A reflection type lithium niobate crystal alternating current or direct current integrated strong electric field sensor

Abstract

The application discloses a reflection type lithium niobate crystal alternating current or direct current integrated strong electric field sensor, wherein the light transmission paths of the input polarization maintaining optical fiber collimator, the polarizer, the quarter-wave plate, the electro-optic crystal, the hollow ridge mirror, the polarization beam splitting prism, the total reflection mirror, the first polarization analyzer, the second polarization analyzer, the first output single-mode optical fiber collimator and the second output single-mode optical fiber collimator are coaxially and parallelly arranged, and are coupled in the packaging shell through insulation glue. The application develops the reflection type lithium niobate crystal alternating current or direct current integrated strong electric field sensor for the measurement of alternating current or direct current electric field by combining the polarization beam splitting prism with the lithium niobate crystal and rotating the shielding electrode.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of optical electric field sensing, and particularly relates to a reflection type lithium niobate crystal alternating current or direct current integrated strong electric field sensor. BACKGROUND

[0002] With the development of modern science and technology, electric power resources have become an indispensable energy in human life. However, in China and even globally, the distribution of electric power resources is extremely unbalanced. In order to rationally distribute electric power resources to various regions in China, it is often necessary to build some cross-regional and long-distance power transmission projects. These power transmission projects often adopt the form of extra-high voltage alternating current and direct current shared transmission corridors to realize long-distance power transmission. Therefore, in order to ensure the stable operation of the power system, it is necessary to monitor the surface electric field of high-voltage equipment or power transmission corridors in real time.

[0003] Electric field sensors are mainly divided into two categories: electric type electric field sensors and optical electric field sensors. Due to the advantages of high electric field isolation, non-contact, small size, sensitive response, and wide frequency band, the optical electric field sensor has attracted widespread attention from the international community, and researchers in various countries have continuously followed up the research.

[0004] Although the optical electric field sensor has made some progress after years of development, in a complex alternating current and direct current mixed large power grid, the optical electric field sensor still cannot realize alternating current and direct current mixed integrated measurement. Therefore, designing and researching an optical electric field sensor capable of simultaneously measuring alternating current and direct current mixed electric field has good development prospects and application prospects. SUMMARY

[0005] In view of the deficiencies of the prior art, the application designs a reflection type lithium niobate crystal alternating current or direct current integrated strong electric field sensor, which realizes small size, sensitive response, and simultaneous measurement of alternating current and direct current electric field.

[0006] To achieve the above purpose, the application provides the following scheme: the application provides a reflection type lithium niobate crystal alternating current or direct current integrated strong electric field sensor, which comprises: an input polarization maintaining optical fiber collimator, a polarizer, a quarter-wave plate, an electro-optic crystal, a shielding electrode, a hollow ridge mirror, a polarization beam splitter prism, a total reflection mirror, a first polarization analyzer, a second polarization analyzer, a first output single-mode optical fiber collimator, a second output single-mode optical fiber collimator, and a packaging shell.

[0007] The light transmission paths of the input polarization maintaining optical fiber collimator, the polarizer, the quarter-wave plate, the electro-optic crystal, the hollow ridge mirror, the polarization beam splitter prism, the total reflection mirror, the first polarization analyzer, the second polarization analyzer, the first output single-mode optical fiber collimator, and the second output single-mode optical fiber collimator are coaxially and parallelly arranged, and are coupled in the packaging shell by an insulating adhesive.

[0008] The surface of the shielding electrode is parallel to the surface of the electro-optic crystal.

[0009] The light wave of the output of the tunable laser is input into the input polarization maintaining fiber collimator to converge into a parallel light beam through an optical fiber, is converted into linearly polarized light through a polarizer, the polarization direction of the linearly polarized light is 45° to the slow axis of the quarter-wave plate, the light wave is converted into circularly polarized light after passing through the quarter-wave plate, the circularly polarized light is injected into the electro-optic crystal to be electro-optically modulated, the output light wave after the electro-optical modulation is reflected by the hollow ridge mirror and then enters the electro-optic crystal again to be electro-optically modulated, and the modulated light wave is divided into light wave one and light wave two by a polarization beam splitter prism.

