JP3355503B2 - Electric field sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a measuring instrument used for measuring characteristics of radio waves and electrode noise in the field of EMC (electromagnetic compatibility), and more particularly to an electric field sensor for measuring the electric field strength of an electromagnetic wave propagating in space. .

[0002]

2. Description of the Related Art Information devices and communication devices such as computers,
Many electrical devices, such as FA devices such as robots, and controllers such as automobiles and railways, are always at risk of being affected by malfunctions due to external electromagnetic noise.
In the field of EMC, it is important to accurately measure the external electromagnetic environment, the magnitude of noise that may have an effect, and the noise generated by itself.

Conventionally, the electromagnetic noise measurement system as described above includes (a) a system which receives a signal using a normal antenna and guides it to a measuring instrument via a coaxial cable, and (b) detects a signal received using an antenna. (C) a system in which the intensity of transmitted light changes according to the applied electric field intensity, and the electric field intensity change is converted into light intensity. There is a system in which the optical element is connected to a light detector connected to a light source and a measuring device by an optical fiber.

The above-mentioned system (a) is the most common, but there are problems such as the electric field distribution being disturbed by the presence of an electric cable such as a coaxial cable and the possibility of noise being mixed in the middle of the cable. The systems (b) and (c) using an optical fiber have been developed.

[0005] Among the above systems, the system (b) is as follows:
The signal detected by the diode is amplified and added to the light emitting diode, converted to an optical signal, and guided to the photodetector by an optical fiber.However, since an electric circuit and a battery are required for the sensor head, a certain size is required. However, there is a disadvantage that the metal part exists and the shape becomes large, and the detection sensitivity of the electric field is low and the response speed is low.

In the system (c), a crystal having an electro-optical effect is used as an optical element for converting an electric field intensity into a change in transmitted light intensity. The element structure is such that the light emitted from the optical fiber is converted into parallel light by a lens, passes through a crystal equipped with a small antenna, changes the polarization state by an electric field in the crystal, and is converted into a change in intensity by an analyzer, and then converted again into light. There are a bulk-type element coupled to a fiber and a waveguide-type element constituting the above-mentioned optical element by an optical waveguide provided on a crystal.
Detection sensitivity is higher than 0 times.

FIG. 5 shows a configuration example of an electric field sensor head 101 using a conventional waveguide element. The electric field sensor head 101 is composed of a lithium niobate crystal substrate 102 cut out perpendicular to the c-axis, an incident optical waveguide 103 by diffusing titanium onto the substrate 102, and a phase shift optical waveguide branched from the incident optical waveguide 103. Waveguides 104 and 105 and an output optical waveguide 106 in which these phase-shifted optical waveguides 104 and 105 are joined and coupled. An incident optical fiber 107 is coupled to an incident end of the incident optical waveguide 103, and an exit optical fiber 1 is coupled to an exit end of the exit optical waveguide 106.
08 is connected.

Also, phase shift optical waveguides 104 and 105
A pair of electrodes 109 is provided on the top, and these electrodes 10
9 is connected to the rod antenna 110. In FIG. 5, the incident light 111 from the incident optical fiber 107 enters the incident optical waveguide 103, and then enters the phase-shifted light emitting waveguide 1.
The energy is divided into 04 and 105. When an electric field is applied, a voltage is induced in the electrode 109 by the rod antenna 110, and electric field components in the phase-shifted optical waveguides 104 and 105 are generated in opposite directions in the depth direction. As a result, a change in the refractive index occurs due to the electro-optic effect, and a phase difference corresponding to the magnitude of the applied electric field occurs between the light waves propagating through the phase shift optical waveguides 104 and 105. When coupled, the light intensity changes due to interference. That is, the intensity of the outgoing light 112 emitted to the outgoing optical fiber 108 changes according to the intensity of the applied electric field, and the intensity of the applied electric field can be measured by measuring the change in the light intensity with a photodetector.

FIG. 6 shows an electric field sensor using the conventional electric field sensor head 101 shown in FIG. An incident optical fiber 107 of the electric field sensor head 101 in FIG. 5 is connected to a light source 114 via a transmitting optical fiber 113, and an emitting optical fiber 108 is connected to a photodetector 116 via a receiving optical fiber 115. Although omitted in FIG. 6,
The detected electric signal from the photodetector 116 is connected to a measuring instrument such as a normal voltmeter, an ammeter, or a spectrum analyzer.

