JPH0259674A - Current-voltage measuring instrument - Google Patents

Abstract

PURPOSE:To reduce the loss of an optical power with high precision and to easily and exactly perform assembling by making a core diameter and the numbers of aperture of light receiving side optical fiber larger than those of light transmitting side. CONSTITUTION:The light from a light source 10 is allowed to pass by a sensor part 15 consisting of a polarizer 3, Faraday element 4 and analyser 5 through a light transmitting side optical fiber 16 and light transmitting side lens 12. The light is then converged at a light receiving side lens 13 and made incident on a light receiving side optical fiber 17, and thereafter, received at a detector 7. At this time, by making the core diameter and the number of aperture of the light receiving side optical fiber 17 larger than those of the light transmission side optical fiber 16, it is possible to reduce the loss of the optical power even if the optical fiber 17 slightly deviates in the direction of an optical axis or a fiber terminal surface tilts slightly.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an optical current and voltage measuring device using an optical fiber as a signal transmission path.

(Prior Art) In recent years, various methods of optically measuring current, voltage, etc. have been studied. Normally, the Faraday effect is used in principle as a means for optically measuring current, and the Pockels effect is similarly used as a means for measuring voltage.

In the following, an optical current measuring device that mainly uses the Faraday effect will be explained as an example.

Here, the Faraday effect is when linearly polarized light is transmitted through a magneto-optical element (hereinafter referred to as a Faraday element) placed in a magnetic field in the same direction as the magnetic field, the polarization plane of the light is proportional to the strength of the magnetic field and θ This is a phenomenon in which the object rotates. Now, if the strength of the magnetic field is the length of the H1 Faraday element in the magnetic field direction, then the rotation angle θ of the plane of polarization is θ-■·HL...■. Here, V is called the Verdet constant, and is a value determined by the material of the Faraday element.

FIG. 3 is a configuration diagram showing a current measuring device using the Faraday effect, which includes a light source 1 consisting of a light emitting diode, a laser diode, etc., a spatial transmission path 2, a polarizer 3, a Faraday element 4, an analyzer 5, and a spatial transmission path. 6. It consists of a detector 7. The detector 7 includes a light-receiving element 8 such as a photodiode, and a light-receiving element 8 such as a photodiode.
It consists of an electrical converter 9.

After passing through the Faraday element 4 installed in the magnetic field created by the polarization, the plane of polarization undergoes Faraday rotation by θ shown by the equation. By detecting this rotation angle θ using the analyzer 5 and the detector 7, the strength of the magnetic field, that is, the current value can be measured.

However, such a configuration has the following drawbacks. In other words, since the light passes through the space transmission paths 2 and 6, it can only travel straight, and therefore a large number of reflecting mirrors must be used to bend the optical path. However, in an optical path consisting of a large number of reflecting mirrors, the optical axis may be bent due to earthquakes, etc., resulting in a significant decrease in measurement accuracy, making it impractical.

In an attempt to solve the above drawbacks, the conventional Japanese Patent Application Laid-Open No. 56-677
64 Something like the one shown in @ is being considered.

Its configuration is shown in FIG. Parts that are the same as in Figure 3 are indicated by the same symbols.

Figure 4 shows a light source 10 that is close to circularly polarized light, and an optical fiber 1 on the transmitting and receiving side.
1.14, a light transmitting lens 12, a light receiving lens 13, a sensor section 15 consisting of a polarizer 3, a Faraday element 4, and an analyzer 5, and a detector 7. In this way, since the optical fiber 11.14 is connected between the light source 10 and the sensor section 15 and between the sensor section 15 and the detector 7 as a signal transmission path, the optical axis will fluctuate during earthquake or other imaging. This makes it possible to perform stable and reliable measurements.

(Problems to be Solved by the Invention) However, the configuration shown in FIG. 4 has the following problems. In other words, since the same type of optical fiber was used for the transmitting side optical fiber 11 and the receiving side optical fiber 14, the light beam emitted from the transmitting side optical fiber 11 spreads at an angle θ0, enters the transmitting side lens 12, and becomes parallel. After passing through the sensor unit 15 consisting of a polarizer 3, a Faraday element 4, and an analyzer 5, the light is focused by a light-receiving lens 13 and sent to a light-receiving optical fiber 1.
4. Note that θC is a unique value determined by the numerical aperture (NA>) of the fiber, and there is a relationship of NA=sinθc ””■.

