JPH04308811A - Optical switch - Google Patents

Abstract

PURPOSE:To realize the optical switch which has high isolation between ports and is easily manufactured without using any polarizing prism. CONSTITUTION:This optical switch consists of three birefringent crystal plates 22-24, a 1st group of reciprocal and nonreciprocal rotators 25 interposed between the birefringent crystal plates 22 and 23, a 2nd group of reciprocal and nonreciprocal rotators 26 interposed between the birefringent crystal plates 23 and 24, >=1 light beam incidence port 27, and plural light beam projection ports 28 and 29. The separation directions of ordinary light beams and extraordinary light beams of the birefringent crystal plates are so set that the directions of the birefringent plate 23 are different from those of the birefringent crystal plates 22 and 24 and the directions of the birefringent crystal plates 22 and 24 match each other. Further, the rotating direction of the 1st group of rotators 25 and the direction of an external magnetic field are so set that the polarizing directions of the light beams match each other in the birefringent crystal plate 23. Further, the rotating direction of the 2nd group of rotators 26 and the direction of the external magnetic field are so set that the planes of polarization of the light beams cross each other in the birefringent crystal plate 24.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical switch for switching optical paths which is suitably used in optical communication or optical experiment systems.

0002

[Prior Art] Conventionally, various types of optical switches for switching optical paths in optical communications or optical experimental systems have been developed and provided. Switches are one of them.

As an example of the above optical switch, an optical switch 1 (Japanese Patent Publication No. 59-44606) as shown in FIG.
Publication No.) is provided. The optical switch 1 includes polarizing prisms 2 and 3 and a Faraday rotator (non-reciprocal rotator) 4.
, an optical compensator 5, total reflection mirrors 6 and 7, light beam entrance ports 8 and 9, and light beam exit ports 10 and 11.

Here, the polarizing prisms 2 and 3 separate the polarized light of the incident light beam into two orthogonal components (S-wave component and P-wave component) or combine the two incident orthogonal components. be.

The Faraday rotator 4 and the optical compensator 5 are set as follows with respect to the incident light. That is,
When the light travels from the left to the right in FIG. 12, the polarization direction of the light does not change due to the canceling effect of the rotation directions of the Faraday rotator 4 and the optical compensator 5, and the light travels from the right to the left in the diagram. When the light travels, the optical rotations overlap and the polarization direction of the light becomes 9.
The direction of the external magnetic field H acting on the Faraday rotator 4 and the direction of the crystal axis of the optical compensator 5 are set so that the Faraday rotator 4 rotates by 0°.

Therefore, in this optical switch 1, the light Li entering from the beam incidence port 8 is divided into two orthogonal components (s-wave component and p-wave component) by the polarizing prism 2.
These orthogonal components are ultimately combined again by the polarizing prism 3, and this combined light Lf is emitted from the light emitting port 10.

Similarly, the light Lj incident from the light incidence port 9 is separated and multiplexed by the polarizing prisms 2 and 3.
The combined light Lg is emitted from the light emitting port 11.

[0008] Also, the optical switch 1 set as described above
In this case, if the direction of the external magnetic field H acting on the Faraday rotator 4 is reversed by some method, the rotation direction of the optical compensator 5 and the Faraday rotator 4 will change when the light travels from the right to the left in FIG. Due to the canceling effect of , the polarization direction of the light does not change, and when the light travels from left to right in the figure, their optical rotations overlap and the polarization direction of the light rotates by 90°.

[0009] Therefore, in this optical switch 1, the light Li entering from the light beam entrance port 8 is transmitted to the light beam exit port.
The light beam is emitted from the light emitting port 11 without emitting from the port 10,
Similarly, the light Lj that has entered through the light input port 9 is outputted from the light output port 10 without exiting from the light output port 11, so that the light Lj can operate as an optical switch.

0010

[Problems to be Solved by the Invention] However, the optical switch 1 described above has a drawback in that it is not possible to increase the isolation between the light emitting ports 10 and 11 because the polarizing prisms 2 and 3 are used. was there.

The reason for this is that it is technically difficult to suppress the amount of leakage of the p-wave component that should be transmitted into the s-wave component that should be reflected by the polarizing prism 2 (3) to below -30 dB. This is because light is also emitted from the light emitting port, which is not originally desired.

Furthermore, when combining two lights separated into orthogonal components, the traveling direction of the lights is changed by reflection from the total reflection mirrors 6 and 7, so it is difficult to combine them on the same optical path. It also has the disadvantage of requiring a high level of skill.

In the example shown in FIG. 12, the traveling direction of light is changed by polarizing prisms 2 and 3 and total reflection mirrors 6 and 7. Here, if the optical path length from the reflected position to the combined position is L, if there is an error in the reflection angle by Δθ, a positional shift by LΔθ will occur at the combined point. Misalignment at the combining point increases the coupling loss with the optical waveguide connected to the light beam exit port 10 (11) and causes polarization dependence. It is necessary to configure and mount each component with accuracy within 5 seconds.

The present invention has been made in view of the above circumstances, and it is possible to increase the isolation between the light beam emission ports, easily combine the light beams on the same optical path, and An object of the present invention is to provide an optical switch for switching optical paths that does not require manufacturing precision.

[0015]

[Means for Solving the Problems] In order to solve the above problems, the present invention employs the following optical switch.

