JP2013076891A - Optical signal selection switch - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical signal selection switch where crosstalk occurring between output ports is suppressed.SOLUTION: The optical signal selection switch includes: at least one input port; a plurality of output ports; a condenser lens which condenses an optical signal emitted from the at least one input port; and deflecting means which gives phase shifts to the optical signal condensed by the condenser lens and reflects the optical signal so that the optical signal to which the phase shifts are given is coupled with the output ports via the condenser lens. A period of a phase-shifted waveform in one output port due to the deflecting means is different from 1/i (i is an integer other than 0) of periods of the phase-shift waveform in the other output ports due to the deflecting means, so that crosstalk between ports can be suppressed because, in one output port, diffracted light of second and higher orders of the other output ports are not coupled.

Description

  The present invention relates to an optical signal selection switch. Specifically, the present invention relates to an optical signal selection switch that prevents high-order diffracted light from entering an output port other than a desired output port.

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

  FIG. 1 shows an example of a conventional wavelength selective switch (see, for example, Patent Document 1). FIG. 1 is a schematic diagram showing the configuration of a conventional wavelength selective switch. Coordinate axes are set as shown in FIG. Specifically, the direction perpendicular to the light wave traveling direction (that is, the optical axis) in the optical waveguide substrate 210 and horizontal to the input / output end face of the signal light in the optical waveguide substrate 210 is defined as X, and the direction perpendicular to the optical waveguide substrate 210 is defined as X. Y is assumed to be Z, and the traveling direction (that is, the optical axis) of the light wave in the optical waveguide substrate 210 is assumed to be Z. FIG. 1 is a side view seen from the X-axis direction.

  The wavelength selective switch 200 includes an optical waveguide substrate 210, a cylindrical lens 220, a polarization separation unit 230, a beam size conversion unit 240, a spectroscopic unit 250, a condensing lens 260, and an optical deflection unit 270.

  Although not shown in FIG. 1, an input / output waveguide, a slab waveguide connected to the input / output waveguide, and an arrayed waveguide connected to the slab waveguide are manufactured on the optical waveguide substrate 210. Has been.

  Although not shown in FIG. 1, there are a total of 21 input / output waveguides, with one waveguide at the center serving as an input port and 10 waveguides formed on both sides of the input port as outputs. Port. Here, the waveguides produced on both sides of the input port are called output ports # 1, 2,..., 10 and # -1, -2,.

  The slab waveguide acts to distribute light input from the input port of the input waveguide and couple it to the arrayed waveguide. In the case of reflection, the slab waveguide couples the light input from the arrayed waveguide to one of the output ports of the input / output waveguide according to the phase relationship between the light waves propagating through each arrayed waveguide. Acts like

  An arrayed waveguide is a row of a plurality of waveguides having an optical path length difference of zero. The arrayed waveguide enters light from the slab waveguide into the cylindrical lens 220 and couples the light from the cylindrical lens 220 to the slab waveguide.

  The cylindrical lens 220 acts so that light emitted from the arrayed waveguide enters the beam size conversion unit 240 without spreading in the Y-axis direction.

  The polarization separation unit 230 separates the light incident from the cylindrical lens 220 into two orthogonal polarization components (horizontal component and vertical component). The polarization separation unit 230 emits the two polarized light beams from different portions in the Y-axis direction. The light emitted from the polarization separation unit 230 enters the beam size conversion unit 240.

  The beam size converter 240 acts to spread the light incident from the polarization separator 230 in the Y-axis direction. FIG. 1 shows an example in which the beam size conversion unit 240 is configured by arranging two cylindrical lenses 242 and 244 in parallel to a plane including the X axis.

  The spectroscopic unit 250 acts to diffract the light incident from the beam size conversion unit 240 and separate the wavelength. FIG. 1 shows an example in which the spectroscopic unit 250 is configured using a transmission type bulk diffraction grating 252. As a result of diffraction by the spectroscopic unit 250, each wavelength-separated optical signal forms an interference fringe on the corresponding phase grating of the optical deflecting unit 270.

  The condensing lens 260 acts to condense the light transmitted through the spectroscopic unit 250 onto the light deflecting unit 270. FIG. 1 shows an example in which a cylindrical lens is used as the condenser lens 260.

