JPH08160324A - Polarization state varying device and instrument for measuring dependency on polarization using the same - Google Patents

Abstract

PURPOSE: To provide a polarization state varying device which easily varies a polarization state to the entire state and an instrument for measuring dependency on polarization which is capable of quantitatively measuring the dependency on polarization or the characteristics of an optical device. CONSTITUTION: This polarization state varying device has a first wedge type double refractive crystal plate 25 arranged in such a manner that its optical axis intersects orthogonally with the optical axis of an incident side optical transmission line 11 and that its one plane intersecting orthogonally with the optical axis faces the exit face of this incident side optical transmission line 11, a second wedge type double refractive crystal plate 26 arranged in such a manner that its slope parallels in proximity to the slope of the first wedge type double refractive crystal plate 25 and that its optical axis intersects orthogonally with the optical axis of the first wedge type double refractive crystal plate 25 and the optical axis of the incident side optical transmission line 11, an exit side optical transmission line 15 which transmits the exit light of the second wedge type double refractive crystal plate 26 and a driving means which moves either one of the first and second wedge type double refractive crystal plates back and forth in a direction where the optical path length changes.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polarization state variator and a polarization dependence measuring device using the same. In recent years, a rare earth element-doped optical fiber that transmits an optical signal with a wavelength in the vicinity of 1.55 μm with a length of several meters to several hundred meters is injected with pumping light with a wavelength of about 1.48 μm from a pumping light source and then combined. An optical communication system using an optical amplifier that amplifies an optical signal by stimulated emission of a rare earth element-doped optical fiber is being provided.

An optical amplifier will be described below with reference to FIG. In FIG. 10, reference numeral 1 denotes an optical fiber doped with a rare earth element such as erbium and having a long length of several meters to several hundred meters.

Reference numeral 1-1 is an incident side fiber / lens assembly mounted on the exit end of the rare earth element-doped optical fiber 1. Reference numeral 3-1 is an excitation side fiber lens assembly for introducing the excitation light of the excitation light source 3 into the rare earth element-doped optical fiber 1, and 2-1 is an emission side fiber lens attached to the incident end of the output optical fiber 2. It is an assembly.

4-1 is a selected side wall 4A, a first adjacent side wall 4B orthogonal to the side wall 4A, an opposite side wall 4C orthogonal to the first adjacent side wall 4B, and a second adjacent side wall 4D orthogonal to the opposite side wall 4C. It is a quadrangular casing having four side walls.

Reference numeral 5 is a wavelength division optical film which transmits the excitation light (wavelength is about 1.48 μm) among the light emitted from the excitation light source 3 and reflects the light emitted from the rare earth element-doped optical fiber 1 (wavelength is 1.55 μm). Is.

An optical isolator 6 is inserted between the wavelength division optical film 5 and the output side fiber / lens assembly 2-1. Incident fiber / lens assembly 1-1
Vertically penetrates the selected side wall 4A of the housing 4-1.
Installed in 1. The excitation side fiber lens assembly 3-1 has an optical axis on the incident side fiber lens assembly 1-1.
It is attached to the housing 4-1 by vertically penetrating the opposing side wall 4C so as to coincide with the optical axis of.

The wavelength division optical film 5 is tilted by 45 degrees with respect to the optical axis of the incident side fiber lens assembly 1-1 to form an incident side fiber lens assembly 1-1 and an excitation side fiber lens assembly 3-1. It is mounted in the case 4-1 at a position approximately midway between.

On the other hand, in the output optical fiber 2, the reflected light of the wavelength division optical film 5 enters through the optical isolator 6,
It is attached to the housing 4-1 by vertically penetrating the adjacent side wall 4D.

With the above configuration, the pumping light from the pumping light source 3 is incident on the rare earth element-doped optical fiber 1 and amplifies the signal light transmitted to the rare earth element-doped optical fiber 1.

The amplified signal light is emitted from the incident side fiber / lens assembly 1-1, projected on the wavelength division optical film 5, reflected by the wavelength division optical film 5 in the direction of 90 degrees, and then reflected by the optical isolator 6. Then, the light enters the output side fiber / lens assembly 2-1 and is transmitted to the output optical fiber 2.

As described above, in the optical communication system to which the optical amplification technology is applied, the polarization state transmitted through the single mode optical fiber changes momentarily due to disturbances such as stress, tension and temperature applied to the optical fiber. The sensitivity also fluctuates accordingly, and a code error occurs.

That is, the optical amplifier has polarization dependency. Therefore, in an optical communication system in which amplification and relay are performed in tens to hundreds of stages, if the polarization dependency is large, the accumulated level changes by several dB to several tens of dB.

Therefore, the optical amplifier is required to have stable amplification characteristics in any polarization state of incident light.
As described above, since the optical amplifier has polarization dependence, when performing the performance test of the optical amplifier, the polarization state of the incident light (linear polarization, circular polarization, elliptically polarized light with different ellipticity, etc.) is changed. Need to be implemented.

[0014]

2. Description of the Related Art Conventionally, a single mode optical fiber is used to connect a light source such as an LD or an edge emitting high output LED to a rare earth element-doped optical fiber of an optical amplifier.

Then, the polarization state of the light incident on the optical amplifier is changed by twisting the single mode optical fiber to give stress or bending the single mode optical fiber in a circular shape to give stress.

[0016]

As described above, the conventional means for changing the polarization state by twisting or bending the optical fiber into a circular shape and applying a stress to the optical fiber has a plurality of different polarization states. Not only did it take a lot of time to change, but it was not possible to confirm whether the polarization state was changed to all states (linear polarization, circular polarization, or all polarization states of elliptical polarization with different ellipticities). .