That is, in the optical switch according to claim 1, three birefringent crystal plates are arranged at a predetermined interval along the traveling direction of the light beam, and between the first and second birefringent crystal plates, A first group of reciprocal and non-reciprocal rotators that rotate the polarization direction of the light beam by the same angle are inserted between the second and third birefringent crystal plates to provide the same function as the first group of rotators. A second group of rotors having a rotator is inserted so that the direction in which the ordinary ray and extraordinary ray of the birefringent crystal plate are separated is set so that the direction in which the second birefringence crystal plate is separated is the same as that of the first and third birefringent crystals. Unlike the direction in which the plates separate, the directions in which the first and third birefringent crystal plates separate are set to match, and the polarization directions of the ordinary ray and extraordinary ray separated by the first birefringence crystal plate are The rotation directions of the reciprocal and non-reciprocal rotors of the first group and the strength and direction of the external magnetic field acting on the non-reciprocal rotors are adjusted such that they coincide with each other at the incident end surface of the second birefringent crystal plate. 2, which coincide at the output end of the second birefringent crystal plate.
The rotation direction of the reciprocal and non-reciprocal rotators of the second group and the non-reciprocal rotator are set so that the polarization planes of the main rays are orthogonal to each other at the incident end surface of the third birefringent crystal plate. The strength and direction of the external magnetic field that acts is set, the first birefringent crystal plate is provided with one or more light beam entrance ports, and the third birefringent crystal plate is provided with a plurality of light beam exit ports. It is characterized by

The optical switch according to the second aspect of the present invention includes three birefringent crystal plates arranged at a predetermined interval along the traveling direction of the light beam, and between the first and second birefringent crystal plates,
A first group of rotators that rotate the polarization direction of the light beam by the same angle is inserted, and a second group of rotators having the same function as the first group of rotators is inserted between the second and third birefringent crystal plates. a liquid crystal plate is inserted between the first group of rotors and a second birefringent crystal plate, and the first group of rotors and the second group of rotors are a pair of reciprocal rotors. and either a reciprocal rotator or a non-reciprocal rotator, and the direction in which the ordinary ray and extraordinary ray of the birefringent crystal plate are separated is the same as the direction in which the second birefringence crystal plate separates the ordinary ray and the extraordinary ray. The separation directions of the first and third birefringent crystal plates are set to match the directions of separation of the first and third birefringent crystal plates, and the two birefringent crystal plates are separated by the first birefringent crystal plate. The rotation direction of each of the rotators of the first group is set so that the polarization directions of the ordinary ray and the extraordinary ray coincide with each other at the incident end surface of the second birefringent crystal plate, and the polarization direction of the liquid crystal plate is set. the second birefringent crystal plate so that the planes of polarization of the two light beams that coincide at the output end of the second birefringent crystal plate are orthogonal to each other at the input end face of the third birefringent crystal plate. The rotation direction of each rotor of the group is set, the first birefringent crystal plate is provided with one or more light beam entrance ports, and the third birefringent crystal plate is provided with a plurality of light beam exit ports. It is characterized by

Further, the optical switch according to the third aspect of the present invention includes three birefringent crystal plates arranged at a predetermined interval along the traveling direction of the light beam, and two birefringent crystal plates arranged between the first and second birefringent crystal plates.
A first group of rotors consisting of two non-reciprocal rotors is arranged in the same plane so that these non-reciprocal rotors rotate in different directions from each other, and an external magnetic field is applied to each of these non-reciprocal rotors. The magnitude and direction of these external magnetic fields are set so that the directions of the two directions are different from each other, and a second birefringent crystal plate is arranged so that the polarization direction matched by the non-reciprocal rotator becomes an ordinary ray. A second group of rotors consisting of two non-reciprocal rotators is also arranged between the second and third birefringent crystal plates in the same plane so that these non-reciprocal rotators rotate in different directions. At the same time, the magnitude and direction of the external magnetic fields are set so that the directions of the external magnetic fields acting on each of these non-reciprocal rotors are different from each other, and one or more birefringent crystal plates are placed on the first birefringent crystal plate. The third birefringent crystal plate is provided with a plurality of light beam entrance ports, and the third birefringent crystal plate is provided with a plurality of light beam exit ports.

[0019]

[Operation] In the optical switch according to claim 1 of the present invention, the light beam entrance port i among the one or more (N) light beam entrance ports
(1≦i≦N), the first group of rotors and the second The strength and direction of the external magnetic field acting on each non-reciprocal rotor of the group of rotors are set.

Here, if the direction of the external magnetic field acting on each of the non-reciprocal rotors of the first group of rotors and the second group of rotors is reversed, the beam incidence port i (1≦i≦N ) is not emitted from the light emitting port k (1≦k≦M), but is emitted from the light emitting port k+1 (1≦k≦M), thereby operating as an optical switch.

Further, in the optical switch according to the second aspect of the present invention, when no electric field is applied to the liquid crystal plate, a light beam entrance port i (1≦i≦N) among one or more (N) light beam entrance ports
In such a way that the light rays incident from
The polarization direction of the liquid crystal plate is set in advance.

Here, if an electric field is applied to the liquid crystal plate to change the polarization direction of the liquid crystal plate, the light beam incidence port i(1
The light beam incident from ≦i≦N) enters the light beam exit port k (1≦
ray exit port k+1 (1 ≤
It operates as an optical switch by emitting light from the point where k≦M).