In FIG. 4, assuming that the focal lengths 11f of the transmitting lens 12 and the receiving lens 13 are equal, and if Fresnel reflection loss at the end face of the optical fiber is ignored, the optical power passing through the receiving lens 13 is 100% of the receiving side light. The distance between the light-receiving side lens 13 and the end face of the light-receiving side optical fiber that can enter the fiber 14 is f.
It ranges from -f to f. Here, φC is the core diameter of the light-receiving optical fiber.

In other words, the distance is determined by the allowable clearance dimension in the optical axis direction of the light-receiving optical fiber. For example, core diameter = 50 mm, clad diameter = 125/
If a general optical fiber with j/ff and NA=0.2 is used, the cost will be ~122 ro. In other words, in order to input 100% of the optical power that has passed through the light-receiving lens 13 into the light-receiving optical fiber 14, the light-receiving lens 13 and the light-receiving optical fiber 14 are required.
This is a difficult task as it is necessary to adjust the distance between the end faces with an accuracy of 122 mm or less.

Furthermore, as shown in FIG. 5, when the lens-side end face of the light-receiving optical fiber 14 is tilted by θ with respect to the optical axis, a portion of the light emitted from the light-receiving lens 13 has an incident angle of θ+θC with respect to the output fiber end face, and the incident criticality is reached. It will exceed the angle θQ and will not enter. That is, if the receiving optical fiber 14 is even slightly tilted with respect to the optical axis, optical power loss will occur.

As described above, in the conventional optical measuring apparatus, even if the receiving optical fiber 14 is slightly displaced in the optical axis direction or the fiber end face is slightly tilted, a large optical power loss occurs.

A large optical power loss means that the photodiode 8 in the detector 7 receives less light. Therefore, the signal from the optical-to-electrical converter is also small and susceptible to electrical noise, which may reduce measurement accuracy.

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical current/voltage measurement device using an optical fiber that can be assembled easily and accurately, has low optical power loss, and has high precision.

[Structure of the invention]

(Means for Solving the Problems) The current and voltage measuring device of the present invention includes a light source, a light transmitting optical fiber, a light transmitting lens, a polarizer, a Faraday element, an analyzer, etc., a sensor section, a light receiving lens, It consists of a light-receiving optical fiber, and the light-receiving optical fiber is configured to have a larger core diameter and a larger numerical aperture than the light-transmitting optical fiber.

(Function) According to the present invention, the light emitted from the light transmitting side optical fiber becomes parallel light beams by the light transmitting side lens, and the polarizer, Faraday element,
After passing through a sensor section consisting of an analyzer, etc., the light is focused by a light-receiving lens and enters an optical fiber on the light-receiving side.

By making the core diameter of the light-receiving optical fiber larger than the core diameter of the light-transmitting optical fiber, the permissible deviation in the optical axis direction of the light-receiving optical fiber can be increased.

Furthermore, by increasing the numerical aperture of the light-receiving optical fiber, light can be input into the fiber without optical power loss even if the fiber end face is tilted to some extent.

(Example) An embodiment of the present invention will be described below with reference to FIG.

In FIG. 1, 10 is a light source, 16 is a light transmitting side optical fiber,
17 is an optical fiber on the light receiving side, 12 is a light transmitting side lens, 13 is a light receiving side lens, and 15 is a polarizer 3, a Faraday element 4, and an analyzer 5 arranged between the light transmitting side lens 12 and the light receiving side lens. The sensor part is placed in the magnetic field created by the conductor to be measured. 7 is a detector consisting of a light receiving element and a photo-electrical converter. Here, the core diameter and numerical aperture of the light-receiving optical fiber 17 are selected to be larger than those of the light-transmitting optical fiber 16.

With this configuration, if the core diameter of the light-receiving optical fiber 17 is made m times the core diameter of the light-transmitting optical fiber 16, then from formula The offset dimension will be multiplied by m.