The present invention has been made in view of the above points, and an object thereof is to provide a polarization state variable device in which the polarization state can be easily changed to all states. Another object of the present invention is to provide a polarization dependence measuring device capable of quantitatively measuring the characteristics of the polarization dependent optical device.

[0018]

In order to achieve the above object, the present invention, as shown in FIG. 1, includes an incident side optical transmission line 11 for emitting a parallel light beam and an incident side optical transmission line having an optical axis. The first wedge-shaped birefringent crystal plate 25 is arranged so that one surface thereof, which is orthogonal to the optical axis of 11 and is orthogonal to each other, faces the exit surface of the incident-side optical transmission path 11.

Further, it has a wedge shape having an inclined surface whose inclination angle is equal to the inclination angle of the first wedge-shaped birefringent crystal plate 25, and the inclined surface is close to the inclined surface of the first wedge-shaped birefringent crystal plate 25. A second wedge-shaped birefringent crystal plate 26 arranged parallel to each other and having an optical axis orthogonal to the optical axis of the first wedge-shaped birefringent crystal plate 25 and the optical axis of the incident side optical transmission line 11. .

Further, the output side optical transmission line 15 for receiving and transmitting the light transmitted through the second wedge-shaped birefringent crystal plate 26, and either the first or the second wedge-shaped birefringent crystal plate, And a driving unit that reciprocates in a direction in which the optical path length of traveling light changes.

As shown in FIG. 2, the first wedge-shaped birefringent crystal plate 25 and the second wedge-shaped birefringent crystal plate 27 are arranged so that their optical axes are parallel to each other. As illustrated in FIG. 3, the first and second wedge-shaped birefringent crystal plates 25, 27
However, the configuration is such that the inclined surfaces are combined so as to face back.

As shown in FIG. 4, the incident side optical transmission line 11
Between the first wedge type birefringent crystal plate 25 and the first wedge type birefringent crystal plate whose optical axis is the optical axis of the incident side optical transmission line 11.
A flat plate type birefringent crystal plate 24 is arranged so as to be orthogonal to the optical axis of 25.

As illustrated in FIG. 5, the driving means for reciprocating either one of the first and second wedge-shaped birefringent crystal plates in the direction in which the optical path length changes is the incident side optical transmission path 11. A base 31 having a guide groove 34 orthogonal to the optical axis, and a guide groove
A slider 32 that is slidably mounted on the slider 34 and has a wedge-shaped birefringent crystal plate to be moved on top, and a slider 32.
The rod-shaped permanent magnet 33 fixed to the slider 32 by penetrating the shaft center of the
6-2 is composed of a pair of electromagnets 35-1 and 35-2 which are arranged so as to face the N extreme surface or the S extreme surface of the permanent magnet 33 with a predetermined gap therebetween so as to face each other. I shall.

The pair of electromagnets 35-1, 35-2 are alternately energized to alternately attract the slider 32. As illustrated in FIG. 6, the incident-side optical transmission line is the incident-side polarization-maintaining single-mode fiber 11-1, and the polarization axis of the incident-side polarization-maintaining single-mode fiber 11-1 is the same as that of the light emitted from the light source 10. The configuration is such that it matches the plane of polarization.

As shown in FIG. 7, between the flat plate type birefringent crystal plate 24 and the incident side optical transmission line 11, the optical axis can be rotated in a plane orthogonal to the optical axis of the incident side optical transmission line 11. As described above, the polarizer 22 is attached.

Further, the rotatable polarizer 22 is replaced by 1/2
The wave plate 23 is connected to the flat birefringent crystal plate 24 and the incident side optical transmission line 11
It will be installed between and. As illustrated in FIG.
Incident-side optical transmission line 11 that emits a parallel light flux, and a plurality of birefringent crystal thin plates 50-1, 50-2, ... 50-n having different lengths in the optical axis direction
Are laminated so as to have a step, and the optical axis of the composite birefringent crystal plate 50 is arranged so as to be orthogonal to the optical axis of the incident-side optical transmission path 11, and the output that transmits the output light of the composite birefringent crystal plate 50. The side light transmission path 15 and a driving means for reciprocating the complex birefringent crystal plate 50 in the direction in which the optical path length changes are provided.

As shown in FIG. 10, the above-mentioned various polarization state changers 100 inserted between the light source 10-1 and the polarization-dependent optical device 200 to be measured, and the output light level of the optical device 200. Monitor current and optical device 200
Computer 300 for inputting the optical output P of

The light emitted from the light source 10-1 is changed in polarization state changer 10
At 0, change to the full polarization state, put 200 into the optical device, read the output current I and the optical output P of the optical device with the computer 300, calculate the output current I / optical output P with the computer, and further calculate the DC component and the AC component. It is configured such that it is decomposed into components and each component value is digitally or analogically displayed on the display panel 310.

The polarization state changer 100 changes the light emitted from the light source 10-1 into all polarization states and inputs the light into the optical device 200. The computer 300 reads the output current I and the optical output P of the optical device 200, calculates the output current I / optical output P, further decomposes them into a DC component and an AC component, and digitally displays the respective component values on the display panel 310. Or, it is an analog display.

[0030]

According to the inventions of claims 1 to 3, a first wedge type birefringent crystal plate and a second wedge type birefringent crystal plate are provided.
Since the wedge-shaped birefringent crystal plate of either the first or the second reciprocates in the direction in which the optical path length of the traveling light changes,
The light incident on the wedge-shaped birefringent crystal plate advances into ordinary light and extraordinary light, and the phase difference thereof repeatedly changes between 0 and 2π.

