film pass through the second LiNbO3 crystal and the first LiNbO3 crystal again, they are restored to the original ordinary and extraordinary light.

[0015] Furthermore, the circulator enables the light incident on the sensor head to be transmitted unidirectionally to the 45° fusion point, and enables the light returning from the sensor head to be transmitted unidirectionally to the photodetector, thus avoiding optical path interference.

[0016] The beneficial effects of this invention are:

[0017] Based on the working principle of a high-sensitivity reciprocal optical voltage sensor that resists environmental interference, this invention proposes a high-sensitivity reciprocal optical voltage sensor that can resist interference from environmental factors such as temperature, magnetic field, and vibration. It utilizes a dual-crystal reflective structure to form a reciprocal optical path, thereby achieving resistance to interference from environmental factors such as temperature, magnetic field, and vibration, and improving the sensor sensitivity.

[0018] 1. Strong resistance to environmental interference: Using double LiNbO3 crystals from the same batch and at the same temperature, the phase difference introduced by non-Paukles effects (such as temperature and stress) cancels each other out, significantly reducing the influence of environmental factors on the measurement;

[0019] 2. High sensitivity: The reflective structure causes the two beams of light to pass through the electro-optic crystal twice, doubling the phase difference and improving the sensitivity of voltage measurement;

[0020] 3. Simple structure: Mode switching is achieved through dual crystals and Faraday rotators, eliminating the need for complex components such as polarization-maintaining circulators, which is conducive to long-term stable operation;

[0021] 4. Excellent reciprocity: The optical path is symmetrical, and the optical path of the two polarized beams is consistent except for the electro-optic crystal, which further reduces environmental interference. Attached Figure Description

[0022] Figure 1 This is a structural diagram of the optical voltage sensor of the present invention;

[0023] Figure 2 This is a schematic diagram of the sensor head structure;

[0024] Figure 3 This is a schematic diagram of the optical path principle of the sensor head;

[0025] In the figure: 1-Broadband light source, 2-Polarizer, 3-Circulator, 4-45° fusion point, 5-Sensing head, 6-Photodetector; 7-Faraday rotator, 8-First metal electrode, 9-Second metal electrode, 10-First LiNbO3 crystal, 11-Second LiNbO3 crystal, 12-Reflective film. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] like Figure 1 As shown, the present invention proposes a high-sensitivity reciprocal optical voltage sensor resistant to environmental interference, comprising a broadband light source 1, a polarizer 2, a circulator 3, a 45° fusion point 4, a sensing head 5, a photodetector 6, a Faraday rotator 7, a first metal electrode 8, a second metal electrode 9, a first LiNbO3 crystal 10, a second LiNbO3 crystal 11, and a reflective film 12.

[0028] Broadband light source 1, polarizer 2, circulator 3, 45° fusion point 4, and sensor head 5 are connected in sequence. Circulator 3 and photodetector 6 are connected.

[0029] The natural light emitted by the broadband light source 1 sends an optical signal to the polarizer 2. After passing through the polarizer 2, it becomes single-polarized light, and then after passing through the circulator 3, it is transmitted to the 45° fusion point 4, where it is split into two mutually perpendicular polarized beams. These two beams enter the sensor head 5. When an external voltage is applied, the Pockels effect causes a phase difference between the two beams in the sensor head 5. The beams continue to propagate to the reflective film 12 of the sensor head 5, and the reflected beams pass through the sensor head 5 again. At this time, the phase difference is doubled, and the sensitivity is amplified. The sensor head 5 realizes the mode interchange of orthogonally linearly polarized light, forming an optical path reciprocity, thus resisting interference from environmental factors such as temperature, magnetic field, and vibration. The reflected light returns to the circulator 3 along the original optical path, and then enters the photodetector 6. By establishing a linear relationship between the change in optical phase difference and the change in voltage, voltage measurement is finally achieved.

[0030] The sensor head 5 includes a Faraday rotator 7, LiNbO3 crystals, metal electrodes, and a reflector. The two LiNbO3 crystals are selected from the same batch of crystals grown, cut, and processed, with their consistency maximized. They also share the same temperature environment, resulting in a nearly identical phase difference introduced by the non-Paukles effect. One end of the Faraday rotator is a fiber optic pigtail, while the other end is directly connected to one of the light-transmitting surfaces of the first LiNbO3 crystal 10. The second LiNbO3 crystal 11 is aligned in the same direction, i.e., parallel along the x-axis and at a 90° angle to the first LiNbO3 crystal 10 along the y-z axis. Both LiNbO3 crystals have x×y×z dimensions of 10mm×5mm×5mm and are first polished to increase transmittance. Subsequently, metal electrodes are added to the xy-plane of the first LiNbO3 crystal 10, and a reflective film 12 is deposited at the end of the second LiNbO3 crystal 11, achieving 100% reflectivity.

