JPS6166969A - Optical voltage sensor - Google Patents

Abstract

PURPOSE:To improve characteristics by providing two voltage measurement systems which are equal in half-wavelength voltage and different in phase difference and measure the same voltage on the same substrate. CONSTITUTION:The two voltage measurement systems A and B which are equal in half-wavelength voltage and difference in phase difference are provided on the same substrate. Those measurement systems A and B are applied with output light from the same light source 50 and also applied with a measurement voltage from the same signal source 40, and measurement light output signals P1 and P2 of those measurement systems A and B are converted by photodetecting elements 60 and 70 into electric signals, which are applied to a signal processing circuit 80. Those signals P1 and P2 have a phase difference based upon the difference in length between photoconductor bodies. For example, when the measurement voltage applied from a signal line 40 is lower than a half-wavelength voltage, it is nearly proportional to the measurement voltage of the signal P2 of the measurement system B. The noise component of the signal P1 of the measurement system A, on the other hand, is obtained from a specific expression and calculated by the circuit 80 to obtain a measurement output; the noise is canceled and a voltage measurement with a superior S/N is taken.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a photovoltage sensor, and more particularly to a photovoltaic sensor configured to intensity-modulate light passing through a guiding waveguide body with a measurement electric field. This invention relates to improvements in voltage measurement characteristics in sensors.

[Conventional technology]

By thermally expanding a metal impurity such as titanium (T1) on a substrate made of an electro-optic material It such as lithium niobium (LiNbO), a leading waveguide with a higher refractive index than the substrate is formed, and the electro-optic effect is enhanced. A leading waveguide body with extremely high efficiency can be obtained. When an electric field is applied to such a leading wavepath,
The light passing through the leading waveguide is intensity modulated by the electro-optic effect.

One type of such a leading waveguide body is a branching interference type optical waveguide body as shown in No. 3150.

In FIG. 3, 10 is a substrate, 20 is a leading waveguide, and 30 is! Pole 40 is a signal source.

The substrate 10 is made of niobium-dipped lithium (L), which has an electro-optic effect.
It is made of an electro-optical material such as iNbO, and is cut so that, for example, the X and Z axes are horizontal planes and the Y axis is a vertical plane.

The optical waveguide 20 is formed into a linear shape by thermally expanding a metal impurity such as titanium (Ti) on the substrate 10.
It has a higher refractive index than the figure 7-shaped branch 21. A mutually parallel phase Ht shifting portion 22 and a 7-shaped coupling portion 23 are continuously integrated. The electrode 30 connects the leading waveguide 20 to intensity modulate the light passing through the optical waveguide 20.
The first electrode 31 and the second electrode 32 are connected to the substrate 1 with the phase striking part 22 in between.
0-1:. These electrodes are formed by laminating, for example, gold and tarom in a predetermined pattern. The signal source 40 supplies an electric field, and the first
is connected between the electrode 31 and the second electrode 32.

An optical fiber for transmitting light from a light source such as a laser diode is connected to the end of the figure-7-shaped branching part 21 of the leading waveguide 20, and an optical fiber for transmitting light from a light source such as a laser diode is connected to the end of the figure-7-shaped coupling part 23. An optical fiber for transmitting light to a light receiving element such as a phototransistor is connected, but is not shown.

In such a configuration, when light from a light source is applied to the end of the 7-shaped branching section 21 of the leading waveguide 20, the light is divided into two by the branching section 21 and transmitted to the phase shifting section 22. In the phase shifting section 22, a phase difference corresponding to the magnitude of the output of the signal source 40 applied via the electrode 30 is applied between the two divided lights.

Then, these lights having a phase difference are combined again at the coupling part 23. As a result, intensity-modulated light is sent out from the end of the coupling section 23.

Here, since the phase shift unit 22 has λ/4! /By applying intensity-modulated light to the light receiving element by giving a phase difference, the electrode 3
0 can be obtained according to the magnitude of the output of the signal source 4o.

(Problems to be Solved by the Invention) By the way, the intensity-modulated light in such a conventional device is limited by the magnitude of the output of the signal source 40 applied via the Wi pole 30, for example, as shown in FIG. Therefore, it is difficult to measure a voltage larger than the half-wavelength voltage Noise caused by output fluctuations etc. cannot be reduced, and resolution and accuracy will be limited.

The present invention solves these conventional drawbacks, and its purpose is to expand the voltage measurement range and increase the measurement output value () in an optical voltage sensor using a guiding waveguide.
The objective is to cancel out noise caused by fluctuations in the output of the light source included in the image, thereby increasing resolution and sharpness.