Therefore, polarized light which repeats linearly polarized light-elliptically polarized light-circularly polarized light-elliptically polarized light-linearly polarized light is emitted from the second wedge-shaped birefringent crystal plate. Therefore, the entire polarization state can be reliably obtained in a short time. Further, in the invention of claim 2, both the inclined surfaces of the first wedge-shaped birefringent crystal plate and the second wedge-shaped birefringent crystal plate are close to each other. With this arrangement, the optical axis of the light emitted from the second wedge-shaped birefringent crystal plate coincides with the optical axis of the incident-side optical transmission line.

According to the invention of claim 3, the optical axis of the light emitted from the second wedge-shaped birefringent crystal plate is the incident side optical transmission line 11.
It becomes parallel to the optical axis of. In the invention of claim 4, by selecting the thickness of the flat plate type birefringent crystal plate, the phase difference between the light components traveling in the central portion and the outer portion of the traveling parallel light flux can be made zero. A polarization state variator with good characteristics can be obtained by applying it when the beam diameter of the outgoing light from the side optical transmission line is large.

According to the invention of claim 5, the structure of the driving means for reciprocating one of the first and second wedge-shaped birefringent crystal plates is simple. According to the invention of claim 6,
The incident side optical transmission line is a polarization-maintaining optical fiber, and the polarization axis of the incident-side polarization-maintaining optical fiber is made to coincide with the polarization plane of the polarized light emitted from the light source, so that the linearly polarized light becomes the first wedge-shaped birefringence It is incident on a crystal plate or a flat plate type birefringent crystal plate. Therefore, by adjusting the starting point of the reciprocating movement to a position where the optical path lengths of the first wedge-shaped birefringent crystal plate and the second wedge-shaped birefringent crystal plate are equal, the output light of the polarization state changer can be changed. The origin can be linearly polarized light.

According to the invention of claim 7, a polarizer is mounted between the flat plate type birefringent crystal plate and the incident side optical transmission line so as to be rotatable in a plane orthogonal to the optical axis of the incident side optical transmission line. Therefore, by adjusting the rotation of the polarizer, linearly polarized light can be incident on the first wedge-shaped birefringent crystal plate or flat plate-shaped birefringent crystal plate regardless of the incident polarization state. In the same manner as in the sixth aspect, it is possible to make the variable starting point of the emitted light of the polarization state variator be linearly polarized light without using a polarization-maintaining optical fiber.

According to an eighth aspect of the invention, a ½ wavelength plate is mounted instead of the rotatable polarizer. The use of the half-wave plate has substantially the same effect as the rotation adjustment of the polarizer of claim 7.

According to a ninth aspect of the present invention, a plurality of birefringent crystal thin plates having different lengths in the optical axis direction are laminated so as to have an optical axis orthogonal to the optical axis of the incident side optical transmission line so as to have a step. The crystal plate is reciprocated in the direction in which the optical path length of the traveling light changes.

Therefore, the phase difference between the extraordinary ray of the light incident on the compound birefringent crystal plate and the ordinary ray changes stepwise between 0 and 2π, so that the light emitted from the compound birefringent crystal plate has a polarization state. It changes in steps.

According to the tenth aspect of the present invention, the light emitted from the light source is changed to the total polarization state by the polarization state variable device, and is input to the polarization-dependent optical device, and the output current I and the optical output P are calculated by the computer. Reading, output current I / optical output P is calculated by a computer, further decomposed into a direct current component and an alternating current component, and the respective component values are displayed digitally or in analog form on a display panel, so an optical device having polarization dependence Can be quantitatively measured.

[0039]

The present invention will be described in detail with reference to the drawings. The same reference numerals indicate the same objects throughout the drawings.

FIG. 1 is a block diagram of the invention of claim 1, FIG. 2 is a block diagram of the invention of claim 2, FIG. 3 is a diagram of an embodiment of the invention of claim 3, and FIG. It is a block diagram of an invention. 5 is a perspective view of an embodiment of the invention of claim 5, and FIG.
FIG. 7 is a block diagram of an embodiment of the invention of claims 7 and 8, FIG. 8 is a block diagram of an embodiment of the invention of claim 9, and FIG. FIG. 3 is a block diagram of the invention.

In the figure, reference numeral 11 denotes an incident-side optical transmission line such as an optical fiber or an optical waveguide that receives the light emitted from the light source and emits a parallel light flux. The illustrated incident side optical transmission line 11 is an optical fiber having an optical fiber lens assembly mounted on the incident side and the emitting side.

Reference numeral 25 denotes a wedge in plan view, which is arranged such that its optical axis is orthogonal to the optical axis of the incident-side optical transmission path 11 and one surface orthogonal thereto is opposed to the exit surface of the incident-side optical transmission path 11. It is the 1st wedge-shaped birefringent crystal plate formed in a shape.

The direction of the optical axis of the first wedge-shaped birefringent crystal plate 25 shown in FIG. 1 is parallel to the paper surface. 26
Is a second wedge-shaped birefringent crystal plate having an inclined surface with an inclination angle equal to the inclination angle of the inclined surface of the first wedge-shaped birefringent crystal plate 25.

The second wedge-shaped birefringent crystal plate 26 has an inclined surface close to and parallel to the inclined surface of the first wedge-shaped birefringent crystal plate 25, and has an optical axis of the first wedge-shaped birefringent crystal plate. It is arranged so as to be orthogonal to the optical axis of the plate 25 and the optical axis of the incident side optical transmission line 11.

Therefore, the direction of the optical axis of the second wedge-shaped birefringent crystal plate 26 shown in FIG. 1 is the direction orthogonal to the paper surface. Reference numeral 15 is an outgoing side optical transmission line such as an optical fiber or an optical waveguide that receives and transmits outgoing light from the second wedge-shaped birefringent crystal plate 26.

