JPH077022B2 - Optical electric field measuring method and device - Google Patents

Description

TECHNICAL FIELD The present invention relates to an optical electric field measuring method and apparatus for measuring an AC electric field or an AC voltage for generating the AC electric field by utilizing the modulation effect of light by the Pockels effect. .

(Background Art) In recent years, as one of the technologies for measuring an electric field or voltage,
A measurement method using the Pockels effect, which is one of the electro-optical effects, is receiving attention. This is because according to this method, light serves as a medium, and as a result, it exhibits excellent characteristics such as good insulation and no electromagnetic induction noise.

By the way, in the measurement of the electric field (voltage) using the Pockels effect, as is well known, a sensor unit including a Pockels element and a polarizer and an analyzer arranged before and after the light transmission direction, A light emitting unit that emits light that is transmitted to the sensor unit, and light that is transmitted through the sensor unit is received,
An apparatus having a structure including a light receiving section that outputs an electric signal corresponding to the received light is used.

In such a device, when the light from the light emitting portion is transmitted through the sensor portion, the transmitted light is modulated according to the electric field strength acting on the Pockels element, and the light emitted from the analyzer is The intensity, that is, the intensity of the light received by the light receiving part is changed, and therefore, the electric field acting on the Pockels element or the voltage that gives the electric field is measured based on the electric signal output from the light receiving part. Can be done.

Thus, it has been recognized that the conventional optical electric field measurement device utilizing the Pockels effect has a problem that the output signal magnitude changes due to the environmental change of the installation position of the Pockels element. There is. One of the causes is that temperature dependence exists in the electro-optic constants of the Pockels element included in the relational expression for obtaining the electric field to be measured (voltage). Of course, various methods have been studied to solve this problem, but none of them have sufficiently solved such problems, or the method is complicated, or the device is large. However, there was a problem that it was not practical.

(Problems to be Solved) Here, the present invention has been made in view of such circumstances, and the problem to be solved is that the magnitude of the output signal does not change due to environmental changes, An object of the present invention is to provide an optical electric field measuring method and device capable of maintaining stable detection accuracy, and also in an optical electric field measuring device manufactured using a Pockels element whose electro-optical constant has temperature dependence, It is to compensate the characteristics and to realize the optical electric field / voltage measurement with a simple device structure.

(Solution) In order to solve the problem, the present invention arranges a polarizer and an analyzer in series before and after the light transmission direction of the Pockels element, and transmits the transmitted light in an electric field acting on the Pockels element. A light-receiving part that transmits the light emitted from the light-emitting part and outputs a signal corresponding to the received light while causing the AC electric field to be measured to act on the Pockels element of the sensor part configured to modulate At this time, when the transmitted light transmitted through the sensor unit is received and the AC electric field or the AC voltage for generating the AC electric field is obtained from the output signal of the light receiving unit, the Pockels element, together with the AC electric field, has a predetermined DC voltage. The light emitted from the light-emitting portion to the sensor portion while allowing the transmitted light to be received by the light-receiving portion, while the output signal of the light-receiving portion is used to transmit the light. The signal component (Eω) having the same angular frequency as the flowing electric field and the signal component (E ₂ ω) having twice the angular frequency are extracted, and the AC electric field or the AC voltage is obtained from their relative ratio. .

Further, in the present invention, in order to carry out such an optical electric field measuring method, (i) a Pockels element, and a polarizer and an analyzer arranged in series before and after the light transmission direction of the Pockels element are included. A sensor unit configured such that transmitted light is modulated by an electric field acting on the Pockels element, (ii) a DC electric field applying means for applying a predetermined DC electric field to the Pockels element, and (iii) the A light emitting portion that emits light to be transmitted to the sensor portion; (iv) a light receiving portion that receives the transmitted light that has passed through the sensor portion and that outputs a signal corresponding to the received light; and (v) the light receiving portion. The first output means for extracting a signal component (Eω) having the same angular frequency as the AC electric field acting on the Pockels element from the output signal of (1), and (vi) an AC acting on the Pockels element from the output signal of the light receiving unit. A second extracting means for extracting twice the angular frequency of the signal component of the field (E ₂ omega), relative ratio detection for obtaining the relative ratio of the signal component extracted by (vii) which first and second extracting means The optical electric field measuring apparatus is configured to include the means.

