JP5432047B2 - Optical switch and wavelength selective switch - Google Patents

Description

  The present invention relates to an optical switch and a wavelength selective switch used as a routing device or the like in optical fiber communication.

  Optical communication technology using an optical fiber as a transmission medium has led to an increase in signal transmission distance, and a large-scale optical communication network has been constructed. In recent years, with the widespread use of Internet communication, communication traffic has increased rapidly, and demands for large capacity, high speed, and high functionality for communication networks are increasing. Up to now, it has become possible to increase the transmission capacity between two points by introducing a wavelength division multiplex communication technique for simultaneously transmitting a plurality of optical signals having different wavelengths through one transmission line. However, in a communication network, it is necessary to set (route) or switch (switch) a signal path at a node where a plurality of transmission paths are gathered. Signal processing has become a bottleneck. Up to now, a method has been used in which a transmitted optical signal is once converted into an electrical signal, route setting and switching are performed, and the electrical signal is converted again into an optical signal and sent to the transmission path. It is expected that the throughput of a node can be drastically increased by using a method for setting and switching a signal path without converting an optical signal into an electrical signal.

  As one of such methods, a reconfigurable optical add / drop multiplexing (ROADM) system in which a plurality of nodes are connected in a ring shape or a bus shape is known. Each node of the ROADM system is equipped with an optical switch that switches connection for each wavelength, and an optical signal input from one optical fiber transmission line for an optical signal of an arbitrary wavelength among wavelength multiplexed optical signals, The through mode that is output to the other optical fiber transmission line, and the optical signal that is input from the optical fiber transmission line side is output to the terminal device connected to the node (drop operation), and the optical signal that is input from the terminal device Can be switched to the add / drop mode (add operation).

  For the optical signal switching unit of such a ROADM system, a combination of a wavelength multiplexer / demultiplexer and multiple optical switches has been mainly used so far. Recently, however, a wavelength selective switch (WSS: Wavelength Selective Switch) that wavelength-multiplexes all input and output ports, including add / drop ports, has features such as wide passband characteristics and scalability to multiple ports. Has been attracting attention.

  Conventionally, various types of wavelength selective switches are known, and one of them is a slab waveguide for multi-beam interference manufactured on a planar lightwave circuit (PLC). In addition, a configuration including a plurality of arrayed waveguide gratings (AWG), a condenser lens system, and a phase modulator connected thereto is known (see Patent Document 1).

FIG. 1 is a schematic diagram of a conventional one-input five-output wavelength selective switch described in Patent Document 1. In FIG.
The conventional optical switch shown in FIG. 1 includes a silica-based optical waveguide 100, 14 cylindrical lenses 200-1 to 200-14, 14 condenser lenses 300-1 to 300-14, and 14 phases. Modulators 400-1 to 400-14. In FIG. 1, the horizontal direction of the signal light emission end face of the substrate of the silica-based optical waveguide 100 is x, the vertical direction is y, and the traveling direction of the light wave, that is, the optical axis is z.

  The silica-based optical waveguide 100 includes a first slab waveguide 104 and 14 arrayed-waveguide diffractometers connected to five input / output waveguides 102-1 to 102-5, which are respectively produced on a silica-based substrate. The grating 110-1 to 110-14 and 14 connection waveguides 106-1 to 106-14 connecting the first slab waveguide 104 and the arrayed waveguide diffraction gratings 110-1 to 110-14 are provided.

  Each of the arrayed waveguide gratings 110 includes a second slab waveguide 112 connected to the connection waveguide 106 and an arrayed waveguide 114 connected to the second slab waveguide 112.

  Cylindrical lenses 200-1 to 200-14 are arranged at ends different from the second slab waveguides 112-1 to 112-14 of the array waveguides 114-1 to 114-14, respectively. Each optical signal emitted after being wavelength-separated from −14 is incident on the condenser lens 300 without spreading in the direction (y direction) perpendicular to the quartz substrate surface.

  Each of the condensing lenses 300-1 to 300-14 condenses the respective wavelength-separated optical signals onto the phase modulators 400-1 to 400-14.

  Each of the phase modulators 400-1 to 400-14 gives an arbitrary phase shift to each wavelength-separated optical signal, and collects lenses 300-1 to 300-14 and cylindrical lenses 200-1 to 200-. 14 includes a phase control element that reflects to be coupled to the arrayed waveguides 114-1 to 114-14 via 14.

  The input / output waveguide 102, the first slab waveguide 104, and the connection waveguide 106 constitute a switching unit. The arrayed waveguide grating 110, the cylindrical lens 200, and the condensing lens 300 constitute a spectroscopic unit. The phase modulator 400 constitutes a phase modulation unit.

Next, the operation of the conventional wavelength selective switch shown in FIG. 1 will be described.
The signal light in which a plurality of wavelengths are multiplexed is guided through the input / output waveguide 102-3 serving as the input / output and enters the first slab input / output surface of the first slab waveguide 104. The signal light incident on the first slab input / output surface is branched into 14 signal lights in the first slab waveguide 104 and coupled to the connection waveguides 106-1 to 106-14, respectively.

  Each signal light is guided through the connection waveguides 106-1 to 106-14 and enters the arrayed waveguide gratings 110-1 to 110-14. The signal light guided through the connection waveguide 106-1 and incident on the arrayed waveguide grating 110-1 is guided through the second slab waveguide 112-1 and the arrayed waveguide 114-1 of the arrayed waveguide grating 110-1. By being waved, the wavelength is separated and emitted from the silica-based optical waveguide 100. Similarly, the signal light guided through the connection waveguides 106-2 to 106-14 is wavelength-separated and emitted from the silica-based optical waveguide 100.

  Each of the optical signals having a plurality of wavelengths separated by the arrayed waveguide grating 110-1 passes through the cylindrical lens 200-1 and the condenser lens 300-1, and enters the phase modulator 400-1. A phase shift is given in the phase modulator 400-1, and the optical path is inverted by reflection. Similarly, each of the optical signals having a plurality of wavelengths separated by the wavelength in the arrayed waveguide gratings 110-2 to 110-14 is incident on the phase modulators 400-2 to 400-14 to be independently phase-shifted. Thus, the optical path is reversed by reflection.

  The optical signals of the respective wavelengths whose optical paths are inverted by being phase-shifted in the phase modulator 400-1 are transmitted through the condenser lens 300-1 and the cylindrical lens 200-1, and enter the arrayed waveguide grating 110-1. Combined. Further, the optical signals of the respective wavelengths whose optical paths are inverted are wavelength-combined in the arrayed waveguide grating 110-1, coupled to the connection waveguide 106-1, and enter the first slab waveguide 104 again. Similarly, the optical signals having the respective wavelengths, which have been subjected to the phase shift in the phase modulators 400-2 to 400-14 and whose optical paths are inverted, enter the first slab waveguide 104 again.

  A certain wavelength component of the optical signal incident on the first slab waveguide 104 again forms interference fringes on the input / output surface P of the first slab waveguide due to multi-beam interference. At this time, the position where the interference fringes are formed and the light intensity of the interference fringes can be controlled by controlling the amount of phase modulation applied in the phase modulators 400-1 to 400-14. Therefore, the desired wavelength component of the optical signal incident on the wavelength selective switch can be coupled to the desired input / output waveguides 102-1 to 102-5 with the desired light intensity.

JP 2009-198826 A

  However, the wavelength selective switch as shown in FIG. 1 has a problem that the extinction ratio is limited by side lobes generated by multi-beam interference.

  Table 1 shows parameters of the optical circuit described in Patent Document 1. At this time, the relative ratio of the electric field amplitude that passes through each connection waveguide and is coupled to the output waveguide is calculated as shown in Table 2.

  FIG. 2 shows a calculation result of interference fringes formed on the first slab input / output surface P when the above parameters are used. A side lobe of about −30 dB is generated in the vicinity of the center (x = 0), and the intensity decreases due to the diffraction effect as the distance from the center interference fringe increases, but the position (x = 65.4 μm), a side lobe of about −40 dB is also generated in the vicinity of the intermediate point. Such side lobes cause crosstalk due to waveguide manufacturing errors and phase setting errors, and cause a deterioration in the extinction ratio of the blocking port.

  The present invention has been made in view of such problems, and an object of the present invention is to provide an optical switch and a wavelength selective switch having a high extinction ratio by suppressing side lobes caused by multi-beam interference. .

In order to achieve such an object, the present invention provides an optical switch according to claim 1, wherein the input port and N are integers of 3 or more, and light waves input to the input port are An input branching unit that branches into N units, a phase shifter unit that modulates the phase of each of the branched optical waves, M is an integer not smaller than 2 and not larger than N, and M light waves are multiplexed by modulating the phase-modulated optical waves. An output multiplexing unit for outputting to the output port, and the input branching unit is formed on a planar lightwave circuit, the input branching means for branching the lightwave input from the input port into N pieces, and the branched N N input-portion output waveguides through which each of the light waves are guided, the input branching means is a slab waveguide, and the light waves from the input port are incident from the center of the incident surface. The position of the exit surface where the output waveguides are connected at equal intervals The center of the emission surface is configured to be optically coupled with higher light intensity, the output multiplexing unit is a slab waveguide, and the phase-modulated light waves are incident on the incident surface at equal intervals. The M output ports are optically coupled to the positions of the emission surfaces connected at equal intervals with a higher light intensity toward the center of the emission surface, and the input branching means and the input section output guide The waveguide has a relative ratio of the electric field amplitude of the light wave guided through the i-th input waveguide of the N input waveguides and coupled to the output port.

It is comprised so that it may become.

The invention according to claim 3 is a wavelength selective switch, wherein an input port, N is an integer equal to or greater than 3, and an input branching unit for branching N light waves input to the input port, and the branched A phase shifter that modulates the phase of each of the lightwaves, and an output combiner that combines M with the modulated lightwaves and outputs them to M output ports. The input branching unit is formed on a planar lightwave circuit, the input branching means for branching the lightwaves inputted from the input port into N pieces, and the N input part outputs through which the branched N lightwaves are respectively guided. At least (N-1) wavelength separation means for separating an input light wave into light waves of L wavelengths, each connected to a waveguide and one of the N input section output waveguides. with the door, said input branch means is a slab waveguide, said input A light wave from the center is incident from the center of the incident surface, and the N input output waveguides are optically coupled to the position of the output surface connected at equal intervals with higher light intensity toward the center of the output surface. The output multiplexing part is a slab waveguide, and the light wave whose phase is modulated is incident on the incident surface at equal intervals, and the M output ports are connected at equal intervals. The center of the emission surface is optically coupled to the position of the output surface with a higher light intensity, and the output multiplexing section is separated into the L wavelengths formed on the planar lightwave circuit, and the phase At least (N-1) wavelength multiplexing means for wavelength multiplexing optical waves modulated, N output wave input waveguides for coupling N light waves whose phases are modulated, and the output unit An output that is connected to the input waveguide and outputs the input light wave to the M output ports. Branching means, and the input branching means and the input section output waveguide, and the output combining and branching means and the output section input waveguide are among the N input section output waveguides and the output section input waveguide. The relative ratio of the electric field amplitude of the light wave that passes through the i-th input output waveguide and the output input waveguide and is coupled to the output port is

It is comprised so that it may become.

  In one embodiment, the phase shifter unit may be configured by a reflection type phase modulator, and the input branching unit and the output multiplexing unit may be configured by the same optical circuit.

  As described above, according to the present invention, the relative ratio of the electric field amplitude of each optical signal causing multi-beam interference in the optical switch and wavelength selective switch operating by multi-beam interference is obtained.

By setting so as to be, it is possible to suppress side lobes of interference fringes caused by multi-beam interference and obtain a high extinction ratio.