The output side optical transmission line 15 shown in the figure is an optical fiber having an optical fiber lens assembly mounted on the incident side. Further, in the direction in which the optical path length of the traveling light changes, one of the first and second wedge-shaped birefringent crystal plates,
In the figure, a driving means (not shown) for reciprocating the second wedge-shaped birefringent crystal plate 26 is provided.

The driving means may be a combination of an electromagnet and a compression coil spring, an air cylinder, a step motor, or the like. However, a combination of a pair of electromagnets and permanent magnets, which will be described later, has a simple structure and reciprocates. It is preferable because of its high speed.

The direction in which the optical path length of the traveling light changes is the direction toward the inclined surface of the wedge-shaped birefringent crystal plate, that is, the arrow A direction shown by the solid line, and the optical axis of the incident side optical transmission path 11. There is an orthogonal direction, that is, an arrow B direction indicated by a dotted line.

The direction of the arrow B shown by the dotted line has the advantage that the arrangement of the drive means can be simplified, while the optical axis of the light emitted from the second wedge-shaped birefringent crystal plate 26 and the incident side optical transmission line 11 are provided. However, there is a drawback that the optical axis of the optical axis is misaligned.

In the direction of arrow A shown by the solid line, when both inclined surfaces are arranged close to each other, the optical axis of the light emitted from the second wedge-shaped birefringent crystal plate 26 and the optical axis of the incident-side optical transmission line 11 are defined. Has the advantage that they match.

When the parallel light flux emitted from the incident side optical transmission line 11 is incident on the first wedge-shaped birefringent crystal plate 25 of the polarization state variable device constructed as shown in FIG. 1, the light is an ordinary ray and an extraordinary ray. Then, the first wedge-type birefringent crystal plate 25 is advanced.

Then, the ordinary light enters the second wedge-shaped birefringent crystal plate 26 as extraordinary light and advances. Also, the extraordinary light enters the second wedge-shaped birefringent crystal plate 26 as ordinary light and advances. Here, n ₁ ... Refractive index of ordinary light, n ₂ ... Refractive index of extraordinary light, a ... Mechanical length of traveling light on the optical axis of the first wedge-shaped birefringent crystal plate b ₁ ... Mechanical length on optical axis of second wedge-shaped birefringent crystal plate of traveling light before movement, b ₂ ... Second wedge-shaped birefringence of traveling light after movement The mechanical length of the crystal plate on the optical axis is, and the optical path difference before moving the second wedge-shaped birefringent crystal plate 26 is (an ₁ + b ₁ n ₂ ) − (an ₂ + b ₁ n ₁ ) = A (n
_{1 -n 2) + b 1 (} n 2 -n 1) optical path difference after moving the second wedge type birefringent crystal plate _{26, (an 1 + b 2 n} 2) - (an 2 + b 2 n 1) = a (n
_{1 -n 2) + b 2 (} n 2 -n 1) it becomes.

That is, since the optical path length is changed by moving the second wedge-shaped birefringent crystal plate 26, when the second wedge-shaped birefringent crystal plate 26 is reciprocated by a distance larger than the diameter of the parallel light flux, The phase difference repeatedly changes between 0 and 2π.

Therefore, polarized light that repeats linearly polarized light-elliptically polarized light-circularly polarized light-elliptically polarized light-linearly polarized light is emitted from the second wedge-shaped birefringent crystal plate 26. In FIG. 2, reference numeral 27 indicates that the inclined surface is close to and parallel to the inclined surface of the first wedge-shaped birefringent crystal plate 25, and the optical axis is parallel to the optical axis of the first wedge-shaped birefringent crystal plate 25. A second wedge-shaped compound having an inclined surface having an inclination angle equal to the inclination angle of the inclined surface of the first wedge-shaped birefringent crystal plate 25, which is arranged so as to be orthogonal to the optical axis of the incident side optical transmission line 11. It is a refraction crystal plate.

Therefore, the direction of the optical axis of the second wedge-shaped birefringent crystal plate 27 shown in FIG. 2 is parallel to the paper surface. When the parallel light flux emitted from the incident side optical transmission line 11 enters the first wedge-shaped birefringent crystal plate 25 of the polarization state variable device configured as shown in FIG. 2, the light is divided into ordinary light and extraordinary light. Proceed through the first wedge-shaped birefringent crystal plate 25.

The ordinary light enters the second wedge-shaped birefringent crystal plate 27 as ordinary light and advances, and the extraordinary light enters the second wedge-shaped birefringent crystal plate 27 as extraordinary light and advances.
Here, n ₁ ... Refractive index of ordinary light, n ₂ ... Refractive index of extraordinary light, a ... Mechanical length of traveling light on the optical axis of the first wedge-shaped birefringent crystal plate b ₁ ... Mechanical length on optical axis of second wedge-shaped birefringent crystal plate of traveling light before movement, b ₂ ... Second wedge-shaped birefringence of traveling light after movement mechanical length on the optical axis of the crystal plate, and when the optical path difference before moving the second wedge type birefringent crystal plate 2 _{7, (an 1 + b 1 n} 1) - (an 2 + b 1 n ₂ ) = a (n
_{1 -n 2) + b 1 (} n 1 -n 2) optical path difference after moving the second wedge type birefringent crystal plate _{26, (an 1 + b 2 n} 1) - (an 2 + b 2 n 2) = a (n
₁ -n ₂₎ + b ₂ a (n ₁ -n _2).

That is, since the optical path length is changed by moving the second wedge-shaped birefringent crystal plate 27, when the second wedge-shaped birefringent crystal plate 27 is reciprocated by a distance larger than the diameter of the parallel light flux, The phase difference repeatedly changes between 0 and 2π.

