JP5508368B2 - Wavelength selective switch - Google Patents

Description

  The present invention relates to a wavelength selective switch using a spatial optical system, and specifically to a wavelength selective switch that can be downsized and has a constant transmission band width for each channel.

  There is a need for a device that has a plurality of optical input / output ports and can selectively operate wavelength division multiplexed optical signals (WDM: Wavelength Division Multiple) as they are. One such device is a wavelength selective switch (WSS). The wavelength selective switch is a device that can selectively distribute input WDM light to different outputs for each wavelength.

  A general wavelength selective switch is a spatial optical system optical communication device using a multiplexing element, a dispersing element, and a polarizing element. The light that is combined and incident is demultiplexed into position-dependent light for each wavelength via a dispersion element such as a diffraction grating, and an output port is selected by a deflection element such as a MEMS mirror, thereby Switching is realized.

  FIG. 1 shows an example of a conventional wavelength selective switch (see, for example, Patent Document 1). A wavelength selective switch 400 shown in FIG. 1 converts an input / output port array 410 in which input ports and output ports are arranged in a predetermined direction, and converts polarized light into parallel light in order to input / output optical signals to / from the input / output ports. It comprises an fθ lens 420, a cylindrical lens 430 that makes the beam cross section of the optical signal from the fθ lens 420 elliptical, a first lens 441, a diffraction grating 442 that multiplexes and demultiplexes the optical signal, and a second lens 443. 4f optical system 440 that projects an optical signal having an elliptical cross section collected through cylindrical lens 430 onto mirror array 450 and a mirror in which a plurality of MEMS mirrors 451 are arranged in a line along a predetermined direction An array 450 is provided, and these are arranged in a line along the z-axis in FIG. 1 in this order. The input / output ports are arranged in a direction along the y axis. The plurality of MEMS mirrors are arranged in a direction along the x axis.

  Here, the input / output port array 410 is generally a fiber collimator in which optical fibers for input ports and optical fibers for output ports are one-dimensionally arranged and fixed in the same block (fixing tool). It is configured. The fiber collimator array may have either a configuration in which a fiber array and a lens array are combined, or a configuration in which lensed fibers in which fibers and lenses are integrated are arrayed.

  As shown in FIG. 2, each MEMS mirror 451 in FIG. 1 can rotate about an x axis orthogonal to the z axis and a y axis orthogonal to the x axis. The MEMS mirror 451 is a deflecting element for deflecting the optical signal of each wavelength demultiplexed and coupling it to a target port in an arbitrary coupling state. The MEMS mirror 451 is perpendicular to the wavelength dispersion direction (θy direction) and the wavelength dispersion direction. It has the ability to deflect the beam in two directions (θx direction). The angle θx of the MEMS mirror that deflects the beam in the direction perpendicular to the chromatic dispersion direction is a rotation around the x axis, and is an angle for mainly selecting an optical port to be coupled. On the other hand, the angle θy for deflecting the beam in the chromatic dispersion direction is a rotation about the y-axis, mainly to make the coupling state arbitrary, that is, to adjust the attenuation factor (ATT) of the wavelength selective switch. Is the angle.

  FIG. 3 shows another example of a conventional wavelength selective switch (see, for example, Patent Document 2). The wavelength selective switch 1 includes a collimator array 11 constituting an input / output optical system, a spectroscope 12 constituting a spectroscopic optical system for separating input WDM light for each wavelength, and a condensing optical system on a substrate 10. The condensing lens 13 which comprises, and the MEMS mirror array unit 14 which is a switching element are provided.

