JP3494525B2 - Optical fiber current measuring device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber current measuring device utilizing the principle that the plane of polarization of linearly polarized light propagating in an optical fiber is rotated by the Faraday effect, and particularly in high voltage equipment such as substation equipment and power transmission equipment. The present invention relates to an optical fiber current measuring device particularly preferably used for current measurement.

[0002]

2. Description of the Related Art As a current measuring method, a method utilizing the Faraday effect in which the polarization plane of light propagating through an optical fiber is rotated by the action of a magnetic field is known. By using an optical fiber having the Faraday effect, it is possible to greatly reduce the size and weight of the current measuring instrument.

The configuration of such an optical fiber current measuring device is roughly classified into the following two types. The first method is to input linearly polarized light from one end of the optical fiber,
This is a method of measuring the rotation angle of the plane of polarization of the light emitted from the other end of the optical fiber. This is called a transmission type.

In the second method, linearly polarized light is made incident from one end of the optical fiber and the light is reflected at the other end of the optical fiber.
This method measures the rotation angle of the plane of polarization of the returned light. This is called a reflection type.

As an example of the reflection type optical fiber current device,
There is one disclosed in JP-A-49-90973.
In the optical fiber current measuring device shown in this example, light is incident from one end of the optical fiber and reflected by the film provided at the other end. When the reflected light returns through the same path and is emitted from the optical fiber again, the optical path of the light is bent by the beam splitter, and this is detected by the analyzer. Then, the Faraday rotation angle of the detected light is measured.

From the light detected by such an optical fiber current measuring device, the current value can be calculated by the following method. When linearly polarized light in the 0 degree direction is incident on a fiber having the Faraday effect (hereinafter referred to as “sensing fiber”), the light emitted from the fiber due to the Faraday rotation is divided into the 0 degree component and the 90 degree component (each I ₀ , I ₉₀ ),

[0007]

## EQU1 ## I ₀ = P (1 + cos (2F)) (1)

[0008]

## EQU2 ## I ₉₀ = P (1-cos (2F)) (2)

[0009]

## EQU3 ## F = VIN (3) Here, P is the light intensity which is half the input intensity, F is the Faraday rotation angle, V is the Verdet constant, I is the current value, and N is the number of turns of the optical fiber around the conductor.

According to this equation, since the Faraday rotation angle is entered in the form of the argument of the cosine function, it is impossible to distinguish the sign of the Faraday rotation angle by measuring I ₀ or I ₉₀ . As an effective method to avoid this problem, the two axes of the analyzer that separates the light emitted from the sensing fiber are
There is a method in which the light intensities I ₋₄₅ and I ₊₄₅ of the respective axial components are measured by setting them to 45 degrees and +45 degrees. At this time,

[0011]

[ _Equation 4] I ₋₄₅ = P (1 + sin (2F)) (4)

[0012]

## _EQU5 ## I + ₄₅ = P (1-sin (2F)) (5) Since the Faraday rotation angle is included in the form of the argument of the sine function in I _-45 and I ₊₄₅ , I _-45 or I
The sign of the Faraday rotation angle can be distinguished by measuring either ₊₄₅ .

Since it is a sine function, when the current is small, that is, when the Faraday rotation angle is small, a linear approximation is performed.

[0014]

[ _Equation 6] I ₋₄₅ = P (1 + sin (2F)) = P + 2PF (6) holds. Therefore, the signal processing mechanism for obtaining the Faraday rotation angle from the light intensity is greatly simplified.

However, also in this method, the magnitudes of the equations (4) and (5) depend on the light intensity P of the light source, and when this varies, a measurement error occurs. As a way to avoid this drawback,

[0016]

## _EQU7 ## S = (I ₋₄₅ −I ₊₄₅ ) / (I ₋₄₅ + I ₊₄₅ ) _..

[0017]

## EQU8 ## S = sin (2F) .multidot.2F (8) Since this does not depend on the intensity of the incident light, it is not affected by the light intensity fluctuation of the light source, and high-precision measurement is possible.

That is, in order to eliminate the influence of the fluctuation of the light intensity incident on the fiber and to obtain the linearity of the current measurement, the axis of the analyzer is tilted at 45 degrees with respect to the incident polarization plane (hereinafter, "45 degrees" It is called "optical bias"), and two polarization components in the axial direction of the analyzer need to be detected. In other words, the sign of the Faraday rotation angle cannot be distinguished unless an optical bias of 45 degrees is applied, and the influence of the fluctuation of the light intensity cannot be eliminated by only detecting one polarization component of the analyzer. I can't expect a good current measurement.