By disposing the first wedge-shaped birefringent crystal plate 25 and the second wedge-shaped birefringent crystal plate 27 so that their inclined surfaces are close to each other, the second wedge-shaped birefringent crystal plate is formed. Board
The optical axis of the outgoing light of 27 coincides with the optical axis of the incident side optical transmission line 11. Therefore, the incident-side optical transmission line 11 and the outgoing-side optical transmission line 15 can be arranged on the same straight line, which has the effect of facilitating the arrangement accuracy and ease.

The polarization state variator shown in FIG. 3 comprises a first wedge-shaped birefringent crystal plate 25 and a second wedge-shaped birefringent crystal plate.
27 and 27 are arranged so that the inclined surface faces the back and one surface orthogonal to the high side approaches.

The arrangement described above has the advantage that the arrangement of the drive means device can be simplified. Further, since the optical axis of the light emitted from the second wedge-shaped birefringent crystal plate 27 is parallel to the optical axis of the incident side optical transmission line 11, the incident side optical transmission line 11 and the emission side optical transmission line 15 are the same. Even if they are arranged on a straight line, there is an effect that the light emitted from the second wedge-shaped birefringent crystal plate 27 is efficiently incident on and transmitted to the light transmission path 15 on the emission side.

In FIG. 3, the optical axes of the first wedge-shaped birefringent crystal plate 25 and the second wedge-shaped birefringent crystal plate 27 are parallel to each other. The crystal plate 25 and the second wedge-shaped birefringent crystal plate may be arranged so as to be orthogonal to each other.

The polarization state variator shown in FIG. 4 has the following structure between the incident side optical transmission line 11 and the first wedge-shaped birefringent crystal plate 25.
The flat plate type birefringent crystal plate 24 is arranged so that its optical axis is orthogonal to the optical axis of the incident side optical transmission line 11 and is orthogonal to the optical axis of the first wedge type birefringent crystal plate 25.

Select the thickness of the flat plate type birefringent crystal plate 24,
For example, at the starting point, the first wedge-shaped birefringent crystal plate 25
By making the plate thickness of the flat plate-type birefringent crystal plate 24 equal to the combined thickness of the wedge-shaped birefringent crystal plate 27, the phase difference between the light components traveling in the central portion and the outer portion of the parallel light flux that progresses It becomes zero.

Therefore, when the beam diameter of the outgoing light from the incident side optical transmission line is large, a polarization state variable device with good characteristics can be obtained. Further, by selecting the plate thickness of the flat plate type birefringent crystal plate 24 as described above, at the starting point of the reciprocating motion, the polarization state of the polarized light emitted from the incident side optical transmission line 11 and the incident side optical transmission line 15 are incident. The polarization state of the polarized light is the same.

In FIG. 5, reference numeral 30 is a flat base made of a non-magnetic material such as stainless steel.
Reference numeral 38 is a V-groove block mounted on one side edge of the base 30. Reference numeral 39 denotes another V-groove block mounted on the other side edge of the base 30 so as to face the V-groove block 38.
The V-groove blocks 38 and 39 are mounted on the base 30 such that the respective V-grooves have their axes aligned on the same straight line.

The ferrule portion of the optical fiber lens assembly 11A is placed in the V groove of the V groove block 38 so that the emitting end face is on the center side of the base 30 and the incident side optical transmission line is formed.
11 is fixed to the V groove block 38.

On the other hand, the ferrule portion of the optical fiber lens assembly 11B is placed in the V groove of the V groove block 39 so that the incident end face is on the center side of the base 30, and the output side optical transmission line 15 is connected to the V groove. It is fixed to the groove block 39.

Reference numeral 31 is a rectangular plate-shaped base made of a non-magnetic material such as stainless steel, and is mounted on the base 30 between a pair of opposed V groove blocks 38 and 39. The base 31 is provided with a rectangular guide groove 34 orthogonal to the optical axis of the incident side optical transmission line 11 at a position from the V groove block 39 on which the emission side optical transmission line is mounted.

The guide groove 34 is not orthogonal to the optical axis of the incident side optical transmission line 11, and is formed on the incident side by an angle equal to the inclination angle of the inclined surface of the second wedge-shaped birefringent crystal plate 27 described later. It is desirable that the optical transmission line 11 is inclined to the optical axis.

The reference numeral 32 designates a rectangular cylindrical shape made of a non-magnetic material such as a copper alloy, the height of which is slidably mounted in the guide groove 34 of the base 31 is equal to the depth of the guide groove 34. Is the slider.

Reference numeral 33 denotes a rod-shaped permanent magnet inserted and fixed in the shaft center hole of the guide groove 34, and N at both ends of the permanent magnet 33.
The extreme surface and the S extreme surface coincide with the end surface of the slider 32 or slightly project therefrom.

In the second wedge-shaped birefringent crystal plate 27, the optical axis is orthogonal to the optical axis of the incident side optical transmission line 11, and one surface (the surface parallel to the optical axis) orthogonal to the optical axis is the longitudinal direction of the slider 32. It is fixed to the upper surface of the slider 32 so that the inclined surface is parallel to the side surface in the direction and the inclined surface is on the incident side optical transmission line 11 side.

In the first wedge-shaped birefringent crystal plate 25, the inclined surface is close to and parallel to the inclined surface of the second wedge-shaped birefringent crystal plate 27, and the optical axis is the second wedge-shaped birefringent crystal plate. It is fixed to the upper surface of the base 31 so as to be parallel to the optical axis of the plate 27.

The flat plate type birefringent crystal plate 24 is so constructed that its optical axis is orthogonal to the optical axis of the incident side optical transmission line 11 and is orthogonal to the optical axis of the first wedge type birefringent crystal plate 25. 31 is stuck on.

