JPH0989961A - Electric field detecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect a high electric field by forming a plurality of phase shifting optical waveguides in the Z-axial direction of the crystalline axis of an electrochemical crystal plate to enhance the half-wavelength electric field. SOLUTION: The light from a light source 6 passed through a single mode fiber 6 is incident on a sensor head 1. The head 1 is formed of an optical waveguide for propagating the light in the Z-axial direction by use of an X-plate 11 and a modulating electrode 15, the incident light from an incident optical waveguide 12 is passed through two phase shift optical waveguides 13, recombined in an emitting optical waveguide 14, and emitted to a fiber 7. With the result that a voltage guided to an antenna 60 by electric field is applied to a pair of demodulating electrodes 15 near the phase shift optical waveguides 13 to change the phase of the light passed through the phase shift optical waveguides 13, the guided lights bonded in the emitting optical waveguide 14 are mutually interfered, passed through the fiber 7, and incident on a light detector 63, and the light intensity is converted into electric signal, and measured and displayed by a measuring instrument 64. The head 1, which is of polarization independent type independent from polarizing surface, requires no polarizing regulation, and is functioned by a single mode fiber 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for detecting the electric field strength of radiated electromagnetic waves and the like, especially the electrostatic field or the electric field in a relatively low frequency band.

[0002]

2. Description of the Related Art Electric field detection is essential for maintenance and condition monitoring of electric power equipment including transmission and distribution lines. In recent years, in this field, electric field detection utilizing the electro-optic effect has been put into practical use and is effective.

FIG. 7 is a diagram showing the structure of a conventional electric field detecting device. In FIG. 7, the light incident on the sensor head 4 is guided to the antenna 60 by the electric field, modulated by applying the voltage guided to the sensor head 4, and the emitted light intensity is measured to detect the electric field intensity. be able to.

FIG. 8 is a diagram showing an outline of a sensor head used in the electric field detecting device shown in FIG. Sensor head 4
Is a substrate 41 that exhibits an electro-optical effect, such as lithium niobate.
It consists of the optical waveguide element formed on the above. Conventionally, the normal line of the substrate has been set to the X
The axis (hereinafter, X plate) or the normal is the Z axis (hereinafter, Z plate)
A substrate to be used as a plate was used. In addition, when a voltage is applied in the Z-axis direction, the electro-optical effect is high, so in the case of the X-plate substrate, the optical waveguide is in the Y-axis direction, and in the case of the Z-plate substrate, the X-axis direction or the Y-axis direction. It is desirable to take, and many of the sensor heads have been manufactured and used accordingly. In this case, a conductive film is provided on the surface of the substrate in order to prevent deterioration of temperature characteristics due to the pyroelectric effect.

Since the electric field detecting device according to this method uses the optical fiber as the signal transmission line, not only the transmission loss is small and long-distance transmission is possible, but also the transmission and reception of noise between the optical fiber and the environment. There are features such as not being

[0006]

However, the electric field detection loss has some disadvantages described below.

First, the presence of the conductive film between the electrodes causes deterioration of characteristics particularly in the low frequency region required in the electric power field. Second, the half-wavelength voltage (hereinafter, Vπ), which is one of the characteristics of the sensor head 4, is about 2 volts (V), which limits the detection of a high electric field. Thirdly, the modulation characteristics of the sensor head 4 are different depending on whether the incident light of the sensor head 4 is TE polarized light or TM polarized light, so that it is unavoidable to define the polarization of the incident light. Therefore, it is necessary to add polarization adjusting means 62 such as a wavelength plate near the emission end of the light source 61, and to use the polarization plane holding fiber 46 as the input optical fiber of the sensor head 4. Therefore, a polarization plane adjusting operation is required for the assembly adjustment of the electric field detecting device, and in addition,
The use of 6 causes a cost increase. As described above, with the realization of long-distance transmission, in the case of performing electric field detection in a remote place, the economic disadvantages are large. Also, a polarization separator is placed on the end face of the incident optical waveguide of the sensor head,
A method of separating the polarized light and making it incident is also possible. However, in this case, the optical loss increases and the output varies due to the stress applied to the fiber, which cannot solve the problem.

The present invention makes it possible to detect a high electric field by compensating for the disadvantages of the above-mentioned electric field detecting device according to the prior art, that is, by increasing the half-wave electric field Vπ, and to depend on the polarization of incident light. Therefore, an electric field detecting device using a single mode fiber is provided instead of the polarization maintaining fiber, which does not require polarization adjusting means and causes a cost increase.

