JP2009009073A - Wavelength selecting switch - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small wavelength selecting switch having high resolution of a diffraction grating and excellent wavelength transmission band characteristics. <P>SOLUTION: The wavelength selecting switch 10 includes: a lens array 20; a first lens 30; a beam expander 40 disposed between the first lens 30 and a focus 30a of the first lens 30 on the opposite side to light input/output ports 101 with the first lens 30 placed between, and converging convergent light from the first lens 30 as it is in the arrayed direction of the light input/output ports 101 at the focus 30a of the first lens 30 while converging light transmitted through the first lens 30, larger in a direction orthogonal to the arrayed direction of the light input/output ports 101; the diffraction grating 60; and a plurality of mirrors 80. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a wavelength selective switch capable of branching or combining light of different wavelengths in optical wavelength division multiplexing communication.

  With the spread of optical wavelength division multiplexing communication, wavelength selective switches that multiplex or demultiplex optical signals for each wavelength have become key devices for optical communication.

  FIG. 5 shows a schematic configuration diagram of a conventional wavelength selective switch.

  The wavelength selective switch 200 in FIG. 5 includes a microlens array 102 that collimates the light output from the light input / output port 101c disposed at the focal position, and a high numerical aperture lens that converges the light from the microlens array 102. 103, the second lens 104 having the same focal position as the high numerical aperture lens 103, the diffraction grating 105 that reflects light from the second lens 104 at different angles for each wavelength, and the focal point of the second lens 104. And an array mirror 106 that reflects light transmitted through the second lens 104 from the diffraction grating 105 at an arbitrary angle toward the second lens 104 (see, for example, Patent Documents 1 to 3).

As a result, the light reflected by the array mirror 106 at an arbitrary angle can be converged to different light input / output ports for each wavelength according to the angle of each mirror of the array mirror 106. As described above, the high numerical aperture lens 103 changes the angle of the light reflected by the diffraction grating 105 and transmitted through the second lens 104 out of the light reflected by the array mirror 106, and the light from the light input / output port 101c. It has a function of giving an offset to the optical axis.
JP 2003-101479 A JP 2006-276216 A JP 2006-284740 A

FIG. 6 shows a schematic configuration diagram of a wavelength selective switch in which the reflection type diffraction grating of FIG. 5 is replaced with a transmission type diffraction grating. In FIG. 6, P5-1, P5-2, and P5-2 ′ are confocal optical systems. Further, if the focal length of the microlens array 102 is f1, and the focal length of the first lens 103 is f2, the image magnification can be expressed by Equation 1.
(Expression 1) Image magnification = f2 / f1

Assuming that the mode field diameter of the optical input / output port 101 is M1, the beam spot size at P5-2 can be expressed by Equation 2. Here, since P5-2 and P5-2 ′ are confocal optical systems in which the same second lens 104 is disposed, the image magnification is 1 and the beam spot sizes at P5-2 and P5-2 ′ are equal. .
(Expression 2) Beam spot size = M1 × f2 / f1

When the reflection angle of the array mirror 106 is θ, the pitch between the light input / output port 101 and the microlens array 102 can be expressed by Equation 3. Here, since the reflection angle θ of the array mirror 106 is limited, in order to obtain a predetermined inter-port pitch, it is necessary to increase the focal length of the first lens 103.
(Expression 3) Port pitch = tan (2θ) × f2

  Therefore, the beam spot size at the array mirror 106 becomes larger from the above formula 1, and there is a problem that the wavelength transmission band characteristic becomes insufficient unless the area of each reflection mirror of the array mirror 106 is enlarged. Here, when the area of each reflection mirror of the array mirror 106 is enlarged, the wavelength transmission band characteristics can be satisfied, but there is a problem that the array mirror 106 is enlarged. Furthermore, in order to improve the resolution of the diffraction grating 105, it is necessary to enlarge the beam size irradiated to the diffraction grating 105 and to make the focal length of the second lens 104 sufficiently long, and the wavelength selective switch 200 is enlarged. There was a problem.