35-1 is a rod-shaped yoke 36 at the axial center of the coil.
-1 is an electromagnet, and one end of the yoke 36-1 thereof is projected from the coil. Further, 35-2 is an electromagnet having a rod-shaped yoke 36-2 at the axial center of the coil and having a bilaterally symmetrical structure with respect to the aforementioned electromagnet 35-1.

One electromagnet 35-1 is mounted on the base 30 so that the end surface of the yoke 36-1 faces the N extreme surface of the permanent magnet 33. The other electromagnet 35-2 is a slider so that the end surface of the yoke 36-2 faces the S extreme surface of the permanent magnet 33.
It is mounted on the base 30 so as to face the electromagnet 35-1 with 32 interposed therebetween.

When the electromagnet 35-1 is energized, the yoke 36
The end portion of -1 becomes the S pole, the permanent magnet 33, that is, the slider 32 is attracted to the electromagnet 35-1 side, and the N extreme surface of the permanent magnet 33 stops in a state of contacting the end surface of the yoke 36-1.

When the other electromagnet 35-2 is energized, the end of the yoke 36-2 becomes the N pole and the permanent magnet 33, that is, the slider.
32 is attracted to the electromagnet 35-2 side, and stops with the S extreme surface of the permanent magnet 33 in contact with the end surface of the yoke 36-2.

Therefore, by alternately energizing the pair of electromagnets 35-1 and 35-2, the slider 32, that is, the second wedge-shaped birefringent crystal plate 27 reciprocates. The first wedge-shaped birefringent crystal plate 25 and the second wedge-shaped birefringent crystal plate 25 with the permanent magnet 33 in contact with the yoke 36-1 of the one electromagnet 35-1.
The combined plate thickness of 27 and 27 is set to be equal to the plate thickness of the flat plate type birefringent crystal plate 24.

Further, with the permanent magnet 33 in contact with the yoke 36-2 of the other electromagnet 35-2, the first wedge-shaped birefringent crystal plate 25 and the second wedge-shaped birefringent crystal plate 27 are attached. The combined plate thickness is set so that the phase at the used wavelength is an even multiple of π or more than the plate thickness of the flat plate type birefringent crystal plate 24.

As described above, by setting the plate thickness of the flat plate type birefringent crystal plate 24 and the movement amount of the second wedge type birefringent crystal plate 27, at the starting point of the reciprocating movement, the incident side optical transmission line 11 is formed.
The polarization state of the polarized light emitted by the light source and the polarization state of the polarized light incident on the output side optical transmission line 15 match, and the phase difference continuously changes while the second wedge-shaped birefringent crystal plate 27 is moving. Therefore, all polarization states can be continuously obtained.

In FIG. 6, reference numeral 10 denotes an edge emitting high output LE.
It is a light source that emits polarized light such as D or a semiconductor laser.
11-1 is an optical fiber lens assembly 11B on the incident side
Is an incident side polarization-maintaining optical fiber in which the optical fiber lens assembly 11A is mounted on the output side.

Reference numeral 15-1 is an exit side single mode optical fiber in which the optical fiber lens assembly 15A is mounted on the entrance side. Light source 10, 10-1, Input side polarization-maintaining optical fiber 11
-1, the first wedge-shaped birefringent crystal plate 25, the second wedge-shaped birefringent crystal plate 27, the exit side single mode optical fiber 15-1 are arranged in this order, and the incident side polarization plane preserving optical fiber 11- The 1 polarization axis (the direction connecting the pair of stress applying portions) is aligned with the polarization plane of the light emitted from the light source 10.

Therefore, the linearly polarized light emitted from the light source 10 enters the first wedge-shaped birefringent crystal plate 25. Therefore, the first wedge-shaped birefringent crystal plate 25 or the second wedge-shaped birefringent crystal plate 25 is located at a position where the optical path lengths of the first wedge-shaped birefringent crystal plate 25 and the second wedge-shaped birefringent crystal plate 27 are equal. By setting the optical path lengths of the first wedge-shaped birefringent crystal plate 25 and the second wedge-shaped birefringent crystal plate 27 to be equal at the position of the starting point for reciprocating one of the plates 27, It is possible to make the variable starting point of the emitted light of the state changer (the polarized light incident on the emitting side single mode optical fiber 15-1) to be the linearly polarized light.

In FIG. 7, the incident side optical transmission line 11, the polarizer 22 whose optical axis is rotatable in the plane orthogonal to the optical axis of the incident side optical transmission line 11, the flat plate type birefringent crystal plate 24, the first A wedge-shaped birefringent crystal plate 25, a second wedge-shaped birefringent crystal plate 27, and an outgoing side optical transmission line 15 are arranged in this order.

More specifically, the polarizer 22 has a disc shape with its optical axis oriented in the diametrical direction. Reference numeral 40 denotes a guide body which is installed between the incident side optical transmission line 11 and the flat plate type birefringent crystal plate 24 by fixing the bottom surface to the base in close contact.

Circular stepped hole that penetrates the axis of the guide body 40
41 is provided, the polarizer 22 is inserted into the stepped hole 41 on the great circle side, and the ring-shaped pressing plate 42 is attached to the opening surface on the great circle side, so that the polarizer 22 can be freely rotated in the stepped hole 41. I am trying.

Then, the set screw 45 is screwed into a desired position on the outer peripheral portion of the stepped hole 41 so that the polarizer 22 is fixed at a desired rotated position. Therefore, the polarizer
By adjusting the rotation of 22, the linearly polarized light can be incident on the flat plate type birefringent crystal plate 24 regardless of the polarization state of the light emitted from the incident side optical transmission line 11.