[0010]

However, this type of conventional electric field sensor, when detecting a high electric field, is induced by applying a voltage to two electrodes at intervals of only a few to several tens of microns. There is a problem that it is difficult to apply the method to detection of a high electric field because the electrodes are easily damaged due to discharge of electric charges.

It is an object of the present invention to provide an electric field sensor suitable for detecting a high electric field.

[0012]

According to the present invention, there is provided a sensor head configured to change the intensity of transmitted light in accordance with the intensity of an applied electric field.
An input optical fiber and an output optical fiber connected to the sensor head; a light source coupled to one end of the input optical fiber for irradiating the input optical fiber with light; and a light source transmitted through the sensor head and emitted from the output optical fiber. In an electric field sensor comprising a photodetector for detecting transmitted light, the sensor head has a substrate having an electro-optical effect, and an incident optical waveguide formed on the substrate and connected to the incident optical fiber, Two branch optical waveguides formed on the substrate and branched from the incident optical waveguide, an output optical waveguide connected to the output optical fiber by combining these branch optical waveguides, and these branch optical waveguides; Alternatively, there is provided an electric field shielding member provided near at least a part of the branch portion to shield an electric field.

Further, the present invention provides a sensor head configured to change the intensity of transmitted light according to the intensity of an applied electric field, an input / output optical fiber connected to the sensor head, and an input / output optical fiber. An electric field comprising: a circulator coupled to an input / output end of the optical fiber; a light source for irradiating the input / output optical fiber with light through the circulator; and a photodetector for detecting transmitted light emitted from the circulator. In the sensor, the sensor head includes a substrate having an electro-optic effect, and an input / output optical waveguide formed on the substrate and connected to the input / output optical fiber,
Two branch optical waveguides formed on the substrate and branched from the input / output optical waveguide, a reflection mirror provided on the substrate and reflecting light from the branch optical waveguide, and at least a part of the branch optical waveguide. And an electric field shielding member provided in the vicinity to shield the electric field.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a first embodiment of the present invention will be described with reference to FIG. The electric field sensor according to the present invention includes a sensor head 1 configured so that the intensity of light passing therethrough changes according to the intensity of an applied electric field, and an input optical fiber 2 and an output optical fiber 3 connected to the sensor head 1. And a light source (not shown) such as a semiconductor laser coupled to one end of the incident optical fiber 2 for irradiating the incident optical fiber 2 with light, and transmitting through the sensor head 1 and emitting from the output optical fiber 3. Photodetector (not shown) for detecting transmitted light
And

The sensor head 1 comprises a substrate 4 having an electro-optic effect, an incident optical waveguide 5 formed on the substrate 4 and connected to the incident optical fiber 2, and an incident optical waveguide 5 formed on the substrate 4 5, and an outgoing optical waveguide 7 connected to the outgoing optical fiber 3 by joining the two branched optical waveguides 6 and joining them.
And an electric field shielding member 8 provided near a part of the branch optical waveguide 6 to shield an electric field. The electric field shielding member 8 is made of a conductive material or a radio wave absorbing material.

The electric field is shielded by the electric field shielding member 8 disposed on the branch waveguide 6, and the refractive index of the other branch optical waveguide 6 changes depending on the applied electric field. A phase difference of the light wave is generated in the outgoing light waveguide 7, and the intensity of the outgoing light corresponding to the change in the intensity of the applied electric field is detected.

More specifically, the branch optical waveguide 6 includes a substrate (Z plate) 4 made of lithium niobate crystal.
It is symmetrically branched upward. After coating the entire surface of the branch optical waveguide 6 with a silicon dioxide (SiO ₂ ) film as a buffer layer for preventing light absorption, the branch optical waveguide 6
An electric field shielding member 8 made of metal is formed on a part of the.

FIG. 2 shows a second embodiment of the present invention. In the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals. The sensor head 1 of FIG.
The electric field shielding member 8 is formed on both of the branch optical waveguides 6 and the electric field shielding members 8 on the branch optical waveguide 6 have different lengths. The second embodiment has substantially the same characteristics as the first embodiment.