  Therefore, an object of the present invention is to provide a small wavelength selective switch having a high diffraction grating resolution and excellent wavelength transmission band characteristics.

  In order to achieve the above object, a wavelength selective switch according to the present invention is characterized in that a beam expander is disposed between the first lens and the focal point of the first lens.

  Specifically, the wavelength selective switch according to the present invention inputs / outputs light including one or more wavelengths, and faces the plurality of light input / output ports provided in a side-by-side straight line from the light input / output port. A lens array arranged to make the light parallel light, and a first lens arranged on the opposite side of the light input / output port with the lens array in between, and making the light from the lens array converged light; The light input / output port is disposed on the opposite side of the light input / output port with the first lens in between and between the first lens and the focal point of the first lens. The beam expander for converging the convergent light from the first lens as it is in the arrangement direction of the light, and converging the light transmitted through the first lens more greatly in the direction orthogonal to the arrangement direction of the light input / output ports. A second lens arranged so that the light from the spanner is parallel light; and the light input / output port on a surface that receives light transmitted through the second lens out of light input / output from the light input / output port A diffraction grating that reflects light transmitted through the second lens at a different angle for each wavelength on a grating surface on which a plurality of gratings parallel to the arrangement direction of the light is formed, and is output from the light input / output port and reflected by the diffraction grating Then, the light transmitted through the second lens is reflected, and each reflected light is transmitted through the second lens, reflected by the diffraction grating, and again transmitted through the beam expander, the first lens, and the lens array. And a plurality of mirrors each having a light reflection angle set so as to converge on one of the light input / output ports.

  The wavelength selective switch has a high diffraction grating resolution, excellent wavelength transmission band characteristics, and a small size.

  In order to achieve the above object, a wavelength selective switch according to the present invention is characterized in that a beam expander is disposed between the first lens and the focal point of the first lens.

  Specifically, the wavelength selective switch according to the present invention inputs / outputs light including one or more wavelengths, and faces the plurality of light input / output ports provided in a side-by-side straight line from the light input / output port. A lens array arranged to make the light parallel light, and a first lens arranged on the opposite side of the light input / output port with the lens array in between, and making the light from the lens array converged light; The light input / output port is disposed on the opposite side of the light input / output port with the first lens in between and between the first lens and the focal point of the first lens. The beam expander for converging the convergent light from the first lens as it is in the arrangement direction of the light, and converging the light transmitted through the first lens more greatly in the direction orthogonal to the arrangement direction of the light input / output ports. A second lens arranged so that the light from the spanner is parallel light; and the light input / output port on a surface that receives light transmitted through the second lens out of light input / output from the light input / output port A diffraction grating that transmits light transmitted through the second lens at a different angle for each wavelength on a grating surface on which a plurality of gratings parallel to the arrangement direction of the grating are formed, and opposite the second lens with the diffraction grating in between A third lens disposed on the side, and the light output from the light input / output port and transmitted through the lens array, the first lens, the beam expander, the second lens, the diffraction grating, and the third lens Respectively reflected, each of the reflected light is transmitted again through the third lens, the diffraction grating, the second lens, the beam expander, the first lens, and the lens array. Characterized in that it comprises a plurality of mirrors reflection angle of light is set respectively so as to converge to one of the input and output ports.

  The wavelength selective switch has a high diffraction grating resolution, excellent wavelength transmission band characteristics, and a small size.

  In the wavelength selective switch according to the present invention, it is preferable that the diffraction grating has a length in a direction orthogonal to the arrangement direction of the optical input / output ports longer than the arrangement direction of the optical input / output ports.

  The wavelength selective switch can be further downsized.

  In the wavelength selective switch according to the present invention, it is preferable that the length of the mirror in a direction orthogonal to the arrangement direction of the optical input / output ports is shorter than the arrangement direction of the optical input / output ports.

