JP2003302604A - Magnetooptic optical switch - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make a device more small-sized on the whole by making the device not only small in diameter, but also short. <P>SOLUTION: A birefringent element 10 for polarized light demultiplexing, a birefringent element 12 for optical path shifting, and a birefringent element 14 for polarized wave multiplexing are arranged and polarized wave rotation control means 16 and 18 are interposed among the birefringent elements; and a 1-input port part composed of a single-core ferrule 29 and a lens 30 is installed at one end part of them and a 2-output port part composed of a two-core ferrule 34 and a common lens 36 is installed at the opposite-side end part. The polarized wave rotation control means comprise combinations of variable Faraday rotators 20 and 24 and 1/2-wavelength plates 21 and 22, and 25 and 26 and rotate one polarization direction by 90° by controlling applied magnetic fields. An optical path changing prism 38 which changes the angles of one or both light beams is interposed between the optical path shifting birefringent element and polarized wave multiplexing birefringent element and output ports are selected according to a differences in light beam direction. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical switch for controlling light on / off and switching an optical path in the fields of optical communication and optical measurement, and more specifically, an optical switch. The present invention relates to a magneto-optical switch that is miniaturized by inserting an optical path correction prism into a functional unit and using an angle shift of a light beam to select an output port.

[0002]

2. Description of the Related Art An optical switch is an optical device having an optical path switching function of outputting input light from an input port to any one selected from different output ports. The 1 × 2 type (1 input / 2 outputs) is the most basic form, but other 2 × 2 types (2 inputs / 2 outputs) and the like have also been developed.

An optical switch for optical communication is required to be polarization-independent, and it is possible to satisfy such requirements by, for example, a plurality of birefringent elements, a wave plate, and a Faraday rotator. There is a configuration in which optical components are arranged to form an optical switch function section, and an input port section is arranged at one end of the optical switch function section and an output port section is arranged at the other end (for example, Japanese Patent Laid-Open No. 5-61001). See the bulletin). The optical switch function part mechanically moves the permanent magnet,
Alternatively, the optical path is switched by controlling the applied external magnetic field and changing the polarization direction by an electromagnetic method.

However, in the prior art, when a plurality of ports are installed at the end of the optical switch function section, each port is constructed by combining one lens corresponding to a single-core ferrule having one fiber. It was done. That is, collimate coupling is achieved by combining individual lenses for each fiber. Therefore, the distance between the fibers needs to be a distance commensurate with the lens diameter, and inevitably each optical component of the optical switch function unit must be large, which is an obstacle to downsizing and cost reduction of the optical switch. It was

Therefore, two fibers that are housed side by side
A combination of a core ferrule, a lens common to these two fibers, and an optical path correction prism that makes the obliquely emitted light from the lens a parallel beam and makes the parallel beam obliquely incident on the lens. A technique for forming an input / output port of a switch has been proposed (Japanese Patent Laid-Open No. 11-26).
4954).

[0006]

This technique is extremely effective in reducing the diameter of the device. However, the input / output port section located at the end of the optical switch function section requires a longer space length by incorporating an optical path correction prism, and therefore the size of the entire device in the direction along the optical axis is reduced (that is, a shorter length). Is insufficient.

It is an object of the present invention to provide a magneto-optical switch which allows not only a reduction in the diameter of the device but also a reduction in the size thereof, thereby achieving a further reduction in size as a whole.

[0008]

According to the present invention, a birefringent element for polarization splitting, a birefringent element for optical path shift depending on a polarization direction, and a birefringent element for polarization combination are arranged in this order. And a single-core ferrule having one fiber at the end of the array on the side of the birefringent element for polarization separation, and the polarization rotation control means inserted between the birefringent elements. Three-port type optical system with one input port consisting of two lenses, a two-core ferrule in which two fibers are juxtaposed at the end on the opposite side of the polarization-combining birefringent element, and two output ports consisting of a common lens. In the switch, the polarization rotation control means comprises a combination of a variable Faraday rotator and a linear phaser, and by controlling the applied magnetic field of the variable Faraday rotator, the polarization direction of either one of the separated light beams is controlled. To rotate the 90 degrees Then, insert an optical path changing prism that angularly shifts one or both light beams between the optical path shifting birefringent element and the polarization combining birefringent element, and select the output port according to the difference in the light beam direction. The magneto-optical switch is characterized in that

Here, the polarization rotation control means is, for example, ± 45.
The variable Faraday rotator has a degree-switching type and a pair of half-wave plates symmetrically arranged with their optical axes inclined by 22.5 degrees in both optical paths of the separated light beams.

The present invention also includes a birefringent element for polarization splitting,
The birefringence element for optical path shift according to the polarization direction and the birefringence element for polarization combination are arranged in a row in that order with a space therebetween, and the polarization rotation control means is inserted between each birefringence element. , A single-core ferrule having one fiber at the end of the array on the side of the birefringent element for polarization separation and one lens
In the three-port type optical switch in which the input port section is provided with a two-core ferrule in which two fibers are juxtaposed at the end on the opposite side of the polarization-combining birefringent element and a two-output port section with a common lens, One of the wave rotation control means is composed of a combination of a variable Faraday rotator and a linear retarder, and by controlling the applied magnetic field of the variable Faraday rotator, the polarization direction of either one of the separated light beams is 90 degrees. The polarization rotation control means has a function of rotating, the other of the polarization rotation control means is a linear phase shifter, and has a function of rotating the polarization direction of one of the separated light beams by 90 degrees. And a birefringent element for polarization combination, an optical path changing prism that angularly shifts one or both light beams is inserted, and the output port is selected according to the difference in the light beam direction. A magneto-optical optical switch according to symptoms.