These requirements are common to both the transmission type and the reflection type. However, in the reflection type, the incident light to the sensing fiber and the light emitted from the sensing fiber overlap with each other in the same optical path. It is necessary to separate the emitted light and to apply a 45-degree optical bias between them.

From the above requirements, for example, "Electronic Cur
rent Sensors Employing Spun Highly Birefringent Op
tical Fibers, Journal of Lightwave Technology Vol.7
No. 12, 2084 (1989) '' (Richard I. Laming and David N.
In Payne,), a linearly polarized light having a polarization plane in the direction of 45 degrees is incident on the sensing fiber through a polarizer that adjusts the incident light in the direction of 45 degrees, and the optical path of the light emitted from the fiber is bent by a beam splitter, Two polarized components are detected by an analyzer having an axis in the direction of 90 degrees. Then, based on the detected polarization component, signal processing is performed according to the equation (7) and converted into a current value.

That is, in the reflection type structure, the incident end of the sensing fiber is also the outgoing end of the returned light. Therefore, it is necessary to separate the incident light and the emitted light, and in the above example, the beam splitter is used for separation.

However, since the P-wave and S-wave of linearly polarized light have different reflectances in the beam splitter, the plane of polarization of the reflected light rotates when the linearly polarized light is reflected by the beam splitter. As a result, it becomes impossible to accurately measure the Faraday rotation angle. That is, separating the incident light and the emitted light by the beam splitter causes a decrease in measurement accuracy.

Therefore, in the method disclosed in Japanese Patent Laid-Open No. 6-337275, a phase compensator is added to the optical path of outgoing light split by the beam splitter. FIG. 8 is a diagram showing an optical fiber current measuring device using a phase compensator. In this example, a transmission compensator is used as the phase compensator. The light emitted from the light transmitting fiber 81 passes through the collimator lens 82 and the polarizer 83 to become linearly polarized light.
The linearly polarized light passes through the beam splitter 84 and the collimator lens 85 and enters the sensing fiber 86. The linearly polarized light is reflected by the reflection mirror 87 and emitted from the sensing fiber 86. At this time, the conductor 88 is used for the linearly polarized light.
The Faraday rotation angle due to the current flowing through is added. The reflected light emitted from the sensing fiber 86 is
It is reflected by the beam splitter 84 and the plane of polarization is rotated. The rotation of the plane of polarization is restored when the light passes through the transmission compensating plate 89, and is separated into two polarization components by the analyzer 90. The two separated polarization components pass through the collimator lenses 91 and 92, and enter the light receiving fibers 93 and 94. As a result, two polarization components are detected.

In the transmission compensator used here, the transmittance of the P wave and the S wave changes depending on the angle of the transmitted light. Therefore, the polarization plane rotated by the beam splitter can be returned to the original state by adjusting the angle of the transmission compensating plate with respect to the outgoing light split by the beam splitter.

Further, Japanese Patent Application Laid-Open No. 7-248338 discloses a method of separating emitted light by a fiber coupler without using a beam splitter. FIG. 9 is a diagram showing an optical fiber current measuring device for separating emitted light by a fiber coupler. In this example, the light emitted from the light source 101 is linearly polarized by the polarizer 102. The linearly polarized light passes through the fiber coupler 103, further passes through the polarizer 104a in the thin film type polarizer unit 104, and then enters the sensing fiber 106. The linearly polarized light is reflected by the reflection mirror 107, and the sensing fiber 1
It is emitted from 06. At this time, the Faraday rotation angle due to the current flowing through the conductor 108 is added to the linearly polarized light.
Further, an optical bias of 45 degrees is applied to the linearly polarized light by the permanent magnet 105 provided at the entrance of the sensing fiber 106. A part of the reflected light emitted from the sensing fiber 106 is sent to the light receiving element 109 by the fiber coupler 103. Then, the light receiving element 109
Then, the amount of light is converted into an electric signal.

According to this method, since the beam splitter is not used, it is not necessary to consider the rotation of the polarization plane when separating the light emitted from the sensing fiber.