  In the collimator array 11, for example, a plurality of collimating lenses are formed and arranged on one surface of a glass substrate, and an optical axis, that is, the center of the collimating lens is provided in a portion corresponding to each of the plurality of collimating lenses on the other surface. A plurality of optical fibers connected to each other by adhesion, fusion, or the like in a state where the center of the fiber core coincides with each other. The collimator array 11 converts the light incident on the collimator lens from the input optical fiber 11-1 into collimated light and outputs the collimated light to the spectroscope 12. Conversely, the collimated light incident on the collimator lens from the spectroscope 12 is output fiber 11 It has the function of condensing on the cores of -2, 11-3, and 11-4. The collimator array 11 in FIG. 3 includes a total of four input fibers 11-1 corresponding to the input ports and three output fibers 11-2, 11-3 and 11-4 corresponding to the output ports. It has a fiber and is configured as a 1-input 3-output collimator array.

  The spectroscope 12 reflects incident light in different directions (angles) depending on the wavelength. In general, a diffraction grating is used as a spectroscope. FIG. 4 is an enlarged partial sectional view showing a configuration of a general diffraction grating. The diffraction grating is an optical element in which a large number of parallel grooves are periodically carved on the glass substrate 120. By using the light diffraction phenomenon, the diffraction grating is used for a plurality of wavelength components incident at a certain angle (α). On the other hand, a different emission angle (β) is given for each wavelength. This action makes it possible to separate the input WDM light for each wavelength.

  The MEMS mirror array unit 14 functions as a switching element for performing port switching by reflecting incident light from the input fiber 11-1 to any one of the output fibers (11-2, 11-3, 11-4). . The MEMS mirror array unit 14 is configured by arranging MEMS mirrors in an array. The MEMS mirror array unit 14 is configured such that one MEMS mirror is arranged for one wavelength separated by the spectrometer 12.

  The condensing lens 13 condenses the light of one wavelength separated by the spectroscope 12 on a predetermined MEMS mirror. Thereafter, the condensing lens 13 condenses the light reflected by any one of the MEMS mirrors and outputs it to the collimator array 11 via the spectroscope 12.

  In such a conventional wavelength selective switch 1, the WDM light input through the input fiber 11-1 of the collimator array 11 is converted into collimated light and then enters the spectroscope 12. Next, the light incident on the spectroscope 12 is emitted from the spectroscope 12 at different angles for each wavelength and is incident on the condenser lens 13. Next, the light incident on the condenser lens 13 is condensed by the condenser lens 13 onto a corresponding MEMS mirror in the MEMS mirror array unit 14. The light that is incident on the MEMS mirror and reflected is an optical path different from the forward path, and again passes through the condenser lens 13 and the spectroscope 12, and is output to any one of the output fibers (11-2, 11-3) of the collimator array 11. , 11-4). When changing the output fiber to which the reflected light is coupled, the tilt angle of each MEMS mirror is changed. In this way, output switching in units of wavelengths is realized.

JP 2011-2669 A Patent No. 4445373

Marom et al. "Wavelength-Selective 1 × K Switches Using Free-Space Optics and MEMS Micromirrors: Theory, Design, and Implementation" IEEE Journal of Lightwave Technology, Volume 23, No. 4, April 2005 pp. 1620-1630

  One performance index of wavelength selective switches is the transmission band. The upper limit of the bit rate is improved as the transmission band of the wavelength selective switch is wider. The transmission band of the wavelength selective switch is determined by the ratio of the beam diameter to the mirror width, and the transmission band becomes wider as the mirror width is larger and the beam diameter is smaller.

  For this reason, in order to ensure a wide transmission band, it is necessary to make the beam diameter of the wavelength hitting each MEMS mirror as small as possible with respect to the mirror width (W). It is also necessary to make the beam strike the center of the MEMS mirror as much as possible.