[0031] Polarized light propagating along the fast and slow axes of the polarization-maintaining fiber enters the Faraday rotator 7, where its polarization direction is rotated by 45°. It then enters the first LiNbO3 crystal 10, vibrating along the y and z axes, respectively. After the signal light enters the second LiNbO3 crystal 11, due to its 90° rotation, the two principal axes of induction also rotate by 90°. Ordinary light in the first LiNbO3 crystal 10 becomes extraordinary light upon entering the second LiNbO3 crystal 11, and vice versa. After reflection by the reflective film 12, it passes through the second LiNbO3 crystal 11 again, and then re-enters the first LiNbO3 crystal 10, reverting to its original ordinary and extraordinary states. The two linearly polarized beams emitted from the first BGO crystal pass through Faraday rotator 7 again, and their rotation direction is rotated by 45°. Compared with the original incident light, they are rotated by 90°. That is, the light that originally propagated along the fast axis of the polarization-maintaining fiber propagates along the slow axis, and the light that originally propagated along the slow axis of the polarization-maintaining fiber propagates along the fast axis. This achieves mode interchange and forms a reciprocal optical path structure.

[0032] The structure of sensor head 5 is as follows Figure 2 and Figure 3 As shown, its fabrication is as follows: This invention uses a first LiNbO3 crystal 10 and a second LiNbO3 crystal 11 as electro-optic materials. These materials have a large electro-optic constant, resulting in high sensitivity. The dimensions of both the first LiNbO3 crystal 10 and the second LiNbO3 crystal 11 are 10mm × 5mm × 5mm. When the voltage changes, a Pockels effect occurs in the first LiNbO3 crystal 10, resulting in a phase difference between the y-axis and z-axis light beams. The phase difference φ is expressed as:

[0033]

[0034] In the formula, L is the length of the first LiNbO3 crystal 10, which is 10 mm; λ is the incident light wavelength, which is 1550 nm; d is the thickness of the first LiNbO3 crystal 10, which is 5 mm; no is the ordinary light refractive index, which is 2.21; ne is the extraordinary light refractive index, which is 2.14; γ33 is the electro-optic coefficient of the first LiNbO3 crystal 10, which is 30.8 × 10⁻¹² m / V; and γ13 is the electro-optic coefficient of the first LiNbO3 crystal 10, which is 8.6 × 10⁻¹² m / V.

[0035] Additional phase difference can be caused by defects in the first LiNbO3 crystal 10, temperature, stress, etc. Therefore, the phase difference introduced by the unidirectional light passing through the first LiNbO3 crystal 10 is actually... The phase difference introduced by the unidirectional light passing through the second LiNbO3 crystal 11 is: The phase difference is introduced by the non-Pockels effect. Since both crystals were grown, cut, and processed from the same batch, the phase difference introduced by the non-Pockels effect is the same, i.e. pass Figure 2 , Figure 3 The sensor head structure shown achieves the conversion between ordinary and extraordinary light, thereby canceling out the phase difference introduced by the non-Pockels effect. The light passes through the first LiNbO3 crystal 10 twice, and the Pockels effect causes the phase difference to double, resulting in... This improves voltage sensitivity.

[0036] This sensing unit features a simple structure, small size, and light weight. Made of insulating materials, it exhibits excellent insulation performance. Optical path compensation is achieved using two crystals, offsetting the unwanted phase difference caused by natural birefringence and temperature variations. Mode interchange of orthogonally linearly polarized light is realized using a Faraday rotator and a reflective optical path structure. Except for the first LiNbO3 crystal 10 and the second LiNbO3 crystal 11, the two orthogonally linearly polarized modes travel the same optical path, forming a reciprocal optical path structure. The returning orthogonally linearly polarized light carries only the phase difference introduced by the Paulclaw effect, thus resisting interference from environmental factors such as temperature, magnetic fields, and vibration, improving the optical path's anti-interference capability.

