JPS59107273A - Photocurrent and magnetic field sensor - Google Patents

Abstract

PURPOSE:To attain a small-sized and high-sensitive sensor, by using an oxide crystal having optical Farady effect as a magneto-optic element. CONSTITUTION:The light emitted from a light source 1 reaches a polarizer 3b through an optical fiber 2 and is coverted to a linearly polarized light, and the plane of polarization is rotated at 45 deg. by the optical rotatory power of BGO (Bi12GeO20) constituting a magnetooptic element 4b while this linearly polarized light passes through the element 4b to reach an analyzer 5b; and at this time, if a magnetic field H acts upon the element, 4b, a rotation angle DELTAphi of the plane of polarization satisfies equation DELTAphi=(V2H+theta)l. In this equation, V2 is the verdet's constant of BGO, and theta is its optical rotatory capability. Since the Verdet's constant of BGO is 4-5 times as high as that of a lead glass, the rotation angle of the plane of polarization and the sentivity are 4-5 times high as those of a conventional sensor.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a photocurrent/magnetic field sensor that includes a polarizer, an analyzer, and a magneto-optical element, and detects a current/magnetic field by utilizing the optical Faraday effect Z of the magneto-optical element. .

Conventionally, there has been a photocurrent/magnetic field sensor of this type as shown in FIG. In the figure, 1 is a light source, 2 is an optical fiber, 3a is a polarizer, 41 is a magneto-optical sensor made of lead glass, 5a is an analyzer, 6 is an optical fiber, and 7 is an optical receiver.

The light emitted from the light R1 is passed through the optical fiber 2 to the polarizer 3a.
K is guided. Since the light guided by the optical fiber 2 is non-polarized, it is linearly polarized by the polarizer 3a. Now, if we consider that the magnetic field 11 is acting on the magneto-optical element 4a, the linearly polarized light guided to the magneto-optical element 4a is rotated by the rotation angle expressed by the optical Faraday effect. Here, V is the Werde constant of the lead glass constituting the magneto-optical element 4a, l
is the length of the magneto-optical element 4a, and these values are constant for the same magneto-optical element, so the rotation angle Δψ is the length of the magnetic field H
It will be proportional to ttc.

The light emitted from the magneto-optical element 4IL is intensity-modulated by an analyzer 5IL, and then guided to an optical receiver 7 through an optical fiber 6'a', where it is photoelectrically converted. By measuring the electric signal corresponding to this light intensity, we can determine the magnitude of the applied magnetic field H? If the source of this applied magnetic field is an electric current, the magnitude of the electric current can be detected.

In the conventional photocurrent/magnetic field sensor configured as described above, the Weerde constant V of the lead glass constituting the magneto-optical element 4a is small, and in order to obtain sufficient sensitivity, the dimensions of the element must be increased. The drawback was that it had to be done. There are also ferromagnetic materials such as YI (J) with a large Werde constant value, but these have the disadvantage of poor temperature characteristics.Also, regardless of the material they are made of, polarizers, analyzers, and magneto-optical elements are Since each component is constructed as an independent component, there are uncertainties such as assembly accuracy, and reliability is also lacking.

This invention was made in order to eliminate the drawbacks of the conventional devices as described above, and as a magneto-optical device, Bib,
(By using oxide crystals such as Jo026, Bi, 5i02o, etc. that exhibit an optical Faraday effect, the purpose is to provide a small and highly sensitive photocurrent/magnetic field sensor.

An embodiment of the present invention will be described below with reference to the drawings. Second
In the figure, 1 is a light source, 2 is an optical fiber, and 3b is a polarized light □
4b is a magneto-optical element, 5b is an analyzer, 6 is an optical fiber, and 7 is an optical receiver. In this example, the magneto-optical element 4
b consists of B1□OeO,I, (hereinafter referred to as 1B00), and its length l is such that the plane of polarization rotates exactly 45 degrees due to the optical rotation that BGO has, and the polarizer 3b and analyzer The value is selected so that the optical axis of 5b is equivalently at an angle of 45°. Also, polarizer 3b and analyzer 5b
teeth.

It consists of polarizing beam splitters formed by vapor deposition at both ends of the magneto-optical element 4b.