Further, in the optical switch according to claim 3, 1
The light beam entering from the light beam input port i (1≦i≦N) among the three or more (N) light beam input ports is the light beam entering the light beam exit port k (1≦k≦M) among the plurality (M) light beam output ports. The magnitude and direction of the external magnetic fields are set so that the directions of the external magnetic fields acting on the non-reciprocal rotors of the first group of rotors are different from each other so that the non-reciprocal rotors of the second group of rotors are emitted from the Also in the rotor, the magnitude and direction of the external magnetic fields are set so that the directions of the external magnetic fields acting on each of the non-reciprocal rotors are different from each other.

Here, if the direction of the external magnetic field acting on each of the non-reciprocal rotors is reversed, the light beam entrance port i (1≦
The light ray entering from i≦N) passes through the light beam exit port k (1≦k
≦M) without emitting from the beam exit port k+1 (1≦k
≦M), which acts as an optical switch.

[0025]

[Embodiments] Each embodiment of the present invention will be described below with reference to the drawings.

First, the optical switch according to claim 1 will be explained based on FIG.

The optical switch 21 includes first to third birefringent crystal plates 22 to 24 arranged at predetermined intervals along the direction of propagation of the light beam, and a first birefringent crystal plate 22 and a second birefringent crystal plate 22. A first group of rotors 25 inserted between the birefringent crystal plate 23 and a second group of rotors inserted between the second birefringent crystal plate 23 and the third birefringent crystal plate 24. The rotor 26 and the first
The second birefringent crystal plate 22 is provided with a ray entrance port 27, and the third birefringent crystal plate 24 is provided with ray exit ports 28 and 29.

A lens 31 and an optical fiber 32 are coaxially provided between the first birefringent crystal plate 22 and the light beam entrance port 27, and a third birefringent crystal plate 24 and the light beam exit port 28 are provided coaxially. A lens 33 and an optical fiber 34 are coaxially provided between the third birefringent crystal plate 24 and the light beam exit port 29, and a lens 35 and an optical fiber 36 are coaxially provided between the third birefringent crystal plate 24 and the light beam exit port 29. It is provided.

The first group of rotators 25 consists of reciprocal and non-reciprocal rotators that rotate the polarization direction of the light beam by the same angle, and includes a first reciprocal counterclockwise 45° rotator (hereinafter referred to as
It is simply referred to as the first reciprocal left rotator. ) 41, first reciprocal clockwise 45° rotator (first reciprocal right-handed rotator) 42,
A first non-reciprocal Faraday rotator (first Faraday rotator) 43.

The second group of rotors 26 has the same structure as the first group of rotors 25 described above, and has a second reciprocal counterclockwise 45° rotor (second reciprocal left rotor) 44. , second reciprocal clockwise 45° rotator (second reciprocal right-handed rotator) 45,
A second non-reciprocal Faraday rotator (second Faraday rotator) 46.

The birefringent crystal plates 22, . . . are made of calcite or rutile crystal, the reciprocal rotators 41, . is Y. I. G crystal and GBIG thin film crystal are preferably used.

The birefringent crystal plate 22 of this optical switch 21,
The direction in which the ordinary ray and extraordinary ray are separated is that the direction in which the second birefringent crystal plate 23 separates is different from the direction in which the first birefringent crystal plate 22 and the third birefringent crystal plate 24 separate, The directions in which the first birefringent crystal plate 22 and the third birefringent crystal plate 24 are separated are set to be the same.

In addition, the first reciprocity left polarizer is arranged so that the polarization directions of the ordinary ray and the extraordinary ray separated by the first birefringent crystal plate 22 coincide with each other at the end surface 23a of the second birefringent crystal plate 23. The rotation directions of the rotor 41, the first reciprocal right-handed rotor 42, and the first Faraday rotator 43 are set. Furthermore, the strength and direction of the external magnetic field H acting on the first Faraday rotator 43 are also set.

Furthermore, the end surface 23 of the second birefringent crystal plate 23
so that the polarization planes of the two light rays that coincide at b are orthogonal to each other at the end surface 24a of the third birefringent crystal plate 24,
The rotation directions of the second reciprocal left rotor 44, the second reciprocal right rotor 45, and the second Faraday rotator 46 are set. Furthermore, the strength and direction of the external magnetic field H acting on the second Faraday rotator 46 are also set.

In FIG. 1, solid lines with arrows drawn in the first to third birefringent crystal plates 22 to 24 represent ordinary rays, and broken lines with arrows represent extraordinary rays.

FIGS. 2 and 3 show the Faraday rotator 43 (
46) shows a specific means for changing the direction of the external magnetic field H acting on the magnetic field H.

In FIG. 2, the Faraday rotator 43 (46)
A permanent magnet 52 is provided near the side surface 51 and parallel to the side surface 51, and by rotating this permanent magnet 52 in a plane parallel to the side surface 51, the direction of the external magnetic field H acting on the Faraday rotator 43 (46) can be changed. It's changing. In addition, in FIG. 3, a cylindrical electromagnet 53 is provided at a position surrounding the Faraday rotator 43 (46), and by switching the direction of the current of this electromagnet 53, the external magnetic field H acting on the Faraday rotator 43 (46) is reduced. changing direction.

