JPH06347836A - Optical switch - Google Patents

Abstract

PURPOSE:To provide a small-sized optical path switching type optical switch capable of attaining a high shift amount by controlling reflection/transmission of a shutter device provided for every output port and allowing a beam to pass several times through the inside of a deflection device of one stage constitution. CONSTITUTION:This switch is provided with a polarizing device 21 making an input signal beam linear polarization, the deflection device 22 provided with a function capable of shifting in parallel the signal beam according to a polarization direction, a 1/4 wavelength plate 23 shifting the phase of the signal beam by pi/2, the shutter device 24 capable of reflecting/transmitting the signal beam according to a prescribed control signal and a reflection device 25 deflecting the incident signal beam. Then, the signal beam is outputted to a output port optionally selected from among plural output ports by shifting in parallel the signal beam in multistage in the deflection device 22 of one stage constitution by controlling the polarizing condition of the signal beam and the shutter device 24 using a cholesteric liquid crystal.

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 an optical path of signal light in a spatial connection of light applied to optical communication, optical switching, etc., and more particularly to an optical switch having a function of shifting an optical path in parallel by switching. Regarding

[0002]

2. Description of the Related Art Optical switching is one of the important basic techniques in optical information processing and optical switching for realizing spatial connection of light by utilizing incoherence and parallelism of light. Functions required for optical switching include a shutter function that controls transmission and blocking of signal light, and an optical deflection technology that controls the traveling direction of light, that is, an optical path switching change function. The switching of the optical path in the optical path switching technique includes changing the output angle of the signal light or shifting the optical path in parallel, and is selected according to the system configuration.

As a method for changing the output angle of the signal light,
A method using an acousto-optic effect is known. The acousto-optic effect is based on the periodic refractive index distribution created by ultrasonic waves in the acousto-optic medium and the diffraction phenomenon of light due to that distribution.By changing the frequency of the ultrasonic waves applied to the acousto-optic medium, the output light The emission angle of can be changed. However, this method has drawbacks such that the drive system for generating ultrasonic waves becomes large and expensive, and it is difficult to form a matrix.

Further, a mechanical method has been studied in which a reflecting mirror or the like is formed in the device and the outgoing angle of the signal light is changed by rotating this mirror. There is a problem in the reliability of the drive unit.

On the other hand, as a technique for shifting the optical path in parallel, a technique based on the electro-optical effect is known. Deflection due to the electro-optic effect is achieved by using an electro-optic switch
Alternatively, it is realized by combining a mirror and the like. Here, the electro-optical switch is a device that uses liquid crystal, ceramics, or the like to modulate the intensity, angle, polarization direction, etc. of light by electrical input, and includes a so-called spatial light modulator and the like. In electro-optical deflection, the polarization direction of signal light is changed by this electro-optical switch. The birefringent prism in the latter stage can separate the input light into an ordinary ray and an extraordinary ray by its birefringence action.The ordinary ray and the extraordinary ray have an optical path that is equal to the retardation value of the material forming the birefringent prism. It will shift.
Therefore, by making the plane of polarization of the signal light, which is linearly polarized light, correspond to the ordinary ray or the extraordinary ray with respect to the birefringent prism, and rotating the polarization direction of the signal light by π / 2 by the electro-optic switch, By switching,
It is possible to shift the optical path, that is, change the optical path. Thus, the electro-optical deflection is a method of shifting the optical path by the amount of birefringence by using a birefringent material such as calcite.

As a method using the electro-optical effect, for example, a configuration described in "Japanese Patent Application Laid-Open No. 3-7916" is known. In these conventional methods, a liquid crystal switch is used as the electro-optical switch,
Calcite is often used as the birefringent material.

FIG. 9 shows a structural example of a conventional optical switch using a birefringent crystal such as calcite. Hereinafter, calcite will be described as an example of the birefringent crystal. In FIG. 9, the ordinary ray and the extraordinary ray in the calcite 11 are indicated by solid lines and dotted lines, respectively. In FIG. 9, the input signal light is linearly polarized light that coincides with or is orthogonal to the ordinary ray direction of calcite. The polarization rotation device 12
It has a function of rotating the polarization direction of the input signal light by 90 °. The signal light in each stage is set by the polarization rotation device 12 as an ordinary ray or an extraordinary ray with respect to the calcite 11 arranged in the subsequent stage, and follows the path in the figure according to the ordinary ray and the extraordinary ray. Polarization rotation device 12 at each stage
By controlling the polarization rotation function of, the output signal light can be extracted by selecting any of the output ports “a” to “d”. In such a configuration, one stage of calcite is required for the signal light to be parallel-shifted once,
Multiple stages of calcite are required as the number of output ports increases. Further, in order to increase the distance between the output ports, it is necessary to increase the thickness of calcite, which also leads to an increase in the size and cost of the entire device.

