Electro-optical crystal electric field sensing device and method based on dual-wavelength differential measurement

Abstract

The invention discloses an electro-optical crystal electric field sensing device and method based on dual-wavelength differential measurement, and relates to the technical field of sensing. Incident light emitted by a light source enters from a first port and is output to an electro-optical crystal through a second port by utilizing the port isolation characteristic of a polarization-maintaining circulator; the modulated optical signal is reflected by the reflector plate, returns along the original optical path, passes through the electro-optical crystal, the collimating lens and the polarization-maintaining circulator again, is guided to the third port and is output to the spectrograph, so that bidirectional input and output transmission of the optical signal in the same optical fiber is completed; the complexity of an electric field sensing system is reduced, so that the cost is reduced; moreover, a single-fiber two-way transmission reflection structure is realized through the polarization-maintaining circulator, the originally separated input / output optical paths are integrated into a common path, polarization state drift caused by environmental disturbance is counteracted, and thus the measurement accuracy is improved. Therefore, the cost is reduced while the measurement accuracy of the electric field sensing device is ensured.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sensing, in particular to an electro-optic crystal electric field sensing device and method based on double-wavelength differential measurement. BACKGROUND

[0002] In a typical transmission type electro-optic electric field sensor, the transmission type optical path structure has defects: the optical path is unidirectional transmission, and the light source and the detection system need to be arranged on the two sides of the electro-optic crystal.

[0003] Due to the separation of the optical path, the optical fiber connection between the light source end and the detection end needs to be arranged separately, that is, independent input optical fiber and output optical fiber need to be configured, which increases the number of use of polarization maintaining optical fiber and the difficulty of axial alignment; further increases the complexity of the electric field sensor, resulting in high cost; and the long-distance separated optical fiber link is easily affected by environmental temperature changes, mechanical vibration and other factors, resulting in polarization state drift, measurement error and low measurement accuracy.

[0004] Therefore, in the related art, it is impossible to reduce the cost while ensuring the measurement accuracy of the electric field sensing device. SUMMARY

[0005] The main purpose of the present application is to provide an electro-optic crystal electric field sensing device and method based on double-wavelength differential measurement, which aims to solve the technical problem of reducing the cost while ensuring the measurement accuracy of the electric field sensing device.

[0006] To achieve the above-mentioned purpose, the present application provides an electro-optic crystal electric field sensing device based on double-wavelength differential measurement, which comprises a light source, an electro-optic crystal, a polarization maintaining circulator, a collimating lens, a polarizer, a 1 / 8 wave plate and a reflecting sheet, one port of the polarization maintaining circulator is optically connected with one end of the light source, two ports are optically connected with one end of the electro-optic crystal, and three ports are optically connected with one end of the spectrometer. The light source is used to generate incident light. The optical path of the incident light comprises: the incident light enters the polarization maintaining circulator through the one port, exits from the two ports into the collimating lens, passes through the polarizer and the electro-optic crystal, the linear electro-optic effect of the electro-optic crystal loads the applied electric field to be measured in the form of phase difference into the optical path, and the linearly polarized light is converted into elliptically polarized light, the elliptically polarized light generates a fixed phase difference after entering the 1 / 8 wave plate, and after being reflected by the reflecting sheet, it passes through the 1 / 8 wave plate, the electro-optic crystal and the polarizer again, and the elliptically polarized light is converted into linear light by the polarizer, and the linear light enters the collimating lens and exits from the three ports into the spectrometer.

[0007] To achieve the above object, the application further provides an electro-optic crystal electric field sensing method based on double-wavelength differential measurement, applied to the electric field sensing device as described above, and comprising the following steps of: After the incident light generated by the light source enters the electro-optic crystal placed in the electric field to be measured, a first spectrum is acquired by the spectrometer; According to the first spectrum, a target wavelength is determined, which is the corresponding two wavelengths when the response trend of transmittance to the light wavelength is opposite; According to the transmittance corresponding to the target wavelength, a first differential signal is calculated; According to the first differential signal, a target electric field intensity of the electric field to be measured is calculated.