For example, one polarization rotation control means is ± 4
It consists of a 5 degree switchable Faraday rotator and a pair of half-wave plates symmetrically arranged with their optical axes inclined by 22.5 degrees in both optical paths of the separated light beams, and the other polarization rotation. The control means is composed of two half-wave plates with the optical axes inserted in the optical paths in a diagonal relationship and tilted in the same direction by 45 degrees.

The present invention further comprises a polarization splitting birefringent element,
The first and second birefringent elements for optical path shift depending on the polarization direction and the birefringent element for polarization combining are arranged in a line in this order with a space therebetween, and the birefringent element for polarization separation and Polarization rotation control means is inserted between the first optical path shifting birefringent element and between the second optical path shifting birefringent element and the polarization combining birefringent element, respectively, for the first and second optical path shifting. A linear phase shifter that rotates the polarization direction of the light beam in a part of the optical path by 90 degrees is inserted between the birefringent elements, and two linear phase shifters are provided at one end of the array.
4-port optical switch with a 2-core ferrule with two fibers arranged side by side and a common lens with two input ports, and a two-core ferrule with two fibers arranged side by side and a two-output port with a common lens The polarization rotation control means is composed of a combination of a variable Faraday rotator and a linear phaser, and by controlling the applied magnetic field of the variable Faraday rotator, polarization of either one of the separated light beams Between the polarization splitting birefringent element and the first optical path shifting birefringent element and between the second optical path shifting birefringent element and the polarization combining birefringent element, which has a function of rotating the direction by 90 degrees. In addition, an optical path changing prism that angularly shifts one or both light beams is inserted, and the output port is selected according to the difference in the light beam direction. It is a switch.

Here, the polarization rotation control means comprises a variable Faraday rotator of ± 45 degree switching type and a pair of symmetrically arranged optical axes which are inclined by 22.5 degrees in both optical paths of the separated light beams. It is composed of a half-wave plate and a half-wave plate having an optical axis of 45 degrees inserted in a part of the optical path.

The optical path changing prism is a right-angled triangular or wedge-shaped columnar body inserted in one optical path, or a parallelepiped inserted in both optical paths, in which two adjacent parallel ridges are obliquely cut or trapezoidal. Columnar body. In the case of the 3-port type, these optical path changing prisms are preferably inserted between the polarization rotation control means and the polarization-combining birefringent element, and in the case of the 4-port type, the polarization splitting birefringence is preferred. It is preferable to insert them between the element and the first polarization rotation control means and between the second polarization rotation control means and the polarization combining birefringent element.

As the birefringent element, for example, rutile single crystal, lithium niobate, yttrium vanadate or the like is used. Quartz is preferably used for the half-wave plate. A variable Faraday rotator is a magnetic garnet single crystal (for example, B
An Faraday element composed of an i-substituted rare earth iron garnet film) is applied with an external magnetic field by an electromagnet or an electromagnet and a permanent magnet to control the drive current and thereby control the direction of the external magnetic field to control the Faraday rotation angle. The structure is such that switching can be done without the need. When two sets of polarization rotation control means of the same kind are incorporated, it is preferable that the constituent optical components are arranged symmetrically in the z direction.

In the present invention, the direction of the external magnetic field is switched by the variable Faraday rotator and the Faraday rotation angle by the Faraday element is switched to +45 degrees or -45 degrees to control the polarized light, thereby switching the optical path and changing the angle by the optical path changing prism. Output port is selected using shift.
Instead of shifting the position of the optical path to select the output port as in the prior art, the angle of the optical path is shifted to select the output port, which is a feature of the present invention.

[0017]

1 is a block diagram showing an embodiment of a magneto-optical switch according to the present invention, showing an optical path of a 1 × 2 type (1 input / 2 output) example. Further, FIG. 2 shows the arrangement of the optical components and the polarization state. The arrows in each optical component indicate the direction of the optical axis and the Faraday rotation direction. In order to make the description easy to understand, the following coordinate axes are set in the following embodiments. The arranging direction of the optical components is the z direction (right-hand direction in the drawing), and the two directions orthogonal thereto are the x direction (horizontal direction) and the y direction (vertical direction). In addition, as for the rotation direction, the clockwise direction when viewed in the z direction is the + side.

