JPS63241365A - Optical voltage/electric field sensor - Google Patents

Abstract

PURPOSE:To reduce scattering of bias points between probes due to anisotropy of crystal and variations in the degree of modulation, by reducing the thickness of a BSO or BGO element having Pockels effect. CONSTITUTION:Light emitted from a light source 1 is introduced to a sensor section 10 through an optical fiber 3a to be converted into a linearly polarized light with the passage thereof through a polarizer 5 and further into a circularly polarized light with a 1/4 wavelength plate 6. The circularly polarized light passes through BGO elements 7 having Pockels effect to cause a change in the polarization state thereof according to an AC voltage applied. The change in the polarization state thereof is converted with an analyzer 8 to a change in the intensity of light and received with a photodetector 2 through a rod lens 4b and an optical fiber 3b to be converted into an electrical signal. here, anisotropy between the BGO elements 7 can be lessened by reducing below 400mum the thickness of a surface in the direction of light passes.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical voltage/electric field sensor using a BSO or BGO element.

[Conventional technology]

Conventionally, BSO (Bi12SiO20) or BGO (
An optical voltage sensor using a tortoise crystal of B i 1zGeozo is described, for example, in Japanese Patent Application Laid-Open No. 57-98863. Figure 1 shows a conventional optical voltage sensor of this type, including a light source (1) and a photodetector (2).
) are connected to rod lenses (4a) and (4b) via optical fibers (3a) and (3b), respectively.

The rod lens (4a) is equipped with a polarizer (5) that converts the light parallelized by the rod lens (4a) into linearly polarized light, and a quarter-wave plate (6) that converts this into circularly polarized light. The next BGO single crystal element (7) converts the voltage applied thereto into a change in the polarization state of light.

The analyzer (8), which converts changes in the polarization state of light into changes in light intensity, leads to the rod lens (4b) K.

The electric circuit (9) converts the light intensity signal received by the photodetector (2) into an electric signal, and converts it into a value Kf proportional to the modulation UK. (1o) is a probe forming a sensor section.

With the above configuration, light emitted from the light source (1) is guided to the sensor section (10) via the optical fiber (3a). This light is converted into linearly polarized light by passing through a polarizer (5). It is further converted into circularly polarized light by a quarter wavelength plate (6). This circularly polarized light has a Pockels effect.
By passing through the GO element (7), the BGO element (7)
) The polarization state changes depending on the alternating current voltage applied to the polarization state. This change in polarization state is converted into a change in light intensity by an analyzer (8). This light is Rondo Lens' (4b
), the light is received by the photodetector (2) via the optical fiber (3b), and converted into an electrical signal. This electrical signal is transmitted through K, a quarter-wave plate (6
) and a DC signal generated by applying an optical bias.
This is the adjustment of the AC signal (12) according to the AC voltage applied to the BGO element (7). The electric circuit (9) divides this DC signal (11) and the original signal (12), and divides the AC signal (12) by the DC signal valve (11) to connect the optical fiber (3a). , (3b') and outputs an AC signal proportional to the AC signal applied to the BGO element (7).

[The problem that the invention is trying to solve]

In the conventional optical voltage sensor as described above, the BGO element (7) has a thickness of 1f1 or more, and has optical anisotropy due to internal stress or the like. This optical anisotropy is a characteristic of many BGOs.
There is a variation in retardation of about 0.5 degrees between the elements (7), which causes an optical bias variation of 44.5 to 45.5 degrees between each probe (10). Therefore, the DC component differs between each probe (1o),
Since variations in the modulation degree occur, there is a problem in that it is necessary to adjust the gain of the electronic circuit for each probe.

This invention was made in order to solve the above-mentioned problems, and it eliminates the variation in the modulation degree of the globe (10) from one surface to the other, and fixes the gain to the same value for all the probes (10). It is an object of the present invention to provide an optical voltage/electric field sensor that can be handled by a built-in electronic circuit (9) and that does not require gain adjustment of the electronic circuit (9).

[Means for solving problems]

The optical voltage-electric field sensor according to the present invention has a BGO element with minimal anisotropy.

[For production]

In this invention, variations in the modulation degree of the probe are reduced, and compatibility between the probe and the electronic circuit is realized.

〔Example〕

The overall configuration of this invention is the same as that shown in FIG. 1, and its explanation will be omitted. However, the thickness of the surface of the BGO element (7) in the direction in which light passes is 400 μm or less.

With the above configuration, the thickness of the BGO element (7) is 400 μm.
It is kept small, less than m. Since the anisotropy of the BGO element (7) is proportional to the thickness, the thickness of the BGO element (7) is approximately 115 mm or less than the conventional one. Therefore, B.G.O.
The variation in anisotropy between the elements (7) is smaller than that of the conventional device, and is 115 degrees or less, that is, 0.1 degree or less.

Further, the direct current component due to the optical bias is proportional to 5 in2θ. On the other hand, since the AC component is proportional to this differential, 2 si
nθ is proportional to strong θ. Therefore, the modulation degree M is proportional to the following value.

Mocωt(θ) where θ is the optical bias value of the entire probe for the anisotropy of the BGO element (7) and the retardation of the quarter-wave plate (6).

Probe (1) of modulation degree due to anisotropy of BGO element (7)
0) is expressed by the following formula.

cot (ψ) where ψ is the retardation of the quarter-wave plate (6), α
is the maximum value of the anisotropic retardation variation of the BGO element (7). Therefore, ψ=45°.

Since α≦o2°deg, the variation in modulation degree between probes (1o) is 1.4% or less. Since the accuracy of current optical voltage sensors is about 1.5%, each probe (1o) can be used even if the electronic circuit (9) is fixed to the same gain.

That is, compatibility is obtained between the glove (1o) and the electronic circuit (9).

Note that although the above embodiments have been described using BGO crystals, the same applies to cases where BSO crystals are used.

In addition, although we have explained an example in which the 1/4 wavelength plate (6) is interposed between the polarizer (5) and the BGO element (7), May intervene.

In addition, although the voltage sensor was explained in the above embodiment,
Needless to say, it can also be used as a blind or field sensor.

〔Effect of the invention〕

As described above, this invention is based on BS with Pockels effect.
Because the thickness of the O or BGO element is thin, the variation in the bias point between globes due to the anisotropy of these crystals is reduced, and therefore the variation in modulation depth due to this is reduced, improving compatibility between the probe and the electrical circuit. is obtained.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a conventional optical voltage sensor, and FIG. 2 is a diagram showing the signal output state of the sensor. (7)...BGO element (single crystal). In each figure, the same reference numerals indicate the same or equivalent parts. 7: BGO strenuous + (single, g&)

Claims (1)

[Claims] Bi_1_2SiO_2_0 and Bi_1_2GeO
_2_0 An optical voltage/electric field sensor that detects either a voltage or an electric field applied to any of the single crystals, comprising the single crystal having a thickness of 400 μm or less on a surface perpendicular to the direction in which light passes. An optical voltage/electric field sensor characterized by the following.