  The optical deflecting unit 270 includes a phase control element that reflects incident light while deflecting it with a phase grating corresponding to each wavelength-separated optical signal, and couples it to the bulk diffraction grating 252 via the condenser lens 260. The optical deflection unit 270 can be configured using a spatial phase modulator called LCOS (Liquid Crystal on Silicon). The LCOS is a reflective device in which liquid crystal elements (pixels) are arranged on the surface of a complementary metal-oxide semiconductor (CMOS). The liquid crystal element acts as a phase control element to give a phase difference to the incident optical signal, to form a phase grating, and to reverse the optical path.

  FIG. 2 is a diagram showing an outline of a light incident surface in the light deflecting unit 270 of the wavelength selective switch shown in FIG. As shown in FIG. 2, a plurality of pixels 272 are arranged on a lattice on the light incident surface (XZ plane) of the light deflector (LCOS) 270. Each pixel can be controlled independently, and the amount of phase imparted to the light at each pixel can be controlled. Each optical signal wavelength-separated by the spectroscopic unit 250 is condensed by the condenser lens 260 onto a corresponding pixel group on the Z axis. That is, the light incident from the input port of the input / output waveguide is wavelength-separated in the Z-axis direction by the light deflection unit 270.

FIG. 3 is a diagram illustrating a state in which a phase shift is imparted to light having a certain wavelength λ by the arrangement of certain pixels in the Z-axis direction of the light deflecting unit 270. In FIG. 3, d = n × p (n is an integer and the number of pixels constituting one phase grating) where d is the pitch of one phase grating and p is the length of one side of each pixel. In this case, the deflection angle θ _d of the light in the phase grating can be expressed as sin θ _d = λ / d. When the pitch d of the phase grating increases (that is, when n increases), the deflection angle dependency of the pixel angle becomes linear, but the deflection angle decreases. On the other hand, when the pitch d of the phase grating is reduced, the deflection angle is increased, but the dependence of the deflection angle on the number of divided pixels is nonlinear.

  As shown in FIG. 3, in a wavelength selective switch using LCOS, spatial sawtooth phase modulation (serodyne modulation) is applied to input light by LCOS.

Here, with respect to the phase setting of each pixel constituting the phase grating on which light of a certain wavelength is incident (that is, pixels arranged in the X-axis direction), the difference between the phase setting amounts set in adjacent pixels is expressed as ε (FIG. 3), the relationship between the desired deflection angle θ _d and the phase setting amount difference ε should be calculated in advance using a known calculation formula in consideration of various lenses, the arrangement of the optical waveguide substrate 210, and the like. Is possible (see Non-Patent Document 1). FIG. 3 illustrates a case where three pixels form a phase grating having a periodic structure in a direction in which the light deflecting unit 270 deflects light. However, a phase grating having a periodic structure with three or more pixels is illustrated. It may be configured.

  In the wavelength selective switch 200 shown in FIG. 1, when a WDM optical signal in which optical signals of a plurality of wavelengths are multiplexed is incident from an input port, the WDM optical signal is guided through a slab waveguide, and each of the WDM optical signals is passed through an array waveguide. It is coupled to the constituent waveguide.

  After the WDM optical signal emitted from the arrayed waveguide is converted into collimated light through the cylindrical lens 220, it enters the polarization separation unit 230 and is separated into a horizontal polarization component and a vertical polarization component. Two WDM optical signals having the same polarization component are output.

  The two WDM optical signals emitted from the polarization separation unit 230 are each subjected to wavelength separation in the spectroscopic unit 250.

  Each optical signal subjected to wavelength separation in the spectroscopic unit 250 is condensed on a corresponding phase grating of the light deflecting unit 270 by the condenser lens 260. In FIG. 1, the optical signal is incident on the phase grating so that the Z axis is the wavelength axis. Optical signals of the same wavelength that have been wavelength-separated from the two WDM optical signals incident on the spectroscopic unit 250 from the polarization separation unit 230 are collected on the same phase grating.