[0027]

However, Japanese Patent Laid-Open No. 6-3
The method disclosed in Japanese Patent No. 37275 reduces the problem caused by the different reflectances of the P wave and the S wave, but since the phase compensator has a high temperature dependence, it has high accuracy in a wide temperature range. Measurement is difficult. Moreover, since a polarizer, a beam splitter, an analyzer and a phase compensator are required, the optical system becomes complicated and large.

On the other hand, in the method disclosed in Japanese Patent Application Laid-Open No. 7-248338, only one of the polarized components can be detected, and therefore the influence of the light intensity of the light source is unavoidable and high-precision measurement is difficult. is there.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide an optical fiber current measuring device capable of detecting two polarization components without rotating the polarization plane of the light emitted from the optical fiber. To aim.

[0030]

According to the present invention, in order to solve the above-mentioned problems, light is made incident from an input / output end of an optical fiber wound around a conductor, reflected at the end of the optical fiber and returned. Based on the Faraday rotation angle of reflected light, in the optical fiber current measuring device for measuring the current flowing through the conductor, is connected to a light source, the light emitted from the light source is sent to the optical fiber side, An optical component that sends light traveling backward from the fiber side to the first light receiving element,
Provided between the optical component and the optical fiber, the light traveling from the optical component to the optical fiber is shaped into linearly polarized light and sent to the optical fiber, and the reflected light sent from the optical fiber is Split into two polarization components,
An optical fiber current measuring device is provided, which comprises: a bidirectional analyzer that sends the polarized component to the optical component and a second light receiving element, respectively.

According to such an optical fiber current measuring device, the light emitted from the light source passes through the optical component and is incident on the bidirectional analyzer. The light is shaped into linearly polarized light by the bidirectional analyzer and is incident on the optical fiber. The linearly polarized light that has entered the optical fiber is reflected at the end of the optical fiber and becomes reflected light with the Faraday rotation angle added to it, and enters the bidirectional analyzer from the opposite direction. The reflected light is reflected by the bidirectional analyzer.
The two polarized components are separated, one polarized component is sent to the optical component, and the other polarized component is sent to the second light receiving element. The polarization component sent to the fiber coupler is sent to the first light receiving element through the fiber coupler.

Thus, the two polarization components of the reflected light from the optical fiber can be detected without rotating the plane of polarization of the linearly polarized light.

[0033]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of an optical fiber current measuring device of the present invention. This optical fiber current measuring device includes a light source 1 for generating a laser beam, a fiber coupler 2 serving as a light propagation path between the light source 1 and the polarizer / analyzer unit 10, and a built-in polarizer / analyzer for reflection. A polarizer / analyzer unit 10 for separating light, a Faraday rotation element 4 for applying an optical bias of 45 degrees by the Faraday effect, a sensing fiber 3 having the Faraday effect, and a reflection mirror for reflecting light at the end of the sensing fiber 3. 6 and light receiving elements 8 and 9 for converting the polarization component of the reflected light extracted from the polarizer / analyzer unit 10 into an electric signal.

The light source 1, the polarizer / analyzer unit 10 and the light receiving element 8 are respectively connected to the fibers 2a, 2b and 2c which are the ports for entering and exiting the fiber coupler 2. The fiber coupler 2 sends the light entered from the fiber 2a to the fiber 2b, and sends part of the light entered from the fiber 2b to the fiber 2c. On the other hand, the light receiving element 9
Are connected to the polarizer / analyzer unit 10 by the light receiving fiber 7.

The sensing fiber 3 has one end (entrance / emission end) connected to the polarizer / analyzer unit 10 via the Faraday rotation element 4, and the other end (termination) at the reflection mirror 6.
Is provided. The Faraday rotator 4 applies a 45-degree optical bias to the light passing through the inside by applying a predetermined magnetic field from the outside. The sensing fiber 3 is bent so as to circulate around the conductor 5 through which the current to be measured flows, and is affected by the magnetic field generated by the current in the conductor 5 to add Faraday rotation to the light passing through the inside.

FIG. 2 is a diagram showing the structure of the polarizer / analyzer unit. In the housing 12 of the polarizer / analyzer unit 10, the fiber 2b and the sensing fiber 3 are fixed so as to face each other in a straight line. A Glan laser prism 11 having a function as a bidirectional analyzer is arranged between the fiber 2b and the sensing fiber 3. Also,
The light receiving fiber 7 is fixed in the direction in which the light reflected by the Glan laser prism 11 travels.