The polarization splitting birefringent element 10, the optical path shifting birefringent element 12 depending on the polarization direction, and the polarization combining birefringent element 14 are arranged in a line in this order at intervals.
First and second polarization rotation control means 1 are provided between each birefringent element.
Insert 6,18. The first polarization rotation control means 16 is
A variable Faraday rotator 20 of ± 45 degree switching type, and a pair of ½ wavelength plates 21 and 22 whose optical axes in both optical paths are arranged symmetrically with respect to the x axis by ± 22.5 degrees and the y axis. By controlling the applied magnetic field of the Faraday rotator 20,
It has the function of rotating the polarization direction of either one of the light beams split left and right by 90 degrees. Similarly, the second polarization rotation control means 18 has a variable Faraday rotator 24 of ± 45 degree switching type, and the optical axis of both side optical paths is ± 22.5 from the x axis.
A pair of half-wave plates 25 symmetrically arranged about the y-axis,
The variable Faraday rotator 24 has a function of rotating the polarization direction of one of the left and right light beams by 90 degrees by controlling the magnetic field applied to the variable Faraday rotator 24.

A single input fiber 28 is provided at the end of the optical switch function section arranged in this way on the side of the birefringent element for polarization separation.
A single-core ferrule 29 having 1 and a single lens 30 and a 2-core ferrule 34 in which two output fibers 32 and 33 are juxtaposed at the opposite side of the polarization-combining birefringent element side. A common lens 36 is provided with two output ports to form a three-port configuration.

An optical path changing prism 38 having a wedge-shaped columnar body is inserted in the lower optical path between the variable Faraday rotator 24 of the second polarization rotation control means 18 and the polarization combining birefringent element 14. , Angle shift the light beam. Accordingly, the one output fiber 33 is located at the center of the ferrule 34, and the other output fiber 32 is located eccentrically upward. The input fiber 28 is located at the center of the ferrule 29.

Here, each birefringent element is made of rutile single crystal. The optical axes of the polarization splitting birefringent element 10 and the polarization combining birefringent element 14 are tilted in the same direction with respect to the z axis in the xz plane, and the optical axis of the optical path shifting birefringent element 12 is yz.
It is tilted in the plane with respect to the z axis. 1/2 wave plate 21,2
Crystals are used for 2, 25 and 26. The variable Faraday rotators 20 and 24 apply an external magnetic field by an electromagnet or an electromagnet and a permanent magnet to a Faraday element composed of a magnetic garnet single crystal (for example, Bi-substituted rare earth iron garnet), and switch the direction of the drive current to change the direction of the external magnetic field. The Faraday rotation angle can be switched by controlling the.

Next, the operation of this magneto-optical switch will be described. 2A shows a case where both variable Faraday rotators 20 and 24 rotate the Faraday rotation angle together by −45 degrees to couple the input to the output 1 of the upper stage, and FIG.
Shows the case where the variable Faraday rotators 20 and 24 both rotate the Faraday rotation angle by +45 degrees and the input is coupled to the output 2 in the middle stage.

(Input → Output 1) Both the Faraday rotation angles of both variable Faraday rotators 20, 24 are set to −45 degrees. The light in the middle optical path introduced from the input fiber 28 becomes collimated light at the lens 30 and is input to the optical switch function section. The input light is polarized by the birefringence element 10 for polarization separation, the ordinary light goes straight, and the extraordinary light is separated in the x direction, and the variable Faraday rotator 20 of the first polarization rotation control means 16 changes the polarization direction to -4.
It rotates 5 degrees, and the pair of ½ wavelength plates 21 and 22 rotate the polarization direction by 45 degrees to be polarized waves parallel to the y-axis. 1 /
This is because the two-wave plate has a function of converting the polarization direction of the input light symmetrically with respect to its optical axis. That is, in the first polarization rotation control means 16, the polarization direction of the light on the right side optical path is changed to 9
Rotate 0 degrees. The polarized light parallel to the y-axis becomes extraordinary light for the optical path shifting birefringent element 12, so it is refracted in the -y direction and shifted to the lower optical path. The polarization direction is 45 with the pair of half-wave plates 25 and 26 of the second polarization rotation control means 18.
And the polarization direction is -4 with the variable Faraday rotator 24.
Rotate 5 degrees. That is, the second polarization rotation control means 18 rotates the polarization direction of the light on the left optical path by 90 degrees. Since these light beams pass through the lower optical path, an angle shift occurs in the optical path changing prism 38 and the direction is changed obliquely upward. Both lights enter the polarization-combining birefringent element 14, the ordinary light goes straight, and the extraordinary light x
The light is refracted in the direction, is synthesized, is condensed by the lens 36, and is coupled to the upper output fiber 32 (output 1).

(Input → Output 2) Both the Faraday rotation angles of both variable Faraday rotators 20, 24 are set to +45 degrees. The light introduced from the input fiber 28 is reflected by the lens 3
When it is 0, it becomes collimated light, which is input to the optical switch function section. The input light is polarized by the birefringence element 10 for polarization separation, the ordinary light travels straight, and the extraordinary light is separated in the x direction.
The variable Faraday rotator 20 rotates the polarization direction by +45 degrees, and the pair of half-wave plates 21 and 22 rotate the polarization direction by 45 degrees, and the polarized waves are parallel to the x-axis. That is, the first polarization rotation control means 16 changes the polarization direction of the light on the left optical path to 9
Rotate 0 degrees. The polarized light parallel to the x-axis becomes ordinary light for the optical path shifting birefringent element 12, and therefore goes straight on. The polarization direction is rotated by 45 degrees by the pair of half-wave plates 25 and 26 of the second polarization rotation control means 18, and the polarization direction is rotated by +45 degrees by the variable Faraday rotator 24. That is, the second polarization rotation control means 18 rotates the polarization direction of the light on the right optical path by 90 degrees. Since the light beam passes through the middle optical path,
The optical path changing prism 38 is bypassed. Both lights enter the polarization-combining birefringent element 14, the ordinary light travels straight, and the extraordinary light is refracted in the x direction to be combined, collected by the lens 36, and coupled to the output fiber 33 (output 2) in the middle stage.