FIG. 3 shows a third embodiment of the present invention. In the third embodiment, the same components as those in the first embodiment are denoted by the same reference numerals. The electric field sensor shown in FIG. 3 includes a sensor head 1 configured so that the intensity of light passing therethrough changes according to the intensity of an applied electric field, and the sensor head 1.
And the circulator 10 coupled to the input / output end of the input / output optical fiber 9.
A light source 11 for irradiating the input / output optical fiber 9 with light via the circulator 10 and the lens 12; a light detector 13 for detecting transmitted light emitted from the circulator 10; And a measuring device 14 for measuring a detection signal from the device.

As shown in FIG. 4, the sensor head 1
Is a substrate 4 having an electro-optic effect, an input / output optical waveguide 15 formed on the substrate 4 and connected to the input / output optical fiber 9, and a branch from the input / output optical waveguide 15 formed on the substrate 4 The two branched optical waveguides 6, a reflection mirror 16 provided on the substrate 4 for reflecting light from the branched optical waveguide 6, and an electric field shield provided near a part of the branched optical waveguide 6 for shielding an electric field. And a member 8.
The input / output optical fiber 9 is a polarization maintaining fiber. The reflection mirror 16 is constituted by a dielectric mirror, a normal mirror or a reflection coat.

In the third embodiment, the electric field is shielded in the range where the electric field shielding member 8 exists, and the refractive index of the other branch optical waveguide 6 changes depending on the applied electric field. As a result, the incoming and outgoing optical waveguide 1 where these converge
In 5, the phase difference of the light wave occurs, and the intensity of the emitted light corresponding to the change in the applied electric field intensity is measured.

[0022]

The electric field sensor according to the present invention is suitable for detecting a high electric field because the electric field shielding member formed on the optical waveguide is single, so that the electric discharge and the destruction due to the electric discharge do not occur.

[Brief description of the drawings]

FIG. 1 is a front view showing a first embodiment of the present invention.

FIG. 2 is a front view showing a second embodiment of the present invention.

FIG. 3 is a block diagram showing a third embodiment of the present invention.

FIG. 4 is a front view showing a main part of a third embodiment of the present invention.

FIG. 5 is a front view showing a sensor head of a conventional electric field sensor.

FIG. 6 is a block diagram showing a conventional electric field sensor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sensor head 2 Incident optical fiber 3 Outgoing optical fiber 4 Substrate 5 Incident optical waveguide 6 Branch optical waveguide 7 Outgoing optical waveguide 8 Electric field shielding member 9 Incoming / outgoing optical fiber 10 Circulator 11 Light source 12 Lens 13 Photodetector 14 Measuring instrument 15 Incoming / outgoing light guide Wave path 16 Reflection mirror

Claims (2)

(57) [Claims] 1. A sensor head configured to change the intensity of light transmitted according to the intensity of an applied electric field, an input optical fiber and an output optical fiber connected to the sensor head, and the input optical fiber A light source coupled to one end of the optical fiber for irradiating the incident optical fiber with light, and a light detector for detecting transmitted light transmitted through the sensor head and emitted from the output optical fiber; The sensor head includes a substrate having an electro-optical effect, an incident optical waveguide formed on the substrate and connected to the incident optical fiber, and two branch optical waveguides formed on the substrate and branched from the incident optical waveguide. An outgoing optical waveguide connected to the outgoing optical fiber by merging these branched optical waveguides, and at least one of these outgoing optical waveguides or branches. An electric field sensor comprising: an electric field shielding member provided near a part of the electric field shielding member. 2. A sensor head configured to change the intensity of transmitted light in accordance with an applied electric field intensity, an input / output optical fiber connected to the sensor head, and an input / output end of the input / output optical fiber. A circulator coupled to a light source for irradiating the input / output optical fiber with light through the circulator, and an electric field sensor including a photodetector for detecting transmitted light emitted from the circulator, The sensor head includes a substrate having an electro-optic effect, an input / output optical waveguide formed on the substrate and connected to the input / output optical fiber, and two branches formed on the substrate and branched from the input / output optical waveguide. An optical waveguide, a reflection mirror provided on the substrate for reflecting light from the branch optical waveguide, and a reflection mirror provided near at least a part of the branch optical waveguide. An electric field sensor, comprising: an electric field shielding member that shields an applied electric field.