JPH09113557A - Operating point adjusting method for electric field sensor and electric field sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily adjust the operating point of an optical probe showing the characteristic curve having a finite bias by applying a voltage of a specific value to the modulating electrode of the optical probe. SOLUTION: The light from the first light source 5 is guided to the light wave guide 24 of an optical probe 2 by an optical fiber 3, and it is converted into an electrical signal by a photo-detector 6 via an optical fiber 4 and transmitted to a measuring instrument 10. The light from the second light source 7 is guided by an optical fiber 11, and the DC voltage generated by a photoelectric transfer means 8 is applied to a modulating electrode 22 via a conductor 9. When the output of the light source 7 is adjusted, voltages ranging from the voltage giving the minimum value of the output light intensity in the characteristic curve of the optical probe 2 to the voltage giving the maximum value can be applied. The voltage is applied to the modulating electrode 22 so that the output light intensity of the optical probe 2 when the applied voltage is zero coincides with the output light intensity which is 1/2 of the sum of the maximum output light intensity and the minimum output light intensity, thus the bias voltage is corrected to 0.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for adjusting an electric field sensor, which is a measuring instrument for measuring the strength and waveform of an electric field generated in various electric devices, cables, etc., in addition to the field of EMC and measurement of electric noise. , And an electric field sensor equipped with its adjusting means.

[0002]

2. Description of the Related Art Information equipment such as computers, communication equipment,
Many electric devices such as robots and other FA devices, automobiles, railways, and other controllers are at risk of being affected by malfunctions due to electromagnetic noise from the outside. It is important to accurately measure the magnitude of the noise that is exerted and the noise generated by itself.

Conventionally, in the measurement of electromagnetic noise as described above, firstly, a method of receiving by using an ordinary antenna and leading to a measuring instrument by a coaxial cable, and secondly, a signal received by using the antenna is used. Method of detecting and converting to an optical signal and guiding it to a measuring device by an optical fiber. Thirdly, electric field intensity change using an optical element configured so that intensity of transmitted light changes according to applied electric field intensity. Is converted into a light intensity change, and the optical element and the light source and the photodetector connected to the measuring device are connected by an optical fiber. The method using the first antenna is the most general, but there is a problem that the electric field distribution is disturbed due to the presence of an electric cable such as a coaxial cable and there is a risk of noise intrusion in the middle of the cable. The second and third methods using fibers have been developed.

Of these, in the third method, a crystal having an electro-optical effect is used as an optical element for converting an electric field intensity into a change in intensity of transmitted light. The element structure is that the light emitted from the optical fiber is made into parallel light by the lens and passes through the crystal with the small antenna attached, the polarization state is changed by the electric field in the crystal, and the light is converted again by the analyzer to change the intensity. There are a bulk type element coupled to a fiber and a waveguide type element that constitutes the above optical element by an optical waveguide provided on a crystal. Usually, the waveguide type has a detection sensitivity 10 times or more higher than that of the bulk type.

FIG. 7 shows a configuration example of an optical element (optical probe) using a conventional waveguide type element. An optical waveguide 21 is formed by diffusing titanium on a lithium niobate (LiNbO ₃ ) (hereinafter referred to as LN) crystal substrate 20 cut out perpendicularly to the c-axis, and the optical waveguide 21 is formed by an incident optical waveguide 24, The phase shift optical waveguides 25 and 26 branched from one end of the incident optical waveguide 24, and the output optical waveguide 2 in which the two phase shift optical waveguides 25 and 26 are joined and coupled.
7. The input optical fiber 3 is coupled to the incident end of the incident optical waveguide 24, and the output optical fiber 4 is connected to the emission end of the outgoing optical waveguide 27. A pair of modulation electrodes 22 are provided on the phase shift optical waveguides 25 and 26, and are connected to an antenna 23, respectively. In FIG. 7, after the incident light from the input optical fiber 3 is incident on the incident optical waveguide 24, the energy is split into the phase shift optical waveguide 25 and the phase shift optical waveguide 26. When an electric field is applied, a voltage is induced in the modulation electrode 22 by the antenna 23, and electric field components in opposite directions in the depth direction are generated in the phase shift optical waveguide 25 and the phase shift optical waveguide 26. As a result, a change in 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 in the phase shift optical waveguides 25 and 26, and these merge and merge into the output optical waveguide 27. When combined, the light intensity changes due to interference. That is, the intensity of the output light emitted to the output optical fiber 4 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 (not shown). .