Next, the operation of the optical switch 21 will be explained in FIG.
This will be explained based on FIG.

FIG. 4 shows the incident light ray Lp traveling along the optical path A from the input port 27 to the light exit port 28 in the optical switch 21, observed from above, and FIG. The polarization state is observed from the incident light side (the light beam entrance port 27 side). below,
These polarization states are indicated using symbols Z1 to Z8.

Now, the direction of the external magnetic field H and the rotational directions of the first reciprocal left rotor 41, the first reciprocal right rotor 42, the second reciprocal left rotor 44, and the second reciprocal right rotor 45, respectively. By appropriately selecting , it is possible to configure such that when the incident light ray Lp travels from left to right in the figure, the polarization direction at the end surface 23a of the second birefringent crystal plate 23 becomes an ordinary ray.

The light beam Lp incident from the light beam entrance port 27
is in the state Z1, but the first birefringent crystal plate 22 separates the light beam into a light beam L11 and a light beam L12 on the XZ plane. The light ray L11 is an ordinary ray (O-ray) with respect to the first birefringent crystal plate 22, and the light ray L12 is an extraordinary ray (E-r
ay). Each polarization direction is perpendicular to the Y-axis direction and the X-axis direction, as shown by Z2.

Ray L11 and light ray L1 are orthogonal to each other
The two polarization directions become the same direction by passing through the first reciprocal left rotator 41 or the first reciprocal right rotator 42 having different rotation directions. Here, the first reciprocal left rotor 41
rotates in a counterclockwise direction as viewed from the incident direction of the light beam L11, and the first reciprocal right rotator 42 rotates in a clockwise direction as seen from the incident direction of the light beam L12. The polarization state at this time is Z3.

Next, the first Faraday rotator 43 further rotates the light rays L11 and L12 counterclockwise by 45 degrees, so that the polarization direction of these light rays L11 and L12 becomes the X-axis direction. As a result, at the position (Z4) of the end surface 23a of the second birefringent crystal plate 23, the light ray L11 is rotated by 90° compared to the polarization direction at Z2, and the light ray L12 is not rotated.

The crystal axis of the second birefringent crystal plate 23 is arranged so that the two rays L11 and L12 polarized in the X-axis direction become ordinary rays. The two light rays L11 and L12 (state of Z4) passing through the second birefringent crystal plate 23 are
It will pass through the group rotor 26.

Here, the second reciprocal left rotator 44 is configured to rotate the polarization direction of the light beam L12 by 90 degrees without rotating the polarization direction of the light beam L11, contrary to the action of the first group of rotators 25. A second reciprocal right-handed rotator 45 and a second Faraday rotator 46 are respectively arranged. Note that the second Faraday
The rotation direction of the rotor 46 may be the same as that of the first Faraday rotator 43.

In this case, the light ray L11 passes through the second reciprocal right-handed rotator 45 and the second Faraday rotator 46, so that the rotation of the polarization direction is canceled out, and as a result, the polarization direction does not rotate. When the light beam L12 passes through the second reciprocal left rotator 44 and the second Faraday rotator 46, the polarization direction is rotated counterclockwise by 45 degrees, and as a result, the polarization direction is rotated by 90 degrees ( Z7 condition).

Therefore, at the end surface 24a of the third birefringent crystal plate 24, the polarization directions of the two light beams L11 and L12 are orthogonal to each other. At this time, the ray L11 becomes an extraordinary ray (E-ray) and the ray L12 becomes an ordinary ray (O-ray) with respect to the third birefringent crystal plate 24, so that the end face of the third birefringent crystal plate 24 24b, the two light beams L11 and L12 are spatially matched and combined (light beam Lq), and the light beam exit port 2
It is emitted from 8.

Next, a case where the direction of the external magnetic field H acting on the Faraday rotator 43 (46) is reversed will be described with reference to FIGS. 6 and 7.

In this case, the light beam Lp incident from the light beam entrance port 27 is converted into a light beam L1 by the first birefringent crystal plate 22.
1 and the light beam L12, and the first reciprocal left rotator 41
Alternatively, by passing through the first reciprocal right-handed rotator 42, they become in the same direction (state Z3) and enter the first Faraday rotator 43.

[0050] The light beams L11 and L12 are the first Faraday
Since the direction of the external magnetic field H acting on the rotator 43 is reversed, the polarization direction is rotated clockwise by 45 degrees by the first Faraday rotator 43. Therefore, the polarization directions of the rays L11 and L12 at Z4 are in the Y-axis direction, and they become extraordinary rays with respect to the second birefringent crystal plate 23. Since these extraordinary rays propagate in the second birefringent crystal plate 23 while shifting in the Y-axis direction, the rays L are shifted by Yd in the Y-axis direction compared to the case where the external magnetic field H is not reversed.
11 and L12 will be shifted (state of Z5).

The shifted light beam L11 passes through the second reciprocal right-handed rotator 45 and the second Faraday rotator 46, so that the polarization direction is rotated clockwise by 45 degrees, and as a result, the polarization direction is rotated by 90 degrees. However, the light ray L1
2 passes through the second reciprocal left rotator 44 and the second Faraday rotator 46, the rotation of the polarization direction is canceled out, and as a result, the polarization direction is not rotated (state Z7).

