JPH08233883A - Electric field sensor - Google Patents

Abstract

PURPOSE: To improve frequency characteristics and obtain sufficient reliability. CONSTITUTION: The sensor consists of a light source 11 for transmitting light to an electric field sensor head 1 as an input light, a photodetector 13 for detecting an output light output from the electric field sensor head 1, the electric field sensor head 1 and optical fibers 16, 17. The electric field sensor head 1 has a crystal substrate 20, branching interference-type optical waveguide elements 21, 22, 23, 24 formed on the crystal substrate 20, modulation electrodes 25, 26 arranged in the vicinity of the optical waveguide elements 21, 22, 23, 24 and an elastic body 10 attached to at least, a part of the crystal substrate 20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric field sensor for measuring electric field strength in space, and more particularly to an electric field sensor for high electric field.

[0002]

2. Description of the Related Art In recent years, there has been a problem that a device such as a computer system malfunctions due to an electromagnetic interference wave caused by an electric device such as an inverter air conditioner. Countermeasures against these EMC (electromagnetic compatibility) tests and malfunctions. Therefore, it is necessary to measure the electromagnetic interference wave radiated from the device or the electromagnetic interference wave entering the device.

In particular, recently, measurement of electromagnetic pulses in the time domain and measurement of theoretically determining a radiation electromagnetic field have become important. Based on such a background, an electric field sensor in which a branch interference optical waveguide type electric field sensor head and a level measuring device are connected by an optical fiber has been studied.

In such an electric field sensor, an unmodulated optical signal is input to the electric field sensor head via an optical fiber,
The light is modulated by the electric field level detected by the dipole antenna and transmitted to the level measuring device through the optical fiber.

As shown in FIG. 4, a branch interference optical waveguide type electric field sensor head 100 has a crystal substrate 120 exhibiting an electro-optical effect, a branch interference optical waveguide element formed on the crystal substrate 120, and a branch interference. Type dipole antenna-shaped modulation electrodes 125, 12 provided near the optical waveguide element
6.

The branch interference type optical waveguide device includes two phase shift optical waveguides 123 and 124, an incident optical waveguide 121 connected to one end of the two phase shift optical waveguides 123 and 124, and two optical waveguides. Phase shift optical waveguides 123, 12
4 and the output optical waveguide 122 connected to the other end side.

On the crystal substrate 120, the modulation electrodes 125 and 1 are provided in the vicinity of the two phase shift optical waveguides 123 and 124.
26 are provided.

The electric field sensor head 100 includes an incident waveguide 1
21 is connected to the light source 11 via the optical fiber 116,
The photodetector 113 and the measuring instrument 114 are connected to the output waveguide 122 via an optical fiber 117. The dipole antenna 1 is provided on each of the modulation electrodes 126, 126.
35 is connected.

In the branch interference optical waveguide type electric field sensor head, the modulation electrode 12 provided near the dipole antenna 135 and the two phase shift optical waveguides 123 and 124.
5 and 126, the electric field level detected by the dipole antenna 135 becomes opposite to each other due to the electro-optic effect of the two phase shift optical waveguides 123 and 124 via the modulation electrodes 125 and 126. Since the changes in phase are opposite to each other, the intensity of the combined light changes.

Further, as shown in FIG. 5, by forming the dipole antenna 135 shown in FIG. 4 on the substrate 120, the electric field sensor head 100 becomes compact and measurement in a narrow space becomes possible. It has also been applied to the measurement of high electric fields.

[0011]

However, the substrate 1
Although the electric field sensor head 100 in which the dipole antenna 135 is formed on the antenna 20 is small, good frequency characteristics cannot be obtained in electric field measurement, and there is room for improvement in reliability of measurement results.

Therefore, an object of the present invention is to improve the frequency characteristics of a small-sized electric field sensor head having a dipole antenna formed on a crystal substrate and provide an electric field sensor having sufficient reliability.

[0013]

According to the present invention, an electric field sensor head, a light source for transmitting light to the electric field sensor head as input light, and a light detector for detecting output light output from the electric field sensor head. And an electric field sensor head,
The electric field sensor head includes an optical fiber in which the light source and the photodetector are connected to each other, and the electric field sensor head includes a crystal substrate, a branch interference optical waveguide element formed on the crystal substrate, and the branch interference optical waveguide. An electric field sensor having a dipole antenna-shaped modulation electrode arranged in the vicinity of a waveguide element and an elastic body attached to at least a part of the crystal substrate can be obtained.

Further, according to the present invention, the branch interference type optical waveguide device includes an input optical waveguide formed on the crystal substrate, two phase shift optical waveguides branched from the input optical waveguide, and An electric field sensor having an output optical waveguide to which two phase shift optical waveguides are coupled, and the modulation electrode being arranged in the vicinity of the two phase shift optical waveguides.