[0008] The one or more technical solutions provided by the application have at least the following technical effects: The application utilizes the port isolation characteristics of the polarization maintaining circulator, so that the incident light emitted by the light source enters from the first port, is output to the electro-optic crystal through the second port, the modulated light signal is reflected by the reflecting sheet and returns along the original light path, passes through the electro-optic crystal, the polarizer, the collimating lens and the polarization maintaining circulator again, and is guided to the third port to be output to the spectrometer, thereby realizing the bidirectional transmission of the input and output of the light signal in the same optical fiber; so that the light source and the detection system can be connected with the electro-optic crystal through the same polarization maintaining optical fiber, avoiding the need to set independent input and output optical fibers on both sides of the crystal in the traditional structure, significantly reducing the number of polarization maintaining optical fibers used, and reducing the material cost and system complexity; and the single-fiber bidirectional transmission reflection structure realized by the polarization maintaining circulator integrates the originally separated input / output light paths into a common path, effectively offsets the polarization state drift caused by environmental disturbances by utilizing the common mode rejection effect of the round-trip light path, thereby significantly improving the measurement accuracy.

[0009] Moreover, the transmission type structure needs to maintain the accurate alignment between the two distal optical fiber end faces, the free space light path is longer and is a one-way asymmetric layout, and the stability is poor; in comparison, the reflection type structure used by the application has a simple light path, and the optical components are concentrated on one end of the probe, reducing the disturbance sensitive links in the free space propagation path, and thus having stronger resistance to environmental disturbances such as temperature changes and mechanical vibrations; especially suitable for electric field measurement in complex electromagnetic environments such as high-voltage direct current and strong electromagnetic pulses, and only a single optical fiber is needed to realize the long-distance connection between the sensing probe and the rear-end equipment, and the probe end does not need to be powered, realizing complete passivation, and effectively isolating the influence of high voltage or strong electromagnetic interference on precision instruments such as light sources and detectors; at the same time, the complexity and material cost of on-site optical fiber wiring are greatly reduced, the safety is improved, and the safety of equipment and personnel is ensured.

[0010] Therefore, the application can reduce the cost while ensuring the measurement accuracy of the electric field sensing device. Attached Figure Description

[0011] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0012] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0013] Figure 1 This is a schematic diagram of the electric field sensing device provided in Embodiment 1 of the electro-optic crystal electric field sensing method based on dual-wavelength differential measurement of this application; Figure 2 This is a flowchart illustrating an embodiment of the electro-optic crystal electric field sensing method based on dual-wavelength differential measurement provided in this application. Figure 3 This is a schematic diagram of the first scenario provided in Embodiment 1 of the electro-optic crystal electric field sensing method based on dual-wavelength differential measurement of this application; Figure 4 This is a schematic diagram of the second scenario provided in Embodiment 1 of the electro-optic crystal electric field sensing method based on dual-wavelength differential measurement of this application; Figure 5 This is a schematic diagram of the third scenario provided in Embodiment 2 of the electro-optic crystal electric field sensing method based on dual-wavelength differential measurement of this application.

[0014] The purpose, features, and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0015] It should be understood that the specific embodiments described herein are merely illustrative of the technical solutions of this application and are not intended to limit this application.

[0016] To better understand the technical solution of this application, a detailed description will be provided below in conjunction with the accompanying drawings and specific implementation methods.

[0017] This application provides an embodiment of an electro-optic crystal electric field sensing device based on dual-wavelength differential measurement, referring to... Figure 1 The electric field sensing device includes a light source, an electro-optic crystal, a polarization-maintaining circulator, a collimating lens, a polarizer, an 1 / 8 wave plate, and a reflector. One port of the polarization-maintaining circulator is optically connected to one end of the light source, the second port is optically connected to one end of the electro-optic crystal, and the third port is optically connected to one end of the spectrometer.

[0018] The light path of the incident light comprises: the incident light enters the polarization maintaining ring through the first port, is emitted from the second port into the collimating lens, passes through the polarizer and the electro-optic crystal, the linear electro-optic effect of the electro-optic crystal causes the applied to-be-measured electric field to be loaded into the light path in the form of a phase difference, and the linearly polarized light is converted into elliptically polarized light, the elliptically polarized light enters the 1 / 8 wave plate, the 1 / 8 wave plate generates a fixed phase difference, is reflected by the reflecting sheet, and then passes through the 1 / 8 wave plate, the electro-optic crystal and the polarizer again, and the elliptically polarized light is converted into linear light by the polarizer, and the linear light enters the collimating lens and is emitted from the third port into the spectrometer.