[0008]

DISCLOSURE OF THE INVENTION The present invention provides an optical switch using a birefringent crystal such as calcite, which enables multidirectional output with a single-stage configuration without using calcite in multiple stages. The configuration is provided.

The method using such an electro-optical effect is
High-speed operation and low power consumption are possible depending on the configuration of the electro-optical switch, but the shift amount of the optical path is determined by the retardation value of the birefringent material. Generally, the birefringence of optical materials is small, and a thick birefringent material is required to obtain a large optical path shift amount, resulting in a large mounting volume and high material costs such as calcite. was there.

The present invention has been made to solve the above-mentioned problems in a system using a birefringent material such as calcite, and it is an object of the present invention to provide an optical path switching type optical switch which is compact and capable of a high shift amount. Has an aim.

[0011]

In order to achieve this object, the present invention provides an optical switch for switching a signal light to an arbitrary one of a plurality of output ports and outputting the signal light. A deflecting device that transmits straight or parallel shifts depending on the direction and outputs, and at least one first quarter-wave plate that changes the phase of the input light from the deflecting device by π / 2 to form circularly polarized light. And circularly polarized input light from the first quarter-wave plate provided corresponding to each of the plurality of output ports is reflected or output to the corresponding output port according to an applied voltage. A shutter device, and the first 1/4 reflected by the shutter device
The phase of the signal light that has passed through the wave plate and the deflector again is π
/ 2 at least one second quarter-wave plate, and the signal light from the second quarter-wave plate is reflected to the deflecting device through the second quarter-wave plate again. At least one reflecting device for inputting is provided.

[0012]

In the optical path switching device according to the present invention, by controlling the polarization state of the signal light and controlling the shutter device using the cholesteric liquid crystal, the signal light is parallel-shifted in multiple stages in the one-stage deflecting device. By doing so, it is possible to output the signal light from the plurality of output ports to the arbitrarily selected output port.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An optical switch according to the present invention will be described below with reference to the drawings.

FIG. 1 shows a schematic structure of an optical switch according to the present invention.

The optical switch according to the present invention comprises a polarizing device 21 for converting input signal light into linearly polarized light, and a deflecting device 22 having the function of shifting the signal light in parallel depending on the polarization direction.
A quarter-wave plate 23 that shifts the phase of the signal light by π / 2;
It comprises a shutter device 24 capable of reflecting or transmitting signal light and a reflecting device 25 reflecting incident signal light in accordance with a predetermined control signal.

The realization function of the optical switch according to the present invention is
In FIG. 1, a predetermined control signal is used to switch the reflection / transmission function of the shutter device 24 corresponding to each output port “a” to “d”, and the input signal light is shifted by a predetermined number of steps to obtain a predetermined output position. For example, it is possible to output as output signal light to any of the output ports “a” to “d” in FIG.

The function of the optical switch according to the present invention will be described in detail below with reference to FIG.

FIG. 2 shows the optical path switching function 2 in FIG.
It is the figure which showed the step.

In FIG. 2, a line connecting the input signal lights shows an optical path. The left and right arrows shown on the optical path indicate the traveling direction of the signal light, and the arrows orthogonal to or diagonally intersecting with the traveling direction indicate the polarization direction of the signal light that is linearly polarized light. For example, in the figure, the up and down arrows indicate the polarization direction in the up and down direction of the paper, and the diagonal arrows indicate the polarization in the vertical direction of the paper, which is orthogonal to the up and down arrows. Further, an arrow that turns around the arrow that indicates the path direction indicates the optical rotation direction of the signal light that is circularly polarized light.

First, the function of each component will be described.

The deflecting device 32 has a function of directly advancing and transmitting as it is, or after being parallel-shifted by a predetermined amount and transmitting according to the polarization direction of the input signal light. Such a function can be realized by a birefringent plate in which both surfaces are parallel to each other using a uniaxial crystal exhibiting birefringence such as calcite. In the birefringent plate, when linearly polarized light is input so that it becomes an ordinary ray, it goes straight through the birefringent plate, and the input linearly polarized light that becomes an extraordinary ray is output after shifting a certain amount in parallel in the direction determined by the crystal structure. It will be.