Furthermore, in the present invention, instead of (vii) the relative ratio detecting means in the above apparatus, (viii) the signal component (Eω) extracted by the first extracting means is constant so that the output from the light emitting section is constant. The gist is also an optical electric field measuring device provided with a feedback control means for controlling the intensity of the emitted light.

(Specific Configuration / Examples) The present invention will be described more specifically below with reference to the drawings showing some examples of the present invention.

First, FIG. 1 shows an example of an optical electric field (voltage) measuring apparatus according to the present invention, in which 2 is a sensor head section as a measuring section, and a Pockels element 4
A structure in which the polarizer 6 and the analyzer 8 are arranged in series before and after the light transmission direction of, and the fiber collimators 10 and 10 are arranged in series before and after the polarizer 6 and the analyzer 8. have. Then, electrodes 12, 12 are arranged on the surfaces of the Pockels element 4 of the sensor head portion 2 which face each other, and an AC voltage applying device for applying a measured AC voltage: V to the electrodes 12, 12. 13 and the predetermined DC voltage:
A DC voltage applying device 14 for applying V _DC is connected. Here, the DC voltage applying device 14 constitutes a DC electric field applying means.

On the other hand, in FIG. 1, reference numeral 15 denotes a light emitting section, which includes a light emitting element 16 and a light emitting element drive circuit 18 for driving the light emitting element 16, and the light emitted from the light emitting element 16 of the light emitting section 15 is ,
The light is guided to the fiber collimator 10 on the entrance side of the sensor head portion 2 through the optical fiber 20, and is made incident on the sensor head portion 2 from the fiber collimator 10 on the entrance side. Then, the light incident on the sensor head portion 2 from the input side fiber collimator 10 is transmitted through the polarizer 6, the Pockels element 4, and the analyzer 8 in order, and is emitted from the output side fiber collimator 10. The fiber collimator 10 is guided to the light receiving section 24 through the optical fiber 22 connected to the fiber collimator 10.

The light receiving unit 24 is configured to include a light receiving element such as a photodiode and a light receiving circuit that outputs an electric signal: E corresponding to the intensity of light received by the light receiving element: P, and the electric signal: E Are supplied to the same angular frequency component detector 26 and the double angular frequency component detector 28, respectively.

The same angular frequency component detector 26 to which the electric signal: E from the light receiving section 24 is supplied has the same angular frequency as the measured AC voltage: V applied to the Pockels element 4 by the AC voltage applying device 13:
A signal component of ω: Eω is taken out from an electric signal: E, and is composed of an electric filter, a phase detection circuit, etc., and a signal component taken out from the electric signal: E: E
ω is supplied to the division circuit 30. Also, 2
The double angular frequency component detector 28 is for extracting a signal component: E ₂ ω having an angular frequency: 2ω that is twice the measured AC voltage: V from the electrical signal: E, and the same angular frequency component detector 26 Similarly, it is composed of an electric filter, a phase detection circuit, etc., and supplies a signal component: E ₂ ω extracted from the electric signal: E to the division circuit 30. The division circuit 30 then outputs the signal component from the double angular frequency component detector 28:
E ₂ ω is divided by the signal component from the same angular frequency component detector 26: E ω, and the divided signal: E _T (= E ₂ ω / E ω) is output, which will be described later. as, according divided signals: from said E _T measured AC voltage: so that the V is measured.

In addition, as is apparent from the above description, here, the same angular frequency component detector 26 and the double angular frequency component detector 28 constitute the first extracting means and the second extracting means, respectively. Further, the division circuit 30 constitutes a relative ratio detecting means.

In such a device, the light emitted from the light emitting element 16 of the light emitting section 15 enters the sensor head section 2 from the optical fiber 20, passes through the optical fiber 22, and is received by the light receiving section 24. When the light incident on the sensor head portion 2 passes through the Pockels element 4, it is modulated according to the voltage (V, V _DC ) applied to the Pockels element 4. As a result, in the light receiving section 24, in the case of a parallel polarizer in which the relative angle of the polarization directions of the polarizer 6 and the analyzer 8: θ is 0 °, it is caused in the Pockels element 4 by the AC applied voltage: V. Assuming that the optical phase difference due to the direct current applied voltage: _VDC is ψ, the light having the intensity: P shown by the following formula (1) can be received.

^{_{P = cP o cos 2 {(}} φ + ψ) / 2} ··· (1) [where, c: proportional constant P _o: output light intensity of the light emitting element 16] Here, optical phase difference: phi is Pockels element Assuming that the half-wave voltage of 4 is Vπ, the amplitude of AC applied voltage: V is V _o , and its angular frequency is ω, it can be expressed as the following formula (2), so the above formula (1) can be expressed as the following (3) Therefore, the light receiving section 24 outputs the electric signal: E represented by the following expression (4).

φ = (π / Vπ) ・ V = (π / Vπ) ・ V _o・ sinωt ・ ・ ・ (2) [However, Eo: Amplitude of electric signal (E) A = (π / Vπ) · V _o ] Here, when the equation (4) is expanded using the Bessel function, the following equation (5) is obtained.

Therefore, as is apparent from the equation (5), the measured AC voltage V output from the same angular frequency component detector 26 and the signal component Eω having the same angular frequency are as shown in the following equation (6). Also, the measured AC voltage output from the doubled angular frequency component detector 28: the signal component with an angular frequency double that of V: E ₂ ω is expressed by the following equation (7) and output from the division circuit 30. The division signal: E _T to be expressed is expressed by the following equation (8).

Eω = −E _o・ J ₁ (A) ・ sin ψ ・ ・ ・ (6) E ₂ ω ＝ E _o・ J ₂ (A) ・ cos ψ ・ ・ ・ (7) Now, select A to 8.8 ° or less and ψ to 3.1 °.
If you choose below, A ^2/24 and [psi ^2/3 in the above (8)
Are both becomes a small value of 1 / 1,000 or less, still measured AC voltage: DC voltage applying voltage according to V: Adjust the V _DC, reduce the difference between the A ^2/24 and [psi ^2/3 if they A ^2/24
And [psi ^2/3 is further reduced, the equation (8) can be approximated as follows (9).

In the equation (9), A is A = (π / Vπ) V _o , and ψ is expressed as ψ = (π / Vπ) · V _DC , as described above. Equation (9) is given by (10) below.
It will be expressed like the formula.

That is, the division signal output from the dividing circuit 30: E _T is such (10) As is apparent from the equation, the AC voltage applying device 13
Measured AC voltage is applied to the Pockels element 4 in: the V amplitude: is than a value proportional to V _o, therefore, the division signals: from E _T, the measured applied to the Pockels element 4 AC voltage: V (amplitude: V _o) and than can be obtained, and its amplitude: from V _o, it is possible to determine the electric field applied to the Pockels cell 4.

And here, as is clear from the equation (10),
Divided signal: Measured AC voltage proportional to E _T : Amplitude of V: Proportional constant of V _o includes only DC applied voltage: V _DC , and half-wave voltage of Pockels element 4 having temperature dependence: Vπ Since it is not included in the proportionality constant, the division signal according to the change in environmental temperature at the installation position of the Pockels element 4 is:
Since E _T does not fluctuate, it is possible to stably obtain a measurement result without error due to environmental temperature.

