JP3673611B2 - Electric field sensor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a measuring instrument used for measuring characteristics of radio waves and electromagnetic noise, and in particular, an electric field sensor for measuring the electric field strength of electromagnetic waves propagating in space in the EMC field, and detecting a signal radio wave of a specific frequency such as a broadcast radio wave. The present invention relates to an electric field sensor that also functions as an antenna.
[0002]
[Prior art]
Many electrical devices such as information devices such as computers and communication devices, FA devices such as robots, controllers for automobiles, railways and the like always have a risk of being affected by malfunctions due to electromagnetic noise from the outside. In the EMC field, it is important to accurately measure the magnitude of noise that affects the external electromagnetic environment and electrical equipment and the noise generated by itself.
[0003]
An electric field sensor that detects and converts electric field strength into light intensity using an optical element configured to emit light with the intensity of incident light changing according to the applied electric field strength. Has been developed.
[0004]
A conventional electric field sensor will be described with reference to FIGS.
[0005]
FIG. 3 shows a configuration diagram of a conventional electric field sensor. 4 shows a configuration diagram of a reflective sensor head 3 used in the electric field sensor of FIG.
[0006]
3 and 4, the linearly polarized light emitted from the two light sources 1 and 2 passes through the polarization plane holding fiber 5 and enters the optical combiner 9 where they are combined so as to be orthogonal to each other. Then, the light enters the incident / exit optical waveguide 11 of the sensor head 3.
[0007]
The sensor head 3 includes optical waveguides 11 and 12 formed on the substrate 10, a modulation electrode 14, and a light reflecting portion 16 provided at the end of the optical waveguide. An input / output optical waveguide 11 and a phase shift optical waveguide 12 branched from and coupled to the substrate 10 of a lithium niobate single crystal cut out perpendicular to the c-axis are formed. 16 is provided. A pair of modulation electrodes 14 are installed on the phase shift optical waveguide 12 and connected to the antenna 15. A single mode fiber 6 is coupled to the end of the input / output optical waveguide 11.
[0008]
The light incident on the input / output optical waveguide 11 is divided into energy into the phase shift optical waveguide 12, further reflected by the light reflecting portion 16, and output through the input / output optical waveguide 11. When an electric field is applied, a voltage is induced in the modulation electrode 14 by the antenna 15, and electric field components in opposite directions in the depth direction are generated in the phase shift optical waveguide 12.
[0009]
As a result, the refractive index changes due to the electro-optic effect, and the phase difference corresponding to the magnitude of the applied electric field changes between the light waves propagating back and forth through the phase shift optical waveguide 12. That is, the intensity of the emitted light that is emitted to the single mode fiber 6 changes according to the applied electric field intensity. Further, the emitted light is separated from the incident light by the optical circulator 8, and the intensity of the applied electric field is measured by measuring the change in the light intensity by the photodetector 17.
[0010]
In particular, the reflection type sensor head has higher sensitivity than that of the transmission type, and the incident light and the outgoing light of the sensor head propagate through the same optical fiber. It is advantageous if the sensor head and the light receiver are separated by a long distance.
[0011]
[Problems to be solved by the invention]
However, particularly when the distance between the optical combiner and the sensor head is long, beat noise 19 is observed on both sides of the original waveform 18 in the conventional electric field sensor as shown in FIG. FIG. 5 shows a waveform observed in a configuration in which a 1.5 km single mode fiber is used and an optical circulator is installed immediately before the optical synthesizer. Even if the above is used, the above phenomenon cannot be suppressed.
[0012]
Accordingly, an object of the present invention is to provide an electric field sensor capable of observing only an original waveform without beat noise on both sides of the waveform even when the distance between the optical combiner and the sensor head is long.
[0013]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention provides an electric field sensor comprising a light source, a sensor head, a light receiver, an optical fiber as a transmission path for incident light and outgoing light of the sensor head, and an antenna. It consists of two light sources that are polarized light, and these two linearly polarized lights are combined so as to be orthogonal to each other by a light combiner and incident on a reflective sensor head. An electric field sensor configured to be separated from incident light by an optical circulator provided immediately before and incident on a light receiver.
