JP2001242420A - Four-port optical circulator and four-port optical switch - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small four-ports optical circulator improved in optical coupling efficiency at a low cost. SOLUTION: A first birefringent plate 11, the first polarized wave rotating device (18, 19a, 19b), an optical path shifting device 30, the second polarized wave rotating device (19c, 19d, 20), and the second birefringent plate 12 are disposed in the order in a forward direction in an optical path. The first and second polarized wave rotating devices include one 45-degree Faraday rotor and a half-wave plate. In the optical path shifting device 30, first birefringent plate pair (13, 14) laminating the tow birefringent plates in a direction intersecting the optical path, and the second birefringent plate pair (15, 16) are disposed to face opposite along the optical path, and a prism 17 is inserted and disposed between the first birefringent plate pair and the second birefringent plate pair.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical circulator and an optical switch which are components of an optical fiber communication system and the like, and more particularly to a method of multiplexing a plurality of systems of light by interposing between four optical fibers. The present invention relates to a four-port optical circulator and a four-port optical switch that are used to regulate the input / output direction of a light beam or to switch an input / output port by demultiplexing.

[0002]

2. Description of the Related Art FIGS.
The four-port optical circulator (hereinafter referred to as an optical circulator) disclosed in Japanese Patent Publication No. 01-001 is shown as a conventional example. (A)
Shows a perspective view of the arrangement of each optical element in the XYZ three-dimensional orthogonal coordinate system, and (B) shows an arrangement position of each port to. (C) to (E) show the optical axis direction of the half-wave plate used in this optical system. In the following description, in order to define the traveling direction of a light beam passing through an optical system and the rotation direction of the vibration direction (polarization plane) of an electric field component, the direction traveling in the Z-axis direction from the origin is defined as a forward direction. When viewed in the Z-axis direction from the origin, clockwise is defined as + (clockwise), and counterclockwise is defined as-(counterclockwise).

According to this conventional example, the birefringent plates 1-4 are Z
The birefringent plates 1 and 4 have an optical axis (slow axis or fast axis) in the ZX plane, and the birefringent plates 2 and 3 have an optical axis in the YZ plane. I have. A 45 is used between the adjacent birefringent plates 1 to 4 as a non-reciprocal rotator.
The Faraday rotators 5a to 5c are interposed. The Faraday rotators 5a to 5c rotate the plane of polarization of the incident light beam by +45 degrees irrespective of the traveling direction and emit the light beam. Further, a reciprocal rotator group (6a to 6a) including one or a plurality of reciprocal rotators is provided between the birefringent plates 1 to 4.
d, 6e and 6f to 6i) are interposed. In this figure, it is assumed that a half-wave plate is adopted as a reciprocal rotator,
The optical axis of each half-wave plate is set appropriately. As is well known, the half-wave plate performs an operation of rotating the plane of polarization of the incident light beam in a direction symmetric with respect to the optical axis.

In this example, the birefringent plates 1 and 4 convert a light beam incident from a port into two light beams whose polarization directions (polarization planes) of electric field components are orthogonal to each other (hereinafter referred to as a polarization orthogonal beam pair). At the same time, the polarization orthogonal beam pair is incident, combined as one light beam, and exits from the port. The optical system composed of the birefringent plates 2 and 3 and the half-wave plate 6e and the 45-degree Faraday rotator 5b interposed between these birefringent plates has two light beams whose polarization planes are parallel to each other. (Hereinafter referred to as a "polarized parallel beam pair"), and operates as an optical path shifter 7 for directing the light beam or shifting the optical path and emitting the light beam according to the incident directions of the two light beams. In this example, when the polarization planes of the two light beams in the parallel polarization beam pair are parallel to the ZX plane or the YZ plane, the light beams travel straight in the forward direction and shift out in the Y-axis direction in the reverse direction. It has become.

Between the birefringent plates 1 and 2 and between the birefringent plates 3
The reciprocal rotators intervening between and 4 are four ４
The configuration is such that the wave plates are arranged on a straight line parallel to the Z axis passing through the ports (C) and (E). Thereby, the two light beams transmitted between the birefringent plates 1 and 4 individually transmit through any of these four half-wave plates.

With the above optical system, the optical circulator inputs and outputs a light beam according to the optical path direction of the port →→→→. 2 (A1) to (A3), (B1) to
(B3) shows the optical path diagram. (A1) to (A3)
Indicates an optical path from the port (solid line) and an optical path from the port (dashed line). (B1)-
(B3) shows an optical path (solid line) from the port and an optical path (dashed line) from the port. Also,
(A1) and (B1) are optical paths viewed from the YZ plane.
3) (B3) is an optical path viewed from the XY plane. (A2)
(B2) shows the origin O when the light beam is projected on the XY plane.
The polarization plane viewed from the side is shown.

In the optical system of the optical circulator, a variable Faraday rotator is used instead of the 45-degree Faraday rotator, and the rotation angles of the polarization plane are set to +45 degrees and -45 degrees according to the direction of the magnetic field applied in the Z-axis direction. By appropriately switching, the light beam incident from the port (port) is switched between the port and the port (port and port) and output, or the light incident from the port (port) is output to the port and the port (port and port). And a four-port optical switch (hereinafter referred to as an optical switch) for switching and outputting.

[0008]

In the above conventional example, four half-wave plates are interposed between the birefringent plates 1 and 2 and between the birefringent plates 3 and 4. The optical axes of these four half-wave plates must be set so that the plane of polarization of the incident light beam is exactly rotated clockwise or counterclockwise by 45 °. If this optical axis is slightly deviated, the two light beams in the polarization orthogonal beam pair or the polarization parallel beam pair existing in the middle of the optical path will not be exactly orthogonal or parallel, and the incident light A large loss occurs in the ratio of the light intensity of the light beam to the light beam to be emitted (light coupling efficiency). That is, two light beams orthogonal to each other are incident on the birefringent plate 1 in the reverse direction or the birefringent plate 4 in the forward direction, and a light beam that travels straight as ordinary light and a light beam that refracts as extraordinary light are emitted on the exit surface side. When the light is coupled by the optical axis, the optical axis of the birefringent plate and the polarization plane of the light beam corresponding to ordinary light or extraordinary light are not exactly orthogonal or parallel, and a part of the incident light beam is separated as extraordinary light or ordinary light. Resulting in.

In this conventional optical circulator or optical switch, as many as nine half-wave plates are interposed in the optical path. Therefore, it is difficult to accurately control the polarization plane of the light beam, and there is a problem that the optical coupling efficiency is deteriorated. Further, the conventional optical circulator uses three Faraday rotators. As is well known, the Faraday rotator applies a magnetic field generated by a permanent magnet or an electromagnet to Y ₃ Fe ₅ O.
₁₂ (YIG) is an element applied to a magneto-optical crystal to rotate the plane of polarization of light traveling in the direction of the magnetic field. Therefore, conventional optical circulators and optical switches using three Faraday rotators are extremely difficult to reduce in size in addition to reducing the cost. Of course, there are problems such as an increase in the number of parts due to the use of a large number of half-wave plates and an increase in manufacturing costs for accurately setting the optical axis and arrangement of the half-wave plates. The circulator and the optical switch have a configuration that is essentially difficult to reduce in price and reduce in size.

Accordingly, the present invention provides a four-port optical circulator and a four-port optical switch in which the number of parts including the half-wave plate is reduced, the optical coupling efficiency is improved, and the cost and size are reduced. It is intended to be.

[0011]

According to a first aspect of the present invention, a first birefringent plate, a first polarization rotator, an optical path shifter, a second polarization rotator, and a second birefringence are traced along the optical path in a forward direction. An optical system in which the plates are arranged in order, and a first optical system for inputting and outputting a light beam to and from the optical system
1st port → 2nd port → 3rd port
A 4-port optical circulator for inputting / outputting a light beam in accordance with an optical path direction from a port to a fourth port to a first port, wherein the first birefringent plate receives the light beam from the first port and the third port in a forward direction. A polarization orthogonal beam pair composed of two light beams whose electric field vibration components are orthogonal to each other is emitted from the first position and the third position, and the polarization orthogonal beam pair is inverted from the first direction and the third position. From the first port and the third port after being multiplexed into one light beam, and the second birefringent plate receives the light beam from the second port and the fourth port in the opposite direction. The polarization orthogonal beam pair is emitted from the second position and the fourth position, and the polarization orthogonal beam pair is incident from the second position and the fourth position from the forward direction and multiplexed into one light beam. The second port And the first and second polarization rotators are configured to include one 45-degree Faraday rotator and a half-wave plate, so that electric field vibration components are parallel to each other. The polarization parallel beam pair consisting of the light beam is incident and emitted as the polarization orthogonal beam pair, and the polarization orthogonal beam pair is emitted as the polarization parallel beam pair, and the optical path shifter is A first birefringent plate pair and a second birefringent plate pair formed by laminating two birefringent plates in a direction intersecting the optical path are arranged to face each other along the optical path, and the first birefringent plate pair and the second birefringent plate pair A prism is inserted between the refraction plate pair, and a polarized parallel beam pair consisting of two light beams whose electric field vibration components incident in the forward or reverse direction are parallel to each other according to the vibration direction of the component. Optical path with and without the prism Is selectively transmitted, and the incident polarized parallel beam pair is emitted from a position corresponding to straight traveling, or a distance between the first position and the third position or between the second position and the fourth position. The light is shifted by an amount corresponding to the light to be emitted.

[0012] The second invention is directed to the fourth invention according to the first invention.
An optical switch having an optical system in which the 45-degree Faraday rotator is replaced with a variable Faraday rotator in the port optical circulator, wherein the electric field oscillation direction of the light beam incident on the variable Faraday rotator is +45 degrees or a predetermined direction. According to the operation of rotating the light beam by −45 degrees, the light beam incident from each of the first, second, third, and fourth ports is changed to the second or fourth port, and the third light beam, respectively.
Alternatively, a four-port optical switch that switches and emits light to the first port, the fourth or second port, or the first or third port.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS === Optical System === FIGS. 3A to 3C show an optical system of a four-port optical circulator according to an embodiment of the present invention. (A) is XY
FIG. 2 is a perspective view showing an arrangement of each optical element in a Z three-dimensional orthogonal coordinate system. FIG.
The arrangement relationship of the half-wave plate and the optical axis direction are shown. (C) shows a layout of ports.

In the optical circulator of this embodiment, the positional relationship between the ports and the input / output relationship of the light beam are the same as those of the conventional optical circulator illustrated in FIG. However, in the present embodiment, the configuration of the optical path shifter 30 is significantly different from the conventional one. Another difference is that the number of half-wave plates disposed before and after the optical path shifter 30 along the optical path is two instead of the conventional four. (A) (B).

The birefringent plate 11 emits a port or a light beam incident in a forward direction from the port as a polarization orthogonal beam pair, and outputs a polarization orthogonal beam pair having the same polarization plane as this emission state from this emission position. The light enters in the opposite direction, is combined into one light beam, and is emitted to the port or the port. Similarly, the birefringent plate 12 also emits a port or a light beam incident in the opposite direction from the port as a polarization orthogonal beam pair, and also forwards a polarization orthogonal beam pair having the same emission state from its emission position in a forward direction. Out to the port or port.

The optical path shifter 30 includes two birefringent plates 13
, 14 and 15 and 16 are superposed in the Y-axis direction, and two pairs of birefringent plates 21 and 22 are arranged to face each other along the Z-axis.
And a prism 17 in the form of a regular prism is interposed therebetween. The optical axes of the birefringent plates 13 to 16 are parallel to the YZ plane, and the optical axes of the two birefringent plates 13 and 14 and 15 and 16 included in each birefringent plate pair are respectively relative to the ZX plane. It is symmetric. In the two birefringent plate pairs 21 and 22, the optical axes of the birefringent plates 13 and 15 and the birefringent plates 14 and 16 facing each other are symmetric with respect to a plane parallel to the XY plane. The regular prism prism 17 is
When the light beam enters the slope along the Z-axis direction, the light beam shifts in the Y-axis direction while maintaining the X coordinate of the optical path, and exits along the Z-axis from the opposing surface. And prism 1
Numeral 7 is disposed so as not to intervene on any of the four straight lines assuming four straight lines parallel to the Z-axis passing through each port 1 to.

