JPH04366783A - Photomagnetic field and current sensor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

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/current sensor that measures a magnetic field or current using light.

0002

[Prior Art] Fig. 2 shows a conventionally known optical magnetic field of this type (Mitsubishi Electric Technical Report Vol. 57, No. 10 (1983)).
An example of the configuration of a current sensor is shown, but in the figure, 11
is a light source, 12 and 16 are optical fibers, 13 is a polarizer, 14
1 is a magneto-optical element, 15 is an analyzer, and 17 is an optical receiver. The polarizer 13 and analyzer 15 are each constituted by a beam splitter made of laminated thin films, and a magnetic field 18 as shown by the arrow, for example, is applied to the magneto-optical element 14. It has become.

In such an optical magnetic field/current sensor, light generated by a light source 11 first enters an optical fiber 12, but in this case, the light propagating within the optical fiber 12 is normally unpolarized. The light emitted from the optical fiber 12 and incident on the polarizer 13 becomes linearly polarized light by the polarizer 13. Analyzer 15 is typically placed at a 45 degree angle with polarizer 13 to maximize its detection sensitivity. Furthermore, the light emitted from the analyzer 15 is guided to an optical receiver 17 via an optical fiber 16, where it is photoelectrically converted.

[0004] Here, the magnetic field 18 is applied to the magneto-optical element 14 as described above, and the plane of polarization of the linearly polarized light emitted from the polarizer 13 is rotated in proportion to the magnitude of the applied magnetic field 18. It will be done. The rotation angle θ at this time is expressed by the following equation (1). θ=vtH

(1) In the above equation (1), v is the Verdet constant of the magneto-optical element 14, t is the length of the magneto-optical element 14, and H is the magnetic field strength. In this case, the larger the value of the Verdet constant v, the larger the rotation angle θ becomes. However, the light emitted from the magneto-optical element 14 whose plane of polarization is rotated in this way is converted into light intensity by the analyzer 15. Ru. By electrically measuring the light intensity output from the analyzer 15, the magnitude of the applied magnetic field 18 can be determined. Note that when the source of the magnetic field 18 is an electric current, the magnitude of the electric current can be determined.

[0005]

[Problems to be Solved by the Invention] However, such an optical magnetic field/current sensor has a characteristic that depends on the inclination of the polarization plane of the light that should be incident on the polarizer 13. When using an optical fiber that cannot be specified in advance, there is a problem that the error in the measured value becomes significantly large, making it impossible to effectively and fully perform the function of this type of sensor.

In view of the above circumstances, it is an object of the present invention to provide an optical magnetic field/current sensor that does not require any consideration of the state of the polarization plane of light that should be incident on a polarizer, and that can perform its proper functions. With the goal.

[0007]

[Means for Solving the Problems] An optical magnetic field/current sensor according to the present invention transmits light through a magneto-optical element having a Faraday effect, a polarizer and an analyzer disposed before and after the magneto-optical element, and In an optical magnetic field/current sensor configured to measure current and magnetic field by receiving transmitted light whose polarization plane is rotated according to a magnetic field applied to a magneto-optical element, there is a polarization separation/current sensor on the light incident side. A first optical system comprising a combining element and a polarization rotator, a second optical system comprising a polarization rotator and a polarization separation/combining element on the light output side, and the first optical system on the input side.
The polarization plane of the polarization component of the optical path separated by the optical system coincides with the polarization plane of the polarizer on the input side, and the polarization component of the separated optical path is input to the second polarizer on the output side. They are recombined by an optical system.

[0008]

[Operation] According to the present invention, light incident through an optical fiber is first separated into two optical paths having polarization components forming an angle of 90 degrees to each other by the polarization separation/synthesis element of the first optical system. . Then, after the planes of polarization of the polarization components of the two optical paths are matched by a polarization rotator disposed only in one of the separated optical paths, a magneto-optical element whose polarization plane is adjusted to the polarization components of both of these optical paths. incident on the polarizer. Further, in the second optical system, a polarization rotator disposed only in the other of the separated optical paths causes the plane of polarization of the polarized light component in the other optical path to be orthogonal to the plane of polarization of the polarized light component in the one optical path. After this, the polarization components of both optical paths are combined by a polarization separation/synthesis element. This combined light is then transmitted to the optical receiver via the optical fiber of the second optical system. Therefore, no matter what the angle of the polarization plane of the light that enters the first optical system through the optical fiber, the light whose polarization plane is always set at a constant angle will always enter the magneto-optical element. Accurate magnetic field measurements corresponding to the rotation angle of the polarization plane of incident light can be performed.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the magneto-optical field/current sensor according to the present invention will be described below with reference to FIG. In the figure, 1 is an optical transmitter configured to generate laser light, 2 and 6 are optical fibers, 3 is a polarizer, 4 is a magneto-optical element, 5 is an analyzer, and 7 is an optical receiver. These basic structures are the same as those of the conventional example, that is, the polarizer 3 and analyzer 5 are each formed of a beam splitter made of laminated thin films. Further, a magnetic field 8 is applied to the magneto-optical element 4. A first optical system and a second optical system, which will be described later, are arranged on both sides of the magneto-optical element 4, but here, the first optical system is assumed to be on the light incident side.

Furthermore, in the figure, numeral 9 is a polarization separation/synthesis element made of a birefringent plate made of TiO2 (rutile), and 10 is a polarization rotator made of, for example, a 1/2 wavelength plate. An optical system is constructed. On the other hand, on the output side opposite to the input side where this first optical system is arranged, there is a polarization separation/synthesis element 9' configured similarly to the polarization separation/synthesis element 9 and the polarization rotator 10, respectively. A second optical system composed of a polarization rotator 10' and a polarization rotator 10' is arranged.