For example, consider a plane-parallel plate made of calcite having a thickness t and a normal line of the boundary surface forming an angle θ with the optical axis. When vertically incident light is an extraordinary ray, parallel rays are paralleled by an amount determined by the following equation. It is known to shift (for example, Masao Tsuruta: Applied Optics II, p.156, published by Baifukan).

[0023]

[Formula 1] l = t ・ (n _o ² -n _e ² ) ・ sin θ ・ cos θ / (n _e ²・ cos ² θ + n _o ²・ sin ² θ) (1) where l is the shift amount And n _o is the ordinary refractive index, n
_e is the extraordinary ray refractive index. Since the pitch of the output port is an integral multiple of the shift amount of this deflection device, it is necessary to determine the thickness of calcite or the like according to the pitch required for the output port.

The deflecting device 32 is not limited to the above-mentioned calcite, and it is possible to use an optical crystal such as rutile or a birefringent material such as liquid crystal.

The shutter device (34, 38) has a function of reflecting the input light when the control signal is OFF (ON) and transmitting the input light when the control signal is ON (OFF). Such a function can be realized by a liquid crystal cell using cholesteric liquid crystal. It is known that the cholesteric liquid crystal has a helical structure in a planar structure and has a function of reflecting circularly polarized light in the same rotation direction as the helical direction. (For example, Shoichi Matsumoto: "Latest Liquid Crystal Technology", p28, published by Industrial Research Society). In that case, the wavelength of the light that is most efficiently reflected is

[0026]

## EQU2 ## λ = n · p (2) λ is the wavelength of light, n is the average refractive index of the liquid crystal in a plane orthogonal to the helical axis, and p is the helical pitch. Therefore, by selecting n and p so that the signal light wavelength satisfies λ in the equation (2), it is possible to reflect the signal light that is right-handed or left-handed circularly polarized light. On the other hand, when the dielectric anisotropy of the cholesteric liquid crystal is positive, a phase transition from the cholesteric phase to the nematic phase occurs when a voltage is applied, and thus the input light is transmitted. Therefore, it becomes possible to control the reflection / transmission of the signal light by controlling the voltage application to the cholesteric liquid crystal cell,
The shutter device according to the present invention can be realized.

FIG. 3 is a schematic view of the shutter device according to the present invention. In FIG. 3, the cholesteric liquid crystal 41 is held in a liquid crystal cell having a cell thickness sufficiently larger than the wavelength of the signal light. The liquid crystal cell is composed of two transparent substrates 45, and holds a cholesteric liquid crystal 41 between them, and the periphery thereof is sealed with a sealing material 44. A transparent electrode 42, which is patterned in a predetermined shape, is formed on the transparent substrate,
An alignment film 43 for aligning the cholesteric liquid crystal 41 is formed thereon. The cholesteric liquid crystal 41 is homogeneously aligned by the alignment film 43 and forms a helical structure between the transparent electrodes 45. Here, as the cholesteric liquid crystal 41, one having a positive dielectric anisotropy is used. As described above, the cholesteric liquid crystal has a property of forming a helical structure in a planar structure and reflecting circularly polarized light having the same optical rotation direction as the rotation direction of the spiral. In FIG. 3, for example, assuming that the cholesteric liquid crystal 41 forms a right-handed helix with respect to the optical axis, when the input light is right-handed circularly polarized light, it is reflected and becomes reflected light.

When no voltage is applied to the electrodes on both sides of the liquid crystal cell, the cholesteric liquid crystal has a helical structure as described above, so that the liquid crystal cell is in the reflection mode. On the other hand, when a voltage higher than the threshold voltage determined by the liquid crystal cell structure, liquid crystal physical properties, etc. is applied to the liquid crystal cell, the helical structure of the cholesteric liquid crystal unravels and transitions to the nematic phase, so that it transmits incident light. It becomes a mode. In this way, with the shutter device using cholesteric liquid crystal,
It becomes possible to switch between the reflection mode and the transmission mode for incident light, and the shutter device according to the present invention can be realized.

The above-mentioned cholesteric liquid crystal has a positive dielectric anisotropy, but when the cholesteric liquid crystal is homeotropically aligned, a negative dielectric anisotropy is used. , The same effect can be expected. In this case, since the helical structure is formed by applying a voltage equal to or higher than the threshold voltage, the transmission mode is set when no voltage is applied, and the reflection mode is set when voltage is applied.