[0019] It can be understood that, in the actual measurement process, the incident light enters the polarization maintaining ring through the first port of the polarization maintaining ring, and is emitted from the second port into the polarization maintaining collimating lens, so that the incident light becomes convergent parallel light; the incident light is converted into linearly polarized light by the polarizer; the to-be-measured electric field is applied to the electro-optic crystal, and the linear electro-optic effect of the electro-optic crystal causes the to-be-measured electric field to be loaded into the light path in the form of a phase difference, and the linearly polarized light is converted into elliptically polarized light; the 1 / 8 wave plate (the included angle between the fast axis and the light transmission axis of the polarizer is 45°) generates a fixed 45° phase difference; the reflecting sheet reflects the elliptically polarized light back to pass through the 1 / 8 wave plate (to generate a fixed 45° phase difference again), the electro-optic crystal (the electric field information is loaded into the light path again), the polarizer (the elliptically polarized light is converted into linear light), the collimating lens, and is emitted from the third port of the polarization maintaining ring, and the spectrometer acquires a first spectrum in real time, that is, the spectrometer records the light intensity distribution of the entire spectrum.

[0020] It can be understood that, in the actual measurement process, the incident light enters the polarization maintaining ring through the first port of the polarization maintaining ring, and is emitted from the second port into the polarization maintaining collimating lens, so that the incident light becomes convergent parallel light; the incident light is converted into linearly polarized light by the polarizer; the to-be-measured electric field is applied to the electro-optic crystal, and the linear electro-optic effect of the electro-optic crystal causes the to-be-measured electric field to be loaded into the light path in the form of a phase difference, and the linearly polarized light is converted into elliptically polarized light; the 1 / 8 wave plate (the included angle between the fast axis and the light transmission axis of the polarizer is 45°) generates a fixed 45° phase difference; the reflecting sheet reflects the elliptically polarized light back to pass through the 1 / 8 wave plate (to generate a fixed 45° phase difference again), the electro-optic crystal (the electric field information is loaded into the light path again), the polarizer (the elliptically polarized light is converted into linear light), the collimating lens, and is emitted from the third port of the polarization maintaining ring, and the spectrometer acquires a first spectrum in real time, that is, the spectrometer records the light intensity distribution of the entire spectrum.

[0021] In a feasible implementation, the light source generates incident light with a wide spectrum.

[0022] Specifically, the light source for generating light with a wide spectrum can be an ASE light source (amplified spontaneous emission light source), a supercontinuum laser, etc. The ASE light source can generate light with a wide spectrum characteristic (typical wavelength range: 1528-1561 nm).

[0023] Using a wide spectrum light as incident light, multiple lasers are not needed: a single wide spectrum light source can cover a wide wavelength range, which can facilitate wavelength selection in the electric field measurement process.

[0024] In a feasible implementation, the electro-optic crystal includes a z-cut lithium niobate crystal.

[0025] It should be noted that, since the electro-optic coefficient of the lithium niobate crystal is the largest in the z-axis direction, the z-cut lithium niobate crystal is placed in the electric field to be measured, and the direction of the electric field to be measured is consistent with the z-axis direction of the crystal, the electric field is applied to the lithium niobate crystal along the z-axis, thereby maximizing the use of the r6 3 electro-optic coefficient, so that the influence of the electric field on the light wave is the most significant, the electro-optic properties of the lithium niobate crystal material are fully utilized, and the measurement accuracy of the electric field intensity to be measured is improved.

[0026] Therefore, in the actual measurement process, the lithium niobate crystal can be placed in the electric field to be measured, and the direction of the electric field to be measured is consistent with the z-axis direction of the lithium niobate crystal.

[0027] It should be noted that the electro-optic crystal can also be a barium borate crystal, and the electro-optic crystal in this embodiment is preferably a z-cut lithium niobate crystal, which can have a size of 10 mm x 10 mm x 12 mm. Under this size, a long enough optical path can be provided to enhance the electro-optic interaction, improve the sensitivity, and at the same time ensure a sufficient light beam light transmission area, which is convenient for collimation and coupling.

[0028] In this embodiment, through the collaborative design of the reflective optical path and the polarization maintaining ring, the comprehensive optimization of the electric field sensing device in terms of structural simplification, cost reduction, stability improvement, and engineering applicability enhancement is realized while ensuring high sensitivity. It is especially suitable for high-reliability electric field monitoring applications in harsh environments such as high voltage and strong electromagnetic interference, and has outstanding practical value and promotion prospects.