  In each phase grating of the optical deflection unit 270, the optical signal is independently deflected for each wavelength and reflected so as to enter the spectroscopic unit 250 through the focus lens 260. The deflection angle of the optical signal for each wavelength is determined according to the period of the phase grating and the phase shift amount. In other words, by controlling the period of the phase grating and the phase shift amount corresponding to each WDM signal, the deflection angle can be controlled independently for each wavelength.

  The optical signals of the respective wavelengths incident again on the spectroscopic unit 250 are combined and coupled to the arrayed waveguide through the beam size conversion unit 240, the polarization separation unit 230, and the cylindrical lens 220 again.

  The optical signal guided through the arrayed waveguide is guided through the slab waveguide and coupled to one of the output waveguides.

JP 2009-258438 A

By Hector, Hector Optics II, September 2004, p88, p247

  The configuration of the conventional wavelength selective switch has the following problems. FIG. 4 is a conceptual diagram for explaining the problem of the wavelength selective switch according to the prior art. As shown in FIG. 4A, the incident light incident on the LCOS constituting the light deflector is deflected and reflected. Here, let N be the period of the serodyne waveform when the output port is set to # 1. FIG. 4A illustrates the generation of 0th-order, ± 1st-order, and ± 2nd-order diffracted light.

  Here, it is assumed that the output port is arranged so that the period of the serodyne waveform when the output port is set to # 2 is N / 2. The period of the serodyne waveform shown in FIG. 4B is half the period of the serodyne waveform shown in FIG. FIG. 4B illustrates the generation of 0th-order and ± 1st-order diffracted light.

  As shown in FIGS. 4A and 4B, the diffraction angle of the second-order diffracted light when the period of the serrodyne waveform is N is the diffraction angle of the first-order diffracted light when the period of the serodyne waveform is N / 2. Is equal to Accordingly, the second-order diffracted light when the period of the serrodyne waveform is N overlaps with the first-order diffracted light when the period of the serrodyne waveform is N / 2, and the crosstalk between ports deteriorates.

  As described above, even with an ideal serodyne waveform, high-order diffracted light is generated, and signal light is deflected and reflected to an output port other than the desired output port. there were.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide an optical signal selection switch that prevents high-order diffracted light from entering a port other than a desired output port.

  The present invention provides at least one input port, a plurality of output ports, a condensing lens for condensing an optical signal emitted from at least one input port, and a phase shift to the optical signal collected by the condensing lens. A non-wavelength selective switch comprising a deflecting means for reflecting the optical signal so that the optical signal given the phase shift is coupled to the output port via the condenser lens. The period of the phase shift waveform at any output port by the means is different from 1 / i times (i is an integer other than zero) the period of the phase shift waveform at the other output port by the deflection means.

  In the non-wavelength selective switch according to an embodiment of the present invention, the deflection unit is an LCOS element or a MEMS element.

  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 deflection unit that applies a phase shift to the optical signal collected by the lens and the condenser lens, and the optical signal that is given the phase shift is coupled to the output port via the condenser lens and the spectral unit. A wavelength selective switch including a deflecting unit for reflecting a signal, wherein a period of a phase shift waveform at one output port by the deflecting unit is 1 / i times a period of a phase shift waveform at another output port by the deflecting unit ( i is an integer other than zero).

  In the wavelength selective switch according to an embodiment of the present invention, the deflection unit is an LCOS element or a MEMS element.

  In the wavelength selective switch according to an embodiment of the present invention, with respect to an angle formed by a higher-order light component of reflected light corresponding to an output port by the deflecting unit and a main signal of reflected light at another output port by the deflecting unit. Thus, the beam size in the deflecting means is increased so that the optical coupling between the high-order light component and the main signal is sufficiently small to be ignored.

  The present invention can provide an optical signal selection switch that prevents high-order diffracted light from entering a port other than a desired output port.