[0010] The first oscilloscope and the second oscilloscope are used to display the information of the measured electric field.

[0011] In a possible design, the light wave one is subjected to detection by the first polarizer and is input into the second photodetector through the first output single-mode fiber collimator to be photoelectrically converted, the electric signal converted by the second photodetector is transmitted to the second oscilloscope through a radio frequency cable to display the information of the measured electric field.

[0012] The light wave two is input into the second polarizer through the total reflection mirror and is subjected to detection, and then is input into the first photodetector through the second output single-mode fiber collimator to be photoelectrically converted, and the electric signal converted by the first photodetector is transmitted to the first oscilloscope through a radio frequency cable to display the information of the measured electric field.

[0013] In a possible design, the input polarization maintaining fiber collimator, the first output single-mode fiber collimator, and the second output single-mode fiber collimator are all cylindrical glass types, the output ends are all planes, the diameters are all 2 mm, and the lengths are all 8 mm.

[0014] In a possible design, the first polarizer, the second polarizer, and the polarizer are all square optical glass types, and the volume is 3 mm×3 mm×3 mm; the quarter-wave plate is a cylindrical optical glass type, the radius is 1.5 mm, and the thickness is 1 mm.

[0015] In a possible design, the electro-optic crystal is a cuboid lithium niobate crystal of an optical grade and is processed and customized, and the volume is 25 mm×8 mm×2 mm.

[0016] In a possible design, the total reflection mirror and the hollow ridge mirror are both gold-plated glass types of an optical grade, and the height is 6 mm; the shielding electrode is made of aluminum, is composed of three fan-shaped parts with a central angle of 60°, the radius of the fan-shaped part is 25 mm, and the thickness is 1 mm.

[0017] In one possible design, the transmission axis of the polarizer is parallel to the y-axis of the electro-optic crystal, the slow axis of the quarter-wave plate is at 45° to the y-axis of the electro-optic crystal, the transmission axes of the first and second polarizers are at 90° to the y-axis of the electro-optic crystal, and the transmission axis of the second polarizer is at 45° to the y-axis of the electro-optic crystal.

[0018] In one possible design, the surface of the shielding electrode is arranged parallel to the x-axis of the electro-optic crystal.

[0019] In one possible design, the encapsulation shell is made of acrylic material, and its interior has grooves that are compatible with the input polarization-maintaining fiber collimator, polarizer, quarter-wave plate, electro-optic crystal, rotating shielding electrode, hollow roof reflector, polarization beam splitter, total reflection mirror, first analyzer, second analyzer, first output single-mode fiber collimator, and second output single-mode fiber collimator.

[0020] In one possible design, the shielding electrode rotates under the control of an external power supply, thereby periodically shielding the length of the electro-optic crystal from the DC electric field. The periodically shielded electro-optic modulation length can be expressed as:

[0021] ;

[0022] Where L is the length of the electro-optic crystal, h represents the distance between the electro-optic crystal and the shielding electrode axis, T=2π / ωn is the period of the L(t) function, and n is the number of aperture lobes.

[0023] Compared with existing technologies, this invention has the following advantages: This invention provides a reflective lithium niobate AC / DC integrated optical electric field sensor. By utilizing a polarizing beam splitter combined with a lithium niobate crystal and a rotating shielded electrode, a reflective lithium niobate crystal AC or DC integrated strong electric field sensor has been developed for measuring AC / DC electric fields. This sensor can be used for measuring AC / DC electric fields. It provides a new design scheme for the development of lithium niobate crystal electric field sensors. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Fig. 1 This is a top view schematic diagram of a reflective lithium niobate crystal AC or DC integrated strong electric field sensor according to the present invention.

[0026] Fig. 2 This is a side view schematic diagram of a reflective lithium niobate crystal AC or DC integrated strong electric field sensor according to the present invention.