The quarter-wave plate (33, 35,
37) is composed of an optical crystal having birefringence. In the present invention, as long as it has a function of shifting the phase of the signal light by π / 2, the structure and the material are not limited, for example, the liquid crystal material is used.

As the reflecting device 36, one that reflects the signal light wavelength with high efficiency and does not diffuse is desirable. A multilayer film total reflection plate or the like is preferable, but for example, a configuration using a cholesteric liquid crystal in the same configuration as the shutter device is also possible,
The constitution and the material do not matter.

In the polarizing device 31, the input signal light is deflected by the deflecting device 32.
When the input signal light is linearly polarized light that coincides with or is orthogonal to the ordinary ray direction, the input signal light is deflected when the input signal light has other polarization states.
It has a function of making linearly polarized light that coincides with or crosses the ordinary ray directions of 2. Such a polarizing device can be realized by using a polarizer having a high extinction ratio such as a prismatic polarizer using a birefringent crystal. It can also be realized by a polarizer (so-called polarizing plate) using a dichroic material such as an iodine type or a dye type which is generally widely used. In either case, the polarization direction of the polarizer is arranged so as to match or be orthogonal to the ordinary ray direction of the deflecting device as described above.

The operation of the optical switch according to the present invention will be described with reference to FIG.

Now, let us consider a case where the input signal light is converted into the linearly polarized light in the vertical direction shown in FIG. 2 by the polarization device 31, and this polarization direction becomes the ordinary ray direction of the polarization device. in this case,
The signal light (1) goes straight through the deflecting device 32 and is output (2). The signal light (2) is then transmitted to the quarter-wave plate 3
3 converts the light into circularly polarized light (3), and the shutter device 34
To enter. Here, the characteristics of the quarter-wave plate are selected so that the circularly polarized light converted by the quarter-wave plate 33 has the same rotation direction as the reflected optical rotation when the shutter device 34 is in the reflection mode. As described above, the shutter device 34 according to the present invention reflects / reflects the circularly polarized signal light by the external control signal.
It is possible to select the transparent function. Therefore, when it is desired to output the signal light to the output port "a", the signal light can be output to the output port "a" by setting the shutter device 34 in the transmission mode. When outputting the signal light to the output port “b”, first, the shutter device 34 is set to the reflection mode. In this case, the signal light is reflected by the shutter device 34 (4), passes through the quarter-wave plate 33 again, and becomes linearly polarized light (5). This linearly polarized light is a linearly polarized light in the horizontal direction, which is shown by diagonal lines in the drawing and is orthogonal to the polarized light in the vertical direction, and becomes an extraordinary ray of the deflecting device 32. (6). The signal light passes through the quarter-wave plate 35 (7), is reflected by the reflecting device 36 (8), passes through the quarter-wave plate 35 again, and is rotated by 90 ° in the polarization direction (9). ), This time, the deflection device 32 goes straight ahead. Signal light (1
0) becomes circularly polarized light again through the quarter-wave plate 37,
Input to the shutter device 38 (11). Here, when the shutter device 38 is set to the transmission mode, the signal light is output to the output port “b” through the shutter device 38.

Similarly, when it is desired to output the signal light to the output port of the subsequent stage, the shutter devices up to the preceding stage are set to the reflection mode, and the shutter device related to the desired output port is set to the transmission mode. As a result, signal light can be output.

As described above, in the optical switch according to the present invention, by controlling the reflection / transmission of the shutter device provided for each output port, it becomes possible to pass through the deflecting device of one stage a plurality of times, and the distance can be increased. It is possible to output a signal light to a desired output port that is distant from each other.

With the configuration of the present invention, even if the parallel shift amount of the deflecting device itself is small, it is possible to increase the parallel shift amount by repeatedly passing through the deflecting device. It can be realized with a one-stage configuration. Therefore, downsizing of the device can be realized.

In FIG. 2, the polarization device 31 adjusts the polarization direction of the input signal light to the ordinary ray direction of the deflecting device 32. However, the input signal light is linearly polarized in the ordinary ray direction of the deflecting device from the beginning. In some cases, the polarizing device 31 may be omitted. When the polarizing device 31 makes the polarization direction of the input signal orthogonal to the ordinary ray direction of the deflecting device 32, the first input to the deflecting device 32 becomes an extraordinary ray, so that the side opposite to the shift direction in FIG. However, there is no particular difference in terms of configuration, as long as the shift direction is set to the opposite side and the components are arranged in subsequent stages.

Further, the polarization direction is set to 90 ° by the polarization device 31.
By adding a rotatable polarization rotation function, it is possible to expand in the vertical direction in FIG. Such a polarization rotation function can be realized by using, for example, a twisted nematic (TN) mode liquid crystal device. In this TN mode liquid crystal device, the orientation of the liquid crystal molecules is controlled depending on whether or not a voltage is applied to the device, and thereby the polarization direction of the input linearly polarized light is rotated, or it is allowed to go straight without being rotated. It is known that it is possible (for example, “Liquid Crystal / Applied Edition” by Mitsuharu Okano: p.16, published by Baifukan). An example of the above-mentioned polarizing device 31, for example, a polarizing device having a polarization rotating function can be realized by arranging this liquid crystal device in the subsequent stage of the above-mentioned polarizing device 31, for example, at the latter stage of the prism polarizer and setting the rotation angle of the liquid crystal device to 90 °.

FIG. 4 schematically shows a case in which a polarization rotation device 51 having a polarization rotation function added to the polarization device is provided. 52 is a deflecting device, 53 is a quarter wavelength plate, 54 is a shutter device,
55 is a reflecting device. It is possible to expand the signal light in the vertical direction depending on whether or not the polarization rotation device 51 rotates the polarization direction of the input signal light by 90 °. For example, when the input signal light is made into the ordinary ray of the deflecting device 52 by the polarization rotating device 51, the signal light goes straight in the deflecting device 52 in FIG. 4, and the output ports "d" to " It is output to any of g ". On the other hand, when the polarization direction of the signal light input to the deflecting device 52 is rotated 90 ° by the function of the polarization rotating device, this signal light becomes an extraordinary ray for the deflecting device 52, and the deflecting device 5 in FIG.
2 will be shifted upward, and the data will be output to any of the output ports "a" to "c". As described above, since the polarization rotation device 51 has the polarization rotation function, it is possible to spread the signal light in the vertical direction, and it is possible to provide advantages such as an increase in the number of output ports and a decrease in loss.

Hereinafter, an implementation structure of the present invention will be described with reference to embodiments.

[Embodiment 1] FIG. 5 is a schematic perspective view showing an optical path switching type optical switch when there is one input signal light.
FIG. 5 shows an example in which the number of output ports is 7 stages.
Reference numeral 61 is a polarizing device, and 62 is a deflecting device.
The ¼ wavelength plate 63 and the reflecting device 65 on both sides of the above are each one, and it is better than the ¼ wavelength plate and the reflecting device being individually configured in terms of the device configuration. Output port "a" ~
A shutter device 64 (64a) provided corresponding to each "g"
It is possible to output a signal light to a desired output port by switching reflection / transmission of (˜64 g). If the amount of shift in the deflecting device 62 cannot be increased, the shutter device 64
It is also possible to fix the multi-stage reflection mode and to provide the output port after obtaining the desired shift amount.

Although FIG. 5 shows the shift in one direction,
Needless to say, as shown in FIG. 4, it is possible to shift vertically by adding a polarization rotation function to the polarization device 61. The same applies to Examples 2 and 3 below.

[Embodiment 2] FIG. 6 is a schematic perspective view of an optical path switching type optical switch for collectively switching a plurality of signal lights in a one-dimensional array. Reference numeral 71 is a polarizing device, 72 is a deflecting device, and 73.
Is a quarter wavelength plate, and 75 is a reflector. In FIG. 6, a shutter device 74 (74a1 to 74a6, ..., 74)
By adopting a configuration in which reflection / transmission is simultaneously switched in one horizontal row (g1 to 74g6), it becomes possible to collectively switch parallel data of a plurality of bits.

[Third Embodiment] The shutter device 7 in FIG.
When each horizontal row of 4 is independently controlled, that is, when the shutter device 74 (74a1 to 74g6) is two-dimensionally controlled independently, bit shuffling of parallel data becomes possible. FIG. 7 is a diagram showing an example of two-dimensional data shift. By independently controlling the shutter devices 74a1 to 74f5 and independently shifting the parallel data in the X direction bit by bit, shuffling in the Y direction becomes possible. Figure 7
By concentrating in the Y direction at, the shuffled one-dimensional data can be obtained.