Therefore, at the end surface 24a of the third birefringent crystal plate 24, the polarization directions of the two light beams L11 and L12 are perpendicular to each other. At this time, the ray L11 becomes an extraordinary ray (E-ray) and the ray L12 becomes an ordinary ray (O-ray) with respect to the third birefringent crystal plate 24, so that the end face of the third birefringent crystal plate 24 24b, the two light beams L11 and L12 are spatially matched and combined (light beam Lq), and the light beam exit port 2
It is emitted from 9. In this case, the light emitting port 29 is shifted by Yd in the Y-axis direction compared to the light emitting port 28 when the external magnetic field H is not reversed.

As explained above, this optical switch 21
According to the above, the strength of the external magnetic field H acting on each of the first Faraday rotator 43 and the second Faraday rotator 46 is such that the light beam Lp incident from the light beam entrance port 27 is emitted from the light beam exit port 28. By setting the direction and direction of the external magnetic field H acting on the first Faraday rotator 43 and the second Faraday rotator 46, the light ray Lp incident from the light beam entrance port 27 becomes a light beam. It has a function of switching the optical path of emitting light from the light emitting port 29 without emitting from the emitting port 28, and can realize operation as an optical switch. Therefore, 1
It can be used as a ×2 optical switch.

It is clear that in the optical switch 21 described above, by arranging a plurality of light beam entrance ports in the Y-axis direction, it is possible to switch a plurality of channels at the same time. In this way, in the above-described optical switch 21, the number of light beam input/output ports is not limited to the above embodiment, and various changes can be made.

Furthermore, it is of course possible to replace the optical fibers 32, . . . with optical waveguides that can confine and propagate the energy of light, and the mode of these optical fibers 32, . . . may be either single mode or multimode. .

Next, the optical switch according to claim 2 will be explained based on FIG. 8.

This optical switch 61 is similar to the optical switch 2 described above.
The difference from 1 is that a liquid crystal is used to control the polarization direction for switching the optical path instead of switching a magnetic field, that is, a liquid crystal plate is used between the rotor 25 of the first group and the second birefringent crystal plate 23. 62 is inserted and the polarization direction of light is controlled by changing the state of application of an electric field to the liquid crystal plate 62, thereby realizing operation as an optical switch.

Generally, the polarization direction of the liquid crystal plate 62 does not rotate when an electric field is applied, but rotates by 90° when no electric field is applied.

Note that the operation of the optical switch 61 as an optical switch is completely the same as that of the optical switch 21 shown in FIGS. 4 to 7, and a description thereof will be omitted.

This optical switch 61 can also provide the same functions and effects as the optical switch 21 described above. That is, the light beam Lp incident from the light beam entrance port 27 with no electric field applied to the liquid crystal plate 62 is transmitted to the light beam exit port 28.
The polarization direction of the liquid crystal plate 62 is set so that the light beam Lp enters from the light beam entrance port 28 by applying an electric field to the liquid crystal plate 62 to change the polarization direction of the liquid crystal plate 62. It is possible to operate as an optical switch by emitting light from the light emitting port 29 without emitting the light from the emitting port 28.

In this case, since it is not necessary to use the first Faraday rotator 43 and the second Faraday rotator 46 due to the optical configuration, these Faraday rotators 43 and 46 are replaced with two reciprocal rotators. You can also do that. As this reciprocal rotator, an optical rotator or the like is used in the optical compensator.

Next, the optical switch according to claim 3 will be explained based on FIG. 9.

This optical switch 71 is an example in which only a Faraday rotator is used as a polarization rotator in an optical switch that uses magnetic field switching for polarization direction control, and the first group of rotators 25 of the optical switch 21 described above is used as a polarization rotator. is replaced with a non-reciprocal Faraday 45° rotator (Faraday rotator) 72, 73, and the rotor 26 of the second group is replaced with a Faraday rotator 74, 7.
5.

The polarization direction of the Faraday rotator 72 is rotated clockwise with respect to the light beam L11, and the polarization direction of the Faraday rotator 73 is rotated counterclockwise with respect to the light beam L12. Faraday rotators 74 and 75 are arranged in the same plane so as to rotate in different directions.
Similarly to the Faraday rotators 72 and 73, they are arranged in the same plane so as to rotate in mutually different directions, and the second compound is arranged so that the polarization directions that coincide with each other by the Faraday rotators 72 and 73 become ordinary rays. A refractive crystal plate 23 is arranged.

[0065] These Faraday rotators 72,
The magnitude and direction of the external magnetic fields H acting on each of the Faraday rotators 74 and 73 are set so that the directions thereof are different from each other, and the Faraday rotators 74 and 75 have the same magnitude and direction as the Faraday rotators 72 and 73. The magnitude and direction of these external magnetic fields H are set so that the directions of the external magnetic fields H acting on each are different from each other.

Next, the operation of the optical switch 71 will be explained. FIG. 10 shows the polarization state of the light beam on the optical path A heading from the light beam entrance port 27 to the light beam exit port 28, as observed from the incident light side (the light beam entrance port 27 side).

[0067] Light ray L incident from the ray input/output port 27
p is separated on the X-Z plane by the first birefringent crystal plate 22 into a light ray L11 which is an ordinary ray and a light ray L12 which is an extraordinary ray (state Z2).