[0027] The components are: 1. Shielding electrode; 2. Electro-optic crystal; 3. Hollow roof reflector; 4. Quarter-wave plate; 5. Polarizing beam splitter; 6. Total reflection mirror; 7. Polarizer; 8. First analyzer; 9. Second analyzer; 10. Input polarization-maintaining fiber collimator; 11. First output single-mode fiber collimator; 12. Second output single-mode fiber collimator; 13. Encapsulation shell; 14. Sensor; 15. Optical fiber; 16. Tunable laser; 17. First photodetector; 18. Second photodetector; 19. First oscilloscope; 20. RF cable; 21. Second oscilloscope. Detailed Implementation

[0028] 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.

[0029] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0030] like Figs. 1-2 As shown, the present invention provides a reflective lithium niobate crystal AC or DC integrated strong electric field sensor 14, including a tunable laser 16, two identical oscilloscopes 19 and 21, several optical fibers 15, an input polarization-maintaining fiber collimator 10, a first output single-mode fiber collimator 11 and a second output single-mode fiber collimator 12, an electro-optic crystal 2 (lithium niobate crystal), a polarizer 7, a first analyzer 8 and a second analyzer 9, a hollow roof reflector 3, a total reflection mirror 6, a polarizing beam splitter prism 5 for beam splitting, a shielding electrode 1, a first photodetector 17, a second photodetector 18, and several radio frequency cables 20.

[0031] The output light wave of the tunable laser 16 is converted into linearly polarized light by the polarizer 7, and the polarization direction of the linearly polarized light is 45° to the slow axis of the quarter-wave plate 4 and enters the quarter-wave plate 4, and the output light wave after passing through the quarter-wave plate 4 is converted into circularly polarized light and enters the electro-optic crystal 2, and when the spatial alternating / direct current electric field is decomposed into x and y directions, the direct current electric field in the y direction is offset by the reverse electric field in the crystal due to the characteristics of the lithium niobate crystal itself. The rotating shield electrode used in the x direction is used to realize the measurement of the direct current electric field. The output light wave after passing through the electro-optic crystal carries the electric field information, is reflected by the hollow ridge mirror 3 and re-enters the electro-optic crystal 2 for electro-optic modulation, and the light wave after the second electro-optic modulation is divided into light wave one and light wave two by the polarization beam splitter prism 5. The light wave one is subjected to detection by the first detector 8 and then input to the second photodetector 18 through the first output single-mode fiber collimator 11 for photoelectric conversion, and finally the information of the measured electric field is displayed by the second oscilloscope 21. The light wave two is input to the second detector 9 by the total reflection mirror 6 for detection, and the detected light wave is input to the first photodetector 17 through the second output single-mode fiber collimator 12 for photoelectric conversion, and finally the information of the measured electric field is displayed by the first oscilloscope 19.

[0032] The working principle of the present application is as follows: when the reflection type lithium niobate crystal alternating or direct current integrated strong electric field sensor provided by the present application is used to measure the electric field, the vibration direction of the linearly polarized light output by the polarizer 7 is aligned with the y axis of the electro-optic crystal 2, and at this time the electric vector of the output polarized light after passing through the polarizer 7 can be represented by the Jones vector J1 as follows:

[0033] (1);

[0034] When the slow axis of the λ / 4 wave plate 4 is set at 45° to the y axis of the electro-optic crystal 2, its Jones matrix J2 can be represented as:

[0035] (2);

[0036] The Jones matrix J3 of the electro-optic crystal 2 can be represented as:

[0037] (3);

[0038] The first detector 8 and the second detector 9 have their transmission axes at 90° to the y axis, and the Jones matrix J4 thereof is:

[0039] (4);

[0040] Therefore, after the light wave passes through the polarizer 7, the λ / 4 wave plate 4, the electro-optic crystal 2 and the first detector 8 in turn, the electric vector of the output light wave can be represented as:

[0041] (5);

[0042] The light intensity I out1 outputted by the first polarizer 8 is

[0043] (6);

[0044] When the direction of the light transmission axis of the second polarizer 9 is 45° to the x axis, the Jones matrix of the second polarizer 9 is J5 which can be expressed as:

[0045] (7);

[0046] Then, the electric vector of the light wave passing through the polarizer 7, the λ / 4 wave plate 4, the electro-optic crystal 2 and the second polarizer 9 can be expressed as:

[0047] (8);

[0048] The light intensity I out2 outputted by the second polarizer 9 is

[0049] (9);

[0050] According to the electro-optic effect of the lithium niobate crystal, when the spatial alternating / direct current electric field is decomposed into x and y directions, the electric field in x and y directions will respectively rotate the refractive index ellipsoid of the lithium niobate crystal by 45° and 0°, and according to the formula (6) and the formula (9), we can obtain:

[0051] (10);

[0052] It can be seen that the output light of the first polarizer 8 and the second polarizer 9 respectively corresponds to the detection of the electric field in y and x directions. According to the electro-optic effect of the lithium niobate crystal, the phase difference of the polarized light caused by the phase modulation of the spatial electric field is:

[0053] (11);

[0054] In the formula, L is the length of the crystal, E AC+DC is the intensity of the external spatial alternating / direct current electric field, λ is the wavelength of the incident light, n o is the refractive index of o light, is the electro-optic coefficient of the lithium niobate crystal.

[0055] When φ is very small, Therefore, further substituting the formula (11) into the formula (10), we can obtain:

[0056] (12);

[0057] Due to the characteristics of lithium niobate crystal itself, the direct current electric field in y direction is offset by the reverse electric field inside the crystal, thus the output light waves of the two paths are mainly used for detecting alternating current electric field. In x direction, the rotating shield electrode is used to realize the measurement of direct current electric field. Therefore, the further formula (12) can be written as:

[0058] (13);

[0059] It can be seen from formula (13) that the two light wave signals output by the sensor are linearly related to the applied direct current electric field and alternating current electric field respectively.

[0060] The above-described embodiments are only descriptions of the preferred modes of the present application, and do not limit the scope of the present application. Without departing from the design spirit of the present application, various modifications and improvements to the technical solutions of the present application made by those skilled in the art shall fall within the protection scope determined by the claims of the present application.

Claims

1. A reflective lithium niobate crystal AC or DC integrated high-voltage electric field sensor, characterized in that, The sensor (14) includes: an input polarization-maintaining fiber collimator (10), a polarizer (7), a quarter-wave plate (4), an electro-optic crystal (2), a shielding electrode (1), a hollow roof reflector (3), a polarization beam splitter (5), a total reflection mirror (6), a first analyzer (8), a second analyzer (9), a first output single-mode fiber collimator (11), a second output single-mode fiber collimator (12), and a package shell (13). The light transmission paths of the input polarization-maintaining fiber collimator (10), polarizer (7), quarter-wave plate (4), electro-optic crystal (2), hollow roof reflector (3), polarization beam splitter (5), total reflection mirror (6), first analyzer (8), second analyzer (9), first output single-mode fiber collimator (11), and second output single-mode fiber collimator (12) are all coaxially parallel and coupled in the encapsulation shell (13) by insulating glue. The surface of the shielding electrode (1) is arranged parallel to the surface of the electro-optic crystal (2); The output light wave of the tunable laser (16) is input into the input polarization-maintaining fiber collimator (10) through the optical fiber (15) and converged into a parallel beam. It is converted into linearly polarized light through the polarizer (7). The polarization direction of the linearly polarized light is 45° with the slow axis of the quarter-wave plate (4). After passing through the quarter-wave plate (4), the light wave is converted into circularly polarized light. The circularly polarized light enters the electro-optic crystal (2) for electro-optic modulation. The output light wave after electro-optic modulation is reflected by the hollow roof reflector (3) and re-enters the electro-optic crystal (2) for electro-optic modulation. The modulated light wave is divided into light wave one and light wave two by the polarization beam splitter (5). The first oscilloscope (19) and the second oscilloscope (21) are used to display information about the electric field being measured. After the light wave is polarized by the first analyzer (8), it is input into the second photodetector (18) by the first output single-mode fiber collimator (11) for photoelectric conversion. The electrical signal converted by the second photodetector (18) is transmitted to the second oscilloscope (21) via the radio frequency cable (20) to display the information of the measured electric field. The second light wave is input into the second analyzer (9) through the total reflection mirror (6) for polarization analysis, and then input into the first photodetector (17) through the second output single-mode fiber collimator (12) via the fiber (15) for photoelectric conversion. The electrical signal converted by the first photodetector (17) is transmitted to the first oscilloscope (19) via the radio frequency cable (20) to display the information of the measured electric field.