  The wavelength selective switch can be further downsized.

  INDUSTRIAL APPLICABILITY The present invention can provide a small wavelength selective switch with high diffraction grating resolution and excellent wavelength transmission band characteristics.

  Hereinafter, the present invention will be described in detail with specific embodiments, but the present invention is not construed as being limited to the following description. In the following embodiments, light is output from one light input / output port (light input / output port 101d described later) and light is transmitted to other light input / output ports (light input / output ports 101a to 101g described later) for each wavelength. However, the same applies to the configuration in which the light output from any one of the other optical input / output ports 101a to 101g is divided into wavelengths and input to the one optical input / output port 101d. Can be explained. The optical input / output port 101 is a generic term for the optical input / output ports 101a to 101g.

(First embodiment)
FIG. 1 shows a schematic configuration diagram of a wavelength selective switch according to the first embodiment. 1A shows a wavelength selective switch in the xz plane, and FIG. 1B shows a wavelength selective switch in the yz plane. In FIG. 1, the lens array 20, the first lens 30, the beam expander 40, and the second lens 50 are operated for the optical path from the light input / output port 101d, reflected by the diffraction grating 60, and reaching the mirror 80b. In order to express, the spread of the light beam is indicated by a broken line, and the principal ray is indicated by a solid line. For other optical paths, only the principal ray may be indicated by a one-dot chain line in order to avoid complications in the figure.

  The wavelength selective switch 10 has a reflective configuration, that is, a configuration in which light is reflected by the diffraction grating 60. The wavelength selective switch 10 according to the first embodiment inputs / outputs light including one or more wavelengths and opposes a plurality of light input / output ports 101 provided in a side-by-side and straight line. A lens array 20 arranged so as to be parallel light, and a first lens 30 arranged on the opposite side of the light input / output port 101 with the lens array 20 in between to make the light from the lens array 20 converge light The first lens 30 is disposed on the opposite side of the light input / output port 101 and between the first lens 30 and the focal point 30a of the first lens 30. In the arrangement direction of the output port 101, the converged light from the first lens is converged as it is, and in the direction orthogonal to the arrangement direction of the light input / output port 101, the light transmitted through the first lens 30 is more converged. The light transmitted through the second lens 50 among the light input / output from the light input / output port 101 and the second lens 50 arranged so that the light from the expander 40 and the light from the beam expander 40 become parallel light. A diffraction grating 60 for reflecting light transmitted through the second lens 50 at different angles for each wavelength on a grating surface 62 in which a plurality of gratings parallel to the arrangement direction of the light input / output port 101 are formed on the receiving surface; The light output from the output port 101 and reflected by the diffraction grating 60 and transmitted through the second lens 50 is reflected, and each of the reflected light passes through the second lens 50 and is reflected by the diffraction grating 60 and is again reflected by the beam expander 40. , A plurality of mirrors 80 a each having a light reflection angle set so as to pass through the first lens 30 and the lens array 20 and converge to one of the light input / output ports 101. It includes a 80b, a.

  A plurality of optical input / output ports 101 are provided. In FIG. 1, seven optical input / output ports 101a to 101g are shown, but any number greater than or less than this can be arranged. For example, as shown in FIG. 1, optical fibers 140a to 140g are connected to the optical input / output ports 101a to 101g, or optical waveguides (not shown) are connected to the optical input / output ports 101a to 101g. The light input / output ports 101a to 101g input and output light including one or more wavelengths propagating through the optical fibers 140a to 140g, respectively. Further, the optical input / output ports 101a to 101g are provided side by side and linearly. As shown in FIG. 1B, the light input / output ports 101a to 101g are arranged so that the direction of light output from the light input / output ports 101a to 101g is parallel to the z-axis direction. As long as it is converted into parallel light in the array 20, it may be directed in any direction.