The polarization directions of the orthogonal rays L11 and L12 are rotated by 45° in different directions by the Faraday rotators 72 and 73, so that the polarization directions of the orthogonal rays L11 and L12 are changed to the second birefringent crystal plate 2.
The end faces 23a of No. 3 are both tilted by −45° from the X axis. Here, the second birefringent crystal plate 23 is arranged so that a light beam whose polarization direction is tilted by -45 degrees becomes an ordinary light beam.

The light ray L that passed through the second birefringent crystal plate 23
The polarization direction of 11 (L12) is determined by the Faraday rotator 74 (7
The light beams L11 and L12 are rotated by 45 degrees by the clockwise (counterclockwise) action of 5), and these light beams L11 and L12 are once again orthogonal to each other. The two light beams L11 and L12 are combined by the third birefringent crystal plate 24 to become one light beam Lq, which is emitted from the light beam exit port 28.

Next, the Faraday rotators 72, 73 (74
, 75), the case where the direction of the external magnetic field H acting on the magnetic field H is reversed will be explained based on FIG. 11.

In this case, the light beam Lp incident from the light beam entrance port 27 is converted into a light beam L1 by the first birefringent crystal plate 22.
1 and the light beam L12, and the Faraday rotator 72,
73 respectively.

Since the directions of the external magnetic fields H acting on the Faraday rotators 72 and 73 are reversed, the light ray L11
The polarization direction of the light beam L12 is rotated 45 degrees counterclockwise by the Faraday rotator 72, and the polarization direction of the light beam L12 is rotated 45 degrees clockwise by the Faraday rotator 73. Therefore, the polarization directions of the rays L11 and L12 at Z3 are the same, and they become extraordinary rays for the second birefringent crystal plate 23. These extraordinary rays propagate diagonally downward to the right in the second birefringent crystal plate 23 while shifting in the X-axis direction and the Y-axis direction, so compared to the case where the external magnetic field H is not reversed, the X-axis The optical paths of the light rays L11 and L12 are shifted by Xd in the direction and by Yd in the Y-axis direction (state of Z4).

The shifted light ray L11 passes through the Faraday rotator 74, so that its polarization direction is rotated clockwise by 45°, and the light ray L12 passes through the Faraday rotator 75, so that its polarization direction is rotated counterclockwise by 45°. It will rotate (state of Z5).

Therefore, at the end surface 24a of the third birefringent crystal plate 24, the polarization directions of the two light beams L11 and L12 are orthogonal to each other. At this time, the ray L11 becomes an ordinary ray (O-ray) and the ray L12 becomes an extraordinary ray (E-ray) with respect to the third birefringent crystal plate 24, so that the end face of the third birefringent crystal plate 24 24b, the two light beams L11 and L12 are spatially matched and combined (light beam Lq), and the light beam exit port 2
It is emitted from 9. In this case, the light emission port 29 is shifted by Xd in the X-axis direction and by Yd in the Y-axis direction, compared to the light emission port 28 in the case where the external magnetic field H is not reversed.

As explained above, this optical switch 71
According to the above, the strength and direction of the external magnetic field H acting on each of the Faraday rotators 72 to 75 are set so that the light beam Lp incident from the light beam entrance port 27 is emitted from the light beam exit port 28. By reversing the direction of the external magnetic field H acting on each of the rotors 72 to 75, the optical path is switched such that the light beam Lp incident from the light beam entrance port 27 is not emitted from the light beam exit port 28 but is emitted from the light beam exit port 29. function, and can operate as an optical switch. Therefore, it can be used as a 1×2 optical switch.

Note that in the optical switch 71 described above, a liquid crystal plate can be used to control the polarization direction, and in this case, the Faraday rotator can be replaced with a reciprocal rotator as in the optical switch 61 described above.

[0077]

[Effect of the invention] As explained above, claim 1 of the present invention
According to the described optical switch, 3 along the traveling direction of the light beam.
A first group of reciprocal and non-reciprocal rotators that rotate the polarization direction of the light beam by the same angle between the first and second birefringent crystal plates, which are arranged at a predetermined interval. A second group of rotors having the same function as the first group of rotors is inserted between the second and third birefringent crystal plates, and the ordinary ray and extraordinary ray of the birefringent crystal plate are The direction to separate the
The direction in which the second birefringent crystal plate separates is different from the direction in which the first and third birefringent crystal plates separate, and the directions in which the first and third birefringent crystal plates separate coincide with each other. , reciprocity and non-reciprocity of the first group such that the polarization directions of the ordinary ray and the extraordinary ray separated by the first birefringent crystal plate coincide with each other at the incident end surface of the second birefringent crystal plate. The rotation direction of the rotor and the strength and direction of the external magnetic field acting on the non-reciprocal rotor are set, and the polarization planes of the two light beams that coincide at the output end of the second birefringent crystal plate are set. , the rotation directions of the reciprocal and non-reciprocal rotors of the second group and the strength of the external magnetic field acting on the non-reciprocal rotors so as to be orthogonal to each other at the incident end surface of the third birefringent crystal plate; The first birefringent crystal plate is provided with one or more light beam entrance ports, and the third birefringent crystal plate is provided with a plurality of light beam exit ports. A ray that enters from a ray entrance port i (1≦i≦N) among (N) ray entrance ports exits from a ray exit port k (1≦k≦M) among a plurality of (M) ray exit ports. The strength and direction of the external magnetic field acting on each of the non-reciprocal rotors of the first group of rotors and the second group of rotors are set so that the first group of rotors and the second group of rotors By reversing the direction of the external magnetic field acting on each non-reciprocal rotor of the two groups of rotors, the light beam incident from the light beam entrance port i (1≦i≦N) is transferred to the light beam exit port k (1≦k≦ It is possible to operate as an optical switch by emitting light from the light beam exit port k+1 (1≦k≦M) without emitting the light from the light beam M).