In this way, by controlling the magnetic fields of the variable Faraday rotators 20, 24 of the first and second polarization rotation control means 16, 18 and switching them together to either -45 degrees or +45 degrees, Light from the input fiber 28 can be output to either the output fiber 32 (output 1) or the output fiber 33 (output 2).

FIG. 3 is a block diagram showing another embodiment of the 3-port magneto-optical switch. Since the basic configuration is the same as that in FIG. 1, corresponding members are designated by the same reference numerals, and description thereof will be omitted.

In this embodiment, the optical path changing prism 40 is
The shape is such that two parallel and adjacent ridge lines of a rectangular parallelepiped inserted in both the middle and lower optical paths are cut off obliquely.
The structure does not necessarily have to be an integral structure, and may be a structure in which wedge-shaped columnar bodies used in FIG. 1 are vertically symmetrically attached. When such an optical path changing prism is used, 2
The two output fibers 32, 33 are preferably arranged in the two-core ferrule 34 so as to be symmetrical with respect to the central axis. Therefore, in the case of input → output 1, the light beam is angle-shifted obliquely upward at the lower part of the optical path changing prism 40 and coupled with the output fiber 32 in the upper stage, and in the case of input → output 2, the light beam is changed. At the upper part of 40, the angle is shifted obliquely downward, and it is coupled with the lower output fiber 33.

FIG. 4 is a block diagram showing another embodiment of the 3-port type magneto-optical switch. Since the basic structure is the same as that of FIG. 3, the corresponding members are designated by the same reference numerals, and the description thereof will be omitted.

In this embodiment, the second polarization rotation control means, as shown in A, has two halves of the two optical axes inserted in the diagonal optical path and having the optical axis of 45 degrees in the same direction. Wave plate 4
It consists of 2,43. Therefore, in the case of input → output 1, the light beam passes through the lower optical path, so that the optical path on the left side is 1/2
The polarization direction is rotated by 90 degrees by the wave plate 42, and the polarization direction is not rotated because the 1/2 wavelength plate 42 is bypassed in the right optical path. Further, in the case of input → output 2, the light beam passes through the upper optical path, and therefore the half-wave plate 43 is provided in the right optical path.
Causes the polarization direction to rotate 90 degrees, and the left optical path is 1/2
The polarization direction does not rotate because it bypasses the wave plate 43. That is, the polarization state is the same as when passing through the first polarization rotation control means in FIG.

The second polarization rotation control means, as shown in B, has a half-wave plate 44 in the lower optical path and a half-wave plate 44 in the right optical path, respectively.
45 may be inserted. As a result, the lower right optical path is 1 /
Since the two wave plates 44 and 45 overlap each other, and the polarization direction does not change, the same as in the case A above.

Although not shown in the figure, the structure of the second polarization rotation control means using only such a linear retarder is applicable to the structure using the optical path changing prism having the shape shown in FIG. Needless to say.

FIG. 5 is a block diagram showing another embodiment of the magneto-optical switch according to the present invention, which is a 2 × 2 type (2 inputs /
The optical path of the example of 2 outputs) is shown. Further, FIG. 6 shows the arrangement of the optical components and the polarization state.

The polarization splitting birefringent element 50 and the first and second optical path shifting birefringent elements 52 and 5 depending on the polarization directions.
4 and the polarization-combining birefringent element 56 are arranged in a line in that order with a space therebetween, and the polarization-separating birefringent element 50 and the first
First polarization rotation control means 58 between the optical path shifting birefringent elements 52 and the second optical path shifting birefringent elements 54.
The second polarization rotation control means 60 is respectively inserted between the birefringent element 56 for polarization synthesizing and the birefringent element 56 for polarization combination, and the upper optical path is excluded between the first and second birefringent elements 52 and 54 for optical path shift except the intermediate optical path. And a linear phaser that rotates the polarization direction of the light beam in the lower optical path by 90 degrees (the two optical axes whose optical axis is tilted 45 degrees with respect to the x-axis
Two wavelength plates 62, 63) are inserted. The first polarization rotation control means 58 includes a variable Faraday rotator 64 of ± 45 degree switching type, and a pair of 1 / s whose optical axes are symmetrically arranged on the both side optical axes with respect to the x axis by ± 22.5 degrees. Two-wave plate 66, 67
And a half-wave plate 68 with an optical axis inserted in the upper optical path inclined by 45 degrees, the polarization of either one of the separated light beams is controlled by controlling the magnetic field applied to the variable Faraday rotator 64. It has the function of rotating the direction 90 degrees. Second
The polarization rotation control means 60 is a ± 45 degree switchable Faraday rotator 70, and a pair of ½ wavelengths symmetrically arranged on both sides of the optical axis with the optical axis tilted ± 22.5 degrees from the x axis. The plates 72 and 73 and the half-wave plate 74 whose optical axis is inserted in the lower optical path are inclined by 45 degrees. Similarly, by controlling the applied magnetic field of the variable Faraday rotator 70, It has the function of rotating either polarization direction by 90 degrees.