[0037] The specific embodiments described in this invention are merely one possible parameter design scenario and are not intended to limit the invention in any way. Any person skilled in the art can make many possible variations and modifications to the technical solutions of this invention, or modify them into equivalent embodiments, without departing from the scope of the invention. Therefore, any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of this invention, without departing from the scope of the invention, shall still fall within the protection scope of this invention.

Claims

1. A high-sensitivity reciprocal optical voltage sensor resistant to environmental interference, characterized in that, The system includes a broadband light source, a polarizer, a circulator, a 45° fusion splice, a sensing head, and a photodetector. These components are connected sequentially, with the circulator connected to the photodetector. Natural light emitted from the broadband light source sends an optical signal to the polarizer, which converts it into single-polarized light. After passing through the circulator, the light is transmitted to the 45° fusion splice and splits into two mutually perpendicular polarized beams, which then enter the sensing head. When an external voltage is applied, the two polarized beams experience a phase difference due to the Paulclaw effect. The light is reflected by the sensor's reflective film and passes through the sensor again, at which point the phase difference is multiplied, amplifying the sensitivity. The sensing head achieves mode interchange of orthogonally linearly polarized light, forming optical path reciprocity. The reflected light returns along the original optical path to the circulator and enters the photodetector. By establishing a linear relationship between the change in optical phase difference and the change in voltage, voltage measurement is ultimately achieved.

2. The high-sensitivity reciprocal optical voltage sensor resistant to environmental interference according to claim 1, characterized in that, The sensing head includes a Faraday rotator, a first LiNbO3 crystal, a second LiNbO3 crystal, a metal electrode, and a reflective film; one end of the Faraday rotator is a fiber optic pigtail, and the other end is connected to the light-transmitting surface of the first LiNbO3 crystal; the second LiNbO3 crystal is parallel to the first LiNbO3 crystal along the x-axis and arranged at 90° along the yz-axis.

3. The high-sensitivity reciprocal optical voltage sensor resistant to environmental interference according to claim 2, characterized in that, The second LiNbO3 crystal has a reflective film at its end; the first LiNbO3 crystal has a metal electrode on its xy plane.

4. The high-sensitivity reciprocal optical voltage sensor with resistance to environmental interference according to claim 3, characterized in that, The reflective film has a reflectivity of 100%.

5. The high-sensitivity reciprocal optical voltage sensor resistant to environmental interference according to claim 3, characterized in that, The first LiNbO3 crystal and the second LiNbO3 crystal are grown, cut and processed in the same batch and are in the same temperature environment, and the phase difference introduced by the non-Paukles effect is consistent.

6. The high-sensitivity reciprocal optical voltage sensor resistant to environmental interference according to claim 3, characterized in that, The dimensions of the first LiNbO3 crystal and the second LiNbO3 crystal are both 10mm×5mm×5mm (x×y×z), and the light-transmitting surfaces are polished.

7. The high-sensitivity reciprocal optical voltage sensor resistant to environmental interference according to claim 3, characterized in that, The Faraday rotator can rotate the polarization direction of polarized light propagating along the fast and slow axes of the polarization-maintaining fiber by 45°. Then, it enters the first LiNbO3 crystal, and the vibration direction is along the y and z axes respectively. After the signal light enters the second LiNbO3 crystal, the two principal axes of induction rotate by 90°. After the two beams of polarized light are acted on by the Faraday rotator twice, the polarization direction rotates by a total of 90°, realizing the mode interchange along the fast and slow axes of the polarization-maintaining fiber and forming a reciprocal optical path structure.

8. The high-sensitivity reciprocal optical voltage sensor resistant to environmental interference according to claim 7, characterized in that, Ordinary light in the first LiNbO3 crystal is directly converted into extraordinary light when it enters the second LiNbO3 crystal, and extraordinary light in the first LiNbO3 crystal is directly converted into ordinary light when it enters the second LiNbO3 crystal.

9. The high-sensitivity reciprocal optical voltage sensor resistant to environmental interference according to claim 8, characterized in that, After the two beams of polarized light reflected by the reflective film pass through the second LiNbO3 crystal and the first LiNbO3 crystal again, they are restored to the original ordinary light and extraordinary light.

10. The high-sensitivity reciprocal optical voltage sensor resistant to environmental interference according to claim 1, characterized in that, The circulator enables the light incident on the sensor head to be transmitted unidirectionally to the 45° fusion point, and also enables the light returning from the sensor head to be transmitted unidirectionally to the photodetector, thus avoiding optical path interference.

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