That is, the variable starting point of the outgoing light of the polarization state variable device can be linearly polarized light without using the polarization-maintaining optical fiber on the incident side. Further, FIG. 7 shows a polarization state changer in which a half-wave plate 23 is inserted and installed between the incident side optical transmission line 11 and the flat plate type birefringent crystal plate 24 in place of the above-mentioned polarizer 22. It is shown. The half-wave plate 23 does not need to rotate.

The half-wave plate 23 has substantially the same effect as the above-described rotation adjustment of the polarizer 22. In FIG.
50 is a plurality of birefringent crystal thin plates having different lengths in the optical axis direction.
It is a composite birefringent crystal plate in which the optical axis directions are aligned and the layers are fixed in layers so that 50-1, 50-2 ...

The incident side optical transmission line 11 for emitting a parallel light flux, the optical axis direction composite optical birefringent crystal plate 50 whose optical axis is orthogonal to the optical axis of the incident side optical transmission line 11, and the output light of the composite birefringent crystal plate 50 The outgoing side optical transmission line 15 for transmission is arranged in this order, a driving means is provided, and the composite birefringent crystal plate 50 is reciprocated in the direction in which the optical path length of the traveling light changes.

The polarization state variator thus constructed is
By moving the composite birefringent crystal plate 50 back and forth, the phase difference between the ordinary light and the extraordinary light of the light incident on the composite birefringent crystal plate 50 changes stepwise between 0 and 2π. Therefore, the output side optical transmission line
The light incident on 15 changes its polarization state stepwise.

In FIG. 9, the light source 10-1 is an edge emitting high output LED. Reference numeral 90 denotes a bandpass filter that extracts a desired wavelength band from the wavelength band of the light emitted from the light source 10-1.

Reference numeral 100 denotes the polarization state variator of the above (claims 1 to 9), which is a half-wave plate 23, a flat plate type birefringent crystal plate 24, a first wedge type birefringent crystal plate 25, A polarization state changer equipped with two wedge-shaped birefringent crystal plates 27 is desirable.

The light source 10-1, the bandpass filter 90, and the polarization state changer 100 are arranged in this order, and the bandpass filter 90
The polarization state changer 100 is connected to a polarization plane maintaining optical fiber whose polarization axis matches the polarization plane of the light emitted from the light source 10-1.

Reference numeral 200 denotes a polarization-dependent optical device such as an optical amplifier. The optical device 200 includes an input optical fiber, an output optical fiber, and a monitor light receiving element 120 for monitoring the output light level.

The polarization state changer 100 and the optical device 200 are connected by a single mode optical fiber. 300
Is connected to the monitor light receiving element 120 and is connected to the output current I of the optical device 200 and the output optical fiber.
It is a computer for inputting an optical output P of 0. With the configuration described above, the polarization state changer 100
The optical device 200 converts the light emitted by 10-1 into all polarization states.
, The output current I and the optical output P of the optical device 200 are read by the computer 300, and the output current I / optical output P is
It is calculated by the computer 300 and further decomposed into a direct current component and an alternating current component, and the respective component values are digitally or analogically displayed on the display panel 310.

Therefore, the polarization-dependent optical device 200
The polarization dependent characteristic of can be quantitatively measured in a short time.

[0099]

The present invention has the following effects because it is configured as described above. According to the inventions of claims 1 to 3, it is possible to easily obtain all the polarization states in which linearly polarized light-elliptically polarized light-circularly polarized light-elliptically polarized light-linearly polarized light are repeated in a short time.

Further, the invention of claim 2 has an effect that the incident optical axis to the polarization state variable device and the emission optical axis of the polarization state variable device coincide with each other. Further, the invention of claim 3 has an effect that the incident optical axis to the polarization state variable device and the emission optical axis of the polarization state variable device are parallel to each other.

According to the invention of claim 4, when the beam diameter of the outgoing light of the incident side optical transmission line is large, a polarization state variable device having good characteristics can be obtained. According to the invention of claim 5,
The structure of the driving means for reciprocating one of the first and second wedge-shaped birefringent crystal plates is simple.

According to the sixth aspect of the present invention, by using the polarization-maintaining optical fiber on the incident side, it is possible to make the variable starting point of the output light of the polarization state changer linearly polarized. According to the invention of claim 7, by rotating and adjusting the polarizer, it is possible to make the variable starting point of the emitted light of the polarization state changer to be linearly polarized light without using the incident-side polarization-maintaining optical fiber.

Furthermore, since the principal axis of the incident polarized light and the optical axis (crystal axis) direction can be arbitrarily changed, a perfect total polarization state can be easily obtained. According to the invention of claim 8, since it has substantially the same effect as rotating and adjusting the polarizer of claim 7, even though it has a simple structure, the starting point of the variable emitted light of the polarization state variator is changed. It can be linearly polarized light.

Further, since the principal axis of incident polarized light and the optical axis (crystal axis) direction can be arbitrarily changed, a perfect total polarization state can be easily obtained. According to the invention of claim 9, it is possible to provide an inexpensive polarization state changer having a small number of constituent elements.

According to the tenth aspect of the present invention, the polarized light emitted from the light source is changed into all states by the polarization state variable device, and the polarized light is supplied to the polarization-dependent optical device, and the input current I and the optical output P are read by a computer. The input current I / optical output P is calculated by a computer and decomposed into a direct current component and an alternating current component, and the respective component values are digitally displayed on the display panel. Therefore, the characteristics of the polarization-dependent optical device can be quantitatively determined. Can be measured.