Next, the 1C operation will be explained. The light emitted from the light #1 passes through the optical fiber 2, reaches the polarizer 5bVC, is converted into linearly polarized light, passes through the magneto-optical element 4by, and proceeds to the analyzer 5b. If the plane of polarization is rotated by 45° due to the optical rotation of , and at this time the magnetic field I] is acting on the magneto-optical element 4b, the rotation angle Δψ of the plane of polarization is Δψ= (V, H+θ)l! becomes. Here, V represents the Guelde constant of BGO, and θ represents its optical rotation power 7. BOO's Vuelde Sadataka is lead glass 4
5 times, the angle of rotation of the plane of polarization is 4 to 5 times greater than that of the conventional one shown in FIG. 1, and the sensitivity is also 4 to 5 times greater.

In addition, since the polarization plane of the light emitted from the magneto-optical element 4b is rotated by 45° due to the optical rotation of KBOO as described in @, the optical axes of the polarizer 6b and analyzer 5b are relative to each other [45°
angle? This is equivalent to doing so. Therefore, even if the polarizer 6b and the analyzer 5b are not geometrically arranged at 45°, the maximum sensitivity and maximum dynamic range can be achieved. Obtainable. Furthermore, polarizer 3b and analyzer 5b 'a'
When the optical beam splitter is constructed of LLI optical beam splitters deposited on both end faces of the optical element 4b, the volume occupied by each element can be small.

FIGS. 8 and 4 illustrate alternative implementations of the invention.
In the case of FIG. 8 [1:Y, the magneto-optical element 4 is configured to input light from the optical fiber 2 parallel to the magnetic field 1.1 and output it parallel to the optical fiber 6, In the case of FIG. 4, the configuration is such that the light enters the magneto-optical element 4b from the optical fiber 2 at right angles to the magnetic field iI, and exits the light into the optical fiber 6 in parallel.

In either case, an effect χ similar to that shown in Figure 2
Needless to say, it is played.

As described above, according to the present invention, as a magneto-optical element,
331. ,,0eOtn j Bi,, 5io26
Since the oxide crystal Y (e) with a large Werde constant such as
u will be beaten.

Also, magneto-optical elements made of oxide crystals have polarization planes depending on their optical rotation. Since it is rotated, the length in the optical axis direction is set to an appropriate value, that is, the polarization plane is set to 45° + 90°・m (however, m
By selecting the length VC necessary to rotate the polarizer and the analyzer by an amount (0 or an integer), it is possible to set the relative angle χ of the polarizer and analyzer to an equivalent relationship of 45°.
The structure can be simplified.

In addition, when the polarizer and analyzer are configured with polarizing beam splitters provided by vapor deposition on both end faces of a magneto-optical element, the polarizer, analyzer, and magneto-optical element are integrated, resulting in further miniaturization and higher reliability.

Lower prices can be achieved.

[Brief explanation of drawings]

Figure 1 shows the configuration of a conventional photocurrent/magnetic sensor? FIG. 2 is a block diagram showing the configuration of a photocurrent/magnetic field sensor according to one embodiment of the present invention, and FIGS. 8 and 4 are block diagrams showing other embodiments of the present invention. DESCRIPTION OF SYMBOLS 1... Light source, 2... Optical fiber, 3b... Polarizer, 4b... Magneto-optical element, 5b... Analyzer, 6...
- Optical fiber, 7... optical receiver. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (4)

[Claims] (1) In a photocurrent/magnetic field sensor that includes a polarizer, an analyzer, and a magneto-optical element and detects a current or a magnetic field by utilizing the optical Faraday effect of the magneto-optical element, the optical Faraday effect is used as the magneto-optical element. A photocurrent/magnetic field sensor characterized by using an oxide crystal having (2) The oxide crystal is Bil 2 Ge0t o or B'+t Sin. A photocurrent/magnetic field sensor according to claim 1. (3) The photocurrent/magnetic field sensor according to claim 1 or 2, wherein the polarizer and the analyzer are arranged so that their respective optical axes are equivalently at an angle of 45°. (4) The polarizer and the analyzer are comprised of polarizing beam splitters formed by vapor deposition on both end faces of the oxide crystal. Photocurrent/magnetic field sensor.