  An example of the lens array 20 is a microlens array.

  As the first lens 30 and the second lens 50, for example, a convex lens, a doublet lens in which an appropriate convex lens and a concave lens are bonded and combined to reduce optical aberration, and a plurality of lenses such as a triplet lens are combined. There is a lens.

  A plurality of lattices parallel to the y-axis direction in FIG. 1B are formed on the lattice surface 62 in parallel to the x-axis direction in FIG. The grating may be a plurality of concavo-convex grooves formed on the grating surface 62, or may alternately arrange light reflecting portions and absorbing portions. As a result, as shown in FIG. 1A, the light transmitted through the second lens 50 is reflected on the grating surface 62 of the diffraction grating 60 and reflected at different angles for each wavelength in the x-axis direction. It is returned as it is in the z-axis direction of FIG. In FIG. 1, the grating surface 62 of the diffraction grating 60 faces the second lens 50 for simplicity, but generally the optical axis (z axis) so that the normal line of the grating surface 62 is in the xz plane. It is inclined with respect to.

  Although two mirrors 80 a and 80 b are illustrated in FIG. 1, a plurality of mirrors 80 a and 80 b may be arranged for each wavelength according to the number of wavelengths of light propagating in the optical fiber 140. Hereinafter, the description will focus on the mirror 80a, but the same applies to the mirror 80b. The mirror 80a is set to converge the light at the light input / output port 101c and the mirror 80b is converged at the light input / output port 101e, respectively, but it is converged to any of the light input / output ports 101a to 101g depending on the angle. It is possible. For example, if the direction of reflection like the mirror 80a is tilted downward in FIG. 1B, it can be converged on the input / output port 101c, while the direction of reflection like the mirror 80b is shown in FIG. When it is tilted upward, the optical input / output port 101e can be converged. In this way, the wavelength can be selected by changing the angle of the mirror 80a. As the mirror 80a, a small wavelength selective switch can be realized by applying, for example, a MEMS (Micro Electro Mechanical Systems) mirror.

  The wavelength selective switch 10 is preferably arranged so that the lens array 20 and the first lens 30 and the second lens 50 and the diffraction grating 60 constitute a confocal optical system, respectively.

  1A and 1B, the wavelength-multiplexed light from the optical fiber 140d is emitted from the light input / output port 101d, becomes parallel light by the lens array 20, and is converged by the first lens 30. On the surface perpendicular to the traveling direction by the beam expander 40, an elliptical beam having a short x-axis direction is formed at the focal position 30a of the first lens, and an elliptical beam having a long x-axis direction is formed on the second lens incident surface. Become. Further, the second lens 50 converts the light into elliptical parallel light having a long x-axis direction, and the light is reflected by the diffraction surface 62 of the diffraction grating 60 at different angles in the x-axis direction for each wavelength. The reflected light is converged by the second lens 50. For example, light having a wavelength toward the mirror 80a is reflected by the mirror 80a and directed in a desired direction. The light reflected by the mirror 80a is converted into parallel light by the second lens 50, reflected by the diffraction surface 62 of the diffraction grating 60 at the same angle in the x-axis direction, converged by the second lens 50, and the beam expander 40. To return to a circular beam. The light that has returned to the circular beam becomes parallel light by the first lens 30, converges by the lens array 20, and enters the light input / output port 101c. The incident light propagates through the optical fiber 140c. For example, light having a wavelength toward the mirror 80b is reflected by the mirror 80b and enters the light input / output port 101e.