[0029] Based on this, the electro-optic crystal electric field sensing method based on double-wavelength differential measurement is provided, which is applied to the electro-optic crystal electric field sensing device based on double-wavelength differential measurement, and the specific steps are as follows: Figure 2 , Figure 2 The flowchart of the first embodiment of the electro-optic crystal electric field sensing method based on double-wavelength differential measurement of the present application is shown in the figure.

[0030] In this embodiment, the electro-optic crystal electric field sensing method based on double-wavelength differential measurement includes steps S10-S40: Step S10, after the incident light generated by the light source enters the electro-optic crystal placed in the electric field to be measured, a first spectrum is obtained by a spectrometer; It should be noted that the electro-optic sensing technology utilizes the characteristic that the refractive index of the electro-optic crystal changes under the action of an applied electric field, and realizes non-contact and anti-electromagnetic interference measurement of the applied electric field by detecting the phase, polarization or intensity change of the light wave after passing through the crystal. However, in the actual measurement process, the systematic noise such as light source intensity fluctuation, detector noise and optical path loss is coupled in the same light intensity change as the measured electric field signal, resulting in inaccurate measurement of the electric field intensity.

[0031] To solve the above problems, the electric field sensing device further comprises a signal processing unit for performing an electro-optic crystal electric field sensing method based on dual-wavelength differential measurement.

[0032] It can be understood that in the actual measurement process, the electro-optic crystal can be first placed in the electric field to be measured. After the incident light generated by the light source enters the electro-optic crystal, the electric field to be measured changes the birefringence of the electro-optic crystal, resulting in a phase difference between the two orthogonal polarization components passing through the electro-optic crystal related to the electric field. The transmittance can be calculated according to the phase difference, and the target spectrum is used to describe the distribution of the transmittance of the electro-optic crystal to light at different wavelengths.

[0033] Wherein, the electric field to be measured changes the birefringence of the electro-optic crystal, resulting in a phase difference between the two orthogonal polarization components passing through the electro-optic crystal related to the electric field. The transmittance can be calculated according to the phase difference, and the first spectrum is used to describe the distribution of the transmittance of the electro-optic crystal to light at different wavelengths.

[0034] When the electro-optic crystal is a z-cut lithium niobate crystal, the calculation method of the transmittance can be:

[0035] Wherein, E is the electric field to be measured, λ is the wavelength, is the refractive index of o light, is the length of the electro-optic crystal, is a constant.

[0036] Step S20, according to the first spectrum, determine the target wavelength, the target wavelength is the corresponding two wavelengths when the response trend of the transmittance to the wavelength of light is opposite; In this embodiment, the response trend of the transmittance to the wavelength of light is opposite means that the direction of the change of the transmittance with the wavelength is opposite, for example, in a certain wavelength interval, the transmittance increases with the increase of the wavelength (positive slope), and in another wavelength interval, the transmittance decreases with the increase of the wavelength (negative slope), refer to Figure 3 The blue and red curves in the figure respectively represent the corresponding two wavelengths when the response trend of the transmittance to the wavelength of light is opposite.

[0037] Specifically, a large number of spectra under different electric fields can be collected and used to train a model (a classification model or a regression model) to automatically identify the optimal wavelength pair that meets the condition that the response trend of transmittance to light wavelength is opposite; in actual measurement, the target wavelength can be directly output by the trained model according to the first spectrum.

[0038] In step S30, the first difference signal is calculated according to the target wavelength corresponding transmittance. Specifically, the target wavelength corresponding transmittance is the transmittance of light after passing through the electro-optic crystal corresponding to the target wavelength, and the target wavelength may contain noise interference caused by unstable factors such as light source jitter, detector gain drift, and optical path loss.

[0039] Since light source jitter, detector gain drift, and optical path loss will cause the same direction effect (both increase or both decrease) on the transmittance of the two wavelengths, by performing difference operation on the target wavelength corresponding transmittance, the common system noise components will be cancelled out, and the opposite changes caused by the electric field will be preserved or even amplified, thereby realizing high-precision and anti-interference measurement.

[0040] Specifically, the first difference signal can be calculated according to the target wavelength corresponding transmittance by a first calculation formula, which can be:

[0041] wherein, and are the target wavelength corresponding transmittances.