  FIG. 5 shows a part of the wavelength selective switch shown in FIG. As the spectroscopic optical system 112, the diffraction grating shown in FIG. 4 is used. As described above, the wavelength selective switch has a structure in which the WDM light is separated for each wavelength by the diffraction grating and then the light of each wavelength is collimated by the condensing lens 113 and applied to the corresponding MEMS mirror 140. If the wavelength interval of the WDM light is Δλ and the resolution angle of the WDM light by the diffraction grating is β, the wavelength resolution capability of the spectroscopic optical system 112 is expressed by dβ / dλ, and the resolution angle β is β = Δλ · (dβ / dλ ). At this time, between the distance L between the spectroscopic optical system 112 and the condensing optical system 113 and the mirror pitch (distance between adjacent MEMS mirror centers) P,

It is known that this relationship is established.

  At this time, if the spatial distance (beam interval) formed on the exit surface after different wavelengths (wavelength interval Δλ) pass through the condenser lens 113 is dy, the distance between dy and the wavelength interval Δλ is

It is known that this relationship is established. Here, f _L represents the focal length of the condenser lens 113, N represents (the number of grooves of the diffraction grating) / mm, and m represents the diffraction order.

  From (Equation 2), it can be seen that the relationship between the beam interval (ie, the change in the position of the incident light beam) dy and the wavelength interval (ie, the change in wavelength per channel) Δλ depends on the dispersion angle (β).

  In FIG. 6, the wavelength range used is the C band (1528.77 to 1563.05 nm), the wavelength interval (Δλ) is 100 GHz, the number of wavelengths is 44, the number of grooves (N) of the diffraction grating is 1200 / mm, and the diffraction order (m) 1 shows a calculation example when the incident angle α is 68 degrees and the mirror pitch (P) is 250 μm. In FIG. 6, the solid line 62 indicates the position (mm) of the MEMS mirror with respect to the channel number (wavelength), the broken line 64 indicates the beam position (mm) with respect to the channel number, and the single chain line 66 indicates the pitch between adjacent channels with respect to the channel number ( μm).

From FIG. 6, it can be seen that the beam center position (broken line 64) of each wavelength after emission from the diffraction grating is shifted from the position of the MEMS mirrors arranged at equal intervals (solid line 62). That is, when the focal length f _L of the condenser lens 113 is determined so that the beam interval between the channel numbers = 1 and 2 is 250 μm after the diffraction grating is emitted, the beam interval between the channel numbers = 43 and 44 is about 343 μm. You can see that it spreads out.

Accordingly, as shown in FIG. 7, the MEMS mirror array is designed so that the channel pitch is narrow on the short wave side and the channel pitch is wide on the long wave side. In the MEMS mirror array shown in FIG. 7, each MEMS mirror is arranged along the spectral direction. The configuration of the MEMS mirror array, as the short-wave proceeds to the long wave _{side, P a <P b <P} c <··· <P i and _{W a <W b <W c} <··· <W i , and the mirror It can be seen that both the pitch (P) and the mirror width (W) become wider.

  However, the conventional wavelength selective switch has the following problems when the wavelength selective switch is downsized.

  FIG. 8 is a conceptual diagram for explaining the problem of the conventional wavelength selective switch. As shown in FIG. 8A, the optical system of the wavelength selective switch is designed such that the beam waist (BW) is disposed on the MEMS mirror 140. Here, the miniaturization of the optical system of FIG. For further miniaturization, when using a spectroscopic optical system (spectrometer) 112 with improved dispersion capability and a condensing lens 113 with a shorter focal length, the off-axis aberration of the lens increases and field curvature occurs. Therefore, the beam waist cannot be disposed on all the MEMS mirrors 140. For this reason, the conventional wavelength selective switch has a problem that the width of the transmission band for each channel is not constant when it is downsized.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a wavelength selective switch that can be miniaturized and has a constant transmission band width for each channel.