A Faraday rotator 18 is inserted between the birefringent plate 11 and the optical path shifter 30, and the birefringent plate 1
Faraday rotator 20 between optical path shifter 2 and optical path shifter 30
Is inserted. The Faraday rotators 18 and 20 change the plane of polarization of the incident light beam by +4 regardless of the traveling direction.
The light is emitted after being rotated by 5 degrees. Further, between the Faraday rotator 18 and the optical path shifter 30, two half-wave plates 19a and 19b are provided.
Between the optical path shifter 30 and two half-wave plates 19
c and 19d are inserted respectively. 1/2 wave plate 19a
19b and 19c and 19d are arranged symmetrically with respect to the YZ plane, and their optical axes are also symmetrical and set to be inclined by 22.5 degrees with respect to the X axis. In this example,
波長 wavelength plate 19 in the direction rotated by 22.5 degrees of X axis
The optical axis of a is set.

=== Optical Path of Light Beam === FIG. 4 shows an optical path of a light beam in an optical circulator employing the optical system of the present embodiment.
(A3), (B1), and (B3) are the same as those in FIG. (A1) to (A3) show optical paths until the light beam that has entered the port exits from the port.
1) to (B3) show optical paths from port to port.

<Port → Port> The light beam P1a incident on the birefringent plate 11 from the port exits through the ordinary optical path and exits through the extraordinary optical path and the light beam P11 oscillating in the Y-axis direction. Light beam P1 oscillating in the axial direction
2. The light beams P11 and P12 both pass through the Faraday rotator 18 and are individually halved.
When transmitted through the wave plates 19a and 19b, a polarized parallel beam pair consisting of two light beams vibrating in the X-axis direction is formed.
This pair of parallel polarized beams is the birefringent plate 1 of the optical path shifter 30.
3 is incident in the forward direction.

When a light beam oscillating in the X-axis direction is incident, the optical path shifter 30 converts the light beam into the birefringent plates 13 to 13.
The light passes through the ordinary light path at 16 and the light path without the prism 17 interposed. That is, the two light beams that have entered the birefringent plate 13 in the forward direction exit through the ordinary light path of the birefringent plate 13. Since the prism 17 is arranged so as not to be interposed on the optical path that goes straight, the two light beams directly enter the birefringent plate 15 in the forward direction. Since the birefringent plate 15 also receives the light beam oscillating in the X-axis direction as ordinary light, the polarized parallel beam pair incident on the optical path shifter 30 in the forward direction exits from the optical path shifter 30 without shifting the optical path. .

The two light beams in the polarized parallel beam pair emitted from the optical path shifter 30 in the forward direction are individually １ ／.
It passes through the wave plates 19c and 19d, passes through the 45-degree Faraday rotator 20, and becomes a polarization orthogonal beam pair consisting of two light beams vibrating in the X-axis direction and the Y-axis direction, respectively. This polarized orthogonal beam pair is incident on the birefringent plate 12 from the forward direction, and the light oscillating in the X-axis direction is combined with the light beam oscillating in the Y-axis direction that travels straight through the extraordinary optical path and becomes 1
Light beams. By arranging the port corresponding to this coupling position, the light beam P2a is emitted from the port.

<Port → Port> On the other hand, when the light beam P2b is incident on the birefringent plate 12 from the port in the opposite direction, it is emitted as a pair of polarized orthogonal beams P21 and P22, and both light beams in this beam pair are Faraday While transmitting through the rotator 20, the 波長 wavelength plate 1
The light beam passes through 9c and 19d and is incident on the birefringent plate 15 of the optical path shifter 30 in the opposite direction as a polarized parallel beam pair in which the light beam oscillates in the Y-axis direction.