It is the schematic which shows the structure of the wavelength selective switch which concerns on a prior art. It is a figure which shows the arrangement | sequence of the pixel in the optical deflection | deviation part of the wavelength selective switch which concerns on a prior art. It is a figure for demonstrating a mode that a phase shift is provided to the light of a certain wavelength (lambda) by the arrangement | sequence of a pixel in the optical deflection | deviation part of the wavelength selective switch which concerns on a prior art. It is a conceptual diagram for demonstrating the subject of the wavelength selective switch which concerns on a prior art. It is a conceptual diagram for demonstrating the means for solving the conventional subject in the wavelength selective switch which concerns on this invention. 6 is a graph showing the relationship between the diffraction angle (deg) of diffracted light and the transmittance (dB) when an LCOS element is used in the light deflection section in the non-wavelength selective switch according to the example of the present invention. In the non-wavelength selective switch which concerns on the Example of this invention, it is a figure for demonstrating a mode that a phase shift is provided to light with the arrangement | sequence of a pixel at the time of using an LCOS element for an optical deflection | deviation part. It is a graph which shows the beam radius dependence of the Gaussian beam which injects on LCOS of the amount of crosstalk. It is a schematic block diagram of the non-wavelength selective switch which concerns on the Example of this invention. It is a top view of the optical fiber block which comprises the non-wavelength selective switch which concerns on the Example of this invention. It is a graph which shows a mode that the phase shift by LCOS when the period of a sawtooth wave is the number of pixels-11 is provided. It is a graph which shows the switching operation characteristic of the non-wavelength selective switch which concerns on the Example of this invention. In the non-wavelength selective switch which concerns on the Example of this invention, it is a figure for demonstrating a mode that a phase shift is provided to light with the arrangement | sequence of a pixel at the time of using a MEMS element for an optical deflection | deviation part. A sawtooth waveform when the serrodyne period is an integer multiple of the number of pixels and a sawtooth waveform when the serodyne period is a non-integer multiple of the number of pixels are shown. 1 is a schematic configuration diagram of a wavelength selective switch according to an embodiment of the present invention.

  Embodiments of the present invention will be described below. FIG. 5 is a conceptual diagram for explaining means for solving a conventional problem in the wavelength selective switch according to the present invention. FIG. 5 shows a case where the number of output ports is two. As shown in FIG. 5A, incident light incident on the LCOS constituting the light deflector is deflected and reflected. Here, let N be the period of the serodyne waveform when the output port is set to # 1. FIG. 5A illustrates the generation of 0th-order, ± 1st-order, and ± 2nd-order diffracted light.

  In the embodiment of the present invention, as shown in FIG. 5B, the output port is set so that the period of the serodyne waveform when the output port is set to # 2 is N / 3 instead of N / 2. Be placed. FIG. 5B illustrates the generation of 0th-order and ± 1st-order diffracted light.

  As shown in FIGS. 5A and 5B, the diffraction angle of the second-order diffracted light when the period of the serodyne waveform is N is 1 when the period of the serodyne waveform is a value obtained by dividing N by a non-integer. It is different from the diffraction angle of the next diffracted light. Accordingly, the second-order diffracted light when the period of the serrodyne waveform is N does not overlap with the first-order diffracted light when the period of the serodyne waveform is N / 2. Therefore, crosstalk between ports does not deteriorate.

This will be described in more detail. The basic period of the serrodyne waveform is an integer multiple of the LCOS pixel pitch for simplicity. Here, i is the order of diffracted light (diffracted light of i = 1 is diffracted light intended to be output to a desired output port), and the serodyne period when output is set to the jth port is N _j . At this time, the period N _{k of the} serodyne waveform corresponding to the output port _k is

Arrange the output ports so that

  Examples of the present invention will be described below.

(First embodiment)
FIG. 6 shows the diffraction angle (deg) of the diffracted light and the reflected light from the LCOS when the LCOS having a pixel pitch of 20 μm and a spatial period of the serodyne waveform of 380 μm (20 μm × 19 pixels) is used as the light deflector. It is a graph which shows the relationship with spatial intensity distribution (dB). The wavelength of the input light was 1590 nm, and the radius of the Gaussian beam incident on the LCOS was 4.2 mm.

  In the present embodiment, diffracted light as shown in FIG. 6 is generated, and this is due to the fact that the serrodyne waveform is ideally not folded at 2π and has backlash (see FIG. 7).

  FIG. 7 shows an outline of the serrodyne waveform set in the LCOS of the present embodiment. In the actual phase setting, there are locations where a pixel whose phase is close to 2π and a pixel whose phase is close to zero are adjacent to each other, but the phase does not digitally discontinuously change at the boundary, and FIG. As shown in FIG. 5, the slope changes from the vicinity of 2π to zero with a slope that is steep but reverse to the serodyne waveform. This reverse slope phase change generates high-order diffracted light.

  In this embodiment, the serodyne periods are set to N = 6, 7, 8, 9, 10, 11, 13, 17, 19 so that the serodyne periods are relatively prime (that is, satisfying (Equation 1)). Nine were selected and output ports were placed. The first-order diffracted light corresponding to each serrodyne period is as shown in the column of i = 1 in Table 1 below.

  As an example, consider the case of N = 19. The diffraction angle of the higher-order diffracted light produced by the serodyne waveform of N = 19 is 0.48 deg for the second-order diffracted light, 0.72 deg for the third-order diffracted light, 0.96 deg for the fourth-order diffracted light, 1.20 deg., 6th order diffracted light is 1.44 deg, and 7th order diffracted light is 1.68 deg. As shown in Table 1, these higher-order diffracted lights do not exist at the positions of the first-order diffracted lights of other serrodyne waveforms (that is, N = 6, 7, 8, 9, 10, 11, 13, 17). Therefore, no degradation of crosstalk occurs.

  The radius of the Gaussian beam incident on the LCOS only needs to be wide enough to sufficiently separate the second-order or higher-order diffracted light and the main signal (first-order diffracted light).

  Among the angles formed by the higher-order diffracted light and the main signal (first-order diffracted light) in this embodiment, the smallest is between the N = 10 main signal (first-order diffracted light) and N = 19 second-order diffracted light. It is established 0.02 deg.

  The coupling ratio (dB) for coupling the second order diffracted light when N = 19 to the main signal (first order diffracted light) when N = 10 with respect to this angle 0.02 deg, and the beam radius of the Gaussian beam incident on the LCOS The relationship with (um) is shown in FIG.

  As shown in FIG. 8, the amount of crosstalk depends on the beam radius of the Gaussian beam incident on the LCOS. When the ideal crosstalk amount is −50 dB or less, the beam radius of the Gaussian beam incident on the LCOS may be about 5000 μm or more.

(Second embodiment)
FIG. 9 shows a non-wavelength selective switch with one input and four outputs according to an embodiment of the present invention. FIG. 9 is a schematic configuration diagram of a non-wavelength selective switch according to the present embodiment. The non-wavelength selective switch 900 includes an optical fiber block (910) for arranging one input optical fiber (903) and four output optical fibers (901, 902, 904, 905), and five microlenses. Are arranged, a microlens array (912), a condenser lens (914), and an LCOS element (916).

  An optical signal incident from the input optical fiber 903 is converted into parallel light through a microlens. The optical signal converted into parallel light through the microlens is collected by the condenser lens 914. The optical signal collected by the condenser lens 914 is deflected and reflected by the LCOS element 916. The position of the LCOS element 916 is set so that the position of the beam waist of the optical signal condensed through the condenser lens 914 is on the LCOS element. The optical signal deflected / reflected by the LCOS element 916 is coupled to one of the output fibers (that is, one of 901, 902, 904, 905) via the condenser lens 914 and the microlens.

  The optical fiber block 910 has five V grooves for holding five optical fibers on the substrate. The extending direction of the V-groove is formed along the traveling direction of the optical signal.

  FIG. 10 is a top view of the optical fiber block 910. The distance between the optical fiber 901 and the optical fiber 902 is 0.391 mm, the distance between the optical fiber 902 and the optical fiber 903 is 1.761 mm, the distance between the optical fiber 903 and the optical fiber 904 is 1.490 mm, and the optical fiber 904 and the light. A V-groove on the optical fiber block was formed so that the distance from the fiber 905 was 0.447 mm.

  By forming the V groove as described above, the period of the sawtooth wave of LCOS satisfies the relationship shown in the following table.

  Table 2 shows the period of the sawtooth wave of LCOS by the number of pixels per period. Here, when the sign of the number of pixels is positive, it indicates that the slope of the sawtooth wave rises to the left, and when it is negative, the slope of the sawtooth wave rises to the right.