Further, according to the present invention, the branch interference type optical waveguide device includes an input optical waveguide formed on the crystal substrate, two phase shift optical waveguides branched from the input optical waveguide, and A light reflecting portion arranged at the tip of the phase shift optical waveguide of the present invention, wherein the light source transmits the light from the light source as input light to the electric field sensor head and outputs the output light from the electric field sensor head. An electric field sensor having an optical directional separator attached to transmit to a photodetector.

Further, according to the present invention, there is obtained an electric field sensor characterized in that an elastic body is attached to a side surface of the crystal substrate parallel to the two phase shift optical waveguides.

Also, according to the present invention, there is provided an electric field sensor characterized in that one of epoxy resin, silicone resin, rubber or polyester resin is selected and used as the elastic body.

[0018]

The principle of operation of the electric field sensor head of the branch interference optical waveguide type is that, as described in the conventional example, an electric field is applied to the phase shift optical waveguide via the modulation electrode, and the bending rate due to the electro-optical effect resulting therefrom is obtained. The light intensity is modulated through the change of.

By attaching an elastic body to the crystal substrate constituting the electric field sensor head, the frequency characteristic of the electric field sensor is significantly improved.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An electric field sensor according to the present invention will be described below with reference to the drawings. FIG. 1 shows a first embodiment of an electric sensor according to the present invention, which is embodied in a so-called transmission type electric field sensor head. FIG. 2 shows a second electric field sensor according to the present invention.
This is an embodiment and is embodied in a so-called reflection type electric field sensor head. Each of the above electric field sensors has its own characteristics, but its function is basically the same.

As shown in FIG. 1, the electric field sensor of the first embodiment has a transmission type electric field sensor head 1 and a light source 11 connected to the input side of the electric field sensor head 1 via an input optical fiber 16. And a photodetector 13 and a measuring instrument 14 which are connected to the output side via an output optical fiber 17.

The electric field sensor head 1 has a crystal substrate 20 showing an electro-optical effect, a branch interference type optical waveguide element formed on the crystal substrate 20, and a dipole antenna shape provided in the vicinity of the branch interference type optical waveguide element. Modulating electrodes 25, 2
6. Here, the vicinity of the branch interference type optical waveguide device includes the top and the side of the modulation electrodes 25 and 26.

The branch interference type optical waveguide device comprises a crystal substrate 20.
The two phase shift optical waveguides 23 and 24 formed above,
The incident optical waveguide 21 connected to one end side of the two phase shift optical waveguides 23 and 24 and the output optical waveguide 2 connected to the other end side of the two phase shift optical waveguides 23 and 24
And 2.

The light source 11 is connected to the incident waveguide 21 via the input optical fiber 16, and the photodetector 13 and the measuring instrument 14 are connected to the output waveguide 22 via the output optical fiber 17.

The transmission type electric field sensor head 1 of the first embodiment.
Uses a crystal substrate 20 of lithium niobate crystal cut out perpendicularly to the z-axis direction. An incident optical waveguide 21 is provided on the surface of the crystal substrate 20, and 2 is branched from the input optical waveguide 21.
The phase shift optical waveguides 23 and 24, and the output optical waveguide 22 to which the two phase shift optical waveguides 23 and 24 are coupled are formed. These two phase shift optical waveguides 2
Modulation electrodes 25 and 26 are arranged in the vicinity of 3 and 24. An epoxy resin is attached as an elastic body 10 to at least a part of the crystal substrate 20. For the elastic body 10, silicone resin, rubber, polyester resin, or the like can be used in addition to epoxy resin. In the first embodiment, epoxy resin is attached to both side surfaces of the crystal substrate 20 parallel to the two phase shift optical waveguides 23 and 24.

A second embodiment of the electric field sensor will be described with reference to FIG. The same parts as those of the electric field sensor according to the first embodiment described with reference to FIG. As shown in FIG. 2, the electric field sensor of the second embodiment includes a reflection type transmission type electric field sensor head 2 and a light source 11 connected to the input side of the electric field sensor head 2 via an input optical fiber 16. , A light detector 13 and a measuring instrument 14 which are connected to the light source 11 via an optical fiber 18.

The electric field sensor head 2 has a crystal substrate 20 exhibiting an electro-optical effect, a branch interference type optical waveguide element formed on the crystal substrate 20, and a dipole antenna shape provided near the branch interference type optical waveguide element. Modulating electrodes 25, 2
6 and the light reflection part 30.

The branch interference type optical waveguide device includes two phase shift optical waveguides 23 and 24 and an incident optical waveguide 21 connected to one end side of the two phase shift optical waveguides 23 and 24.
And have. Two phase shift optical waveguides 23 and 24
Modulation electrodes 25 and 26 are provided in the vicinity of.