[0042] It can be understood that after the difference processing of the target wavelength corresponding transmittance, which is irrelevant to the noise signal, and Figure 4 ; that is, the system noise δ is eliminated in the difference operation, and the difference signal is inversely enhanced due to the opposite positive and negative values of the two effective signals, which can be expressed as: ΔT noise =[T( )+δ]-[T( )+δ]=ΔT. wherein δ is the system noise caused by light source jitter, detector gain drift, and optical path loss.

[0043] In step S40, the target electric field strength of the measured electric field is calculated according to the first difference signal.

[0044] Specifically, the target electric field strength can be found by looking up the table according to the first difference signal.

[0045] Since the system noise δ is eliminated in the differential operation, and the differential signal The two effective signals are opposite in sign, and the target electric field strength calculated according to the first differential signal is more accurate.

[0046] In the embodiment, the difference between the transmittance and the electric field response characteristics of the electro-optic crystal in a specific wavelength range is used, the two wavelengths with opposite response trends of transmittance to light wavelength are determined as target wavelengths according to the first spectrum, and the two wavelengths with opposite response trends of transmittance to electric field are selected for differential measurement, so that the system noise such as light source intensity fluctuation, detector noise and optical path loss is cancelled out in the differential signal, and the actual signal-to-noise ratio reaches 40 dB or more. According to the first differential signal, the target electric field strength of the measured electric field is calculated, thereby improving the accuracy of the measured electric field strength.

[0047] At the same time, when the light source is a broadband light source, flexible dual-wavelength selection space can be provided. The method of selecting two wavelengths from a single optical path reduces the difficulty of assembly and adjustment, is more suitable for industrial use, and reduces the measurement cost.

[0048] Based on the first embodiment of the present application, in the second embodiment of the present application, the same or similar contents as the above embodiment one can be referred to the above introduction, and will not be described in detail. On this basis, the implementation manner of determining the target wavelength according to the first spectrum can also be: According to the first spectrum, the rate of change of transmittance with wavelength is determined; the wavelength corresponding to the zero rate of change is taken as a characteristic wavelength; and the target wavelength is determined according to the characteristic wavelength.

[0049] Specifically, according to the first spectrum, the rate of change of transmittance with wavelength is determined, that is, the first derivative of the spectrum is calculated, which represents the rate of change (slope) of transmittance T with wavelength λ, referring to Figure 5 , the horizontal axis is wavelength λ, the vertical axis is relative transmittance T, and the curve corresponds to the current measured electric field.

[0050] Among them, the rate of change of transmittance with wavelength can be expressed as: dT / dλ. Positive slope: dT / dλ>0, transmittance increases with wavelength; Negative slope: dT / dλ<0, transmittance decreases with wavelength, zero slope: dT / dλ=0, extreme point (peak or valley).

[0051] Since the zero rate of change corresponds to the extreme point (maximum or minimum) in the transmittance curve, the wavelengths on both sides of the peak or valley have opposite response trends. Therefore, referring to Figure 5The embodiment takes the wavelength corresponding to the zero change rate as a characteristic wavelength, and determines a target wavelength according to the characteristic wavelength, so that the target wavelength, for which the response trend of the transmittance to the light wavelength is opposite, is selected more quickly and accurately, and the requirement of the dual-wavelength differential measurement is met.

[0052] Specifically, the implementation of determining the target wavelength according to the characteristic wavelength can be: selecting a first wavelength in a region with a change rate greater than zero and selecting a second wavelength in a region with a change rate less than zero based on the position of the characteristic wavelength; and taking the first wavelength and the second wavelength as the target wavelength.

[0053] It can be understood that when the characteristic wavelength corresponding to the zero change rate is determined, the position of the characteristic wavelength can be determined, and the position of the characteristic wavelength refers to the position of the characteristic wavelength in the target projection spectrum; and then a wavelength on the left and right sides of the position of the characteristic wavelength can be selected as the target wavelength. That is, a wavelength in a region with a change rate greater than zero is selected as a first wavelength and a wavelength in a region with a change rate less than zero is selected as a second wavelength based on the position of the characteristic wavelength, and the first wavelength and the second wavelength are taken as the target wavelength.

[0054] In another possible implementation, a wavelength point with the maximum absolute value of the change rate of the transmittance can be found on both sides of the characteristic wavelength, and the wavelength point is taken as the target wavelength; that is, a wavelength with the most sensitive change of the transmittance to the wavelength is selected, which can significantly improve the sensitivity of the detection system and enable the system to more accurately capture subtle changes.