The fiber coupler 2, the sensing fiber 3, and the light receiving fiber 7 are all fiber collimators having microlenses incorporated at their ends. According to the optical fiber current measuring device having the above configuration, the light emitted from the light source 1 is guided to the polarizer / analyzer unit 10 through the fiber coupler 2. The light incident on the polarizer / analyzer unit 10 is shaped into linearly polarized light by passing through the Glan laser prism 11. The linearly polarized light is incident on the Faraday rotator 4, and when passing through the Faraday rotator 4, the plane of polarization is rotated by 22.5 degrees. The light that has passed through the Faraday rotation element 4 is incident on the sensing fiber 3. The plane of polarization of the linearly polarized light propagating in the sensing fiber 3 undergoes Faraday rotation by the magnetic field created by the current flowing in the conductor 5. The light reaching the end of the sensing fiber 3 is reflected by the reflection mirror 6 and propagates in the opposite direction along the same optical path. Since the Faraday effect is non-reciprocal, the Faraday rotation in the same direction as the outward path is also applied to the return path. Therefore, the Faraday rotation angle becomes twice as much as the one-way case by reciprocating the sensing fiber 3. When the light is emitted from the sensing fiber 3, it passes through the Faraday rotator 4 again, and the plane of polarization is 22,
Rotate 5 degrees. As a result, the plane of polarization is rotated by 45 degrees in a reciprocating manner, and a 45 degree optical bias is realized.

As a result, the plane of polarization of the light emitted from the Faraday rotator 4 is rotated by 45 degrees with respect to the incident linearly polarized light, and the Faraday rotation angle is added. The light emitted from the sensing fiber 3 is the Glan laser prism 11
By passing through, the polarization components (P
Wave, S wave). One goes straight through the Glan-laser prism 11 and enters the fiber 2b. The other is reflected by the Glan-laser prism 11 in a direction substantially at a right angle and enters the light-receiving fiber 7. The light incident on the fiber 2b is
A part of the light is guided to the fiber 2c and converted into an electric signal by the light receiving element 8. The light incident on the light receiving fiber 7 is converted into an electric signal by the light receiving element 9.

The electric signals detected by the two light receiving elements 8 and 9 are sent to a signal processing circuit (not shown). The electric signal is subjected to the calculation according to the equation (7) in the signal processing circuit to be changed into the Faraday rotation angle, and further the current is calculated according to the equations (1) to (3).

As described above, the two polarization components can be detected from the reflected light without using the beam splitter. Therefore, the polarization state can be measured accurately,
Current measurement with high measurement accuracy is realized.

By the way, in the above example, the Glan laser prism is used as a bidirectional analyzer, but the conditions for being usable as a bidirectional analyzer are as follows. The first condition is that, when light is incident from the first port, the incident light is separated into two polarization components according to the crystal axis of the analyzer, and one polarization component is emitted from the second port. Is.

The second condition is that when light in the opposite direction is incident on the second port, the incident light is separated into two polarized components according to the crystal axis of the analyzer, and one polarized component is polarized on the first port. And the other polarization component is emitted to the third port.

Therefore, any optical element satisfying the above conditions can be used as the bidirectional analyzer of the optical fiber current measuring apparatus of the present invention. Other than the Glan-laser prism, there are, for example, a quartz crystal, a birefringent crystal such as calcite, and a polarization beam splitter. Further, as a bidirectional analyzer, an optical path shift prism or a reflection mirror may be combined to guide one polarization component in a desired direction. Below, a polarizer using these bidirectional analyzers /
A configuration example of the analyzer unit will be described.

FIG. 3 is a diagram showing an example of the construction of a polarizer / analyzer section in which a Glan laser prism and a reflection mirror are combined. In the housing 33 of the polarizer / analyzer unit 30, the fiber 2b of the fiber coupler 2 and the sensing fiber 3 are fixed so as to face each other in a straight line. A Glan-laser prism 31 having a function as a bidirectional analyzer is arranged between the fiber 2b and the sensing fiber 3. Further, a total reflection mirror 32 is arranged in the traveling direction of the light reflected by the Gran laser prism 31. Further, the light receiving fiber 7 is fixed in the direction in which the light reflected by the total reflection mirror 32 should travel. In this example, the light receiving fiber 7 is provided at a position substantially parallel to the fiber 2b.