[Means for solving problems]

The present invention achieves the above object, in which a guide waveguide body and an electrode for applying a measurement electric field to the optical waveguide body are formed on a substrate made of an electro-optic material, and the intensity of light passing through the optical waveguide body is measured by the measurement electric field. In an optical voltage sensor configured to modulate, two voltage measurement systems are provided on the same substrate to measure the same voltage with equal half-wavelength voltages and different phase differences,
Arithmetic processing of the measured voltage based on the measurement signals of these voltage measurement systems is defined as a #+ sign.

(Example〕 Hereinafter, it will be explained in detail using the drawings.

FIG. 1 is an explanatory diagram showing the main parts of an embodiment of the present invention, and the same parts as in FIG. 3 are given the same reference numerals. 1st
In the figure, two voltage measurement systems A are constructed on the same substrate 10 in substantially the same manner as in FIG. 3 so that the 11' wavelength voltages are equal and the phase difference is different.

B is provided. These two voltage measurement systems A and B
Output light is applied from the same light f150 and measurement voltage is applied from the same signal 'a40, and the measurement light output No. 4n of each voltage measurement system A and B is converted into an electric signal by the light receiving element 60, 70, respectively. The converted signal processing circuit 80
has been added to.

The operation of the apparatus configured in this way will be explained using FIG. 2.

FIG. 2 is a diagram showing an example of the measurement light output signal of each of the voltage measurement systems A and H in FIG. 1. In FIG. 2, the solid line indicates the measurement light output signal P of the voltage measurement system A, and the llJ line indicates the measurement light output signal P8 of the voltage measurement system B. As shown in FIG. 2, between these measurement optical output signals r', , P,
A phase difference d+ (90 degrees in this embodiment) is generated based on the difference in length of the leading waveguide body. In the following description, the measurement voltage components of the measurement light output signal P, are P, s, the noise components are P, n, the measurement voltage components of the measurement light output signal P, P, s, and the noise components are P, Let n be the average of the measurement light output signal P, and let P and av be the average of the measurement light output signal P.
, let P and av be the average of .

For example, if the measurement voltage Vin applied from the signal source 40 is lower than the wavelength voltage Vw, then the
Measured voltage component P of the measurement destination output signal P of the 71111 electrical system B.

S is approximately proportional to the measured voltage Vin. on the other hand,
Noise components P, n of the measurement destination output signal P of the voltage measurement system A
is P, n −(P, av/P, av)4. It becomes n. Therefore, in the signal processing circuit 80, Pout=J-4
m − (P, s + P, n) − (P, av / P * av l (P
,s+P,n)=P+5-(F'+av/Lav)4
．． By calculating s and finding the measurement output Pout,
Noises P and n can be canceled, and electrical measurements with an excellent SIN ratio can be performed.

On the other hand, the measurement voltage Vin applied from the signal source 40
is higher than the half-wavelength voltage ■τ, the signal processing circuit 80 compares the measurement optical output signal P of the voltage measurement system A and the measurement optical output signal P3 of the voltage measurement system B to obtain the measurement optical output signal P, In addition to determining the increase or decrease of the measured light output (A No. P
The number of peaks of 1 is decreased by the old iI. Note that the relationship Vd between the peak-to-peak measurement voltage Vin and the measurement optical output signal P1 is prepared in advance in a table. As a result, when the measurement optical output (+!'j P ) is counted by Nf, the measurement voltage Vin becomes Vin=2Vw+Vd, and it is possible to measure the measurement voltage Vin which is sufficiently higher than that of the conventional method.

Note that as the substrate, for example, lithium tantalate (Li
A material made of TaO, ) may also be used.

(Effects of the Invention) As is clear from the above, according to the present invention, in an optical voltage sensor using a guiding waveguide, the voltage measurement range can be expanded, and output fluctuations of the light source included in the measurement output signal can be suppressed. The resolution and accuracy can be improved by canceling the noise caused by the noise, and an optical voltage sensor with excellent characteristics can be realized.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing one embodiment of the present invention;
1 is an explanatory diagram of the operation of FIG. 1, FIG. 3 is an explanatory diagram of the configuration of an example of a conventional optical voltage sensor, and FIG. 4 is an explanatory diagram of the operation of FIG. 3. DESCRIPTION OF SYMBOLS 10... Substrate, 20... Leading wave path, 3o... Electrode, 40... Signal source, 50... Light source, 60.70...
- Light receiving element, 80... Signal processing circuit, A, B... Voltage measurement system.

Claims (1)

[Claims] In a photovoltage sensor, an optical waveguide body and an electrode for applying a measurement electric field to the optical waveguide body are formed on a substrate made of an electro-optic material, and the light passing through the optical waveguide body is intensity-modulated by the measurement electric field. , is characterized in that two voltage measurement systems that measure the same voltage with equal half-wavelength voltages and different phase differences are provided on the same substrate, and the measured voltage is processed based on the measurement signals of these voltage measurement systems. Optical voltage sensor.