JPH05297086A - Optical magnetic field sensor - Google Patents

Abstract

PURPOSE:To obtain an optical magnetic field sensor having a cheap and compact configuration for detecting the current state of a high voltage line. CONSTITUTION:Two pairs of optical fibers contacted with the first optical fibers 21, 27 having an end surface with 45 degree slope and the second optical fibers 22, 26 having a surface perpendicular to the side facing to the end surface, are used in the configuration. By reducing the lens and cube mirror in a optical transmitter and conrolling the length of the optical fibers having vertical end surface, an inexpensive and compact optical magnetic field sensor is realized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical magnetic field sensor for detecting a current state of a high voltage distribution line or the like.

[0002]

2. Description of the Related Art A conventional optical magnetic field sensor will be described below. FIG. 2 is a perspective view showing the configuration of a conventional optical magnetic field sensor. In FIG. 2, 1 is a lens, 2 is a polarization beam splitter, 3 is a magneto-optical element, 4 is a polarization beam splitter, and 5 is a cube mirror.

The operation of the conventional optical magnetic field sensor will be described with reference to the drawings. FIG. 3 is a principle diagram of an optical magnetic field sensor. In FIG. 3, the lens 1 and the cube mirror 5 are omitted. Then, with respect to the light emitted from the light emitting element 6, only the linearly polarized light component 7 is transmitted by the polarization beam splitter 2. When this linearly polarized light component 7 passes through the magneto-optical element 3, it is rotated by the component of the applied magnetic field 8 that is parallel to the light traveling direction. Light 9 that received this rotation
Only the transmission direction component 10 of the polarization beam splitter 4 is detected by the light receiving element 11. Here, the relationship between the applied magnetic field and the detected light intensity is shown in FIG. Further, the polarization beam splitters 2 and 4 are arranged so as to form a 45 ° relationship with each other. This is because bias is applied up to the point 0 in FIG. 4 so as to have linear symmetry with respect to the AC magnetic field.

FIG. 5 shows an application example to a high voltage distribution line. 1
Reference numeral 2 is a distribution line, 13 is a magnetic field loop integration core, and 14 is an optical magnetic field sensor. The magnetic field generated in the gap portion 15 of the magnetic field orbital integration core 13 is detected by the optical magnetic field sensor 14
Apply to. The relationship between the value of the current flowing through the distribution line 12 and the strength of the magnetic field generated in the gap portion 15 at this time is expressed by equation (1). The value of the current flowing through the distribution line 12 can be converted by using the relationship of the equation (1).

Hg = K · I / δ (1) where Hg is the magnetic field strength, K is the proportional constant, I is the current value,
δ represents the gap length.

[0006]

However, the conventional structure as described above requires expensive optical parts, resulting in high cost. Further, in order to increase the current detection sensitivity, it is necessary to increase the magnetic field strength, and it is necessary to shorten the gap length from the relationship of the equation (1), but there is a restriction on the size of the optical system, so miniaturization is not It is difficult to make the gap length short, and there is a limit in increasing the strength of the generated magnetic field.

The present invention solves the above-mentioned conventional problems, and an object of the present invention is to provide an inexpensive and compact optical magnetic field sensor.

[0008]

In order to achieve this object, the optical magnetic field sensor of the present invention has an axial direction of 4 mm.
Two optical fiber pairs in which the vertical end face of the second optical fiber having the end face perpendicular to the axial direction is joined to the side face of the first optical fiber having the end face inclined at 5 ° facing the end face are provided. A set, a magneto-optical element between one optical fiber pair and the other optical fiber pair, and a pair of polarizers located on both sides of the magneto-optical element are provided. In addition, in order to further reduce the size, a thin film polarizer of molecular resonance absorption type is used as the polarizer.

[0009]

With this structure, a lens for transmitting light and a cube mirror for polarizing the optical path are unnecessary. Also, the size of the optical system can be changed by adjusting the length of the second optical fiber having the vertical end face. As described above, an inexpensive and compact optical magnetic field sensor can be provided.

Further, by using a molecular resonance absorption type thin polarizer, further miniaturization is possible.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic view of an optical magnetic field sensor according to an embodiment of the present invention. In FIG. 1, 21 is an optical fiber having an end face inclined at 45 ° with respect to its axial direction, 22 is an optical fiber having an end face perpendicular to its axial direction, 23 is a molecular resonance absorption type thin polarizer, Reference numeral 24 is a magneto-optical element, 25 is a thin polarizer similar to the thin polarizer 23, 26 is an optical fiber having a vertical end face similar to the optical fiber 22, and 27 is an end face inclined at 45 ° similar to the optical fiber 21. It is an optical fiber having. The thin polarizers 23 and 25 are of the molecular resonance absorption type,
For example, it is a glass-based composite material produced by depositing a metal halide on the glass surface and then reducing it.

The operation of the optical magnetic field sensor configured as described above will be described. First, the light introduced into the core of the optical fiber 21 having the end face inclined at 45 ° is
Due to the difference in refractive index from the boundary surface of the end surface inclined at 45 °, Fresnel reflection is performed and the light is emitted from the side surface forming an angle of 45 ° with the end surface. The emitted light is introduced into the core portion of the optical fiber 22 having a vertical end face, and only the linearly polarized light component is incident on the magneto-optical element 24 by the thin polarizer 23. At this time, the polarization plane is rotated by the applied magnetic field component parallel to the optical path. This light is transmitted through a thin polarizer 25, an optical fiber 26 having a vertical end face, and 45 °.
The light is emitted through an optical fiber 27 having an end surface inclined to. At this time, the thin polarizers 23 and 25 have a transmission direction of 4
It is arranged with an angle of 5 °. In addition, the end faces of the optical fibers 22 and 26 having the vertical end faces are mirror-polished, and the optical path length can be freely adjusted by adjusting the length, so that a small and inexpensive optical magnetic field sensor can be provided. can get.

In this embodiment, an example using a molecular resonance absorption type thin polarizer as a polarizer is shown for the purpose of further miniaturization, but other polarizers such as the above-mentioned polarization beam splitter or rutile crystal polarization are used. Even if a child is used, the size can be made smaller than before by adjusting the optical path length of the optical fiber.

[0014]

As described above, according to the present invention, an optical fiber obtained by joining a second optical fiber having an end face perpendicular to the side face opposite to the end face of the first optical fiber having an end face inclined at 45 °. By using two pairs, it is possible to realize an inexpensive and miniaturized excellent optical magnetic field sensor.

[Brief description of drawings]

FIG. 1 is a perspective view of an optical magnetic field sensor according to an embodiment of the present invention.

FIG. 2 is a perspective view of a conventional optical magnetic field sensor.

[Fig. 3] Principle diagram of optical magnetic field sensor

FIG. 4 is a characteristic diagram of an optical magnetic field sensor.

FIG. 5 is a diagram illustrating an application example of an optical magnetic field sensor.

[Explanation of symbols]

 21, 27 Optical fiber having an end surface inclined by 45 ° 22, 26 Optical fiber having a vertical end surface 23, 25 Thin polarizer 24 Magneto-optical element

Claims (2)

[Claims] 1. A second optical fiber having an end face perpendicular to the axial direction on a side surface facing the end face of the first optical fiber having an end face inclined at 45 ° with respect to the axial direction. An optical magnetic field sensor in which two pairs of optical fibers having vertical end faces are joined, and a magneto-optical element and a pair of polarizers located on both sides thereof are provided between one pair of the optical fibers and the other pair of the optical fibers. . 2. The optical magnetic field sensor according to claim 1, wherein a molecular resonance absorption type thin polarizer is used as the polarizer.