  Examples of the beam expander 40 include a convex cylindrical lens and a prism. In FIG. 1, a convex cylindrical lens is disposed as the beam expander 40 with the convex surface facing the first lens 30. As shown in FIG. 1A, the beam expander 40 converges light transmitted through the first lens 30 more greatly in the direction orthogonal to the arrangement direction of the light input / output ports 101, that is, in the x-axis direction. On the other hand, as shown in FIG. 1B, the beam expander 40 converges the convergent light from the first lens 30 as it is in the arrangement direction of the light input / output ports 101, that is, the y-axis direction. For this reason, the convergent light from the first lens 30 becomes an elliptical spot whose x-axis direction is reduced at the focal point 30a of the first lens 30, and expands in the x-axis direction as it approaches the second lens 50. The two lenses 50 produce parallel light. The cross section of light in the second lens 50 is an ellipse enlarged in the x-axis direction.

  FIG. 2 shows a schematic view of the diffraction grating in a state where light is incident as seen from the grating surface side. In FIG. 2, the grating formed on the grating surface of the diffraction grating 60 is indicated by a broken line. As shown in FIG. 2, in the wavelength selective switch 10 according to the first embodiment, the diffraction grating 60 has a length in a direction orthogonal to the arrangement direction of the optical input / output ports longer than the arrangement direction of the optical input / output ports, The length in the x-axis direction is preferably longer than the length in the y-axis direction. For this reason, the diffraction grating 60 can be provided with a large number of gratings. In addition, since the elliptical light “a” expanded in the x-axis direction is incident on the diffraction grating 60, it is possible to irradiate many gratings with light compared to light having a circular cross section. The wavelength selective switch 10 can be further downsized while ensuring the resolution of the diffraction grating 60.

  In addition, the light reflected by the diffraction grating 60 of FIG. 1 passes through the second lens 50 again, becomes an ellipse that is largely converged in the x-axis direction, and enters the mirror 80a. FIG. 3 shows a schematic view of the mirror in a state where light is incident as seen from the reflective surface side. As shown in FIG. 3, in the wavelength selective switch 10 according to the first embodiment, the mirror 80a has a length in a direction orthogonal to the arrangement direction of the optical input / output ports shorter than the arrangement direction of the optical input / output ports. The length in the x-axis direction is preferably shorter than the length in the y-axis direction. In the mirror 80a, since the light a is largely converged in the x-axis direction, the wavelength selective switch 10 can reduce the length of the mirror 80a in the x-axis direction and reduce the size while satisfying the wavelength transmission band characteristics. .

  As described above, the wavelength selective switch 10 has a high resolution of the diffraction grating 60, is excellent in wavelength transmission band characteristics, and can be downsized. The wavelength selective switch 10 distributes light of a plurality of wavelengths output from any one of the optical input / output ports 101a to 101g to another optical input / output port (any one of the optical input / output ports 101a to 101g). Since light output from a plurality of 101a to 101g can be multiplexed by another optical input / output port (any one of optical input / output ports 101a to 101g), an optical wavelength division multiplexing network can be realized. It can be applied as an optical multiplexing / demultiplexing circuit for wavelength multiplexing or a wavelength rearrangement type add-drop wavelength multiplexing circuit.

(Second Embodiment)
FIG. 4 shows a schematic configuration diagram of a wavelength selective switch according to the second embodiment. FIG. 4A shows the wavelength selective switch in the xz plane, and FIG. 4B shows the wavelength selective switch in the yz plane. In FIG. 4, the same reference numerals as those in FIG. 1 are the same as each other, and the description thereof is omitted.