Further, according to the optical switch of claim 2, three birefringent crystal plates are arranged at a predetermined interval along the traveling direction of the light beam, and there is a gap between the first and second birefringent crystal plates. ,
A first group of rotators that rotate the polarization direction of the light beam by the same angle is inserted, and a second group of rotators having the same function as the first group of rotators is inserted between the second and third birefringent crystal plates. a liquid crystal plate is inserted between the first group of rotors and a second birefringent crystal plate, and the first group of rotors and the second group of rotors are a pair of reciprocal rotors. and either a reciprocal rotator or a non-reciprocal rotator, and the direction in which the ordinary ray and extraordinary ray of the birefringent crystal plate are separated is the same as the direction in which the second birefringence crystal plate separates the ordinary ray and the extraordinary ray. The separation directions of the first and third birefringent crystal plates are set to match the directions of separation of the first and third birefringent crystal plates, and the two birefringent crystal plates are separated by the first birefringent crystal plate. The rotation direction of each of the rotators of the first group is set so that the polarization directions of the ordinary ray and the extraordinary ray coincide with each other at the incident end surface of the second birefringent crystal plate, and the polarization direction of the liquid crystal plate is set. the second birefringent crystal plate so that the planes of polarization of the two light beams that coincide at the output end of the second birefringent crystal plate are orthogonal to each other at the input end face of the third birefringent crystal plate. The rotation direction of each rotor of the group is set, the first birefringent crystal plate is provided with one or more light beam entrance ports, and the third birefringent crystal plate is provided with a plurality of light beam exit ports. Therefore, when no electric field is applied to the liquid crystal plate, the number of light beams incident from one or more (N) light beam entrance ports i (1≦i≦N) is The polarization direction of the liquid crystal plate is set so that light is emitted from the light beam exit port k (1≦k≦M) among the light beam emission ports, and an electric field is applied to the liquid crystal plate to change the polarization direction of the liquid crystal plate. By changing
An optical switch in which a light beam that enters from a light beam input port i (1≦i≦N) does not exit from a light beam exit port k (1≦k≦M), but is emitted from a light beam exit port k+1 (1≦k≦M). It is possible to perform operations as follows.

Further, according to the optical switch according to claim 3, three birefringent crystal plates are arranged at a predetermined interval along the traveling direction of the light beam, and there is a gap between the first and second birefringent crystal plates. 2
A first group of rotors consisting of two non-reciprocal rotors is arranged in the same plane so that these non-reciprocal rotors rotate in different directions from each other, and an external magnetic field is applied to each of these non-reciprocal rotors. The magnitude and direction of these external magnetic fields are set so that the directions of the two directions are different from each other, and a second birefringent crystal plate is arranged so that the polarization direction matched by the non-reciprocal rotator becomes an ordinary ray. A second group of rotors consisting of two non-reciprocal rotators is also arranged between the second and third birefringent crystal plates in the same plane so that these non-reciprocal rotators rotate in different directions. At the same time, the magnitude and direction of the external magnetic fields are set so that the directions of the external magnetic fields acting on each of these non-reciprocal rotors are different from each other, and one or more birefringent crystal plates are placed on the first birefringent crystal plate. Since the third birefringent crystal plate is provided with a plurality of light beam entrance ports, and a plurality of light beam exit ports are provided on the third birefringent crystal plate, one or more (N pieces)
Among the ray entrance ports, ray entrance port i (1≦i≦N
) is emitted from the light exit port k (1≦k≦M) among the plurality (M) of light beam exit ports. The magnitude and direction of these external magnetic fields are set so that the directions of the magnetic fields are different from each other, and even in the second group of rotors, the directions of the external magnetic fields acting on each non-reciprocal rotor are different from each other. By setting the magnitude and direction of these external magnetic fields as shown in FIG.
The light beam incident from (1≦i≦N) is the light beam exit port k (
1≦k≦M), the ray exit port k+1 (
1≦k≦M), and can operate as an optical switch.

As described above, according to the optical switch of the present invention, an optical system can be configured without using a polarizing prism and without requiring optical components and mounting with high angular accuracy. It is possible to realize an optical switch that has high isolation between the two and is easy to manufacture.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an embodiment of an optical switch according to claim 1 of the present invention.

FIG. 2 is a diagram showing one means for changing the direction of an external magnetic field acting on a Faraday rotator.

FIG. 3 is a diagram showing another means for changing the direction of an external magnetic field acting on a Faraday rotator.

FIG. 4 is a diagram showing an optical path of the optical switch according to claim 1 of the present invention.

FIG. 5 is a diagram showing the polarization state of the light beam of the optical switch according to claim 1 of the present invention.

FIG. 6 is a diagram showing an optical path when the direction of the external magnetic field of the optical switch according to claim 1 of the present invention is reversed.