Two input fibers 7 are provided at the end of the optical switch function section arranged in this way on the side of the polarization separating birefringent element.
Two-core ferrule 78 with 6 and 77 arranged side by side and common lens 8
The two input port section by 0 and the two output port section by the common lens 86 and the two-core ferrule 84 in which two output fibers 82, 83 are juxtaposed at the end on the opposite side of the polarization-combining birefringent element side are installed. 4 ports configuration.

The polarization splitting birefringent element 50 and the first
Between the optical path shifting birefringent element 52 and between the second optical path shifting birefringent element 54 and the polarization combining birefringent element 56, an optical path changing prism for angularly shifting one light beam is inserted, Select the output port depending on the beam direction. In this embodiment, the polarization splitting birefringent element 50 is used.
And the first variable Faraday rotator 64, an optical path changing prism 88 formed of a wedge-shaped columnar body is inserted in the upper optical path, and the lower stage between the second variable Faraday rotator 70 and the polarization combining birefringent element 56. An optical path changing prism 90 composed of a wedge-shaped columnar body is inserted in the optical path. Accordingly, the one input fiber 76 is located at the center of the two-core ferrule 78, and the other input fiber 77 is located eccentrically downward. One output fiber 83 is located at the center of the two-core ferrule 84, and the other output fiber 82 is located eccentrically upward.

Each birefringent element is made of rutile single crystal. The optical axes of the polarization splitting birefringent element and the polarization combining birefringent element are tilted in the same direction with respect to the z axis in the xz plane, and the optical axes of the first and second optical path shifting birefringent elements. Are tilted in the same direction with respect to the z axis in the yz plane. Quartz is used for the half-wave plate. The variable Faraday rotator applies an external magnetic field from an electromagnet or an electromagnet and a permanent magnet to a Faraday element composed of a magnetic garnet single crystal (for example, a Bi-substituted rare earth iron garnet film), and controls the direction of the external magnetic field to control the Faraday rotation angle. The structure is such that can be switched.

Next, the operation of this magneto-optical switch will be described. In FIG. 6A, both variable Faraday rotators 64 and 70 rotate the Faraday rotation angle by −45 degrees, the light of input 1 in the middle stage is output 1 of the upper stage, and the light of input 2 in the lower stage (shown by a thick line). FIG. 6 shows the case of coupling to the output 2 of the middle stage.
In B, both variable Faraday rotators 64 and 70 rotate the Faraday rotation angle by +45 degrees, the light of the input 1 in the middle stage is output to the output 2 of the middle stage, and the light of input 2 in the lower stage (shown in bold) is the output of the upper stage. The cases of coupling to 1 are shown respectively.

(Input 1 → Output 1, Input 2 → Output 2) By controlling the magnetic fields of both variable Faraday rotators 64 and 70,
Both the Faraday rotation angle by the Faraday element is set to -45 degrees.

(Input 1 → Output 1) Middle input fiber 7
The light introduced from 6 (input 1) becomes collimated light at the lens 80 and is input to the optical switch function unit along the optical axis. The input light is straightened by the polarization separating birefringent element 50 and the ordinary light is separated by the extraordinary light in the x direction, bypasses the optical path correction prism 88, and is polarized by the variable Faraday rotator 64 of the first polarization rotation control means 58. Wave direction rotates -45 degrees, a pair of 1/2
The polarization directions of the wave plates 66 and 67 are rotated by 45 degrees, so that
The polarized light is parallel to the axis and bypasses the half-wave plate 68 in the upper optical path. That is, the first polarization rotation control means 58 rotates the polarization direction of the light on the right optical path by 90 degrees. The polarized light parallel to the y-axis becomes extraordinary light for the first optical-path-shifting birefringent element 52, so it is refracted in the -y direction and shifted to the lower optical path. Then, the polarization direction is rotated 90 degrees by the ½ wavelength plate 63 in the lower optical path and becomes parallel to the x axis. Since the polarized light parallel to the x-axis is the ordinary light for the second optical path shifting birefringent element 54, it goes straight on. The polarization direction is rotated 90 degrees by the half-wave plate 74 in the lower optical path of the second polarization rotation control means 60 and becomes parallel to the y-axis, and the polarization direction is changed by the pair of half-wave plates 72 and 73. The variable Faraday rotator 70 rotates by 45 degrees and the polarization direction rotates by -45 degrees. That is, the second
The polarization rotation control means 60 rotates the polarization direction of the light on the right optical path by 90 degrees. Since these light beams pass through the lower optical path, an angle shift occurs in the optical path changing prism 90 and the direction is changed obliquely upward. Both lights enter the polarization-combining birefringent element 56, the ordinary light travels straight, and the extraordinary light is refracted in the x direction to be combined, and is condensed by the lens 86 to be output from the upper output fiber 82.
Connect to (output 1).