As a result, in the light emitted from the sensing fiber 3 into the polarizer / analyzer unit 30, when one polarization component is reflected by the Glan laser prism 31, the polarization component is reflected by the total reflection mirror 32, The direction can be changed again. Therefore, the light receiving fiber 7 can be fixed at a desired position, and the degree of freedom in designing the optical fiber current measuring device increases.

FIG. 4 is a diagram showing an example of the construction of a polarizer / analyzer section in which a Glan laser prism and an optical path shift prism are combined. Housing 43 of the polarizer / analyzer unit 40
The fiber 2b of the fiber coupler 2 and the sensing fiber 3 are fixed to each other in a straight line. Between the fiber 2b and the sensing fiber 3,
A Glan laser prism 41 having a function as a bidirectional analyzer is arranged. Further, an optical path shift prism 42 is arranged in the traveling direction of the light reflected by the Gran laser prism 41. Further, the optical path shift prism 4
The light receiving fiber 7 is fixed in the direction in which the light reflected by 2 should travel. In this example, the light receiving fiber 7 is provided at a position substantially parallel to the fiber 2b.

As a result, when one polarization component of the light emitted from the sensing fiber 3 into the polarizer / analyzer unit 40 is reflected by the Glan laser prism 41, the polarization component is reflected by the optical path shift prism 42, The direction can be changed again. Therefore, the light receiving fiber 7 can be fixed at a desired position, and the degree of freedom in designing the optical fiber current measuring device is increased as in the example shown in FIG.

FIG. 5 is a diagram showing a configuration example of a polarizer / analyzer part using a birefringent crystal for the bidirectional analyzer. Polarizer /
The fiber 2b of the fiber coupler 2 and the sensing fiber 3 are fixed to the housing 52 of the analyzer unit 50 so as to face each other in a straight line. A birefringent crystal 51 having a function as a bidirectional analyzer is arranged between the fiber 2b and the sensing fiber 3. In addition, the light receiving fiber 7 is directed in the traveling direction of the light refracted by the birefringent crystal 51.
Is fixed. Crystals such as quartz and calcite can be used as the birefringent crystal 51.

Thus, the light emitted from the fiber 2b into the polarizer / analyzer unit 50 is changed in direction by the birefringent crystal 51 and is not emitted to the outside of the polarizer / analyzer unit 50. In the light emitted from the sensing fiber 3 into the polarizer / analyzer unit 50, one polarization component goes straight through the birefringent crystal 51 and enters the fiber 2b, and the other polarization component is refracted by the birefringent crystal 51. And enters the light receiving fiber 7.

FIG. 6 is a diagram showing an example of the construction of a polarizer / analyzer section in which a birefringent crystal and an optical path shift prism are combined. In the housing 63 of the polarizer / analyzer unit 60, the fiber 2 b of the fiber coupler 2 and the sensing fiber 3 are provided.
And are fixed in a straight line. A birefringent crystal 61 having a function as a bidirectional analyzer is arranged between the fiber 2b and the sensing fiber 3. Further, an optical path shift prism 62 is arranged in the traveling direction of the light refracted by the birefringent crystal 61. Further, the light receiving fiber 7 is fixed in the direction in which the light reflected by the optical path shift prism 62 should travel. Birefringent crystal 6
As 1, crystal such as quartz or calcite can be used.

As a result, the light emitted from the fiber 2b into the polarizer / analyzer unit 60 is separated into two polarization components, and one of the components is guided straight to the sensing fiber 3. On the contrary, in the light emitted from the sensing fiber 3 into the polarizer / analyzer unit 60, one polarization component goes straight through the birefringent crystal 61 and enters the fiber 2b. The other polarization component is refracted by the birefringent crystal 61 and is reflected by the optical path shift prism 6
2 is incident on the light receiving fiber 7 after being refracted by the optical path shift prism 62.

In the above example, the bidirectional analyzer and the light receiving element are optically connected via the light receiving fiber, but the light receiving element may be directly attached to the polarizer / analyzer part.

FIG. 7 is a diagram showing an example of a polarizer / analyzer unit having a light receiving element. In the housing 73 of the polarizer / analyzer unit 70, the fiber 2b of the fiber coupler 2 and the sensing fiber 3 are fixed so as to face each other in a straight line. A Glan-laser prism 71 having a function as a bidirectional analyzer is arranged between the fiber 2b and the sensing fiber 3. Further, the light receiving element 72 is fixed in the traveling direction of the light reflected by the Gran laser prism 71.

