JPS5940273A - Electric field meter using polarization surface preserving optical fiber - Google Patents

Abstract

PURPOSE:To make it possible to measure an applied electric field with high accuracy, by calculating a phase change amount by using a polarization surface preserving optical fiber as an optical fiber. CONSTITUTION:Light emitted from a light source 1 is linearily polarized by a polarization plate 2 to be connected to the optical axis of a polarization surface preserving optical fiber by lambda/2 plate 3. The emitted linearily polarized light is passed through an electro-optical element 5 wherein said emitted light is inclined about 45 deg. with respect to the light axis to be projected into a wave dividing polarizing beam splitter 6 of which the optical axis is aligned with that of the element. Two polarization surface preserving optical fiber 4, 4' are respectively aligned in the optical axes thereof and, when oval polarized light is incident to the splitter 6, the components of each axes are respectively transmitted to be again synthesized by a synthesizing polarizing beam splitter 7 and the obtained oval polarized light is received by a light receiving part 8. By analyzing this light, a phase change amount is calculated and an applied electric field is calculated therefrom.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electric field meter using a polarization maintaining optical fiber.

Most conventional electric field meters measure the potential difference between terminals and then calculate the electric field. Generally, the terminal is made of metal, and when the terminal is inserted into the measuring electric field, the electric field is disturbed. -! It is also possible that this terminal may be short-circuited under extremely high voltage conditions.

In electric field measurement using light, there is a method in which both sides of an electro-optical element are sandwiched between crossed polarizing plates, manually operated with a multimode fiber, and output is outputted through the multimode fiber. However, in this case, it will be stable if the polarization plane in the multimode fiber is completely random, but
When the output is not completely random, when the light source itself is unstable, or when there is a disturbance in the multimode fiber, the output becomes unstable and causes errors.

Moreover, since the characteristics of the polarizing plate vary greatly depending on temperature, the environmental resistance of a part of the sensor is poor.

An object of the present invention is to eliminate the drawbacks of the prior art described above and provide a highly accurate electric field meter.

That is, the gist of the present invention is to measure the amount of phase change using a polarization maintaining optical fiber as the optical fiber.

The structure of the present invention will be specifically explained with reference to drawings showing embodiments. In Fig. 1, the light emitted from the light source 1 is polarized by the polarizing plate 2.
The light becomes linearly polarized light, and is coupled to the optical axis of the polarization-maintaining optical fiber 4 by the λ/2 plate 6. The emitted light passes through an electro-optical element 5 arranged so that the emitted linearly polarized light forms an inclination of 45 degrees with the optical axis, and enters a polarizing beam splitter 6 whose optical axis is aligned with the optical axis of the electro-optical element. Ru. Therefore, when no electric field is applied, linearly polarized light is incident on the polarizing beam splitter B, and when an electric field is applied in the direction in which the light travels, it is proportional to the electric field applied between the optical axes of the electro-optical element. A refractive index difference occurs, which causes a phase difference between the two axes of light, and the elliptically polarized light is incident on the polarizing beam splitter B.

The two polarization-maintaining optical fibers 4' and 4'' are aligned with their respective optical axes, and when elliptically polarized light is incident on the polarization beam splitter B, the components of each axis are transmitted, respectively. The light is combined again by the combining polarizing beam splitter 7 to become elliptically polarized light, which is received by the light receiving section 8.By analyzing this, the amount of phase change is determined (for example, by Senarmont's method), and from this the applied electric field is measured. Here, it is not necessary to provide polarizing plates on both sides of the electro-optical element (eg, Pockels element) 5.

As a polarization maintaining optical fiber, for example, Japanese Patent Application Laid-Open No. 57-3
The structure described in Japanese Patent No. 7305 can be applied, but the structure is not particularly limited to this structure.

Note that, as shown in FIG. 2, the phase modulator 9 may be used to apply phase modulation and the amount of change in the modulated signal due to the application of an electric field may be measured, or as shown in FIG. 6, a frequency modulator 10 may be inserted. , the frequency shift caused by the electric field may be measured as a beat frequency by the light receiving section.

The electric field meter of the present invention as described above has the following remarkable effects.

(1) Since no metal is used in the sensor, it has excellent insulation properties.

(2) Since a polarization-maintaining optical fiber is used, polarization fluctuations due to external disturbances are small, and the device has highly accurate and stable characteristics.

(6) Since a polarizing plate is not used in a part of the sensor, it has excellent environmental resistance.

[Brief explanation of the drawing]

FIG. 1, FIG. 2, and FIG. 6 are explanatory diagrams showing different embodiments of the electric field meter of the present invention. 1: Light source, 2: Polarizing plate, 6: λ/2 plate, 4: Polarization maintaining optical fiber, 5: Electro-optical element, 6: Polarizing beam splitter for demultiplexing, 7: Polarizing beam splitter for multiplexing, 8: Light receiving section, 9 two-phase modulator, 10: frequency modulator. Agent Patent Attorney Fujio Sato = 5- Arithmetic 1 Kokumi Z Meki 3121I

Claims (1)

[Claims] 1. A light source 1 that supplies linearly polarized light via a polarization-maintaining optical fiber 4, an electro-optical element 5 that couples the linearly polarized light at an orientation of 45° to the optical axis, and an electro-optical element 5 that couples the output light of the electro-optical element 5 to the optical axis. A polarization beam splitter 6 for demultiplexing, and polarized light for multiplexing that guides and combines the two polarized lights split by the polarization beam splitter 6 through polarization maintaining optical fibers 4z4//. An electric field meter using a polarization maintaining optical fiber, characterized by having a beam splitter 7 and a light receiving section 8 for measuring the phase difference between the beams on both sides.