2. The reflective lithium niobate crystal AC or DC integrated strong electric field sensor according to claim 1, characterized in that, The input polarization-maintaining fiber collimator (10), the first output single-mode fiber collimator (11), and the second output single-mode fiber collimator (12) are all cylindrical glass type, with flat output ends, a diameter of 2 mm, and a length of 8 mm.

3. The reflective lithium niobate crystal AC or DC integrated strong electric field sensor according to claim 1, characterized in that, The first analyzer (8), the second analyzer (9), and the polarizer (7) are all square optical glass with a volume of 3mm×3mm×3mm; the quarter-wave plate (4) is cylindrical optical glass with a radius of 1.5 mm and a thickness of 1 mm.

4. The reflective lithium niobate crystal AC or DC integrated strong electric field sensor according to claim 1, characterized in that, The electro-optic crystal (2) is a custom-made optical-grade cuboid lithium niobate crystal with a volume of 25mm×8mm×2mm.

5. A reflective lithium niobate crystal AC or DC integrated strong electric field sensor according to claim 4, characterized in that, The total reflection mirror (6) and the hollow roof reflector (3) are both optical-grade gold-plated glass with a height of 6 mm; the shielding electrode (1) is made of aluminum and consists of three fan-shaped parts with a central angle of 60°, the radius of which is 25 mm and the thickness is 1 mm.

6. A reflective lithium niobate crystal AC or DC integrated strong electric field sensor according to claim 5, characterized in that, The transmission axis of the polarizer (7) is parallel to the y-axis of the electro-optic crystal (2), the slow axis of the quarter-wave plate (4) is set at 45° to the y-axis of the electro-optic crystal (2), the transmission axes of the first analyzer (8) and the second analyzer (9) are set at 90° to the y-axis of the electro-optic crystal (2), and the transmission axis of the second analyzer (9) is set at 45° to the y-axis of the electro-optic crystal (2).

7. A reflective lithium niobate crystal AC or DC integrated strong electric field sensor according to claim 1, characterized in that, The surface of the shielding electrode (1) is arranged parallel to the x-axis of the electro-optic crystal (2).

8. A reflective lithium niobate crystal AC or DC integrated strong electric field sensor according to claim 7, characterized in that, The encapsulation shell (13) is made of acrylic material, and its interior has grooves that are compatible with the input polarization-maintaining fiber collimator (10), polarizer (7), quarter-wave plate (4), electro-optic crystal (2), rotating shielding electrode (1), hollow roof reflector (3), polarization beam splitter (5), total reflection mirror (6), first analyzer (8), second analyzer (9), first output single-mode fiber collimator (11), and second output single-mode fiber collimator (12).

9. A reflective lithium niobate crystal AC or DC integrated strong electric field sensor according to any one of claims 1-8, characterized in that, The shielding electrode (1) rotates under the control of an external power source, thereby periodically shielding the length of the electro-optic crystal from the DC electric field. The periodic shielding electro-optic modulation length can be expressed as: ； in, L The length of the electro-optic crystal, ,for L ( t The period of the function is n, where n is the number of aperture lobes.

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