[0009]

In order to solve the above problems, the present invention provides an incident optical waveguide formed on an electro-optic crystal substrate, two phase shift optical waveguides branched from the incident optical waveguide, and two phase shift optical waveguides. The shift optical waveguide consists of the re-coupled output optical waveguide, the modulation electrodes formed in pairs near the two phase shift optical waveguides, and the antenna section connected to the modulation electrode. A sensor head that changes the intensity of light emitted through the optical waveguide depending on the voltage applied to the electrode, an input optical fiber and an output optical fiber connected to the sensor head, and the other end of the input optical fiber In the electric field detecting device comprising a light source, a photodetector connected to the other end of the output optical fiber, and a measuring instrument having the output of the photodetector as an input, two phases are provided. To provide a field detecting device forming the shift optical waveguides in the Z-axis direction of the crystal axis of the electro-optical crystal substrate.

The present invention also shows that even if the input optical fiber is a single mode fiber, an electric field detecting device having a similar function can be obtained.

Further, according to the present invention, an optical waveguide formed on an electro-optic crystal substrate, two phase shift optical waveguides branched from the optical waveguide, a light reflecting portion arranged at the other end of the two phase shift optical waveguides, It consists of a pair of modulation electrodes formed in the vicinity of the two phase shift optical waveguides, and an antenna part connected to the modulation electrode, which is induced in the antenna part by an electric field and depends on the voltage applied to the modulation electrode. A sensor head that changes the intensity of light passing through the optical waveguide, an optical fiber connected to the sensor head, a light source with an optical circulator connected to the other end of the optical fiber, and an optical fiber connected to the output end of the optical circulator. In the electric field detection device composed of a photodetector connected to the other end of the optical fiber and a measuring instrument having the output of the photodetector as an input, two phase shift optical waveguides are provided. To provide a field detecting device formed on the Z-axis direction of the crystal axis of the gas-optical crystal substrate.

Even in this case, the present invention shows that an electric field detecting device having a similar function can be obtained even if the optical fiber connected to the sensor head is a single mode fiber.

Further, the function and effect of the present invention will be described below. First, in the present invention, since the electrodes are installed parallel to the Z axis, stable characteristics with respect to temperature can be obtained and low frequency characteristics do not deteriorate even if a conductive film is not installed.

Next, the polarization dependence of the sensor head will be described. FIG. 9 shows the dependence of the intensity of emitted light on the applied voltage for the TE wave and the TM wave in the case of a sensor head according to the related art, which includes an optical waveguide element formed in the Y-axis direction on a substrate of an X plate. It is a figure. FIG. 10 shows that the incident wave in the case of the sensor head according to the present invention, which is composed of the optical waveguide element formed in the Z-axis direction on the substrate of the X plate, is TE wave and T wave.
It is a figure which shows the dependence with respect to the applied voltage of the emitted light intensity about M wave.

In the case of the sensor head 4 according to the prior art, modulation is performed depending on the polarization of incident light. Therefore, in the electric field detecting device according to the prior art, as shown in FIG. 7, it is necessary to specify the polarization of the incident wave, so that the emitted light of the light source is defined by the polarization adjusting means 62, and the polarization adjusting means 62 causes the sensor head to detect. It is unavoidable to use the polarization maintaining fiber 46 as the optical transmission line up to 4.

Further, from FIG. 10, in the case of a sensor head composed of an optical waveguide element formed in the Z-axis direction on an X-plate substrate,
It shows that the modulation characteristic does not depend on the polarization of the incident light. Therefore, in this case, no polarization adjusting means is required in the transmission line between the light source and the sensor head, and a single mode fiber can be used.

Further, the half-wave voltage Vπ is about 9 times higher when an electric field is applied in the Y-axis direction on the X-plate substrate than in the Z-axis direction. The former corresponds to the related art, and the latter corresponds to the sensor head according to the present invention. This indicates that the latter is preferably used for detecting a high electric field and the former is preferably used for a minute electric field.

Further, the sensor head according to the present invention may exhibit good characteristics in a low frequency band, and a sensor head having an optical waveguide formed in the Z-axis direction on a substrate has a relatively low frequency band including an electrostatic field. In addition, by using it in a device that detects a high electric field, its characteristics can be utilized.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to examples.