In the above case, the laser beam emitted from the optical transmitter 1 is transmitted to the first optical system via the optical fiber 2, and in this first optical system, the incident light is separated by the polarization separation/synthesis element 9. The polarization rotator 10 separates into two optical paths a and b, but in this case, the polarization rotator 10
Of these, only the polarized light component of the optical path b passes through, and the polarization plane of the polarized light component of the optical path b is rotated by 90 degrees to match the polarization plane of the polarized light component of the optical path a. Further, the plane of polarization of the polarizer 3 is arranged so as to coincide with the plane of polarization of the polarized light components of the optical path a and the optical path b that are to be incident on the polarizer 3, whose planes of polarization are made to coincide with each other as described above. Furthermore, the polarization planes of the polarizer 3 and the analyzer 5 are arranged so as to make an angle of 90 degrees, but in the second optical system, the polarization rotator 10' is arranged so that only the polarization component of the optical path a passes through. It is located.

Since the optical magnetic field/current sensor according to the present invention is constructed as described above, the laser beam emitted from the optical transmitter 1 is transmitted via the optical fiber 2 to the polarization separation/synthesis element of the first optical system. In this first optical system, the light beam first passes through the polarization separation/synthesizing element 9 and is separated into two optical paths a and b having polarization components forming an angle of 90 degrees to each other. Then, the polarized light component of only one separated optical path b passes through the polarization rotator 10, so that its plane of polarization is rotated by 90 degrees, thereby causing the polarization plane of the polarized light component of the two separated optical paths a and b. matches. The polarized light components of optical path a and optical path b enter the next polarizer 3 with their planes of polarization matching each other in this manner.

Next, the light that has passed through the polarizer 3 is incident on the magneto-optical element 4. Here, when a magnetic field 8 is applied to the magneto-optical element 4, the polarization components of the optical paths a and b are polarized. The wavefront is rotated according to the above equation (1), that is, in proportion to the magnitude of the magnetic field 8. The light emitted from the magneto-optical element 4 is converted into light intensity by an analyzer 5.

Furthermore, in the second optical system, only the plane of polarization of the polarized light component in one optical path a, on which the polarization rotator 10' is disposed, is rotated by 90 degrees by the polarization rotator 10'. The planes of polarization of the polarized light components of the two optical paths a and b are perpendicular to each other when they enter the next polarized light separation/synthesizing element 9'. And this polarization separation/composition element 9
By passing through ', the polarized light components of both optical paths a and b are combined. The combined light is guided from the polarization separation/synthesizing element 9' to the optical receiver 7 via the optical fiber 6, where it is photoelectrically converted. That is, the magnitude of the applied magnetic field 8 can be determined by electrically measuring the intensity of light emitted from the polarization separation/synthesizing element 9'.

In the above embodiment, the light that has passed through the polarization separation/synthesis element 9 and the polarization rotator 10 of the first optical system is made to directly enter the magneto-optical element 4 without passing through the polarizer 3. In this case as well, the same effects as in the above embodiment can be obtained.

[0016]

As described above, according to the present invention, when measuring a magnetic field or current in this type of optical magnetic field/current sensor, it is possible to maintain a constant polarization plane of the optical fiber on the input side. In other words, there is no need to consider the state of the plane of polarization on the incident side at all, so there are advantages such as extremely excellent practical effects. In addition, the function of the optical magnetic field/current sensor can be effectively exerted by significantly reducing measurement errors of the magnetic field and current, which is extremely useful industrially.

[Brief explanation of drawings]

FIG. 1 is an overall configuration diagram of an embodiment of an optical magnetic field/current sensor according to the present invention.

FIG. 2 is an overall configuration diagram of a conventional optical magnetic field/current sensor.

[Explanation of symbols]

1. Optical transmitter 2 Optical fiber 3 Polarizer 4 Magneto-optical element 5 Analyzer 6 Optical fiber 7. Optical receiver 8 Magnetic field 9 Polarization separation/synthesis element 9´　　Polarization separation/synthesis element 10 Polarization rotator 10´　　Polarization rotator

Claims (2)

[Claims] Claim 1: Light is transmitted through a magneto-optical element having a Faraday effect, a polarizer and an analyzer disposed before and after the magneto-optical element, and the plane of polarization is determined according to the magnetic field applied to the magneto-optical element. In an optical magnetic field/current sensor configured to measure current and magnetic field by receiving rotated transmitted light, there is a polarization separation/current sensor on the light incident side.
A first optical system consisting of a combining element and a polarization rotator, a second optical system consisting of a polarization rotator and a polarization separation/combining element on the light output side, and the first optical system on the input side. The polarization plane of the polarization component of the optical path separated by the optical system is made to enter the polarizer so that it matches the polarization plane of the polarizer on the input side, and the polarization component of the separated optical path is transmitted to the second optical system on the output side. An optical magnetic field/current sensor characterized by being recombined by a system. 2. Transmission in which light is transmitted through a magneto-optical element having a Faraday effect and an analyzer disposed after the magneto-optical element, and its plane of polarization is rotated in accordance with the magnetic field applied to the magneto-optical element. In an optical magnetic field/current sensor configured to measure current and magnetic field by receiving light, a first optical system consisting of a polarization separation/synthesis element and a polarization rotator is installed on the light incident side, and A second optical system consisting of a polarization rotator and a polarization separation/synthesizing element is respectively disposed on the output side, and the polarization plane of the polarization component of the optical path separated by the first optical system on the input side is set to the above-mentioned polarization plane on the input side. In addition to making the incident light match the polarization plane of the polarizer,
An optical magnetic field/current sensor characterized in that the polarized light components of the separated optical paths are recombined by the second optical system on the output side.