In addition, the (10) As is apparent from the equation, the division signal output from the dividing circuit 30: The E _T, and the emitted light amount from the light emitting unit 15, the transmission loss of the optical propagation path, or the light receiving portion 24 The electric signal that varies according to the detection sensitivity: the amplitude of E: E _o is also not included, so the amount of light emitted from these light emitting units 15, the transmission loss of the optical propagation path, or the variation in the detection sensitivity of the light receiving unit 24, The division signal: E _T does not fluctuate, therefore
Even if the amount of light emitted from the light emitting section 15 or the detection sensitivity of the light receiving section 24 changes due to the aging of the light emitting element 16 or the light receiving element,
Due to this, there is also a feature that there is no error in the measurement result of the measured AC voltage: V (amplitude; V _o ).

Further, in the present invention, in addition to the above-mentioned device, a device for manufacture as shown in FIG. 2 can be used to detect the measured AC voltage: V (amplitude: V _o ). Is. In the device shown in FIG. 2, the light is emitted from the light emitting element 16 so that the value of the signal component Eω having the same angular frequency as the measured alternating voltage: V extracted by the same angular frequency component detector 26 becomes constant. The light quantity adjuster 32 for adjusting the quantity of light is provided as feedback control means. That is, based on the value of the signal component: Eω output from the same angular frequency component detector 26, the light amount adjuster (electronic circuit) 32 is driven by the light emitting element drive circuit.
18 so that the light quantity of light emitted from the light emitting element 16: P _o is adjusted so that the value of the signal component E E having the same angular frequency as the measured AC voltage V is constant. Is done.

In this way, a feedback circuit (32) that detects the signal component of the same angular frequency: Eω and adjusts the light amount: P _o of the light emitting element 16 so that the value thereof, that is, the value represented by the formula (6) becomes constant. ) is provided, light emission due to such feedback circuit (32) quantity: P _o double angle frequency components under feedback control of: detecting the E ₂ omega, the double angle frequency components: the measured AC voltage from E ₂ omega: V amplitude: be calculated for V _o, it is possible to obtain the same effects as device of the Figure 1. The adoption of such a method is advantageous in simplifying an electronic circuit for measuring an AC voltage (electric field).

The principle of the present invention has been described above based on the two specific examples according to the present invention shown in the drawings. According to the present invention, a technique for measuring an optical electric field (voltage) that is stable against environmental changes or aging changes is provided. Although it has been clarified that the present invention can be provided,
The present invention should not be construed as being limited to the specific examples given above, and does not depart from the spirit of the present invention.
It is to be understood that various changes, modifications, improvements, etc. can be made based on the knowledge of those skilled in the art.

For example, it is possible to use a dedicated power source for the voltage source of the DC voltage applying device 14 that applies a DC voltage to the Pockels element 4, but since the power consumption of such device is small, it is extracted from the measured AC voltage. It is also possible to use the rectified voltage as a voltage source of the DC voltage applying device 14. For example, when measuring the voltage of a transmission line or distribution line in the electric power field, an AC voltage extracted by a current transformer (CT) from the transmission line or distribution line may be used as the voltage source. is there.

Also, as the Pockels element 4 in the present invention, various known ones can be appropriately adopted, and for example, LiNbO ₃ , LiTaO ₃ , Bi ₁₂ SiO ₂₀ , Bi ₁₂ GeO ₂₀ , CdMnTe, and the like,
It will be appropriately used as a Pockels element.

(Effects of the Invention) As is apparent from the above description, the present invention converts light modulated according to the strength of the electric field applied to the Pockels element into an electric signal, and acts on the Pockels element from the electric signal. 2 and a signal component (Eω) of the same angular frequency as the AC electric field
Taking out the signal component (E ₂ ω) of double the angular frequency and measuring the AC electric field or voltage from their relative ratio, the electro-optical constant of the Pockels element and the amount of light emitted from the light emitting part, Alternatively, it is possible to measure the AC electric field or voltage without using the detection sensitivity in the light emitting part, and therefore, it is possible to detect changes over time in environmental temperature, aging of the light emitting element in the light emitting part or the light receiving element in the light receiving part. Stable detection accuracy can be maintained without being affected.