(Embodiment 1) FIG. 1 is a block diagram of an electric field detecting device according to an embodiment of the present invention. FIG. 2 is a diagram showing a configuration of the sensor head in FIG.

The light that has passed through the single mode fiber 6 from the light source 61 enters the sensor head 1. The optical sensor head 1 shown in FIG. 2 includes an X plate substrate 1 of lithium niobate.
1 and is composed of a modulation electrode 15 and an optical waveguide through which light propagates in the Z-axis direction. The incident light is the incident optical waveguide 12
After passing through the two phase-shifting optical waveguides 13 branched from the above, they are coupled again by the emitting optical waveguide 14 and emitted to the single mode fiber 7. Here, a voltage induced in the antenna 60 by an electric field is applied to the pair of modulation electrodes 15 arranged in the vicinity of the two phase shift optical waveguides, and the phase of light passing through the phase shift optical waveguides 13 in the vicinity changes. To do.
As a result, the two guided lights coupled by the outgoing optical waveguide 14 interfere with each other, pass through the single mode fiber 7 and enter the photodetector 63, and the outgoing light intensity is converted into an electric signal. The measuring device 64 performs processing such as measurement and display.

In this embodiment, the sensor head 1 is
By using the single mode fiber 6 instead of the polarization maintaining fiber 46, which is a so-called polarization independent type which does not depend on the plane of polarization and which does not require a polarization adjusting means, it functions sufficiently.

Note that, in the structure of the electric field detecting device shown in FIG. 7, for example, according to the prior art, the sensor head 4 may be replaced by the sensor head 1 which does not depend on the polarization of the incident light used in this embodiment. Of course it is possible.

(Embodiment 2) FIG. 3 is a block diagram of an electric field detecting device according to another embodiment of the present invention. FIG. 4 is a diagram showing the configuration of the sensor head in FIG.

In FIG. 4, the sensor head 2 uses a substrate 21 of lithium niobate, which is an X plate, as in the case of the first embodiment, and two phases on which light propagates in the Z-axis direction. A shift optical waveguide 23 and a modulation electrode 25 sandwiching one of them are formed. The antenna element is integrated with the modulation electrode 25. Therefore, the electric field detecting device according to the present embodiment does not have a so-called external antenna. Although the detection sensitivity is lower than that of the electric field detection device according to the first embodiment described above, it is advantageous in that it can detect a high electric field in a narrow space because of its small size.

(Embodiment 3) FIG. 5 is a block diagram of an electric field detecting device according to another embodiment of the present invention. FIG. 6 is a diagram showing the configuration of the sensor head in FIG.

The electric field detection device of this embodiment is characterized in that a so-called reflective sensor head 3 is used. An X-plate lithium niobate substrate 31 is used, an optical waveguide for propagating light in the Z-axis direction and a modulation electrode 35 sandwiching the optical waveguide are formed on the substrate 31, and one end of the phase shift optical waveguide 33 is formed. A reflecting portion 37 is arranged in the. Light is a reflection part 3
It reflects at 7, returns, and returns to the path that has been incident again.
A voltage induced in the antenna 60 by an electric field is applied to the modulation electrode 35 arranged near the two phase shift optical waveguides 33, and the phase of light passing through the phase shift optical waveguides 33 changes. As a result, the two guided lights coupled by the optical waveguide 32 interfere with each other, pass through the single mode fiber 8, pass through the optical circulator 65, and pass through the photodetector 63.
After that, the intensity of the emitted light is converted into an electric signal, and then measured and displayed by the measuring device 64, as in the above embodiment.

In the case of the present embodiment, the light undergoes modulation in both the forward path and the backward path of the phase shift optical waveguide 33, so it becomes smaller than the so-called transmissive sensor head shown in the first embodiment, and , The half-wave voltage Vπ becomes about 1/2. Therefore, the sensor head can be selected as a transmissive type or a reflective type according to the detected electric field. In addition, since the light entering and exiting the sensor head 3 is performed by one optical fiber, the complexity of the operation is reduced, and its significance is significant in order to realize an inexpensive electric field detection device.

Even in the case of a reflection type sensor head,
Needless to say, the antenna element can be formed on the substrate integrally with the modulation electrode to reduce the size, as in the second embodiment.