FIG. 8 shows a two-dimensional structure of the optical switch according to the present invention, which is a two-dimensional direction, that is, an X direction.
FIG. 6 is a diagram showing an example in which independent parallel shift in the Y direction is performed and concentration is performed on one-dimensional data. With this configuration,
The first-stage shifter S1 performs individual Y-direction shifts, and the second-stage shifter S2 performs individual X-direction shifts. For example, as shown in FIG. It becomes possible to convert the data into a-c-d-b "data.

In the embodiment described above, the output signal light is all circularly polarized light. However, when linearly polarized light is required, a quarter wavelength plate, a polarizing plate, etc. are required after the shutter device. It goes without saying that an optical component may be provided.

In the above description, the optical switch relating to the spatial connection has been mainly described, but the output medium of the input signal light, the optical fiber, the optical waveguide, or the LED is used.
Is not limited to the light emitting module such as the above, and the incident medium of the output signal light is not limited to the spatial light beam, and is not limited to the optical fiber, the optical waveguide, or the light receiving element module such as the PD. Furthermore, it is possible to form an optical switch module relating to a fixed wiring system by forming each component rigidly, and none of them limits the implementation mode of the optical switch according to the present invention.

[0049]

As described above, in the optical path switching type optical switch of the present invention, it is not necessary to provide a mechanically movable part in particular, and a deflector made of calcite or the like is basically a one-stage structure in multiple directions. Since the parallel shift of the output signal light is possible, the optical switch can be downsized and the cost can be reduced, which is a great effect in realizing the optical switch.

[Brief description of drawings]

FIG. 1 is a diagram showing an outline of a configuration of the present invention.

FIG. 2 is a schematic diagram of a configuration related to optical path switching for two stages.

FIG. 3 is a cross-sectional view showing an outline of a shutter device.

FIG. 4 is a diagram showing an outline of a configuration in the case of unfolding in a vertical direction.

FIG. 5 is a schematic perspective view showing an optical switch when the number of input signal lights is one.

FIG. 6 is a schematic perspective view of an optical switch that collectively switches a plurality of signal lights in a one-dimensional array.

FIG. 7 is a diagram showing an example of a shift state of signal light in the configuration of FIG.

FIG. 8 is a schematic diagram showing a configuration for realizing parallel shift in a two-dimensional direction by a two-stage configuration.

FIG. 9 is a diagram showing a configuration example of a conventional optical path switching type optical shutter.

[Explanation of symbols]

 11 Calcite 12 Polarization Rotator 21 Polarizer 22 Deflector 23 1/4 Wave Plate 24 Shutter Device 25 Reflector 31 Polarizer 32 Deflector 33 1/4 Wave Plate 34 Shutter Device 35 1/4 Wave Plate 36 Reflector 37 1 / 4 wavelength plate 38 shutter device 41 cholesteric liquid crystal 42 transparent electrode 43 alignment film 44 sealing material 45 transparent substrate 51 polarization rotation device 52 deflection device 53 1/4 wavelength plate 54 shutter device 55 reflection device 61 polarization device 62 deflection device 63 1 / Four-wave plate 64 Shutter device 65 Reflector 71 Polarizer 72 Deflector 73 Quarter wave plate 74 Shutter device 75 Reflector

Claims (3)

[Claims] 1. An optical switch for switching and outputting signal light to any of a plurality of output ports, and a deflecting device for outputting linearly polarized signal light input by linearly transmitting or parallel shifting according to its polarization direction. And at least one first quarter-wave plate that changes the phase of the input light from the deflector by π / 2 to form circularly polarized light, and is provided corresponding to each of the plurality of output ports. , A shutter device that reflects the circularly polarized input light from the first quarter-wave plate or outputs it to the corresponding output port according to an applied voltage; and Four
The phase of the signal light that has passed through the wave plate and the deflector again is π
/ 2 at least one second quarter-wave plate, and the signal light from the second quarter-wave plate is reflected to the deflecting device through the second quarter-wave plate again. An optical switch comprising at least one reflecting device for inputting. 2. The optical switch according to claim 1, further comprising a polarization device that converts the input signal light into linearly polarized light and inputs the linearly polarized light to the polarization device. 3. When the input signal light is a linearly polarized light that coincides with or is orthogonal to the ordinary ray direction of the deflecting device, the polarizing device allows the input signal light to pass through, and the input signal light is otherwise. 3. The optical switch according to claim 2, which has a function of making the input signal light into linearly polarized light that coincides with or is orthogonal to the ordinary ray direction of the deflecting device in the case of the polarization state.