  The present invention includes a single input port and a plurality of output ports or a single output port and a plurality of input ports, a wavelength separation unit for wavelength-separating a wavelength-multiplexed optical signal emitted from the input port, and wavelength separation by the spectrum unit A MEMS mirror array comprising a condensing lens for condensing an optical signal and a plurality of MEMS mirrors for reflecting an optical signal composed of a plurality of channels collected by the condensing lens, the reflected light The signal is a wavelength selective switch including a condensing lens and a MEMS mirror array coupled to an output port via a spectroscopic unit, and a mirror pitch between adjacent MEMS mirrors of the plurality of MEMS mirrors is chromatic dispersion MEMS mirror corresponding to the channel on the shortest wave side among a plurality of MEMS mirrors, which increases along the direction from the short wave side to the long wave side. Diameter of the incident signal light to above, and is smaller than the diameter of the signal light incident on a plurality of MEMS mirrors corresponding to all the other channels.

  In one embodiment of the present invention, the plurality of MEMS mirrors are characterized in that the ratio of mirror width to mirror pitch is increased in the long wave side channel than in the short wave side channel.

  In one embodiment of the present invention, the plurality of MEMS mirrors have a mirror width and a mirror pitch such that a gap between adjacent MEMS mirrors is equal.

In one embodiment of the present invention, input or output port end or these light and distance from the position entering the condenser lens to the optical axis of the condenser lens, of the light dispersed in the dispersing means The distance from the position where the light incident on the MEMS mirror corresponding to the channel on the shortest wave side enters the condenser lens to the optical axis of the condenser lens is the same .

  It is possible to provide a wavelength selective switch that can be downsized and has a constant transmission band width for each channel.

It is a figure which shows typically the structure of the conventional wavelength selective switch. It is a figure for demonstrating operation | movement of the MEMS mirror of the wavelength selective switch shown in FIG. It is a figure which shows typically the structure of the conventional wavelength selective switch. It is an expanded sectional view showing the composition of a general diffraction grating. It is a figure for demonstrating the relationship between the distance L between spectroscopic optical systems and a condensing lens, and the mirror pitch P of the conventional wavelength selection switch. It is a graph which shows an example of the calculation value of the beam position shift amount from the center of the MEMS mirror with respect to each channel in the conventional wavelength selective switch. It is a figure which shows typically the example of arrangement | positioning of the MEMS mirror array shown in FIG. It is a conceptual diagram for demonstrating the subject of the conventional wavelength selective switch. It is a figure for demonstrating typically the example of arrangement | positioning of the MEMS mirror array in the wavelength selective switch which concerns on embodiment of this invention. It is a figure for demonstrating typically the example of arrangement | positioning of the MEMS mirror array in the wavelength selective switch which concerns on embodiment of this invention. It is a figure which shows typically the structure of the wavelength selective switch which concerns on the Example of this invention.

  Hereinafter, embodiments of the present invention will be described in detail.

  The wavelength selective switch according to the present embodiment includes a single input port and a plurality of output ports or a single output port and a plurality of input ports, a spectral means for wavelength-separating a wavelength multiplexed optical signal emitted from the input port, A condensing lens for condensing the optical signal wavelength-separated by the means and a MEMS mirror array composed of a plurality of MEMS mirrors for reflecting the optical signal condensed by the condensing lens. The optical signal reflected by the MEMS mirror is coupled to the output port via the condenser lens and the spectroscopic means.

In the MEMS mirror array, the plurality of MEMS mirrors are arranged in a line along the direction in which the light is dispersed by the spectroscopic means. FIG. 9 is a schematic diagram of a MEMS mirror array of the wavelength selective switch according to the present embodiment. The configuration of the MEMS mirror array, as the short-wave proceeds to the long wave _{side, P a <P b <P} c <··· <P i and _{W a <W b <W c} <··· <W i , and the mirror Both the pitch (P) and the mirror width (W) become wider as in the conventional wavelength selective switch.

  The wavelength selective switch according to the present embodiment is characterized in that in the MEMS mirror array, as shown in FIG. 9, an optical signal having the narrowest beam diameter is incident on the MEMS mirror corresponding to the channel on the shortest wavelength side.

As shown in FIG. 9, in the wavelength selective switch according to the present embodiment, an elliptical beam is incident on the MEMS mirror. Assuming that the short diameter of the elliptical beam is D, the short diameters D _a , D _b , D _c ,..., D _{i of the} elliptical beams incident on the MEMS mirror corresponding to each CH as the short wave side advances from the short wave side. in, relationship _{D a <D b <D c} <··· <D it is established. Such a relationship is achieved by adjusting components other than the MEMS mirror array of the wavelength selective switch. This will be described later.

  The width (B) of the transmission band is a term that conveniently refers to the flat region of the transmission spectrum, and in order to specifically quantify it, a standard such as “0.5 dB transmission band”, “3 dB transmission band”, etc. It is necessary to show the amount of decrease in transmittance. Further, the unit is a dimensionless amount because it indicates the ratio of the transmission bandwidth (for example, 70 GHz) to the CH interval (for example, 100 GHz).

  The beam diameter (D) is a term that conveniently indicates the beam size diameter of the signal light incident on the MEMS mirror. In general, the size of the Gaussian beam is defined at a point where the beam intensity drops to 13.5% of the beam center.

  When the width of the transmission band of the MEMS wavelength selective switch is B, it is between B, W, and D.

It is known that this relationship is established (see Non-Patent Document 1). Here, W represents the mirror width, P represents the pitch between adjacent mirrors, D represents the diameter of the beam irradiated on the MEMS mirror, and η represents the transmission band reference value (dB).

  From (Equation 3), the width (B) of the transmission band is smaller as the ratio (D / P) of the beam diameter (D) to the mirror pitch (P) becomes smaller, and the mirror width (W) to the mirror pitch (P). ) Increases as the ratio (W / P) increases.

Refer to FIG. 9 again. As described above, in the MEMS mirror array of the wavelength selective switch according to the present embodiment, the mirror pitch (P) of each MEMS mirror increases as it proceeds from the short wave side to the long wave side (P _a <P _b <P _c <. .. <P _i ), the diameter (D) of the signal light incident on each MEMS mirror also increases from the short wave side to the long wave side (D _a <D _b <D _c <... <D _i ).

First, attention is focused on the beam diameter and mirror pitch of the short wave side CH. The beam diameter (D _a ) on the short wave side is the smallest value among the possible beam diameters, and the mirror pitch (P _a ) on the short wave side is the smallest value among the possible mirror pitches. Considering (D _a / P _a ), both the numerator and denominator are minimum values. Next, attention is focused on the beam diameter and mirror pitch of the long wave side CH. The beam diameter (D _i ) on the long wave side is the maximum value among the possible beam diameters, and the mirror pitch (P _i ) on the long wave side is the maximum value among the possible mirror pitches. Considering (D _i / P _i ), both the numerator and denominator are maximum values.

Therefore, the beam diameter ratio (D _i / P _i ) of the long wave side CH does not increase or decrease extremely compared to the beam diameter ratio (D _a / P _a ) of the short wave side CH. Variation in diameter ratio between channels can be minimized. This means an effect that does not generate CH whose transmission bandwidth (B) is extremely reduced.

Here, for comparison, as shown in FIG. 10, unlike the present embodiment, a case where an optical signal having the narrowest beam diameter is incident on the MEMS mirror corresponding to the longest-side CH is considered. While the mirror pitch (P) of each MEMS mirror increases from the short wave side to the long wave side (P _a <P _b <P _c <... <P _i ), the beam diameter of the beam incident on each MEMS mirror ( D) decreases from the short wave side to the long wave side (D _a > D _b > D _c >...> D _i ).

First, attention is focused on the beam diameter and mirror pitch of the short wave side CH. The short-wave side beam diameter (D _a ) is the maximum value among the possible beam diameters, but the short-wave side mirror pitch (P _a ) is the minimum value among the possible mirror pitches. Considering the diameter ratio (D _a / P _a ), it becomes the maximum value among the possible beam diameter ratios. Next, attention is focused on the beam diameter and mirror pitch of the long wave side CH. The beam diameter (D _i ) on the long wave side is the minimum value among the possible beam diameters, but the mirror pitch (P _i ) on the long wave side is the maximum value among the possible mirror pitches. Considering the diameter ratio (D _i / P _i ), it becomes the minimum value among the possible beam diameter ratios.

Therefore, since the beam diameter ratio (D _a / P _a ) of the short wave side CH is maximized and the beam diameter ratio (D _i / P _i ) of the long wave side CH is minimized, the transmission bandwidth is long in the long wave side CH. Although (B _i ) can be expanded, there is a problem that the transmission bandwidth (B _a ) is extremely reduced in the short-wave side CH.

  Another feature of the wavelength selective switch according to the present embodiment is that, in the MEMS mirror array, the ratio (W / P) of the mirror width (W) to the mirror pitch (P) is increased on the long wave side CH. And As described above, the width of the transmission band is the ratio (W) of the mirror width (W) to the mirror pitch (P) as the ratio (D / P) of the beam diameter (D) to the mirror pitch (P) decreases. The larger the / P), the larger the magnification. In a general wavelength selective switch, since the beam diameter ratio (D / P) hardly changes depending on CH, the mirror width ratio (W / P) is designed not to change depending on CH. However, in the wavelength selective switch according to this embodiment, the beam diameter ratio (D / P) often increases slightly from the short wave side CH toward the long wave side CH. In this case, since the band is slightly reduced on the long wave side CH, the mirror diameter ratio (W / P) is increased on the long wave side so as to compensate for the decrease in the band so that the transmission band does not decrease in the entire CH region. It is desirable to do.

  As a specific example, the wavelength selective switch according to the present embodiment is characterized in that in the MEMS mirror array, the inter-mirror gap (gap) (P-W) of each CH is constant. As described above, the width (B) of the transmission band can be increased as the ratio (W / P) of the mirror width (W) to the mirror pitch (P) increases, but the mirror width should be increased beyond the mirror pitch. I can't. Therefore, in order to maximize the mirror width ratio, it is desirable to minimize the inter-mirror gap (P-W) of each CH and make it constant regardless of the CH. The amount of gap that can be minimized depends on the manufacturing method of the mirror, but making the gap between the mirrors constant can make the size of the opening at the time of mirror preparation constant, thus improving the mirror dimensional accuracy and forming the mirror. It has the effect of reducing foreign matters that are sometimes generated, and also has the effect of improving the mirror manufacturing yield.

  Hereinafter, embodiments of the present invention will be described in detail.

  As illustrated in FIG. 11, the wavelength selective switch 500 according to the present embodiment includes an input / output optical system 501, a condenser lens 502, a reflective spectroscopic optical system 503, and a MEMS mirror array 504.

  The input / output optical system 501 includes at least one input port and a plurality of output ports.

  The condensing lens 502 refracts the signal light from the input / output optical system 501 and reaches the reflective spectroscopic optical system 503. The condensing lens 502 condenses the optical signal wavelength-separated by the reflective spectroscopic optical system 503. A doublet lens or a triplet lens can be used as the condenser lens.

  The reflective spectroscopic optical system 503 diffracts and reflects the signal light incident from the condenser lens 502. As the reflection type spectroscopic optical system 503, a combination of a transmission type diffraction grating and a reflection mirror can be used.

  The MEMS mirror array 504 is configured by arranging a plurality of MEMS mirrors in a line. Each MEMS mirror of the MEMS mirror array 504 reflects the separated light of one wavelength so as to be coupled to a predetermined output port. As shown in FIG. 11, in the wavelength selective switch according to the present embodiment, the input / output optical system 501 is arranged closer to the MEMS mirror corresponding to the long wave side CH than the MEMS mirror corresponding to the short wave side CH. Is done.