[0006]

The characteristic curve showing the relationship between the voltage induced in the modulation electrode through the antenna by the applied electric field strength and the optical output strength of the optical probe is shown in FIG.
As indicated by A, it is represented as a periodic function having a maximum value and a minimum value. Near the midpoint between the maximum and minimum values of the characteristic curve, the sensitivity is the highest and the linearity is excellent.

However, in reality, the manufactured optical probes have different voltage dependences. This is because there are many factors in the manufacture of the optical probe, and strict control of these is not realized.

In the following, the point on the characteristic curve when the voltage induced in the modulation electrode through the antenna is 0 is the operating point, and the characteristic curve at half the sum of the maximum value and the minimum value of the optical output is on the characteristic curve. The voltage is called bias.

In FIG. 1, the operating point of the optical probe having the characteristic curve A is a, which is near the minimum value of the output light intensity, and has a bias c that cannot be ignored. When an electric field is detected using an optical probe having a finite bias, it is impossible to always know the reliable electric field strength unless the measured result is corrected. Further, since the optical probe uses a crystal that exhibits an electro-optical effect as a substrate, electric charges are generated on the substrate surface due to a pyroelectric effect due to a change in environmental temperature, which also causes a change in bias.

In view of the above problems, the present invention provides a method for easily adjusting the operating point of an optical probe having a bias with a finite characteristic curve, and is equipped with the adjusting means to enable highly reliable measurement. The present invention is to provide an electric field sensor.

[0011]

According to the present invention, the operating point adjustment of an electric field sensor using an optical probe having a structure in which the intensity of light to be output changes depending on the intensity of an applied electric field to be measured. In the method, the output light intensity of the optical probe when the intensity of the applied electric field is zero is equal to one half of the sum of the maximum output light intensity and the minimum output light intensity of the optical probe. Independently of the applied electric field,
There is provided a method for adjusting an operating point of an electric field sensor, which is characterized in that a voltage is applied to a modulation electrode of the optical probe.

According to the present invention, in the operating point adjusting method for the electric field sensor, the voltage applied to the modulation electrode of the optical probe is generated by coupling the optical irradiation means and the photoelectric conversion means. A method for adjusting the operating point of the electric field sensor is obtained.

According to the present invention, a substrate having an electro-optical effect, an optical waveguide formed on the substrate, an incident optical waveguide, two phase shift optical waveguides branched from the incident optical waveguide, and the optical waveguide An optical waveguide having an exiting optical waveguide where two phase-shifting optical waveguides merge, a modulation electrode provided near the phase-shifting optical waveguide, and an optical probe having an antenna connected to the modulation electrode, the incident optical waveguide and the exiting An input optical fiber and an output optical fiber each having one end connected to the optical waveguide, a first light source connected to the other end of the input optical fiber, and a photodetector connected to the other end of the output optical fiber In the electric field sensor, the second
An electric field sensor comprising: a light source, a photoelectric conversion unit that generates a voltage by irradiation light of the second light source, and a conductor that guides the voltage generated by the photoelectric conversion unit to the modulation electrode. To be

According to the present invention, a substrate having an electro-optical effect, an optical waveguide formed on the substrate, which is an input / output optical waveguide, two phase shift optical waveguides branched from the input / output optical waveguide, And an optical waveguide having a reflection portion provided on an end face opposite to the branch side of the two phase shift optical waveguides, a modulation electrode provided near the phase shift optical waveguides,
And an optical probe having an antenna connected to the modulation electrode, an optical fiber having one end connected to the input / output optical waveguide, and an optical directional separator connected to the other end of the optical fiber,
In an electric field sensor including a first light source connected to the optical directional separator and a photodetector connected to the optical directional separator, a second light source and a voltage generated by light emitted from the second light source are used. An electric field sensor comprising: a photoelectric conversion unit that generates a voltage and a conductor that guides a voltage generated by the photoelectric conversion unit to the modulation electrode.

[0015] Also. According to the present invention, in the electric field sensor, the modulation electrode includes a plurality of divided electrodes divided along a light propagation direction, and the conductor and the antenna are independently connected to the divided electrodes. An electric field sensor characterized by being provided.

According to the present invention, in any one of the electric field sensors described above, a part of the output light of the first light source is branched by an optical branching means in place of the second light source. An electric field sensor is obtained which is configured to irradiate the photoelectric conversion means.

Further, according to the present invention, in the electric field sensor provided with the light branching means, the optical probe, the photoelectric conversion means, and the light branching means are housed in one container made of a non-metallic material. An electric field sensor characterized by being constructed is obtained.

[0018]

The method for adjusting the operating point of the electric field sensor according to the present invention is as follows.
It is characterized in that a voltage equal to and opposite to the voltage corresponding to the bias is directly applied to the modulation electrode.

The bias voltage can be corrected to 0 by applying a properly controlled DC voltage to the modulation electrode of the optical probe in addition to the input signal of the measurement electric field.
That is, the electric field applied to the antenna and the voltage applied for bias adjustment are superimposed on the phase shift optical waveguide of the optical probe.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a characteristic curve A of an optical probe having a finite bias before adjusting the operating point and a characteristic in which the operating point is adjusted by the method according to one embodiment of the present invention so that the bias becomes substantially zero. It is a graph which shows the curve B. The operating point adjusting method for an electric field sensor according to the present invention is directed to an electric field sensor using an optical probe having a configuration in which the intensity of output light changes depending on the intensity of an applied electric field that is a measurement target. In one embodiment of the present invention, the output light intensity of the optical probe when the intensity of the applied electric field to be measured is zero is one half of the sum of the maximum output light intensity and the minimum output light intensity of this optical probe. A voltage is applied to the modulation electrode of the optical probe so as to match the output light intensity, independently of the above-mentioned applied electric field, whereby the characteristic curve is shifted from A to B, which is clear from this characteristic curve B. In addition, the bias voltage is corrected to 0.

In the present embodiment, the voltage applied to the modulation electrode of the optical probe is the optical irradiation means (for example, laser diode) and the photoelectric conversion means (for example, solar cell).
It was made to generate by the combination of.

2 to 6 are schematic configuration diagrams showing an embodiment of the electric field sensor of the present invention. In the electric field sensor shown in each drawing, common portions are given common symbols.

(First Embodiment) FIG. 2 is a schematic diagram of an electric field sensor according to a first embodiment of the present invention. With reference to FIG. 2, the electric field sensor 1 according to the present embodiment includes an optical probe 2
It has an input optical fiber 3, an output optical fiber 4, a first light source 5, a photodetector 6, a second light source 7, a photoelectric conversion means 8, and a conductor 9.

The optical probe 2 is an LN substrate 2 having a c-plane.
0, an optical waveguide 21 formed on the substrate 20, a pair of modulation electrodes 22, and a pair of antennas 23. The optical waveguide 21 includes an incident optical waveguide 24, two phase shift optical waveguides 25 and 26 branched from one end of the incident optical waveguide 24, and two phase shift optical waveguides 25 and 26.
And an exiting optical waveguide 27 where 26 joins. The pair of modulation electrodes 22 includes two phase shift optical waveguides 25, 2
6 and the pair of antennas 2 respectively
3 are connected to the modulation electrodes 22, respectively.

The light emitted from the first light source 5 (a laser diode is used in this embodiment) is guided to the incident optical waveguide 24 of the optical probe 2 by the input optical fiber 3, and the light of the conventional technique described above is used. Similar to the case of the optical probe, the light is guided to the photodetector 6 via the emission optical waveguide 27 and the output optical fiber 4, where it is converted into an electric signal and transmitted to the measuring instrument 10.

The electric field sensor shown in FIG. 2 uses a laser diode as the second light source 7, and guides it to the vicinity of the optical probe 2 by an optical fiber 11, where photoelectric conversion means 8 (using a solar cell). And a DC voltage generated by light irradiation is applied to the modulation electrode 22 through the conductor 9.

By adjusting the output of the second light source 7, it is possible to apply from the voltage giving the minimum value of the output light intensity in the characteristic curve of the optical probe 2 to the voltage giving the maximum value. As a result, the operating point of the optical probe 2 at that time can be actually confirmed, and the operating point can be adjusted so that the electric field strength of the measurement target is zero. One feature of the configuration of the electric field sensor 1 of the present embodiment is that the operating point can be remotely adjusted.

(Second Embodiment) FIG. 3 is a schematic diagram of an electric field sensor according to a second embodiment of the present invention. With reference to FIG. 3, this electric field sensor 1 uses a so-called reflective optical probe 2 as an optical probe. The optical waveguide 21 of the optical probe 2 includes an input / output optical waveguide 28, two phase shift optical waveguides 25 and 26 branched from one end of the input / output optical waveguide 28, and the two phase shift optical waveguides 2
5 and 26, and a reflecting portion 29 provided on the side opposite to the branch side. Therefore, the output light reflected by the reflection unit 29 returns to the same optical fiber 12 as the incident light, is guided by the optical directional separator 13 to the photodetector 6 through the optical fiber 14, and is converted into an electric signal here. It is transmitted to the measuring instrument 10. Therefore, the basic configuration is the same as that of the first embodiment.

That is, a laser diode is provided as the second light source 7 in order to adjust the operating point of the optical probe 2, and it is guided to the vicinity of the optical probe 2 by the optical fiber 11, and the solar as the photoelectric conversion means 8 is introduced here. The operating point can be controlled by combining with a battery and applying a DC voltage generated by light irradiation to the modulation electrode 22 through the conductor 9. Remote adjustment is possible as in the first embodiment.

(Third Embodiment) FIG. 4 is a schematic diagram of an electric field sensor according to a third embodiment of the present invention. The modulation electrode 22 of the electric field sensor 1 includes a phase shift optical waveguide 25,
The divided electrode 22 divided into two along the line 26.
It is composed of a and 22b. And the antenna 23 is
The photoelectric conversion means 8 is connected to the divided electrode 22a through the conductor 9 and to the divided electrode 22b. By thus dividing the modulation electrode 22, convenience in manufacturing the optical probe 2 is increased, and operability can be improved by separating the antenna input and the DC voltage by the photoelectric conversion means 8. .

(Fourth Embodiment) FIG. 5 is a schematic diagram of an electric field sensor according to a fourth embodiment of the present invention. In this electric field sensor 1, the irradiation unit (second unit) for the photoelectric conversion unit 8 is used.
Light source) is replaced with the second light source by branching the light emitted from the first light source 5 by the light branching unit 15, and has a simpler configuration, and the above-described first to third embodiments. The same effect as can be obtained.

(Fifth Embodiment) FIG. 6 is a schematic diagram of an electric field sensor according to a fifth embodiment of the present invention. This electric field sensor 1 is a development of the fourth embodiment, in which the optical probe 2, the photoelectric conversion means 8 for adjusting the operating point, and the optical branching means 15 are housed in a single non-metallic container 16. There is. By housing the optical probe 2 and the like in the container 16 as described above, not only is the mechanical protection provided and the operability is improved, but the optical probe 2 is protected from a sudden change in the environmental temperature that causes a bias change. It has a function of protecting the probe 2. The non-metallic material container 16 is also useful in that it does not disturb the distribution of the electric field to be measured.

[0033]

As described above, according to the present invention,
It is possible to provide a method for easily adjusting a bias, which has been a problem in conventional electric field sensors, and an electric field sensor that includes the adjusting means and that enables highly reliable measurement. Further, although each manufactured optical probe has its own bias, the use of the method of the present invention can eliminate the lack of reliability that has been a concern in electric field measurement. Further, the electric field sensor, which is said to have a relatively easy change in operating point, can be adjusted at any time during the measurement at the measurement site, which gives an impetus to highly reliable measurement.

[Brief description of the drawings]

FIG. 1 is a graph showing a characteristic curve A of an optical probe having a finite bias before adjustment of an operating point and a characteristic curve B of which the operating point is adjusted and the bias is made substantially zero by a method according to an embodiment of the present invention. Is.

FIG. 2 is a schematic diagram of an electric field sensor according to a first embodiment of the present invention.