The permissible deviation dimension in the direction perpendicular to the optical axis also increases. For example, the end face of the optical fiber 17 on the light receiving side is the lens 13 on the light receiving side.
If the core diameter of the receiving optical fiber 17 is m times the core diameter of the transmitting optical fiber, then if the core diameters of the transmitting and receiving optical fibers 16 and 17 are the same, then In comparison, the allowable deviation dimension in the direction perpendicular to the optical axis is multiplied by m.

Further, if the numerical aperture of the light-transmitting optical fiber 16 is NA and the numerical aperture of the light-receiving optical fiber 17 is n-NA, the critical angle of light incident on the light-receiving optical fiber 17 is doubled.

Here, k is expressed by equation (a).

The numerical aperture of the optical fiber 17 on the light side is 0.5, and the transmitting/receiving lens 1
Assuming that 2 and 13 each have a focal length of 5 and are placed at a distance f from the fiber end face, the allowable inclination Δθ of the fiber is Δθ = 5in-1 (0, 5) - 5in-1 (0,
2) 'P18.5°...becomes 0.

Therefore, according to this configuration, the permissible deviation dimension or inclination in the direction of the optical axis or in the direction perpendicular to the optical axis can be increased, making assembly easier and resistant to vibration. Also, optical loss can be reduced.

Another embodiment is shown in FIG. FIG. 2 is a block diagram showing the device for voltage measurement, and FIG. 1 shows the comparison sensor section 15.
The only difference is inside.

That is, the sensor unit 15 in FIG. 2 can receive light without loss of optical power even if the polarizer 3.1/that is, the end face of the light-receiving optical fiber 17 is tilted to some extent with respect to the optical axis.

For example, the numerical aperture of the light transmitting side optical fiber 16 is 0.2.

It goes without saying that the voltage measuring device having this configuration also has the same functions and effects as those of the above embodiment.

〔Effect of the invention〕

A sensor section made of a magneto-optical element or an electro-optic crystal, a detector that receives light from the sensor section, a light transmission side optical fiber that guides the light from the light source to the sensor section, and the light transmission side optical fiber and the sensor section. A current consisting of a light transmitting side lens disposed between the light transmitting side lens, a light receiving side optical fiber guiding the light from the sensor section to the detector, and a light receiving side lens disposed between the light receiving side optical fiber and the sensor section; In the voltage measuring device, the core diameter and numerical aperture of the receiving optical fiber were made larger than the core diameter and numerical aperture of the transmitting optical fiber, so the permissible deviation in the optical axis direction of the receiving fiber was The allowable deviation dimension and allowable inclination can be increased, making assembly easier and resistant to vibration. In addition, since optical power loss can be reduced, the optical power incident on the photodiode in the detector is increased, and the signal after optical-to-electrical conversion is also increased, making it less susceptible to electrical noise and improving stability and measurement accuracy. Current and voltage measuring devices can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a current/voltage measuring device according to an embodiment of the present invention, Fig. 2 is a block diagram showing another embodiment of the present invention, and Figs. 3 and 4 are conventional current/voltage measurement devices. FIG. 5, a block diagram showing the apparatus, is a partially enlarged view of FIG. 4. 10... Light source 3... Polarizer 12.
...Light transmitting side lens 4...Faraday element 13
...Lens on the light receiving side 5...Analyzer 15...
Sensor part 18...1/4 wavelength plate 16...
・Light sending side optical fiber 19... Electro-optic crystal 17・
...Receiving side optical fiber agent Patent attorney Nori Ken Chika Yudoji 1-÷Rin→--Bundai Shimaru Kendai 3 Figure 5 Figure 2 Figure 5

Claims (1)

[Claims] A light source, a sensor section made of a magneto-optical element or an electro-optic crystal placed in a magnetic field or electric field created by a current or voltage to be measured, a detector that receives light from the sensor section, and a sensor that receives light from the light source. a light transmitting side optical fiber that guides the light from the sensor to the detector, a light transmitting side lens placed between the light transmitting side optical fiber and the sensor section, a light receiving side optical fiber that guides the light from the sensor section to the detector, and a light receiving side optical fiber that guides the light from the sensor section to the detector. In a current and voltage measuring device consisting of a light-receiving lens placed between a fiber and a sensor section, the core diameter and numerical aperture of the light-receiving optical fiber are made larger than the core diameter and numerical aperture of the light-transmitting optical fiber. A current and voltage measuring device featuring: