JP2013088615A - Wavelength selection switch - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wavelength selection switch (WSS) capable of entering light with a desired wavelength into a MEMS mirror without changing design of the MEMS mirror.SOLUTION: A WSS according to an embodiment of the present invention comprises: an input/output fiber array; a diffraction grating for multiplexing/demultiplexing; a MEMS mirror array; and a light shielding mask at the stage in front of the MEMS mirror array. A WSS according to another embodiment of the present invention comprises: an input/output fiber array; a diffraction grating for multiplexing/demultiplexing; a MEMS mirror array; and a return mirror at the stage in front of the MEMS mirror array, and a band stop filter consisting of a dielectric multilayer and the like is integrated in any of optical elements composing the WSS. A WSS according to still another embodiment of the present invention includes a band pass filter at the stage in front of a MEMS mirror array and in the middle of a signal light path.

Description

  The present invention relates to a wavelength selective switch, and more specifically to a wavelength selective switch that makes light of a desired wavelength incident on a MEMS mirror array.

  There is a need for a device that has a plurality of optical input / output ports and can selectively operate wavelength-multiplexed optical signals as light. One such device is a wavelength selective switch (WSS). The WSS is a device that can selectively distribute an input wavelength multiplexed signal to different outputs for each wavelength.

  A general WSS is a device for optical communication of a spatial optical system using a multiplexing / demultiplexing element and a polarizing element. The light that is combined and incident is demultiplexed into a position-dependent beam for each wavelength via a dispersive element, and switching for each wavelength is realized by selecting an output port by a MEMS mirror (for example, , See Patent Document 1).

JP 2011-002693 A US Pat. No. 6,625,346

  A conventional WSS example will be described with reference to the drawings.

  FIG. 1 is a conceptual diagram of a conventional WSS. The WSS 100 includes an input / output fiber array 120 composed of one input fiber 122 and two output fibers (124-1, 124-2), a multiplexing / demultiplexing diffraction grating 140, and a biaxial movable MEMS mirror array 160. And an optical / electrical control device 180. The optical signal entering from the input fiber 122 is demultiplexed for each wavelength by the multiplexing / demultiplexing diffraction grating 140. Next, each of the demultiplexed light reaches the MEMS mirror constituting the biaxial movable MEMS mirror array 160 and is reflected. Next, each of the reflected lights is multiplexed by the multiplexing / demultiplexing diffraction grating 140 and output from a predetermined output fiber (124-1 or 124-2). The optical / electrical control device 180 controls the angle of the MEMS mirror to determine the output port for each wavelength.

  FIG. 2 is a perspective view for explaining the configuration of an example of a conventional WSS. The WSS 200 shown in FIG. 2 includes a base 210, an input / output port array in which one input port 222 and three output ports (224-1, 242-2, 224-3) are arranged in a predetermined direction, This is a 1-input-port 3-output-port WSS including a collimator array including a plurality of collimators 230, a diffraction grating 240 as a spectroscopic device, a lens 250, and a MEMS element 260 that switches an optical path of an optical signal.

  A wavelength division multiplexed (WDM) optical signal input from the input port 222 passes through a collimator 230 to become a parallel beam, and is demultiplexed to each wavelength by the diffraction grating 240. The demultiplexed optical signals of the respective wavelengths reach the MEMS mirror of the MEMS element 260 prepared for each wavelength through the lens 250 and are reflected. When the light is reflected, the output port is determined for each wavelength by controlling the angle of the MEMS mirror (see FIG. 3). Thereafter, the optical signals of the respective wavelengths are combined for each output port (224-1, 244-2, 224-3) through the lens 250 by the diffraction grating 240, and output from a desired output port. There are few restrictions on the number of wavelengths that can be connected to each output port and the output port to which the optical signal of each wavelength is connected, and it is possible to handle optical signals of various wavelengths. In this WSS, traffic can be flexibly distributed on the order of milliseconds.

  FIG. 3 is a schematic explanatory view showing a part of the WSS in order to explain the operation of the WSS shown in FIG. In the WSS shown in FIG. 3A, the inclination of the MEMS mirror 262 is a direction perpendicular to the base 210. At this time, the optical signal is output from the output port 224-3. Next, the MEMS mirror 262 is tilted as shown in FIG. At this time, the optical signal is output from the output port 224-2. Thus, the output port from which the optical signal is output is determined by controlling the angle of the MEMS mirror (see, for example, Patent Document 1).

  FIG. 4 is a schematic perspective view for explaining an example of a conventional WSS. The WSS 400 shown in FIG. 4 includes an input / output port array 410 in which input ports and output ports are arranged in a predetermined direction, and an fθ lens 420 that converts polarized light into parallel light in order to input / output optical signals to / from the input / output ports. 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. A 4f optical system 440 that projects an optical signal having an elliptical cross section collected through 430 onto the mirror array at an equal magnification, and a mirror array 450 in which a plurality of MEMS mirrors 451 are arranged in a line along a predetermined direction. These are arranged in a line along the z-axis in FIG. 4 in this order.

  Here, the input / output port array is generally composed of a fiber collimator in which an optical fiber for an input port and an optical fiber for an output port are one-dimensionally arranged and fixed in the same block (fixing tool). Has been. 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.

  Further, the MEMS mirror 451 can be rotated around an x-axis orthogonal to the z-axis and a y-axis orthogonal to the x-axis (see FIG. 5). The input / output ports are arranged in the direction along the y-axis. The MEMS mirrors are arranged in a direction along the x-axis.

  As shown in FIG. 5, the MEMS mirror 451 as a deflecting element for deflecting the optical signals of the demultiplexed wavelengths and coupling the optical signals to the target ports in an arbitrary coupling state is, as described above, the wavelength dispersion direction. (Θy direction) and the ability to deflect the beam in two directions perpendicular to the wavelength dispersion direction (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, and is mainly an arbitrary coupling state, that is, an angle for adjusting the WSS attenuation factor (ATT). It is.

  In the WSS having the above-described conventional configuration, noise in a wavelength band that is not used is incident on the MEMS mirror due to the specifications of the switching device (MEMS mirror). Therefore, in order to suppress light in an unnecessary wavelength band, it is necessary to control the MEMS mirror on which an optical signal in an unnecessary wavelength band is incident so that the MEMS mirror is tilted and not coupled to any output port. It was. For this reason, it is necessary to drive even MEMS mirrors other than the necessary band, and there is a problem that the mirror design must be changed for each device so as to have only the necessary band.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a WSS capable of entering light having a wavelength in a desired band into a MEMS mirror array without changing the design of the MEMS mirror. And

  The present invention provides at least one input port, a plurality of output ports, a spectral unit for wavelength-separating a wavelength multiplexed optical signal emitted from the input port, and a condensing unit for condensing the optical signal wavelength-separated by the spectral unit. A MEMS mirror array including a lens and a plurality of MEMS mirrors that reflect optical signals collected by a condenser lens, and the reflected optical signals are output to an output port via a condenser lens and a spectroscopic unit. A wavelength selective switch including a MEMS mirror array to be coupled, wherein the wavelength selective switch further includes a light shielding mask between the condensing lens and the MEMS mirror array, and the light shielding mask converts an optical signal having a predetermined bandwidth. A rectangular opening having a corresponding width is provided.

  In one embodiment of the present invention, the tilt of the MEMS mirror existing near the edge of the light shielding mask is controlled.

  The present invention provides at least one input port, a plurality of output ports, a spectral unit for wavelength-separating a wavelength multiplexed optical signal emitted from the input port, and a condensing unit for condensing the optical signal wavelength-separated by the spectral unit. A MEMS mirror array including a lens and a plurality of MEMS mirrors that reflect optical signals collected by a condenser lens, and the reflected optical signals are output to an output port via a condenser lens and a spectroscopic unit. A wavelength selective switch including a MEMS mirror array to be coupled, wherein the wavelength selective switch further includes at least one folding mirror between the input port and the MEMS mirror array, and any of optical elements constituting the wavelength selective switch. In this case, a band stop filter made of a dielectric multilayer film is integrated.

  The present invention provides at least one input port, a plurality of output ports, a spectral unit for wavelength-separating a wavelength multiplexed optical signal emitted from the input port, and a condensing unit for condensing the optical signal wavelength-separated by the spectral unit. A MEMS mirror array including a lens and a plurality of MEMS mirrors that reflect optical signals collected by a condenser lens, and the reflected optical signals are output to an output port via a condenser lens and a spectroscopic unit. A wavelength selective switch including a MEMS mirror array to be coupled, wherein the wavelength selective switch further includes a band-pass filter before the MEMS mirror array and in the middle of the optical path of the signal light.

  The WSS according to an embodiment of the present invention can limit the band of light incident on the MEMS mirror array by providing a light shielding mask in the previous stage of the MEMS mirror.

  The WSS according to an embodiment of the present invention can change the band of light incident on the MEMS mirror array without changing the design of the MEMS mirror.

  The WSS according to an embodiment of the present invention limits the band of light incident on the MEMS mirror array by integrating filters on the folding mirror in the previous stage of the MEMS mirror. Therefore, there is an advantage that it is not necessary to add a new component to the WSS when limiting the band of light incident on the MEMS mirror array.

  The WSS according to an embodiment of the present invention limits the band of light incident on the MEMS mirror array by installing a band pass filter in the optical path of the signal light. The band-pass filter can be installed at an arbitrary location as long as it is a front stage of the MEMS mirror. Therefore, free design of WSS is possible.

It is a conceptual diagram of conventional WSS. It is a perspective conceptual diagram for demonstrating the structure of the conventional WSS. It is explanatory drawing for demonstrating operation | movement of WSS shown in FIG. It is a figure which shows the structure of the conventional WSS typically. FIG. 5 is a diagram for explaining the operation of the WSS MEMS mirror shown in FIG. 4. It is a conceptual diagram of one Embodiment of WSS which concerns on this invention. It is a schematic perspective view of the model used in order to obtain the WSS simulation result concerning one embodiment of the present invention. It is explanatory drawing of the model used in order to obtain the simulation result of WSS which concerns on one Embodiment of this invention. It is explanatory drawing of the model used in order to obtain the simulation result of WSS which concerns on one Embodiment of this invention. It is explanatory drawing of WSS which concerns on one Embodiment of this invention. In WSS which concerns on one Embodiment of this invention, it is a graph which shows the experimental result showing the quantity of the light shielded with respect to each channel when the light shielding mask is arrange | positioned in a certain position. It is a conceptual diagram of one Embodiment of WSS which concerns on this invention. It is a graph which shows the characteristic in one Example of WSS which concerns on this invention. It is a graph which shows the characteristic in one Example of WSS which concerns on this invention.

Hereinafter, embodiments of the present invention will be described in detail.
(First embodiment)
FIG. 6 is a conceptual diagram of an embodiment of the WSS according to the present invention. The WSS 100 includes an input / output fiber array 120 including one input fiber 122 and two output fibers 124-1 and 124-2, a multiplexing / demultiplexing diffraction grating 140, a light shielding mask 150, and a biaxial movable MEMS. It comprises a mirror array 160 and an optical / electrical control device 180. The optical signal entering from the input fiber 122 is demultiplexed for each wavelength by the multiplexing / demultiplexing diffraction grating 140. Next, among the demultiplexed optical signals, an optical signal corresponding to the outside of the wavelength band (the short wave side and the long wave side exist) is shielded by the light shielding mask 150. The optical signal that is not shielded reaches the MEMS mirror that constitutes the biaxial movable MEMS mirror array 160 and is reflected. Next, each of the reflected lights is multiplexed by the multiplexing / demultiplexing diffraction grating 140 and output from a predetermined output fiber (124-1 or 124-2). The optical / electrical control device 180 controls the angle of the MEMS mirror to determine the output port for each wavelength.

  A model used for obtaining the simulation result of the present embodiment will be described with reference to FIGS.

  FIG. 7 is an explanatory diagram of a model used for obtaining the simulation result of the present embodiment, and is a schematic perspective view in which only the light shielding mask 150 and the MEMS mirror array 160 are extracted from the constituent elements of the WSS. A light shielding mask 150 is disposed above the z-axis of the MEMS mirror array 160 in FIG. 7, that is, between the diffraction grating 140 for multiplexing / demultiplexing (not shown in FIG. 7) and the MEMS mirror array 160. ing. A plurality of MEMS mirrors are arranged in a line in the direction along the x-axis. Each MEMS mirror is rotatable about the x axis.

  FIG. 8 is another explanatory diagram of the model used to obtain the simulation result of the present embodiment. FIG. 8A is a schematic top view of only the light shielding mask 150 and the MEMS mirror array 160 extracted from the WSS components, and FIG. 8B is a broken line AA ′ shown in FIG. FIG. As shown in FIG. 8B, the distance between the light shielding mask 150 and the MEMS mirror array 160 was set to 3.1 mm. FIG. 9 is an enlarged view of the region IX in FIG.

  As a result of the simulation analysis using the models shown in FIGS. 7 to 9, the optical loss of the incident optical signal in the channel corresponding to the position separated by 0.25 mm or more along the x-axis direction from the edge of the light shielding mask is I couldn't see it. In this specification, the wavelength band used for communication is referred to as an inner band, and the other wavelength band is referred to as an outer band. In the WSS of the present invention, it is necessary to design and install a mask so that no loss occurs in the inner band.

  In order to compare with the simulation analysis results described above, WSS as shown in FIG. FIG. 10 is a schematic top view showing only the light shielding mask 150 and the MEMS mirror array 160 extracted from the constituent elements of the WSS. As shown in FIG. 10, the design is such that a light shielding mask is disposed on a channel of 190.95 THz or more. In addition, the design is such that the edge of the light-shielding mask 150 is arranged to be shifted by 58 μm from the end of the 190.95 THz channel.

  FIG. 11 shows the results of an experiment conducted using the WSS shown in FIG. FIG. 11 is a graph showing the light intensity of the incident optical signal in each channel when the light shielding mask is arranged at the position shown in FIG. As shown in FIG. 10, the attenuation of the incident optical signal was confirmed in the channel of 190.90 THz or more by arranging the light shielding mask. As shown in FIG. 10, when the frequency increased by 130 GHz, there was a 43 dB attenuation. It was also found that the optical signal incident on the 190.95 THz channel that exists immediately below the edge position of the light shielding mask is attenuated by 22 dB by arranging the light shielding mask.

  As described above, the band of signal light incident on the MEMS mirror array 160 can be adjusted by the light-shielding mask 150 that is retrofitted without changing the design of the MEMS mirror array 160.

  For channels that are in the position corresponding to the outer band and into which an optical signal enters, it is necessary to control the inclination of the channel to reflect the light in a direction that does not cause noise, but the number of such channels is small. .

  In the present embodiment, the band of the optical signal incident on the MEMS mirror array can be adjusted by changing the size of the opening of the light shielding mask.

  In the above-described model, a single light shielding mask having a rectangular opening was examined. However, the present invention can be realized by arranging a plurality of light shielding masks having no opening above the MEMS mirror array. it can. As a result, it is possible to shield not only the outer band but also signal light in a desired band.

(Second Embodiment)
Since mounting of electric wiring or the like is easy, the MEMS mirror is often arranged horizontally on the optical base. In such a case, it is necessary to bend the optical path of the light traveling on the optical base at a right angle by the folding mirror so that the light enters the MEMS mirror array (see, for example, FIG. 11). The WSS 200 according to the present embodiment has such a spatial optical system. That is, the WSS 200 according to the present embodiment includes the folding mirror 255 for bending the optical path of the optical signal in the previous stage of the MEMS mirror array 260.

  By laminating a dielectric multilayer film on the folding mirror 255, a band stop filter for suppressing the outer band coated on the folding mirror 255 is realized. Thereby, the reflectance of the folding mirror is made to have wavelength dependency. More specifically, by increasing only the reflectance of a specific band of the folding mirror, it is possible to reflect only an optical signal in a necessary band, thereby suppressing an outer band.

As a material for the filter, tantalum pentoxide (Ta ₂ O ₅ ), silicon dioxide (SiO ₂ ), or the like can be used. Using these materials, a coating that forms a multilayer film by ion-assisted vapor deposition or the like is applied. The coating may be performed by a method other than the vapor deposition method (for example, a sputtering method).

  Further, as a means for attenuating an optical signal other than the desired band, a combination of a high-pass filter and a low-pass filter can be used on the optical path of the optical signal instead of using a band stop filter.

  It is also possible to integrate the filter in an element other than the mirror (for example, a lens). A plurality of filters can be integrated in various elements, and desired filter characteristics can be ensured in the entire system.

  Furthermore, instead of realizing a band stop filter on the folding mirror or realizing a combination of a high-pass filter and a low-pass filter on the optical path of the optical signal, a multilayer is provided in the front stage of the MEMS mirror array and in the middle of the optical path of the signal light. A membrane bandpass filter may be installed.

  Hereinafter, an example of this embodiment will be described. A model in which a multilayer band-pass filter is installed in the upstream stage of the MEMS mirror array and in the optical path of the signal light was examined. The simulation results of the wavelength dependence of the loss due to the insertion of the bandpass filter are shown in FIGS.

  In FIG. 12, the solid line shows the result when one filter is inserted, and the broken line shows the result when the same two filters are inserted. When one filter is installed, the insertion loss of the filter in the short wavelength side stop band (1560.00nm-1567.75nm) is 20dB or more, and the insertion loss of the filter in the long wavelength side stop band (1609.85nm-1617.00nm) Obtained a result of 20 dB or more. On the other hand, when two filters are installed, the insertion loss of the filter in the short wavelength side stop band (1560.00 nm-1567.75 nm) is 43 dB or more, and the filter in the long wavelength side stop band (1609.85 nm-1617.00 nm) The insertion loss was 43 dB or more.

  FIG. 13 is an enlarged view of a part of the region of FIG. When one filter is installed, the insertion loss of the filter in the transmission band (1570.21 nm-1607.25 nm) is less than 0.1 dB, indicating that the flatness in the transmission band is ensured. On the other hand, when two filters were installed, the insertion loss of the filter in the transmission band (1570.21 nm-1607.25 nm) increased compared to when one filter was installed, but was less than 0.2 dB.

  As shown in FIGS. 12 and 13, when two band pass filters are installed, the transmission band is 1570.21 nm to 1607.25 nm, the insertion loss in the transmission band is less than 0.2 dB, and the extinction ratio is 43 dB or more. The filter characteristics were obtained.

  In the WSS according to the present embodiment, the wavelength band of the signal light incident on the MEMS mirror array is adjusted by integrating a filter on an existing mirror or the like. Therefore, it is not necessary to add a new element to WSS.

  As described above, the filter can be integrated into a number of existing elements in the WSS. Thereby, an extinction ratio can be expanded and a plurality of filter functions can be integrated.

DESCRIPTION OF SYMBOLS 100 Wavelength selection switch 120 Input / output fiber array 122 Input fibers 124-1, 124-2 Output fiber 140 Diffraction grating 150 for multiplexing / demultiplexing Shading mask 160 Biaxial rotation type MEMS mirror array 180 Optical / electric control device

200 Wavelength selective switch 210 Base 222 Input port 224-1, 244-2, 224-3 Output port 230 Collimator 240 Diffraction grating 250 Lens 255 Folding mirror 260 MEMS element 262 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

Claims (4)

At least one input port;
Multiple output 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 collected by the condenser lens, wherein the reflected optical signal is output to the output port via the condenser lens and the spectroscopic means. A wavelength selective switch comprising a MEMS mirror array coupled to
The wavelength selective switch further includes a light shielding mask between the condenser lens and the MEMS mirror array,
The wavelength selective switch, wherein the light shielding mask includes a rectangular opening having a width corresponding to an optical signal having a predetermined bandwidth.   2. The wavelength selective switch according to claim 1, wherein the MEMS mirror existing near the edge of the light shielding mask is controlled in inclination. At least one input port;
Multiple output 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 collected by the condenser lens, wherein the reflected optical signal is output to the output port via the condenser lens and the spectroscopic means. A wavelength selective switch comprising a MEMS mirror array coupled to
The wavelength selective switch further includes at least one folding mirror between the input port and the MEMS mirror array,
A wavelength selective switch, wherein a band stop filter made of a dielectric multilayer film is integrated in any one of the optical elements constituting the wavelength selective switch. At least one input port;
Multiple output 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 collected by the condenser lens, wherein the reflected optical signal is output to the output port via the condenser lens and the spectroscopic means. A wavelength selective switch comprising a MEMS mirror array coupled to
The wavelength selective switch further includes a band-pass filter in the front stage of the MEMS mirror array and in the optical path of the signal light.

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