FIG. 7 is a diagram showing the polarization state of a light beam when the direction of the external magnetic field of the optical switch according to claim 1 of the present invention is reversed.

FIG. 8 is a perspective view showing an embodiment of the optical switch according to claim 2 of the present invention.

FIG. 9 is a perspective view showing an embodiment of the optical switch according to claim 3 of the present invention.

FIG. 10 is a diagram showing the polarization state of the light beam of the optical switch according to claim 3 of the present invention.

FIG. 11 is a diagram showing the polarization state of a light beam when the direction of the external magnetic field of the optical switch according to claim 3 of the present invention is reversed.

FIG. 12 is a schematic diagram showing the configuration and operation of a conventional optical switch.

[Explanation of symbols]

21 Optical switch 22 First birefringent crystal plate 23 Second birefringent crystal plate 24 Third birefringent crystal plate 25 First group rotor 26 Second group rotor 27 Light beam entrance ports 28, 29 Light beam output Ports 31, 33, 35 Lenses 32, 34, 36 Optical fiber 41 First reciprocal counterclockwise 45° rotator 42 First
reciprocal clockwise 45° rotor 43 first non-reciprocal Faraday-45° rotator 44 second reciprocal counterclockwise 45
° rotor 45 Second reciprocal clockwise 45° rotor 46
Second non-reciprocal Faraday-45° rotator 61 Optical switch 62 Liquid crystal plate 71 Optical switch

Claims (3)

[Claims] Claim 1: Three birefringent crystal plates are arranged at predetermined intervals along the traveling direction of the light beam, and the polarization direction of the light beam is rotated by the same angle between the first and second birefringent crystal plates. A first group of reciprocal and non-reciprocal rotors is inserted, and a second group of rotors having the same function as the first group of rotors is also inserted between the second and third birefringent crystal plates. and the direction in which the ordinary ray and extraordinary ray of the birefringent crystal plate are separated is such that the direction in which the second birefringent crystal plate separates is different from the direction in which the first and third birefringent crystal plates separate. The directions of separation of the third birefringent crystal plates are set to match, and the polarization directions of the ordinary rays and extraordinary rays separated by the first birefringent crystal plate are set to the incident end face of the second birefringent crystal plate. The rotation directions of the reciprocal and non-reciprocal rotors of the first group and the strength and direction of the external magnetic field acting on the non-reciprocal rotors are set so that they coincide with each other, and the second birefringence The reciprocity and non-reciprocity of the second group are arranged so that the polarization planes of the two light beams that coincide at the output end of the crystal plate are orthogonal to each other at the input end face of the third birefringent crystal plate. setting the rotation direction of the rotor and the strength and direction of an external magnetic field acting on the non-reciprocal rotor, providing one or more light beam entrance ports in the first birefringent crystal plate, and setting the third birefringent crystal plate; An optical switch characterized by having a plurality of light beam output ports provided on a plate. 2. Three birefringent crystal plates are arranged at predetermined intervals along the traveling direction of the light beam, and the polarization direction of the light beam is rotated by the same angle between the first and second birefringent crystal plates. A first group of rotors is inserted between the second and third birefringent crystal plates, and a second group of rotors having the same function as the first group of rotors is inserted between the second and third birefringent crystal plates.
A liquid crystal plate is inserted between the first group of rotors and a second birefringent crystal plate, and the first group of rotors and the second group of rotors are arranged in a pair of opposite directions. a reciprocal rotator and either a reciprocal rotator or a non-reciprocal rotator, and the direction of separating the ordinary ray and extraordinary ray of the birefringent crystal plate is determined by the separation of the second birefringent crystal plate. The direction of separation of the first and third birefringent crystal plates is different from the direction of separation of the first and third birefringent crystal plates. The rotation direction of each rotator of the first group is set so that the polarization directions of the separated ordinary ray and extraordinary ray coincide with each other at the incident end surface of the second birefringent crystal plate, and the rotation direction of the liquid crystal plate is set. Setting the polarization direction so that the polarization planes of the two light beams that coincide at the output end of the second birefringent crystal plate are orthogonal to each other at the input end surface of the third birefringent crystal plate, The rotation direction of each of the second group of rotors is set, the first birefringent crystal plate is provided with one or more light beam entrance ports, and the third birefringent crystal plate is provided with a plurality of light beam exit ports. An optical switch characterized by comprising: 3. Three birefringent crystal plates are arranged at predetermined intervals along the traveling direction of the light beam, and a first birefringent rotator consisting of two non-reciprocal rotators is arranged between the first and second birefringent crystal plates. The rotors of the group are arranged in the same plane so that these non-reciprocal rotors rotate in different directions, and the directions of the external magnetic fields acting on each of these non-reciprocal rotors are different from each other. The magnitude and direction of these external magnetic fields are set, and the second birefringent crystal plate is arranged so that the polarization direction matched by the non-reciprocal rotator becomes an ordinary ray, and the second and third birefringent Also between the crystal plates, a second group of rotors consisting of two non-reciprocal rotors is arranged in the same plane so that these non-reciprocal rotors rotate in different directions from each other, and these non-reciprocal rotators The magnitude and direction of these external magnetic fields are set so that the directions of the external magnetic fields acting on each are different from each other, the first birefringent crystal plate is provided with one or more light beam entrance ports, and the third An optical switch comprising a birefringent crystal plate provided with a plurality of light beam exit ports.