[0030]

The present invention has realized an electric field detecting device which compensates for the disadvantages of the electric field detecting device according to the prior art. That is, according to the present invention, even if a conductive film is not provided, stable characteristics with respect to temperature can be obtained, low frequency characteristics are not deteriorated, and high electric field can be detected by increasing the half-wave voltage Vπ. A sensor head that is possible and does not depend on the polarization of the incident light is used. As a result, an electric field detecting device using a single-mode fiber instead of the polarization-maintaining fiber, which causes a cost increase, without requiring polarization adjusting means has been realized.

As described above, since the electric field detecting device of the present invention uses the optical fiber as the signal transmission line, not only the transmission loss is small and long-distance transmission is possible,
There is no exchange of noise between the optical fiber and the environment,
It inherits the features of conventional electric field detectors.
The present invention enables high electric field detection and shows that a single mode fiber is sufficient for the optical transmission line from the light source to the sensor head, thus contributing to cost reduction. In the case of electric field detection at a remote place, it has a particularly great economic effect.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an electric field detection device described in a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a sensor head in FIG.

FIG. 3 is a configuration diagram of an electric field detection device described in a second embodiment of the present invention.

FIG. 4 is a configuration diagram of the sensor head in FIG.

FIG. 5 is a configuration diagram of an electric field detection device described in a third embodiment of the present invention.

FIG. 6 is a configuration diagram of the sensor head in FIG.

FIG. 7 is a configuration diagram of an electric field detection device according to a conventional technique.

FIG. 8 is a schematic view of a sensor head according to a conventional technique.

FIG. 9 shows TE waves and T waves that are incident waves in the case of a sensor head including an optical waveguide device formed in the Y axis direction on an X plate substrate.
The figure which shows the dependence with respect to the applied voltage of the emitted light intensity about M wave.

FIG. 10 is a diagram showing the dependence of the intensity of emitted light on the applied voltage with respect to TE waves and TM waves of incident waves in the case of a sensor head including an optical waveguide element formed in the Z-axis direction on a substrate of an X plate.

[Explanation of symbols]

 1,2,3,4 Sensor head 6,7,8,9,10 Single mode fiber 11,21,31,41 Substrate 12,22,42 Incident optical waveguide 13,23,33,43 Phase shift optical waveguide 14, 24, 44 Output optical waveguide 15, 25, 35, 45 Modulation electrode 32 Optical waveguide 37 Reflector 46 Polarization maintaining fiber 60 Antenna 61 Light source 62 Polarization adjusting means 63 Photodetector 64 Measuring instrument 65 Optical circulator 66, 67 Conductor

Claims (4)

[Claims] 1. An incident optical waveguide formed on an electro-optic crystal substrate, two phase shift optical waveguides branched from the incident optical waveguide, an outgoing optical waveguide in which the two phase shift optical waveguides are recombined, and the two phases. A modulation electrode formed in a pair near the shift optical waveguide, and an antenna part connected to the modulation electrode, which is guided to the antenna part by an electric field and depends on the voltage applied to the modulation electrode,
A sensor head for modulating the intensity of outgoing light passing through the optical waveguide, an input optical fiber and an output optical fiber connected to the sensor head, a light source connected to the other end of the input optical fiber, and the output optical fiber In an electric field detecting device comprising a photodetector connected to the other end of the photodetector and a measuring instrument using the output of the photodetector as an input, the two phase shift optical waveguides are provided in the Z-axis direction of the electro-optic crystal substrate. An electric field detecting device characterized in that 2. The electric field detecting device according to claim 1, wherein the input optical fiber is a single mode fiber. 3. An optical waveguide formed on an electro-optic crystal substrate, two phase shift optical waveguides branched from the optical waveguide,
A light reflecting portion arranged at the other end of the two phase shift optical waveguides, a modulation electrode formed in pairs near the two phase shift optical waveguides, and an antenna portion connected to the modulation electrode. A sensor head that is guided by the electric field to the antenna section and that modulates the intensity of light that has passed through the optical waveguide depending on the voltage applied to the modulation electrode; an optical fiber connected to the sensor head; Electric field detection comprising a light source with an optical circulator connected to the other end of the optical fiber, a photodetector connected to the output end of the optical circulator by an optical fiber, and a measuring instrument having the output of the photodetector as an input In the device, the two phase shift optical waveguides are formed in the Z-axis direction of the electro-optic crystal substrate, the electric field detecting device. 4. An electric field detecting device, wherein the optical fiber connected to the sensor head according to claim 2 is a single mode fiber.