As a result, the light emitted from the sensing fiber 3 into the polarizer / analyzer unit 70 has one polarization component reflected by the Glan-laser prism 31 in a direction substantially at right angles,
The light directly enters the light receiving element 72. The light receiving element 72 converts incident light into an electric signal and sends the electric signal to a signal processing circuit. With such a polarizer / analyzer unit 70, it is not necessary to separately provide a light receiving element, and the structure of the optical fiber current measuring device is simplified.

The configuration using a polarization beam splitter as the bidirectional analyzer is only the replacement of the Glan laser prism in FIGS. 3, 4 and 7 with a polarization beam splitter, and the other configurations are the same as the above example. Is the same as.

By the way, the calculation in the signal processing circuit is not limited to the expression (7), and another method can be adopted as long as it can cancel the fluctuation of the light intensity of the light source by using the two polarization components. For example, in AC current measurement, a method using the sum or difference of two modulation degrees as disclosed in JP-A-7-270505, or Japanese Patent Application No. 6-3
As shown in No. 25063, there is a method using a product of modulation factors. Although these methods are limited to alternating current, they are useful in that highly accurate measurement can be realized even when the optical bias deviates from 45 degrees.

Further, the method of obtaining the 45-degree optical bias is not limited to the method of using the Faraday rotator, but the method of applying a permanent magnet to the sensing fiber itself can
There is a method of applying an optical bias of 5 degrees.

[0058]

As described above, in the present invention, the reflected light is separated into two polarization components by the bidirectional analyzer, one polarization component is sent to the first light receiving element through the optical component, and the other polarization component is sent. Since the polarization component is sent to the second light receiving element, it is possible to detect the two polarization components without rotating the plane of polarization when the light is emitted from the optical fiber. As a result, the current can be measured without being affected by the temperature change and without depending on the intensity of the incident light, and the current measurement with high measurement accuracy can be realized.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of an optical fiber current measuring device of the present invention.

FIG. 2 is a diagram showing a configuration of a polarizer / analyzer unit.

FIG. 3 is a diagram showing a configuration example of a polarizer / analyzer unit in which a Glan laser prism and a reflection mirror are combined.

FIG. 4 is a diagram showing a configuration example of a polarizer / analyzer unit in which a Glan laser prism and an optical path shift prism are combined.

FIG. 5: A polarizer using a birefringent crystal for a bidirectional analyzer /
It is a figure which shows the structural example of an analyzer part.

FIG. 6 is a diagram showing a configuration example of a polarizer / analyzer unit in which a birefringent crystal and an optical path shift prism are combined.

FIG. 7 is a diagram showing an example of a polarizer / analyzer unit having a light receiving element.

FIG. 8 shows an optical fiber current measuring device using a phase compensator .
FIG.

FIG. 9: Light for separating emitted light by a fiber coupler
It is a figure which shows a fiber current measuring device.

[Explanation of symbols]

1 light source 2 Fiber coupler 3 Sensing fiber 4 Faraday rotator 5 conductors 6 reflection mirror 7 Light receiving fiber 8,9 Light receiving element

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-5-312927 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G01R 15/24 G01R 33/032

Claims (4)

(57) [Claims] 1. Light is made to enter from an entrance / exit end of an optical fiber wound around a conductor, and flows through the conductor based on a Faraday rotation angle of reflected light reflected and returned at the end of the optical fiber. An optical fiber current measuring device for measuring a current, which is connected to a light source, sends light emitted from the light source to the optical fiber side, and sends light traveling backward from the optical fiber side to a first light receiving element An optical component, provided between the optical component and the optical fiber, the light traveling from the optical component to the optical fiber is linearly polarized and sent to the optical fiber, and the optical fiber is sent from the optical fiber. Separate the reflected light into two polarization components,
An optical fiber current measuring device, comprising: a bidirectional analyzer that sends the two polarization components to the optical component and a second light receiving element, respectively. 2. The optical fiber current measuring device according to claim 1, wherein the optical component is a fiber coupler for transmitting a part of light traveling backward from the optical fiber side to the first light receiving element. apparatus. 3. The optical fiber current measuring device according to claim 1, wherein the bidirectional analyzer is a Glan laser prism. 4. The optical fiber current measuring device according to claim 1, wherein the bidirectional analyzer is a birefringent crystal.