  The wavelength selective switch 11 has a transmissive configuration, that is, a configuration in which the diffraction grating 65 transmits light. The wavelength selective switch 11 according to the second embodiment inputs / outputs light including one or more wavelengths and opposes a plurality of light input / output ports 101 arranged in a side-by-side straight line to receive light from the light input / output port 101. A lens array 20 arranged so as to be parallel light, and a first lens 30 arranged on the opposite side of the light input / output port 101 with the lens array 20 in between to make the light from the lens array 20 converge light The first lens 30 is disposed on the opposite side of the light input / output port 101 and between the first lens 30 and the focal point 30a of the first lens 30. In the arrangement direction of the output port 101, the convergent light from the first lens 30 is converged as it is, and in the direction orthogonal to the arrangement direction of the light input / output port 101, the light transmitted through the first lens 30 is more largely converged. A beam expander 40, a second lens 50 arranged to make the light from the beam expander 40 parallel light, and light transmitted through the second lens 50 out of light input / output from the light input / output port 101. A diffraction grating 65 that transmits light transmitted through the second lens 50 at different angles for each wavelength on a grating surface 67 in which a plurality of gratings parallel to the arrangement direction of the light input / output port 101 are formed on the surface, and a diffraction grating 65 A third lens 70 disposed on the opposite side of the second lens 50, and the lens array 20, first lens 30, beam expander 40, second lens 50, diffraction grating output from the light input / output port 101. 65 and the third lens 70 are reflected, and the reflected light is reflected by the third lens 70, the diffraction grating 65, the second lens 50, and the beam expander. 40, comprises a plurality of mirrors 80a to angle of reflection of light is set, respectively, as the first lens 30 and the lens array 20 is again transmitted to converge to one of the optical input-output port 101, and 80b, a.

  In the wavelength selective switch 11, the second lens 50 and the third lens 70 constitute a confocal optical system, that is, the third lens 70 is disposed at a distance equal to the distance between the second lens 50 and the diffraction grating 65. Is preferred.

  4A and 4B, the wavelength-multiplexed light from the optical fiber 140d is emitted from the light input / output port 101d, becomes parallel light by the lens array 20, and is converged by the first lens 30. On the surface perpendicular to the traveling direction by the beam expander 40, an elliptical beam having a short x-axis direction is formed at the focal position 30a of the first lens, and an elliptical beam having a long x-axis direction is formed on the second lens incident surface. Become. Further, the second lens 50 converts the light into elliptical parallel light having a long x-axis direction, and is diffracted by the diffraction surface 67 of the diffraction grating 65 at a different angle in the x-axis direction for each wavelength. The diffracted light is converged by the third lens 70. For example, light having a wavelength toward the mirror 80a is reflected by the mirror 80a and directed in a desired direction. The light reflected by the mirror 80a becomes parallel light by the third lens 70, is diffracted by the diffraction surface 67 of the diffraction grating 65 at the same angle in the x-axis direction, converged by the second lens 50, and the beam expander 40. To return to a circular beam. The light that has returned to the circular beam becomes parallel light by the first lens 30, converges by the lens array 20, and enters the light input / output port 101c. The incident light propagates through the optical fiber 140c. For example, light having a wavelength toward the mirror 80b is reflected by the mirror 80b and enters the light input / output port 101e.

  As in the wavelength selective switch 10 of FIG. 1, the wavelength selective switch 11 can be further downsized while ensuring the resolution of the diffraction grating 65 by lengthening the x-axis direction of the diffraction grating 65. 1 is different from the wavelength selective switch 10 of FIG. 1 in that a third lens 70 for converging the light transmitted through the diffraction grating 65 is provided. The light that has passed through the third lens 70 by the beam expander 40 becomes an ellipse that is largely converged in the x-axis direction. Therefore, by reducing the length of the mirror 80a in the x-axis direction as in the wavelength selective switch 10 of FIG. 1, the wavelength selective switch 11 can be further downsized while satisfying the wavelength transmission band characteristics. As described above, the wavelength selective switch 11 has a high resolution of the diffraction grating 65, excellent wavelength transmission band characteristics, and can be miniaturized.

  The wavelength selective switch according to the present invention can branch or combine light of different wavelengths, and can be used for wavelength multiplexing optical multiplexing / demultiplexing circuits or wavelength rearrangement type add-drop wavelength multiplexing when realizing an optical wavelength multiplexing communication network. It can be applied as a circuit.