[Brief description of drawings]

FIG. 1 is a block diagram of the invention of claim 1;

FIG. 2 is a configuration diagram of the invention of claim 2;

FIG. 3 is a diagram of an embodiment of the invention of claim 3;

FIG. 4 is a configuration diagram of the invention of claim 4;

FIG. 5 is a perspective view of an embodiment of the invention of claim 5;

FIG. 6 is a configuration diagram of an embodiment of the invention of claim 6;

FIG. 7 is a configuration diagram of an embodiment of the invention of claims 7 and 8.

FIG. 8 is a configuration diagram of an embodiment of the invention of claim 9;

FIG. 9 is a block diagram of the invention of claim 10;

FIG. 10 is a configuration diagram of an optical amplifier.

[Explanation of symbols]

 1 Rare earth element-doped optical fiber 2 Output optical fiber 3 Excitation light source 1-1 Incident side fiber / lens assembly 2-1 Emission side fiber / lens assembly 3-1 Excitation side fiber / lens assembly 4-1 Housing 5 Wavelength division optical film 6 Optical isolator 10,10-1 Light source 11 Optical transmission line on the incident side 11-1 Polarization-maintaining optical fiber on the incident side 15 Optical transmission line on the emitting side 15-1 Single mode optical fiber on the emitting side 22 Polarizer 23 1/2 wave plate 24 Flat plate type birefringent crystal plate 25 First wedge type birefringent crystal plate 26,27 Second wedge type birefringent crystal plate 32 Slider 33 Permanent magnet 35-1,35-2 Electromagnet 36-1,36-2 Yoke 40 Guide body 41 Stepped hole 45 Set screw 50 Composite birefringent crystal plate 50-1,50-2,50-n Thin birefringent crystal plate 90 Bandpass filter 100 Polarization state changer 120 Monitor light receiving element 200 Optical device 300 Computer 310 Display board

Claims (10)

[Claims] 1. An incident-side optical transmission line that emits a parallel light beam, and one surface whose optical axis is orthogonal to the optical axis of the incident-side optical transmission line and is orthogonal to each other, is the emission side of the incident-side optical transmission line. A wedge-shaped birefringent crystal plate disposed so as to face the surface, and a wedge shape having an inclined surface with an inclination angle equal to the inclination angle of the first wedge-shaped birefringent crystal plate, wherein the inclined surface is The first wedge-shaped birefringent crystal plate is close to and parallel to the inclined surface of the first wedge-shaped birefringent crystal plate, and the optical axis is orthogonal to the optical axis of the first wedge-shaped birefringent crystal plate and the optical axis of the incident-side optical transmission line. A second wedge-shaped birefringent crystal plate arranged in such a manner, an emission side optical transmission line for receiving and transmitting light transmitted through the second wedge-shaped birefringent crystal plate, and either the first or the second optical transmission line. One wedge type birefringent crystal plate,
A polarization state changer comprising: a drive unit that reciprocates in a direction in which the optical path length changes. 2. The polarization state changer, wherein the first wedge-shaped birefringent crystal plate and the second wedge-shaped birefringent crystal plate are arranged so that their optical axes are parallel to each other. 3. A polarization state variator, characterized in that the first and second wedge-shaped birefringent crystal plates according to claim 1 or 2 are arranged such that their inclined surfaces face back. 4. The optical axis between the incident side optical transmission line according to claim 1, 2 and 3 and the first wedge-type birefringent crystal plate is the optical axis of the incident side optical transmission line and the first optical axis. A polarization state variator characterized in that a flat plate type birefringent crystal plate is arranged so as to be orthogonal to the optical axis of the wedge type birefringent crystal plate. 5. A drive means for reciprocating one of the first and second wedge-shaped birefringent crystal plates in the direction in which the optical path length changes is a guide orthogonal to the optical axis of the incident side optical transmission path. A base having a groove, a slider, which is slidably mounted in the guide groove, and on which a wedge-shaped birefringent crystal plate to be moved is mounted, and a slider which penetrates the axis of the slider, The rod-shaped permanent magnet fixed to the slider and the respective yokes of the electromagnet are arranged so as to face each other across the slider so as to face the N extreme surface or the S extreme surface of the permanent magnet with a predetermined gap. And a pair of electromagnets, wherein the pair of electromagnets are alternately energized to alternately attract the slider. 6. The incident-side optical transmission line according to claim 1, 2, 3, or 4, is a polarization-maintaining optical fiber, and the polarization axis of the incident-side polarization-maintaining optical fiber is A polarization state changer characterized by matching the polarization plane. 7. The optical axis between the flat birefringent crystal plate according to claim 4 and the incident side optical transmission line is rotatable in a plane orthogonal to the optical axis of the incident side optical transmission line. , A polarization state changer having a polarizer attached. 8. A polarization state variator comprising a half-wave plate mounted in place of the rotatable polarizer according to claim 7. 9. An incident-side optical transmission line that emits a parallel light flux and a plurality of birefringent crystal thin plates having different lengths in the optical axis direction are layered so as to have a step, and the optical axis has the incident-side optical transmission line. Compound birefringent crystal plate arranged so as to be orthogonal to the optical axis of, an output side optical transmission line that receives and transmits the light emitted from the composite birefringent crystal plate, and the compound birefringence in the direction in which the optical path length changes. A polarization state changer, comprising: a drive means for reciprocating a crystal plate. 10. A polarization state changer according to claim 1, which is inserted between a light source and a polarization-dependent optical device to be measured, and a monitor current for monitoring the output light level of the optical device.
And a computing computer for inputting the optical output P of the optical device, wherein the polarization state changer converts the light emitted from the light source into all polarization states and inputs the light into the optical device. Reads the output current I and the optical output P of the optical device, calculates the output current I / optical output P, further decomposes into a DC component and an AC component, and displays each component value in a digital or analog manner on the display panel. A polarization dependence measuring device characterized in that