(Input 2 → Output 2) Lower input fiber 7
The light introduced from 7 (input 2) becomes collimated light by the lens 80, and is input obliquely upward to the optical switch function unit. The input light is polarized by the birefringence element 50 for polarization separation, the ordinary light goes straight, and the extraordinary light is separated in the x direction, and passes through the optical path correction prism 88. As a result, a light beam having an upper optical path parallel to the optical axis is formed, and the polarization direction is rotated by -45 degrees by the variable Faraday rotator 64 of the first polarization rotation control means 58, and the pair of half-wave plates 66 and 67 are provided. Then, the polarization directions are rotated by 45 degrees and become polarizations parallel to the y-axis, and the polarization directions are rotated by 90 degrees by passing through the half-wave plate 68 of the upper optical path and polarizations parallel to the x-axis. Becomes That is, the first polarization rotation control means 58 rotates the polarization direction of the light on the left optical path by 90 degrees. These polarized waves parallel to the x-axis are ordinary rays to the first optical path shifting birefringent element 52, and therefore go straight. And 1 / of the upper optical path
The polarization direction is rotated 90 degrees by the two-wave plate 62 and becomes parallel to the y-axis. The polarized light parallel to the y-axis becomes extraordinary light for the second optical path shifting birefringent element 54, and is refracted in the -y direction to travel along the middle optical path and bypass the half-wave plate 74 of the lower optical path. . Then, the pair of 1s of the second polarization rotation control means 60
The polarization direction is rotated by 45 degrees by the / 2 wavelength plates 72 and 73, and the polarization direction is rotated by -45 degrees by the variable Faraday rotator 70.
That is, the second polarization rotation control means 60 rotates the polarization direction of the light on the left optical path by 90 degrees. Since these light beams pass through the middle optical path, they bypass the optical path changing prism 90 and go straight. Both lights enter the polarization-combining birefringent element 56, the ordinary light travels straight, and the extraordinary light is refracted in the x direction to be combined, collected by the lens 86, and coupled to the output fiber 83 (output 2) in the middle stage. .

(Input 1 → Output 2, Input 2 → Output 1) By controlling the magnetic fields of both variable Faraday rotators 64 and 70,
Both the Faraday rotation angle by the Faraday element is set to +45 degrees.

(Input 1 → Output 2) Middle input fiber 7
The light introduced from 6 (input 1) becomes collimated light at the lens 80 and is input to the optical switch function unit along the optical axis. The input light is straightened by the polarization separating birefringent element 50 and the ordinary light is separated by the extraordinary light in the x direction, bypasses the optical path correction prism 88, and is polarized by the variable Faraday rotator 64 of the first polarization rotation control means 58. Wave direction rotates by +45 degrees, a pair of 1/2
The polarization directions are rotated by 45 degrees by the wave plates 66 and 67, and x
The polarized light is parallel to the axis and bypasses the half-wave plate 68 in the upper optical path. That is, the first polarization rotation control means 58 rotates the polarization direction of the light on the left optical path by 90 degrees. Since the polarized light parallel to the x-axis is the ordinary light for the first optical path shifting birefringent element 52, it goes straight on. Then, the half-wave plates of the upper optical path and the lower optical path are bypassed 62 and 63. Since the polarized light parallel to the x-axis is the ordinary light for the second optical path shifting birefringent element 54, it goes straight on. Then, in the lower optical path of the second polarization rotation control means 60,
Bypassing the half wave plate 74, the pair of half wave plates 7
2, 73 rotates the polarization direction by 45 degrees, and the variable Faraday rotator 70 rotates the polarization direction by +45 degrees. That is, the second polarization rotation control means rotates the polarization direction of the light on the right optical path by 90 degrees. Since these light beams pass through the middle optical path, they bypass the optical path changing prism 90 and go straight.
Both lights enter the polarization-combining birefringent element 56, the ordinary light travels straight, and the extraordinary light is refracted in the x direction to be combined, collected by the lens 86, and coupled to the output fiber 83 (output 2) in the middle stage. .