  The wavelength selective switch 500 according to the present embodiment has a configuration as shown in FIG. 11, and the optical path of the input / output light beam and the short-wave optical path of the demultiplexed light beam are arranged at the outer edge of the light beam group. Will be. That is, when the optical axis of the condenser lens 502 is used as a reference, the optical path from the input / output port to the condenser lens 502 is symmetrical to the optical path from the MEMS mirror corresponding to the short-wave CH to the condenser lens 502. is there. Therefore, when the optical axis of the condenser lens 502 is used as a reference, the distance to the position where the optical path from the input / output port enters the condenser lens 502 and the optical path from the MEMS mirror corresponding to the shortest-side CH are collected. The distance to the position incident on the optical lens 502 is the same.

  Due to such a wavelength selective switch configuration, the short-side light beam of the input / output light beam and the demultiplexed light beam has the same spherical aberration from the condenser lens, and the input / output light beam and the short-wave side light beam are separated from each other. The aberration becomes smaller. Therefore, it becomes easy to arrange the beam having the narrowest beam diameter on the MEMS mirror corresponding to the CH on the short wave side.

  Further, as an application example of the present embodiment, by arranging the condensing lens and the MEMS mirror array in an inclined manner, the optical path difference of the incident light beam to the MEMS mirror corresponding to the short wave side CH is reduced, and the short wave side CH is supported. A beam having the narrowest beam diameter can also be arranged on the MEMS mirror.

1 wavelength selection switch 10 substrate 11 collimator array (input / output optical system)
11-1 Input fiber 11-2, 11-3, 11-4 Output fiber 12 Spectroscope [spectral element (diffraction grating); spectroscopic optical system]
13 Condensing lens (Condensing optical system)
14 MEMS mirror array unit (switching element)

112 Spectrometer 113 Condensing lens 120 Glass substrate 140 MEMS mirror

400 Wavelength selection switch 410 I / O port array 420 fθ lens 430 Cylindrical lens 440 4f optical system 441 First lens 442 Diffraction grating 443 Second lens 450 Mirror array 451 MEMS mirror

500 Wavelength selection switch 501 Input / output optical system 502 Condensing lens 503 Reflection spectroscopic optical system 504 MEMS mirror array

Claims (4)

A single input port and multiple output ports or a single output port and multiple input ports;
Spectroscopic means for wavelength-separating the wavelength multiplexed optical signal emitted from the input port;
A condenser lens for condensing the optical signal wavelength-separated by the spectroscopic means;
A MEMS mirror array composed of a plurality of MEMS mirrors that reflect an optical signal composed of a plurality of channels collected by the condensing lens, wherein the reflected optical signal includes the condensing lens and the spectroscopic lens. A wavelength selective switch comprising a MEMS mirror array coupled to the output port via means,
The mirror pitch between adjacent MEMS mirrors of the plurality of MEMS mirrors increases as the wavelength advances from the short wave side to the long wave side along the wavelength dispersion direction.
Of the plurality of MEMS mirrors, the diameter of the signal light incident on the MEMS mirror corresponding to the shortest channel is smaller than the diameter of the signal light incident on the plurality of MEMS mirrors corresponding to all other channels. Wavelength selective switch characterized by   2. The wavelength selective switch according to claim 1, wherein in the plurality of MEMS mirrors, a ratio of a mirror width to a mirror pitch is increased in a long wave side channel than in a short wave side channel.   The wavelength selective switch according to claim 1, wherein the plurality of MEMS mirrors have a mirror width and a mirror pitch such that a gap between adjacent MEMS mirrors is equal. The distance from the position where the entering force or output port end or these light is incident on the condenser lens to the optical axis of the condenser lens, the most short-wave side channel of the dispersed light in the spectroscopic means 2. The wavelength selective switch according to claim 1, wherein a distance from a position where light incident on a corresponding MEMS mirror is incident on the condenser lens to an optical axis of the condenser lens is the same .

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