Therefore, for example, even in the optical electric field measurement device manufactured using the Pockels element having temperature dependence, it was possible to compensate for the temperature characteristics, and in a simple device structure, it was possible to perform accurate measurement, This is where the great industrial significance of the present invention lies.

[Brief description of drawings]

FIG. 1 and FIG. 2 are layout diagrams of devices showing different embodiments of the present invention. 2: Sensor head part, 4: Pockels element 6: Polarizer, 8: Analyzer 10: Fiber collimator 14: DC voltage application device 15: Light emitting part, 18: Light emitting element drive circuit 24: Light receiving part 26: Same angular frequency component Detector 28: Double angle frequency component detector 30: Division circuit, 32: Light intensity adjuster

Claims (3)

[Claims] 1. A sensor unit configured such that a polarizer and an analyzer are arranged in series before and after the light transmission direction of the Pockels element, and the transmitted light is modulated by an electric field acting on the Pockels element, While the AC electric field to be measured is applied to the Pockels element, the light emitted from the light-emitting portion is transmitted, and the light-transmitting portion that outputs a signal corresponding to the received light transmits the light transmitted through the sensor portion. When detecting the AC electric field or the AC voltage for generating the AC electric field from the output signal of the light receiving section, the Pockels element is acted on with the predetermined DC electric field together with the AC electric field, and the sensor section is caused to emit the light. Light emitted from the light receiving portion is transmitted, and the transmitted light is received by the light receiving portion, while a signal component (Eω) having the same angular frequency as the AC electric field is output from the output signal of the light receiving portion. Times the angular frequency of the signal component (E ₂ ω) removed from their relative ratios,
A method for measuring an optical electric field, characterized by obtaining the alternating electric field or the alternating voltage. 2. A Pockels element, and a polarizer and an analyzer arranged in series in front of and behind the light transmission direction of the Pockels element, wherein the transmitted light is modulated by an electric field acting on the Pockels element. A sensor unit, a DC electric field applying unit for applying a predetermined DC electric field to the Pockels element, a light emitting unit for emitting light to be transmitted to the sensor unit, and a transmitted light transmitted through the sensor unit. A light receiving unit that receives light and outputs a signal corresponding to the received light, and a first extracting unit that extracts a signal component (Eω) having the same angular frequency as the AC electric field acting on the Pockels element from the output signal of the light receiving unit. When, from the output signal of the light receiving portion, and the second extracting means for extracting twice the angular frequency of the signal component of the AC electric field acting on the Pockels element (E ₂ omega), which first and The relative ratio detecting means for determining the relative ratio of the signal component extracted by the two-take-out means, the optical electric field measuring device which comprises. 3. A Pockels element, and a polarizer and an analyzer arranged in series in front of and behind the light transmission direction of the Pockels element, wherein the transmitted light is modulated by an electric field acting on the Pockels element. A sensor unit, a DC electric field applying unit for applying a predetermined DC electric field to the Pockels element, a light emitting unit for emitting light to be transmitted to the sensor unit, and a transmitted light transmitted through the sensor unit. A light-receiving unit that receives and outputs a signal corresponding to the received light, and a first extracting unit that extracts a signal component (Eω) having the same angular frequency as the AC electric field acting on the Pockels element from the output signal of the light-receiving unit. When, from the output signal of the light receiving portion, and the second extracting means for extracting twice the angular frequency of the signal component of the AC electric field acting on the Pockels element (E ₂ omega), the first take-out Signal component extracted by stage (Eω)
And a feedback control means for controlling the intensity of the light emitted from the light emitting section so as to be constant.