(Input 2 → Output 1) Lower input fiber 7
The light introduced from 7 (input 2) becomes collimated light by the lens 80, and is input obliquely upward to the optical switch function unit. The input light is polarized by the birefringence element 50 for polarization separation, the ordinary light goes straight, and the extraordinary light is separated in the x direction, and passes through the optical path correction prism 88. As a result, a light beam having an upper optical path parallel to the optical axis is formed, the polarization direction is rotated by +45 degrees by the variable Faraday rotator 64 of the first polarization rotation control means 58, and the pair of half-wave plates 66, 67 is used. The polarization directions rotate by 45 degrees and become polarizations parallel to the x-axis, and by passing through the half-wave plate 68 in the upper optical path, the polarization directions rotate 90 degrees and become polarizations parallel to the y-axis. Become. That is, the first polarization rotation control means 58 rotates the polarization direction of the light on the right optical path by 90 degrees. These polarized waves parallel to the y-axis are extraordinary rays with respect to the first optical path shifting birefringent element 52 and thus are refracted in the -y direction. Then, the half-wave plates 62 and 63 in the upper optical path and the lower optical path are bypassed.
These polarized waves parallel to the y-axis also become extraordinary light for the second optical-path-shifting birefringent element 54, but are refracted in the -y direction and travel in the lower optical path. Then, the polarization direction is rotated by 90 degrees by the half-wave plate 74 in the lower optical path of the second polarization rotation control means 60, and x
It becomes parallel to the axis, and the polarization direction rotates by 45 degrees by the pair of half-wave plates 72 and 73, and the polarization direction rotates by +45 degrees by the variable Faraday rotator 70. That is, the second polarization rotation control means 60 rotates the polarization direction of the light on the left optical path by 90 degrees.
Since these light beams pass through the lower optical path, an angle shift occurs in the optical path changing prism 90 and the direction is changed obliquely upward.
Both lights enter the polarization-combining birefringent element 56, the ordinary light travels straight, and the extraordinary light is refracted in the x direction to be combined, collected by the lens 86, and coupled to the upper output fiber 82 (output 1). .

In this way, by controlling the magnetic fields of the variable Faraday rotators 64 and 70 of the first and second polarization rotation control means 58 and 60 to switch to either -45 degrees or +45 degrees together, The light from the input fiber 76 (input 1) is output to the output fiber 82 (output 1) or the output fiber 84.
The light from the input fiber 77 (input 2) can be output to either of the output fiber 84 (output 2) or the output fiber 82 (output 1) to either (output 2).

FIG. 7 is a block diagram showing another embodiment of a 4-port type magneto-optical switch. Since the basic configuration is the same as that in FIG. 5, corresponding members are designated by the same reference numerals, and description thereof will be omitted.

In this embodiment, the optical path changing prism 92,
Reference numeral 94 is a shape obtained by obliquely cutting two parallel ridgeline portions of a rectangular parallelepiped inserted in both optical paths. The structure does not necessarily have to be an integral structure, and may be a structure in which wedge-shaped columnar bodies as used in FIG. When such an optical path changing prism is used, it is preferable that the two fibers are arranged symmetrically with respect to the center axis of the ferrule. Therefore, the light from the input fiber 76 is input obliquely downward and the light from the input fiber 77 is input obliquely upward to the optical switch function unit, and the upward light from the optical switch function unit is input to the output fiber 82 and the optical switch function unit. The downward light from the will be coupled into the output fiber 83. In both cases, an angle shift is caused by passing through the optical path changing prisms 92 and 94, and a light beam parallel to the optical axis is formed in the optical switch function section.

FIG. 8 is a block diagram showing another embodiment of a 4-port type magneto-optical switch. Since the basic configuration is the same as that in FIG. 5, corresponding members are designated by the same reference numerals, and description thereof will be omitted.

In the above-mentioned embodiment, the optical axes of the first and second birefringent elements for optical path shifting are set parallel to each other, but in the embodiment of FIG. 8, the optical axes are symmetric with respect to the y-axis. It is set to be. Correspondingly, both optical path correction prisms 88 and 90 are arranged in the upper optical path, and
And 1 / between the second birefringent elements 52, 54 for optical path shifting.
The two-wave plate 96 is inserted only in the middle optical path.

A structure having first and second optical path shifting birefringent elements (optical axes are symmetrically arranged) as shown in FIG. 8 and a half-wave plate arranged in the middle optical path is illustrated. Although omitted, it goes without saying that the present invention can also be applied to a configuration using an optical path changing prism having a shape as shown in FIG.

[0050]

As described above, according to the present invention, the optical path correction prism is inserted in the optical switch function section, and the output port is selected according to the difference in the light beam direction. Without making it shorter, it is possible to achieve further miniaturization as a whole.

[Brief description of drawings]

FIG. 1 is a schematic view showing an embodiment of a magneto-optical switch according to the present invention.

FIG. 2 is an explanatory view showing the arrangement of parts and the state of polarization.

FIG. 3 is a schematic view showing another embodiment of the magneto-optical switch according to the present invention.

FIG. 4 is a schematic view showing another embodiment of the magneto-optical switch according to the present invention.

FIG. 5 is a schematic view showing another embodiment of the magneto-optical switch according to the present invention.

FIG. 6 is an explanatory view showing the arrangement of parts and the polarization state.

FIG. 7 is a schematic view showing another embodiment of the magneto-optical switch according to the present invention.

FIG. 8 is a schematic view showing another embodiment of the magneto-optical switch according to the present invention.