  A condenser lens having a wavelength of input light of 1.55 μm, a pixel pitch of LCOS of 8 μm, and a focal length of 100 mm was used.

  The beam radius of the signal light incident on the LCOS needs to be increased so that the crosstalk between the output ports is sufficiently reduced. In this embodiment, the beam radius is 3 mm.

  FIG. 11 shows an outline of phase setting in the LCOS when the period of the sawtooth is 11 pixels. In FIG. 11, the horizontal axis indicates the pixel number, and the vertical axis indicates the phase value (rad) to be given. In FIG. 11, a sawtooth wave having a slope rising to the right and a serodyne period of 11 pixels can be confirmed. The same can be set when the serodyne period of the sawtooth wave is other than the number of pixels-11.

FIG. 12 shows the switching operation characteristics of the non-wavelength selective switch with one input and four outputs according to this embodiment. In FIG. 12, the horizontal axis indicates the output port number, and the vertical axis indicates the transmittance (dB).
As an example, when the optical signal transmission rate of the optical signal to each port when the output port is port 1 is examined, it can be seen that crosstalk between ports of −50 dB or more is secured.

  In this way, by setting the interval between the output ports so that the period of the sawtooth wave is relatively prime (that is, so as to satisfy (Equation 1)), the higher-order diffracted light caused by the periodicity of the sawtooth wave Can be suppressed.

  The range in which the sawtooth periods are relatively prime may be considered up to the region where higher-order diffracted light appears in the range where the output port exists. That is, it is not necessary to consider high-order diffracted light such as the 100th order because it is outside the range of the region where the output port exists.

(Non-wavelength selective switch using MEMS elements)
In the present embodiment, the LCOS element is used as the deflection element, but a MEMS element including a plurality of MEMS mirrors can be used. In the non-wavelength selective switch shown in FIG. 9, a MEMS element is installed at the position of the LCOS element 7 instead of the LCOS element 7.

  FIG. 13 is a diagram illustrating a state in which a phase shift is imparted to light depending on the arrangement of pixels of the MEMS element. As shown in FIG. 13, a phase shift of a sawtooth waveform is given using a MEMS element. FIG. 13A shows a waveform when the serodyne period is 4 pixels, and FIG. 13B shows a waveform when the serodyne period is 3 pixels. The level difference between the lowest-stage MEMS mirror and the highest-stage MEMS mirror is set so that the phase difference of the light generated by them becomes 2π.

  The case where the serodyne period becomes the number of pixels 3 and the number of pixels 4 using the MEMS element was shown. Note that the serrodyne period shown in the previous example (that is, the serodyne period is the number of pixels −9, −10, 11, 13) can also be set using the MEMS element.

  In the above example, the case where the serrodyne period is an integer multiple of the number of pixels is shown, but the serodyne period may be a non-integer multiple of the number of pixels.

  FIG. 14 shows a sawtooth waveform when the serrodyne period is an integer multiple of the number of pixels and a sawtooth waveform when the serodyne period is a non-integer multiple of the number of pixels. A solid line indicates a sawtooth wave whose serodyne period is an integer multiple of the number of pixels, and a broken line indicates a sawtooth wave whose serodyne period is a non-integer multiple of the number of pixels. A sawtooth whose serodyne period is a non-integer multiple of the number of pixels changes the number of pixels constituting each saw tooth, but it appears to the input light as a change in the phase plane of the slope of the sawtooth. There is no practical problem.

(Request for beam radius)
When the beam radius of the beam incident on the LCOS is small, the high-order diffracted light may cause crosstalk to ports other than the output port.

  Therefore, in this embodiment, when the beam radius of the beam incident on the LCOS is w and the wavelength of the input light is λ, the desired crosstalk XT (dB) is obtained.

W was set so that Here, Δθ is the smallest of the angles formed by the diffraction angle of the first-order diffracted light when the optical signal is diffracted (corresponding to the output signal) and the diffraction angle of the higher-order diffracted light depending on the phase setting of the sawtooth wave. Is.

  The diffraction angle of the first-order diffracted light is

It can be expressed as. NSaw represents the number of pixels of the LCOS element constituting one wave of the sawtooth wave (NSaw may be an integer or non-integer), and Pitch represents the pitch of the LCOS element.