When a light beam oscillating in the Y-axis direction enters, the optical path shifter 30 converts the light beam into the birefringent plates 13 to 13.
The light passes through the extraordinary light path at 16 and the light path interposed by the prism 17, and is emitted from a position shifted in the Y-axis direction with respect to the incident position. That is, the light beam oscillating in the Y-axis direction is incident on the birefringent plate 15 in the opposite direction as extraordinary light, and is emitted after being shifted by a predetermined distance in the Y-axis direction. A prism 1 is placed on the optical path of the light beam traveling in the opposite direction from this emission position.
7, the prism 17 emits this light beam while further shifting it in the Y-axis direction. The birefringent plate 14 is placed on the optical path of the light beam traveling in the opposite direction from this emission position.
There is. The vibration direction of the light beam incident on the optical path shifter 30 in the opposite direction is maintained in the Y-axis direction up to this point.
The birefringent plate 14 emits this light beam in the opposite direction while further shifting the light path through the extraordinary light path.

In the optical path shifter 30, the birefringent plate 1
The optical characteristics of the prism 17, the prism 17 and the birefringent plate 14 are such that, when a light beam oscillating in the Y-axis direction is incident, the light path is shifted by a predetermined distance in the Y-axis direction and emitted, and the sum of those distances is calculated. Are set to be equal to the distance between a straight line parallel to the Z-axis passing through the port and a straight line parallel to the Z-axis passing through the port, and the shift direction is set to be a direction from the port toward the port.

The polarized parallel beam pairs emitted in the opposite direction from the optical path shifter 30 pass through the 45-degree Faraday rotator 18 and each light beam of this beam pair is individually
9a and 19b are transmitted to form a polarization orthogonal beam pair. The beam pair is incident on the birefringent plate 11 in the opposite direction, is coupled at the exit surface, and exits from the port as one light beam P3a.

<Port → and Port →> FIG.
The optical paths (A1) to (A3) in which the light beam P3b incident from the port exits as a light beam P4a from the port.
And optical paths (B1) to (B1) in which the light beam P4b incident from the port exits from the port as the light beam P1b.
3). The representation in this figure is the same as in FIG. 2 and FIG.

The light beam P3b incident on the port emits a light beam P4a from the port through a path whose optical path from the port to the port is symmetric with respect to the XY plane. Further, the light beam P4b incident on the port emits the light beam P1b from the port through a path in which the optical path from the port to the port is symmetric with respect to the XY plane. That is,
The optical path from port to port is an optical path shifter 30.
, A path passing through the birefringent plate 14, the prism 17, and the birefringent plate 16 in this order, and an optical path from the port to the port includes a path passing through the optical path shifter 30 in the order of the birefringent plate 16 and the birefringent plate 13.

=== Supplement / Other Embodiments === <Other Optical System> FIGS. 6A and 6B show an example of an optical system substantially equivalent to the above embodiment. (A) shows the optical configuration of the optical path shifter and its operation as a YZ plane projection diagram. (B) shows an arrangement relationship among the ports (1) to (3) as an XY plane projection diagram. In contrast to the optical path shifter 30 of the above embodiment, this optical path shifter 30b has birefringent plates 13-1.
6 are replaced by birefringent plates 13b to 16b, respectively, and the optical axis directions of the birefringent plates 13b to 16b are symmetric with respect to the optical axes of the birefringent plates 13 to 16 on the ZX plane. Has become. As a result, the light beam that has entered the optical path shifter 30b as ordinary light passes through the optical path interposed by the prism 17 indicated by the solid line in the figure, and the optical path shifts before and after the light beam enters the optical path shifter 30b.
On the other hand, the light beam incident as the extraordinary light passes through the optical path shown by the broken line in the drawing without the prism 17, and the optical path does not shift before and after entering the optical path shifter 30b (A).

Further, the ports are arranged such that the distance between the ports and the distance between the ports and the distance between the optical paths shifted by the prism are equal to each other. The position is closer to the X axis, and the distance between the two ports arranged on the same surface is shorter (B).