FIG. 3 is a schematic configuration diagram of an electric field sensor according to a second embodiment of the present invention.

FIG. 4 is a schematic configuration diagram of an electric field sensor according to a third embodiment of the present invention.

FIG. 5 is a schematic configuration diagram of an electric field sensor according to a fourth embodiment of the present invention.

FIG. 6 is a schematic configuration diagram of an electric field sensor according to a fifth embodiment of the present invention.

FIG. 7 is a schematic diagram of an electric field sensor according to a conventional embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electric field sensor 2 Optical probe 3 Input optical fiber 4 Output optical fiber 5 First light source 6 Photodetector 7 Second light source 8 Photoelectric conversion means 9 Conductor 10 Measuring instrument 11 Optical fiber 12 Optical fiber 13 Optical directional separator 14 Optical fiber 15 Optical branching means 16 Container 20 Substrate 21 Optical waveguide 22 Modulation electrode 22a Split electrode 22b Split electrode 23 Antenna 24 Incident optical waveguide 25 Phase shift optical waveguide 26 Phase shift optical waveguide 27 Outgoing optical waveguide 28 Incoming / outgoing optical waveguide 29 Reflector

Claims (7)

[Claims] 1. An operating point adjusting method for an electric field sensor using an optical probe having a structure in which the intensity of light to be output changes depending on the intensity of an applied electric field to be measured, wherein the intensity of the applied electric field is zero. So that the output light intensity of the optical probe at this time is equal to one half of the sum of the maximum output light intensity and the minimum output light intensity of the optical probe,
A method for adjusting an operating point of an electric field sensor, characterized in that a voltage is applied to the modulation electrode of the optical probe independently of the applied electric field. 2. The method for adjusting an operating point of an electric field sensor according to claim 1, wherein the voltage applied to the modulation electrode of the optical probe is generated by coupling an optical irradiation unit and a photoelectric conversion unit. Electric field sensor operating point adjustment method. 3. A substrate having an electro-optical effect, an optical waveguide formed on the substrate, the incident optical waveguide, two phase shift optical waveguides branched from the incident optical waveguide, and the two phase shift optical waveguides. An optical waveguide having an exiting optical waveguide that merges with each other, a modulation electrode provided near the phase shift optical waveguide, and an optical probe having an antenna connected to the modulation electrode, and one end of each of the entrance optical waveguide and the exiting optical waveguide. An electric field sensor including an input optical fiber and an output optical fiber connected to each other, a first light source connected to the other end of the input optical fiber, and a photodetector connected to the other end of the output optical fiber, Light source, a photoelectric conversion unit that generates a voltage by the irradiation light of the second light source, and a conductor that guides the voltage generated by the photoelectric conversion unit to the modulation electrode. An electric field sensor characterized in that 4. A substrate having an electro-optical effect, an optical waveguide formed on the substrate, an input / output optical waveguide, two phase shift optical waveguides branched from the input / output optical waveguide, and the two phase shifts. An optical probe having a reflection portion provided on the end face opposite to the branch side of the optical waveguide, a modulation electrode provided in the vicinity of the phase shift optical waveguide, and an optical probe having an antenna connected to the modulation electrode; An optical fiber having one end connected to the optical waveguide, an optical directional separator connected to the other end of the optical fiber, a first light source connected to the optical directional separator, and the optical directional separator In the electric field sensor including the photodetector, a second light source, a photoelectric conversion unit that generates a voltage by the irradiation light of the second light source, and a conductor that guides the voltage generated by the photoelectric conversion unit to the modulation electrode. And An electric field sensor characterized by being provided. 5. The electric field sensor according to claim 3 or 4, wherein the modulation electrode is composed of a plurality of split electrodes that are split along a light propagation direction, and the conductor and the antenna are respectively split. An electric field sensor characterized by being independently connected to electrodes. 6. The electric field sensor according to claim 3, wherein a part of the output light of the first light source is branched by an optical branching unit in place of the second light source. Then, the electric field sensor is configured to irradiate the photoelectric conversion means. 7. The electric field sensor according to claim 6, wherein the optical probe, the photoelectric conversion means, and the light branching means are housed in one container made of a non-metallic material. Sensor.