[0055] In the embodiment, the point with the zero change rate of the transmittance with the wavelength in the first spectrum is determined as the characteristic wavelength, and the target wavelength is determined based on the characteristic wavelength, which can improve the determination efficiency of the target wavelength to a certain extent. In addition, a wavelength point with the maximum absolute value of the change rate of the transmittance can be found on both sides of the characteristic wavelength, and the wavelength point is taken as the target wavelength, which can significantly improve the sensitivity of the detection system and enable the system to more accurately capture subtle changes.

[0056] Based on the first embodiment, in the second embodiment, the same or similar contents as the above embodiment one can be referred to the above description, and will not be described hereinafter. On this basis, the implementation of calculating the target electric field intensity of the to-be-measured electric field according to the first differential signal can further be: calculating the target electric field intensity of the to-be-measured electric field according to the first differential signal and a preset correlation between the differential signal and the electric field intensity.

[0057] It should be noted that the preset correlation between the differential signal and the electric field intensity can be determined in advance by calibration, and the preset correlation between the differential signal and the electric field intensity can be expressed as:

[0058] Correspondingly, the second calculation formula is obtained: E=( TB) / K; Where K is the scaling factor and B is the offset.

[0059] It can be understood that by substituting the first differential signal into the second calculation formula mentioned above, the target electric field strength of the electric field to be measured can be calculated.

[0060] Specifically, before the step of acquiring the first spectrum using a spectrometer, the calibration process may include: After the incident light generated by the light source enters the electro-optic crystal placed in the reference electric field, a second spectrum is obtained by a spectrometer; based on the second spectrum, two reference wavelengths with opposite trends in the response of transmittance to light wavelength are determined; based on the transmittance corresponding to the two reference wavelengths, a second differential signal is calculated; based on the second differential signal and the preset electric field strength of the reference electric field, the correlation between the differential signal and the electric field strength is determined.

[0061] Specifically, this can be achieved by applying a reference electric field. After the incident light generated by the light source enters the electro-optic crystal placed in the reference electric field, the second spectrum is obtained by a spectrometer. Based on the second spectrum, the differential transmittance value dT / dλ of each wavelength is calculated, and the wavelength corresponding to dT / dλ being zero is selected as the historical characteristic wavelength. Based on the historical characteristic wavelength, two reference wavelengths with opposite trends in transmittance response to light wavelength are determined (the specific selection method is referred to the above actual measurement process).

[0062] Reference Figure 5 By applying a reference electric field Wavelength calibration was performed using a 1000 kV / m scanning spectrum. The wavelength corresponding to zero dT / dλ was selected as the historical characteristic wavelength, which is 1541.76 nm. In the positive slope linear region of lithium niobate crystals, the transmitted light intensity increases with increasing incident light wavelength; conversely, in the negative slope linear region, the transmitted light intensity decreases with increasing incident light wavelength. Therefore, the wavelength located at the rising edge of the transmittance-wavelength curve (dT / dλ>0 region) can be used as the first reference wavelength, and the wavelength located at the falling edge (dT / dλ<0 region) can be used as the second reference wavelength. The first reference wavelength is located in the positive slope region (…). >0), first reference wavelength = 1530 nm; second reference wavelength is located in the negative slope region ( <0), second reference wavelength = 1560 nm.

[0063] Further, a second difference signal is calculated according to the transmittances corresponding to the two reference wavelengths, and an electric field intensity of the reference electric field is output according to a pre-calibrated linear relationship E = (ΔT - B) / K.

[0064] The calibration curve is established in the following manner: measurement is performed at intervals of 5 kV / m in the range of 0-2000 kV / m, the difference processing unit calculates ΔT in real time, the proportionality coefficient K and the offset B are obtained by least square fitting, and the calibration curve E = (ΔT - B) / K is obtained, that is, the correlation between the difference signal and the electric field intensity is calibrated.

[0065] In the embodiment, the correlation between the difference signal and the electric field intensity is established by calibration, the measurement process is standardized, the calibration process unifies the system response characteristics, the accuracy of the measurement results under different times and environments is ensured, the measurement process is simplified, and the measurement efficiency is improved.

[0066] It should be noted that the above examples are only used for understanding the present application and do not constitute a limitation on the electric field sensing method of the electric-optical crystal based on the dual-wavelength difference measurement of the present application, and more forms of simple transformation based on this technical concept are within the protection scope of the present application.