<4 Port Optical Switch> In the above embodiment, the optical circulator can be an optical switch by configuring an optical system in which the Faraday rotator is replaced with a variable Faraday rotator. The Faraday rotator can variably set the direction of rotation of the polarization plane to ± 45 degrees by switching the direction of a magnetic field applied in parallel (Z-axis direction) to the traveling direction of light by using an electromagnet. When set to +45 degrees, the light beam from the port follows the same optical path as the optical circulator and exits to the port, and when set to -45 degrees, the light beam from the port exits to the port.

When the direction of rotation of the Faraday rotator is set to +45 degrees, the light beam incident from the port in conjunction with the operation of switching the output port of the light beam from the port changes the optical path similar to that of the optical circulator. The light is emitted to the port by tracing, and is emitted to the port when the angle is set to -45 degrees. FIG. 7 shows an optical path in the optical system when the Faraday rotator is a variable Faraday rotator. This figure shows the optical path when the direction of the magnetic field is opposite to that of the optical circulator and the direction of rotation of the polarization plane is set to -45 degrees. (A1) to (A3) show that the light beam P1a incident from the port is a light beam P4c from the port.
(B1) to (B3).
Indicates an optical path in which the light beam P2a incident from the port 2 is emitted from the port as the light beam P1c.

<Supplement> In the above embodiment, the light beam travels along the Z axis, and the light beam entrance / exit surface of each optical element is orthogonal to this light beam. As is well known, the light beam input / output surface of the birefringent plate need not necessarily be orthogonal to the light beam. For example, as shown in FIG. 8, a plane intersecting the XY plane may be set as the input / output plane. In this case, the light beam incident from the port is refracted at a predetermined angle according to the respective refractive indexes corresponding to the ordinary light path and the extraordinary light path. In this example, two light beams separated to the left and right with respect to the incident position are emitted.

[0033]

In the four-port optical circulator, by devising the optical configuration of the optical path shifter, it is possible to reduce the number of half-wave plates required from nine conventionally to four. further,
Conventionally, three Faraday rotators, which were required three, can be replaced with two. Therefore, while improving the coupling efficiency,
The size and cost of the four-port optical circulator can be reduced. If the Faraday rotator is a variable Faraday rotator, a small, high-performance four-port optical switch can be realized at low cost.

[Brief description of the drawings]

FIG. 1 shows an example of a conventional four-port optical circulator as a schematic configuration diagram of an optical system. (A) is a perspective view of the entire optical system in the XYZ rectangular coordinate space, (B) is a layout view of ports on the XY plane, and (C) to (E) are optical layout views of a half-wave plate on the XY plane. Is shown.

FIG. 2 shows a path diagram of a light beam passing through the optical system of the conventional example. (A1) to (A3) show an optical path from the port to the port and an optical path from the port to the port, and (B1) to (B3) show an optical path from the port to the port and an optical path from the port to the port. . (A1) and (B1) are YZ plane projection diagrams, and (A1)
2) (B2) is XY plane projection, (A3) (B3) is ZX
Each shows a plane projection view.

FIG. 3 shows a four-port optical circulator according to an embodiment of the present invention as a schematic configuration diagram of an optical system. (A) is a perspective view of the entire optical system in the XYZ rectangular coordinate space,
(B) is an optical arrangement diagram of a half-wave plate on the XY plane,
(C) shows the layout of ports on the XY plane.

FIG. 4 shows a path diagram of a light beam passing through the optical system of the above embodiment. (A1) to (A3) show the optical path from the port to the port, and (B1) to (B3) show the optical path from the port to the port. (A1) (B
1) is a YZ plane projection view, (A2) and (B2) are XY plane projection views, and (A3) and (B3) are ZX plane projection views.

FIG. 5 shows a path diagram of a light beam passing through the optical system of the embodiment. (A1) to (A3) show the optical path from the port to the port, and (B1) to (B3) show the optical path from the port to the port. (A1) (B
1) is a YZ plane projection view, (A2) and (B2) are XY plane projection views, and (A3) and (B3) are ZX plane projection views.

FIG. 6 is a configuration diagram of another embodiment of the four-port optical circulator of the present invention. (A) is an optical configuration diagram on the YZ plane of the optical path shifter, (B) is XY
FIG. 4 shows a layout of ports on a plane.