1 is a schematic configuration diagram of a wavelength selective switch according to a first embodiment. It is the schematic of the diffraction grating of the state in which the light entered seen from the grating surface side. It is the schematic of the mirror in the state in which the light incident seen from the reflective surface side. It is a schematic block diagram of the wavelength selective switch which concerns on 2nd Embodiment. It is a schematic block diagram of the conventional wavelength selective switch. FIG. 6 is a schematic configuration diagram of a wavelength selective switch in which the reflection type diffraction grating of FIG. 5 is replaced with a transmission type diffraction grating.

Explanation of symbols

10, 11 Wavelength selection switch 20 Lens array 30 First lens 30a Focus 40 Beam expander 50 Second lens 60, 65 Grating 62, 67 Grating surface 70 Third lens 80a, 80b Mirror 101, 101a-101g Optical input / output port 102 Micro lens array 103 High numerical aperture lens 104 Second lens 105 Diffraction grating 106 Array mirrors 140, 104a to 104g Optical fiber 200 Wavelength selection switch a Light

Claims (4)

A lens array arranged to input / output light including one or more wavelengths and to collimate the light from the light input / output port facing a plurality of light input / output ports arranged side by side in a straight line; ,
A first lens that is disposed on the opposite side of the light input / output port with the lens array in between, and that converges light from the lens array;
The light input / output port is disposed on the opposite side of the light input / output port with the first lens in between and between the first lens and the focal point of the first lens. A beam expander for converging the convergent light from the first lens as it is in the arrangement direction, and converging the light transmitted through the first lens more greatly in the direction orthogonal to the arrangement direction of the light input / output port;
A second lens arranged to collimate the light from the beam expander;
In the grating plane in which a plurality of gratings parallel to the arrangement direction of the light input / output port are formed on the surface that receives the light transmitted through the second lens among the light input / output from the light input / output port. A diffraction grating that reflects the light transmitted through the lens at different angles for each wavelength;
The light output from the light input / output port and reflected by the diffraction grating and transmitted through the second lens is reflected, and each of the reflected light is transmitted through the second lens and reflected by the diffraction grating and is again reflected by the beam. A plurality of mirrors each having a light reflection angle set so as to pass through the expander, the first lens, and the lens array and converge to one of the light input / output ports;
A wavelength selective switch comprising: A lens array arranged to input / output light including one or more wavelengths and to collimate the light from the light input / output port facing a plurality of light input / output ports arranged side by side in a straight line; ,
A first lens that is disposed on the opposite side of the light input / output port with the lens array in between, and that converges light from the lens array;
The light input / output port is disposed on the opposite side of the light input / output port with the first lens in between and between the first lens and the focal point of the first lens. A beam expander for converging the convergent light from the first lens as it is in the arrangement direction, and converging the light transmitted through the first lens more greatly in the direction orthogonal to the arrangement direction of the light input / output port;
A second lens arranged to collimate the light from the beam expander;
In the grating plane in which a plurality of gratings parallel to the arrangement direction of the light input / output port are formed on the surface that receives the light transmitted through the second lens among the light input / output from the light input / output port. A diffraction grating that transmits the light transmitted through the lens at different angles for each wavelength; and
A third lens disposed on the opposite side of the second lens with the diffraction grating in between;
The light output from the light input / output port reflects the light transmitted through the lens array, the first lens, the beam expander, the second lens, the diffraction grating, and the third lens, and each of the reflected light is reflected. The light reflection angle is such that the third lens, the diffraction grating, the second lens, the beam expander, the first lens, and the lens array are transmitted again and converge to one of the light input / output ports. Multiple mirrors each set,
A wavelength selective switch comprising:   3. The wavelength selective switch according to claim 1, wherein the diffraction grating has a length in a direction orthogonal to the arrangement direction of the light input / output ports longer than the arrangement direction of the light input / output ports.   4. The wavelength selective switch according to claim 1, wherein the mirror has a length in a direction orthogonal to an arrangement direction of the optical input / output ports shorter than an arrangement direction of the optical input / output ports. 5.

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