[0014]
In the present invention, the optical fiber that couples between the two light sources and the optical combiner is a polarization maintaining fiber, the optical fiber that couples between the optical combiner and the sensor head, and the optical circulator and the optical receiver, respectively. It is an electric field sensor which is a mode fiber.
[0015]
Furthermore, the electric field sensor of the present invention is characterized in that the emitted light wavelengths of the two light sources are not equal to each other.
[0016]
In addition, the electric field sensor according to the present invention has a configuration in which at least one of the two light sources is a semiconductor pumped solid state laser such as a semiconductor pumped YAG laser.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0018]
FIG. 1 is a configuration diagram of an electric field sensor according to an embodiment of the present invention. In FIG. 1, a light source 1 and a light source 2 are both semiconductor-pumped YAG lasers, and emitted light wavelengths are 1.3190 μm and 1.3195 μm, respectively. The linearly polarized light emitted from these light sources is guided to the optical combiner 9 by the polarization plane holding fiber 5.
[0019]
These two linearly polarized lights are combined by the optical combiner 9 so that their polarization planes are perpendicular to each other, and enter the sensor head 3 through the single mode fiber 6. The polarization plane of the propagating light is shown with an arrow 20. In the present embodiment, the sensor head 3 composed of the optical waveguide element shown in FIG. 4 is used.
[0020]
The light emitted from the sensor head is separated from the incident light by the optical circulator 8 that does not depend on the plane of polarization, which is mounted immediately before the sensor head 3 by the single mode fiber 6, and propagates through the single mode fiber 7 to detect the light. 17 is incident.
[0021]
FIG. 2 shows a waveform of an electric field by the electric field sensor of the present embodiment. In FIG. 2, only the waveform 18 to be detected is observed. In addition, by making the outgoing light wavelengths of the two light sources different from each other, interference between the two outgoing lights can be avoided, and the electric field sensor functions stably. The optical circulator may be integrated with the sensor head.
[0022]
【The invention's effect】
As described above, in contrast to the conventional electric field sensor in which a plurality of beat noise waveforms have been observed with respect to the original waveform, according to the present invention, an optical circulator is provided immediately before the sensor head. An electric field sensor that can observe only the original waveform has been realized.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of an electric field sensor according to an embodiment of the present invention.
FIG. 2 is a waveform diagram observed by the electric field sensor according to the embodiment of the present invention.
FIG. 3 is a configuration diagram of a conventional electric field sensor.
FIG. 4 is a configuration diagram of a sensor head used in an electric field sensor.
FIG. 5 is a waveform diagram observed by a conventional electric field sensor.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1, 2 Light source 3 Sensor head 5 Polarization surface holding | maintenance fiber 6,7 Single mode fiber 8 Optical circulator 9 Optical synthesizer 10 Substrate 11 (Incoming / outgoing) Optical waveguide 12 (Phase shift) Optical waveguide 14 Modulation electrode 15 Antenna 16 Light reflection part 17 Photodetector 18 Waveform 19 Beat noise 20 Arrow

Claims (4)

In an electric field sensor comprising a light source, a sensor head, a photodetector, an optical fiber as a transmission path for incident light and outgoing light of the sensor head, and an antenna, the light source comprises two light sources whose outgoing light is linearly polarized light, The two linearly polarized lights are combined so as to be orthogonal to each other by a light combiner, and are incident on the reflective sensor head. An optical fiber configured to be separated and incident on the light detector and coupled between the two light sources and the light combiner is a polarization plane holding fiber, between the light combiner and the sensor head, and the light. The optical fiber that couples between the circulator and the photodetector is a single mode fiber. Capacitors. Electric field sensor according to claim 1, wherein the emission wavelength of the two light sources are not equal to each other. 3. The electric field sensor according to claim 1, wherein at least one of the two light sources is a semiconductor-pumped solid-state laser. 4. The electric field sensor according to claim 3 , wherein the semiconductor excitation solid-state laser is a semiconductor excitation YAG laser.

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