  In this case, assuming that a set of NSaws necessary for switching is NPort (in the above embodiment, NPort = {− 9, 10, −11, 13})

It is. k is the order (integer) of the higher-order diffracted light. Regarding k, it is only necessary to consider k in a range where high-order diffracted light appears in a region where an output port exists.

  Consider the case of this example. The diffraction angle of the optical signal output to each port is

It is. In this case, the minimum angle difference Δθ is established between the diffraction angle of the first-order diffracted light output to the port 4 and the diffraction angle of the −1st-order diffracted light output to the port 2, and is 0.018 rad (= 0.0194 rad−0.0176). rad).

  Considering the case where the wavelength λ of the input light is 1.55 μm and k = −1,2 as the order of the high-order diffracted light, the beam radius is 950 μm from (Equation 2) in order to secure 50 dB of crosstalk. It is derived that the above is sufficient.

(Third embodiment)
FIG. 15 shows a 1-input 4-output wavelength selective switch 1500 according to an embodiment of the present invention. FIG. 15 is a schematic configuration diagram of a wavelength selective switch 1500 according to the present embodiment. The wavelength selective switch 1500 includes an optical fiber block 1502 for arranging one input optical fiber and four output optical fibers, a diffraction grating 1504, a condenser lens 1506, and an LCOS element 1508.

  An optical signal incident from the input optical fiber is split by the diffraction grating 1504 for each wavelength. The optical signal dispersed by the diffraction grating 1504 is collected by the condenser lens 1506. The optical signal collected by the condenser lens 1506 is deflected and reflected by the LCOS 1508. The position of the LCOS element 1508 is set so that the position of the beam waist of the optical signal condensed through the condenser lens 1506 is on the LCOS. The optical signal deflected and reflected by the LCOS 1508 is wavelength-multiplexed via the condenser lens 1506 and the diffraction grating 1504, and is coupled in any output fiber.

  The parameters in this example were set to be the same as those in the first example except for the parameters related to the diffraction grating.

200 Wavelength Selection Switch 210 Optical Waveguide Substrate 220 Cylindrical Lens 230 Polarization Separation Unit 240 Beam Size Conversion Units 242 and 244 Cylindrical Lens 250 Spectroscopic Unit 252 Bulk Diffraction Grating 260 Condensing Lens 270 Light Deflection Unit, LCOS
272 Pixels 901, 902, 903, 904, 905 Output optical fiber 903 Input optical fiber 910 Optical fiber block 912 Micro lens array 914 Condensing lens 916 LCOS element 1500 Wavelength selection switch 1502 Optical fiber block 1504 Diffraction grating 1506 Condensing lens 1508 LCOS element

Claims (5)

At least one input port;
Multiple output ports,
A condensing lens that condenses the optical signal emitted from the at least one input port;
Deflection means for giving a phase shift to the optical signal collected by the condenser lens, the optical signal so that the optical signal given the phase shift is coupled to the output port via the condenser lens A non-wavelength selective switch comprising a deflecting means for reflecting
The period of the phase shift waveform at one output port by the deflecting unit is different from 1 / i times (i is an integer other than zero) the period of the phase shift waveform at another output port by the deflecting unit. Wavelength selective switch.   The non-wavelength selective switch according to claim 1, wherein the deflecting unit is an LCOS element or a MEMS element. 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;
Deflection means for giving a phase shift to the optical signal collected by the condenser lens, so that the optical signal to which the phase shift is given is coupled to the output port via the condenser lens and the spectroscopic means. A wavelength selective switch provided with a deflecting means for reflecting the optical signal,
The wavelength of the phase shift waveform at one output port by the deflecting means is different from 1 / i times the period of the phase shift waveform at another output port by the deflecting means (i is an integer other than zero). Select switch.   The wavelength selective switch according to claim 3, wherein the deflecting unit is an LCOS element or a MEMS element. With respect to an angle formed by a component of higher-order light of reflected light corresponding to an output port by the deflecting unit and a main signal of reflected light at another output port by the deflecting unit,
5. The wavelength selective switch according to claim 1, wherein a beam size in the deflecting unit is increased so that optical coupling between the high-order light component and the main signal is sufficiently negligible. .

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