[0067] The above only describes some embodiments of the present application, and does not limit the protection scope of the present application, and any equivalent structural transformation made by using the content of the present application specification and drawings, or direct / indirect application in other related technical fields is included in the protection scope of the present application. All actions of obtaining signals, information or data in the present application are performed under the premise of complying with the corresponding data protection regulations and policies of the country where the present application is located, and with the authorization given by the owner of the corresponding device.

Claims

1. An electro-optic crystal electric field sensing device based on dual-wavelength differential measurement, the electric field sensing device comprising a light source, an electro-optic crystal, a polarization-maintaining circulator, a collimating lens, a polarizer, an 1 / 8 wave plate and a reflector, wherein one port of the polarization-maintaining circulator is optically connected to one end of the light source, the second port is optically connected to one end of the electro-optic crystal, and the third port is optically connected to one end of the spectrometer. The light source is used to generate incident light; The optical path of the incident light includes: the incident light enters the polarization-maintaining circulator through the first port, exits from the second port and enters the collimating lens, passes through the polarizer and the electro-optic crystal, the polarizer is used to convert the incident light into linearly polarized light, the linear electro-optic effect of the electro-optic crystal causes the applied electric field to be measured to be loaded into the optical path in the form of a phase difference, and converts the linearly polarized light into elliptically polarized light, the elliptically polarized light enters the 1 / 8 wave plate and generates a fixed phase difference through the 1 / 8 wave plate, after being reflected by the reflector, it passes through the 1 / 8 wave plate, the electro-optic crystal and the polarizer again, the polarizer converts the elliptically polarized light into linear light, the linear light enters the collimating lens and exits from the third port into the spectrometer.

2. The electro-optic crystal electric field sensing device based on dual-wavelength differential measurement as described in claim 1, characterized in that, The incident light generated by the light source is broadband light.

3. The electro-optic crystal electric field sensing device based on dual-wavelength differential measurement as described in claim 1, characterized in that, The electro-optic crystal includes a z-cut lithium niobate crystal.

4. A method for sensing electric field using an electro-optic crystal based on dual-wavelength differential measurement, characterized in that, Applied to the electric field sensing device as described in any one of claims 1 to 3, the electro-optic crystal electric field sensing method based on dual-wavelength differential measurement includes: After the incident light generated by the light source enters the electro-optic crystal placed in the electric field to be measured, the first spectrum is obtained by a spectrometer. Based on the first spectrum, the target wavelength is determined, wherein the target wavelength is one of two wavelengths corresponding to opposite trends in the transmittance response to light wavelength; The first differential signal is calculated based on the transmittance corresponding to the target wavelength; The target electric field strength of the electric field to be measured is calculated based on the first differential signal.

5. The electro-optic crystal electric field sensing method based on dual-wavelength differential measurement as described in claim 4, characterized in that, The step of determining the target wavelength based on the first spectrum includes: Based on the first spectrum, determine the rate of change of transmittance with wavelength; The wavelength corresponding to zero rate of change is taken as the characteristic wavelength; The target wavelength is determined based on the characteristic wavelength.

6. The electro-optic crystal electric field sensing method based on dual-wavelength differential measurement as described in claim 4, characterized in that, The step of determining the target wavelength based on the characteristic wavelength includes: Based on the location of the characteristic wavelength, a first wavelength is selected in the region where the rate of change is greater than zero, and a second wavelength is selected in the region where the rate of change is less than zero. The first wavelength and the second wavelength are used as target wavelengths.

7. The electro-optic crystal electric field sensing method based on dual-wavelength differential measurement as described in claim 4, characterized in that, The step of calculating the target electric field strength of the electric field to be measured based on the first differential signal includes: The target electric field strength of the electric field to be measured is calculated based on the first differential signal and the preset correlation between the differential signal and the electric field strength.

8. The electro-optic crystal electric field sensing method based on dual-wavelength differential measurement as described in claim 7, characterized in that, Before the step of acquiring the first spectrum using a spectrometer, the method further includes: After the incident light generated by the light source enters the electro-optic crystal placed in the reference electric field, the second spectrum is obtained by a spectrometer. Based on the second spectrum, determine the two reference wavelengths corresponding to the opposite trends in the transmittance response to light wavelength; The second differential signal is calculated based on the transmittance corresponding to the two reference wavelengths. The correlation between the differential signal and the electric field strength is determined based on the second differential signal and the preset electric field strength of the reference electric field.

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