FIG. 7 shows a path diagram of a light beam passing through the optical system of the four-port optical switch according to the embodiment of the present invention. (A
1) to (A3) show the optical path from the port to the port, and (B1) to (B3) show the optical path from the port to the port. (A1) and (B1) are YZ plane projection diagrams,
(A2) and (B2) show XY plane projection diagrams, and (A3) and (B3) show ZX plane projection diagrams, respectively.

FIG. 8 shows, as another embodiment of the present invention, an arrangement diagram of a birefringent plate in which the light beam input / output surfaces of the birefringent plate are not orthogonal to the optical path. (A) is a perspective view in the XYZ orthogonal coordinate space, (B) is an arrangement view in the XY plane.

[Explanation of symbols]

 1-4, 11-16 13b-16b Birefringent plate 5a-5c, 18, 20 Faraday rotator 6a-6i, 19a-19d 1/2 wavelength plate 17 Prism 7, 30, 30b Optical path shifter

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Tomokazu Imura 5-36-11 Shimbashi, Minato-ku, Tokyo Inside Fuji Electric Chemical Co., Ltd. (72) Inventor Tsugio Tokumas 5-36-11 Shimbashi, Minato-ku, Tokyo F-term in Fuji Electric Chemical Co., Ltd. (reference) 2H041 AA14 AA17 AB30 AC04 AZ01 AZ05 AZ08 2H099 AA01 BA06 CA08 CA11 DA00 5K002 AA07 BA05 BA61 FA01

Claims (2)

[Claims] 1. An optical system in which a first birefringent plate, a first polarization rotator, an optical path shifter, a second polarization rotator, and a second birefringent plate are sequentially arranged along an optical path in a forward direction. A system and first to fourth ports for inputting and outputting a light beam to and from the optical system are provided, and a light beam is input / output according to the optical path direction of a first port → second port → third port → fourth port → first port. The first birefringent plate, wherein the first birefringent plate is a polarized wave comprising two light beams in which a light beam is incident in a forward direction from a first port and a third port and electric field vibration components are orthogonal to each other. An orthogonal beam pair is emitted from the first position and the third position, and a polarized orthogonal beam pair is incident from the first position and the third position from the opposite direction and multiplexed into one light beam to be combined with the first port. And a third port, and the second birefringent plate is A light beam is incident from the port and the fourth port in the reverse direction, the polarization orthogonal beam pair is emitted from the second position and the fourth position, and the polarization orthogonal beam pair is forwardly transmitted from the second position and the fourth position. The light enters from four positions, is combined into one light beam, and is emitted to the second port and the fourth port. The first and second polarization rotators each include one 45-degree Faraday rotator and a half. A polarization parallel beam pair composed of two light beams whose electric field vibration components are parallel to each other, and the polarization parallel beam pair is emitted as the polarization orthogonal beam pair and the polarization orthogonal beam pair. Are output as the polarized parallel beam pair, and the optical path shifter includes a first birefringent plate pair and a second birefringent plate pair formed by stacking two birefringent plates in a direction intersecting the optical path. Along with the first A prism is inserted between the birefringent plate pair and the second birefringent plate pair, and a polarized parallel beam pair consisting of two light beams whose electric field vibration components incident in the forward or reverse direction are parallel to each other. Depending on the vibration direction of the component, the prism parallel beam is selectively transmitted through the optical path interposed and the optical path not interposed, and the incident polarized parallel beam pair is emitted from a position corresponding to straight traveling, or the first position. A four-port optical circulator for shifting an optical path by an amount corresponding to a distance between the first position and the third position or the distance between the second position and the fourth position. 2. The four-port optical circulator according to claim 1, further comprising an optical system in which the 45-degree Faraday rotator is replaced with a variable Faraday rotator, wherein light incident on the variable Faraday rotator is incident. In response to the operation of rotating the electric field oscillation direction of the beam by +45 degrees or -45 degrees in a predetermined direction and emitting the light beam, the light beams incident from the first, second, third, and fourth ports are respectively transmitted to the second port. Alternatively, the four-port optical switch switches and emits light to a fourth port, the third or first port, the fourth or second port, or the first or third port.