[Explanation of symbols]

10 Birefringence element for polarization separation 12 Birefringent element for optical path shift 14 Birefringence element for polarization combination 16, 18 Polarization rotation control means 20, 24 Variable Faraday rotator 21,22,25,26 1/2 wave plate 28 input fibers 29 Single-core ferrule 30,36 lens 32,33 output fiber 34 2-core ferrule 38 Optical path changing prism

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hideo Takeshita             F-de, 5-36-1 Shimbashi, Minato-ku, Tokyo             K.K Co., Ltd. (72) Inventor Hiroaki Ono             F-de, 5-36-1 Shimbashi, Minato-ku, Tokyo             K.K Co., Ltd. F-term (reference) 2H099 AA01 BA17 CA00 CA05 CA08

Claims (9)

[Claims] 1. A polarization-splitting birefringent element, an optical path-shifting birefringent element depending on the polarization direction, and a polarization-combining birefringent element are arranged in a line in this order at intervals. A polarization rotation control means is inserted between the birefringent elements, and a single-core ferrule having one fiber at one end of the array on the polarization separating birefringent element side and one input port section by one lens With a two-core ferrule in which two fibers are juxtaposed at the end on the opposite side of the birefringent element for polarization combination on the opposite side and a common lens.
In a three-port type optical switch having an output port section, the polarization rotation control means comprises a combination of a variable Faraday rotator and a linear phaser, and separates by controlling the magnetic field applied to the variable Faraday rotator. An optical path having a function of rotating one of the polarization directions of the light beam by 90 degrees and for angularly shifting one or both of the light beams between the optical path shifting birefringent element and the polarization combining birefringent element. A magneto-optical switch that has a changing prism inserted so that the output port can be selected according to the difference in the light beam direction. 2. The polarization rotation control means comprises a variable Faraday rotator of ± 45 degree switching type and a pair of symmetrically arranged optical axes inclined by 22.5 degrees in both optical paths of the separated light beams. The magneto-optical switch according to claim 1, which comprises a half-wave plate. 3. A polarization-splitting birefringent element, an optical path-shifting birefringent element depending on a polarization direction, and a polarization-combining birefringent element are arranged in a line in this order at a distance from each other. A polarization rotation control means is inserted between the birefringent elements, and a single-core ferrule having one fiber at one end of the array on the polarization separating birefringent element side and one input port section by one lens With a two-core ferrule in which two fibers are juxtaposed at the end on the opposite side of the birefringent element for polarization combination on the opposite side and a common lens.
In a three-port type optical switch having an output port unit, one of the polarization rotation control means is composed of a combination of a variable Faraday rotator and a linear phaser, and is separated by controlling an applied magnetic field of the variable Faraday rotator. Has a function of rotating the polarization direction of one of the two light beams by 90 degrees, and the other of the polarization rotation control means is composed of a linear phase shifter, and can rotate one polarization direction of the separated light beam. Having a function of rotating 90 degrees, an optical path changing prism for angularly shifting one or both light beams is inserted between the optical path shifting birefringent element and the polarization combining birefringent element, and the difference in the light beam direction The magneto-optical switch is characterized in that the output port is selected by. 4. The polarization rotation control means is arranged symmetrically with an optical axis inclined by 22.5 degrees in both optical paths of a variable Faraday rotator of ± 45 degree switching type and a separated light beam. The pair of half-wave plates is composed of a pair of half-wave plates, and the other polarization rotation control means is composed of two half-wave plates in which the optical axes inserted in the diagonal optical paths are inclined in the same direction by 45 degrees. The magneto-optical switch according to claim 3. 5. A polarization-splitting birefringent element, first and second optical path-shifting birefringent elements corresponding to polarization directions, and a polarization-combining birefringent element are spaced in this order. Polarization rotation control is provided between the polarization separating birefringent element and the first optical path shifting birefringent element, and between the second optical path shifting birefringent element and the polarization combining birefringent element. Means for inserting a linear phase shifter for rotating the polarization direction of the light beam of a part of the optical path by 90 degrees between the first and second optical path shifting birefringent elements, and one end of the array body. Two-fiber ferrule in which two fibers are juxtaposed to each other and a two-input port portion by a common lens, and two fibers are juxtaposed to the other end 2
A four-port type optical switch in which two output port sections are provided with a core ferrule and a common lens, wherein the polarization rotation control means comprises a combination of a variable Faraday rotator and a linear phaser, and the variable Faraday rotator is applied. By controlling the magnetic field, it has a function of rotating the polarization direction of either one of the separated light beams by 90 degrees, and it is provided between the polarization separating birefringent element and the first optical path shifting birefringent element, and Insert an optical path changing prism for angle-shifting one or both of the light beams between the birefringent element for optical path shifting and the birefringent element for polarization combination, so that the output port can be selected according to the difference in the light beam direction. A magneto-optical switch that has been characterized. 6. The polarization rotation control means comprises a variable Faraday rotator of ± 45 degree switching type and a pair of symmetrically arranged optical axes of 22.5 degrees in both optical paths of the separated light beams. The magneto-optical switch according to claim 5, wherein the half-wave plate and the half-wave plate having an optical axis inserted in a part of the optical path are 45 degrees. 7. The optical path changing prism is a right-angled triangular or wedge-shaped columnar body inserted in one optical path.
The magneto-optical switch according to any one of 1. 8. The optical path changing prism has a shape obtained by obliquely cutting two parallel ridges of a rectangular parallelepiped inserted in both optical paths, or a trapezoidal columnar body. The magneto-optical switch described. 9. The magneto-optical switch according to claim 1, wherein the birefringent element is made of rutile, lithium niobate, or yttrium vanadate.