The reflection type transmission type electric field sensor head 2 has a z
A crystal substrate 20 of a lithium niobate crystal cut out perpendicularly to the axial direction is used. On the crystal substrate 20, an input optical waveguide 221, two phase shift optical waveguides 23 and 24 branched from the input optical waveguide 21, and a light reflecting portion 30 at the other ends of the two phase shift optical waveguides 23 and 24. Are arranged. At least a part of the crystal substrate 20 has an elastic body 10
Epoxy resin is attached as. In the second embodiment, epoxy resin is attached to both side surfaces of the crystal substrate 20 parallel to the two phase shift optical waveguides 23 and 24.

The light source 11 is provided with an optical directional separator 31 for transmitting light from the light source 11 as input light to the electric field sensor head 2 and transmitting output light from the electric field sensor head 2 to the photodetector 13. Have The light direction separator 31 separates the light from the light source 11 and the output light from the electric field sensor head 2.

In the first and second embodiments, a so-called z plate made of lithium niobate crystal is used, but x plate and y plate are used.
The same effect can be obtained with a plate.

FIG. 3A is a frequency characteristic diagram showing the relationship between the frequency and the optical output of the conventional electric field sensor.
(B) is a frequency characteristic diagram showing the relationship between the frequency and the optical output of the electric field sensor of the present invention.

As shown in FIG. 3A, in the electric field sensor in which the dipole antenna 135 shown in FIG. 4 is formed on the crystal substrate 120, the frequency characteristic of the electric field sensor head 100 does not become flat especially near 700 kHz.
Although the detailed cause of this phenomenon is still being clarified, the present inventor speculates that it is due to the resonance due to the voltage effect due to the substrate crystal exhibiting the electro-optical effect.

In order to solve this problem, it is effective to attach an elastic body 10 such as an epoxy resin to the crystal substrate 20 constituting the electric field sensor head 1 or 2. First
It can be understood that the electric field sensor shown in the second embodiment has the frequency characteristic of FIG. 3B significantly improved as compared with the frequency characteristic of FIG.

[0035]

As described above with reference to each embodiment,
According to the electric field sensor of the present invention, although the dipole antenna is miniaturized by forming it on the crystal substrate, the electric field sensor head that causes a decrease in frequency characteristics is provided with an elastic body on the crystal substrate constituting the electric field sensor head. By providing an electric field sensor with improved characteristics, it is possible to perform measurement in a narrow space and measurement of a high electric field with high reliability.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a first embodiment of an electric field sensor of the present invention.

FIG. 2 is a configuration diagram showing a second embodiment of the electric field sensor of the present invention.

FIG. 3A is a frequency characteristic diagram of a conventional electric field sensor. (B) is a frequency characteristic diagram of the electric field sensor of the present invention.

FIG. 4 is a configuration diagram of a conventional electric field sensor.

FIG. 5 is a configuration diagram of a conventional electric field sensor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Transmission type electric field sensor head 2 Reflection type electric field sensor head 10 Elastic body 11,111 Light source 13,113 Photodetector 14,114 Measuring instrument 16,116 Input optical fiber 17,117 Output optical fiber 20,120 Crystal substrate 21 , 121 incident optical waveguide 22 output optical waveguide 23, 24 phase shift optical waveguide 25, 26, 125, 126 modulation electrode 30 light reflecting portion 31 directional separator

Claims (5)

[Claims] 1. An electric field sensor head, a light source for transmitting light to the electric field sensor head as input light, a photodetector for detecting output light output from the electric field sensor head, the electric field sensor head, and the light source. And an optical fiber in which each of the photodetectors is connected to each other, and the electric field sensor head includes a crystal substrate, a branch interference type optical waveguide element formed on the crystal substrate, and the branch interference type optical waveguide element. An electric field sensor comprising: a dipole antenna-shaped modulation electrode disposed in the vicinity of the crystal substrate; and an elastic body attached to at least a part of the crystal substrate. 2. The electric field sensor according to claim 1, wherein the branch interference type optical waveguide element includes an input optical waveguide formed on the crystal substrate, and two phase shift optical waveguides branched from the input optical waveguide. And an output optical waveguide to which the two phase shift optical waveguides are coupled, and the modulation electrode is arranged in the vicinity of the two phase shift optical waveguides. 3. The electric field sensor according to claim 1, wherein the branch interference type optical waveguide element includes an input optical waveguide formed on the crystal substrate and two phase shift optical waveguides branched from the input optical waveguide. A light reflecting portion arranged at the tips of the two phase shift optical waveguides, wherein the light source transmits light from the light source as input light to the electric field sensor head and outputs from the electric field sensor head. An electric field sensor comprising an optical directional separator attached to transmit light to the photodetector. 4. The electric field sensor according to claim 2 or 3, wherein an elastic body is attached to a side surface of the crystal substrate parallel to the two phase shift optical waveguides. 5. The electric field sensor according to claim 1, wherein the elastic body is selected from epoxy resin, silicone resin, rubber, and polyester resin.