It is the schematic of the conventional wavelength selective switch. It is a figure which shows the calculation result of the interference fringe formed in the 1st slab input / output surface in the conventional wavelength selective switch. 1 is a schematic view of an optical switch according to the present invention. In the optical switch which concerns on this invention, it is a figure which shows the calculation result of the interference fringe formed in a 2nd slab output surface. 1 is a schematic diagram of a wavelength selective switch according to the present invention. In the wavelength selective switch which concerns on this invention, it is a figure which shows the calculation result of the interference fringe formed in a 1st slab input / output surface. It is the schematic of the reflection type optical switch which is a modification of the optical switch shown in FIG. FIG. 6 is a schematic view of a transmission type wavelength selective switch, which is a modification of the wavelength selective switch shown in FIG. 5.

  An optical switch and a wavelength selective switch according to the present invention include an input branch unit that branches a light wave (optical signal) input to an input port, a phase shifter unit that modulates the phase of the light wave branched by the input branch unit, An output multiplexing unit that multiplexes the light waves modulated by the shifter unit and outputs the multiplexed wave to M output ports is provided. M is an integer of 2 or more, and N is an integer of M or more and 3 or more.

  The input branch unit includes input branch means for branching N light waves input from the input port, and N input section output waveguides through which the N light waves branched by the input branch means respectively pass. . The input branching unit has i as an integer equal to or less than N, and the relative ratio of the electric field amplitudes of the light waves that pass through the i-th input unit output waveguide among the N input unit output waveguides and couple to the output port is

Is configured or set to be

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(First embodiment)
FIG. 3 is a schematic diagram of an optical switch with one input and five outputs (one input port and five output ports) according to this embodiment. That is, FIG. 3 is a schematic diagram of an optical switch when M = 5 and N = 14. In FIG. 3, the horizontal direction of the signal light emission end face of the substrate of the silica-based optical waveguide 1100 is x, the vertical direction is y, and the traveling direction of the light wave, that is, the optical axis is z.

  The optical switch shown in FIG. 3 is the same as the conventional wavelength selective switch shown in FIG. 1, except that the spectroscopic unit is deleted, the phase modulation unit is configured by a thermo-optic phase shifter, and the optical circuit is configured as a transmission type switching The part and the phase modulation part are all fabricated on the PLC.

  The optical switch shown in FIG. 3 includes a first slab waveguide 1104 connected to one input waveguide 1102 and 14 thermo-optic phase shifters 1110-1 to 1110-1, which are respectively formed on a silica-based optical waveguide 1100. 1110-14, 14 connection waveguides 1106-1 to 1106-14 connecting the first slab waveguide 1104 and the thermo-optic phase shifters 1110-1 to 1110-14, and 5 output waveguides 1202- The second slab waveguide 1204 connected to 1-1202-5, and 14 connection waveguides 1206-1 to 1206 connecting the second slab waveguide 1204 and the thermo-optic phase shifters 1110-1 to 1110-14. -14.

  The input waveguide 1102 is an input port of the optical switch. The first slab waveguide 1104 constitutes input branching means. The connection waveguides 1106-1 to 1106-14 constitute an input unit output waveguide. The first slab waveguide 1104 and the connection waveguides 1106-1 to 1106-14 together constitute an input branching unit.

  The input branch portion passes through the i-th waveguide among the 14 connection waveguides 1106-1 to 1106-14 and 1206-1 to 1206-14 and is coupled to the output waveguides 1202-1 to 1202-5. The relative ratio of the optical electric field amplitude is

Is set or configured to be Specifically, the intensity ratio when the intensity of light passing through the end connection waveguides 1106-1 and 1206-1 or 1106-14 and 1206-14 is set to 1 is as shown in Table 3-1. Has been. When converting the values in Table 3-1 to 1 when the light intensity passing through the central connection waveguides 1106-7 and 1206-7, or 1106-8 and 1206-8 is 1, as shown in Table 3-2 become.

  As shown in Table 4-1, the light intensity ratio as shown in Tables 3-1 and 3-2 is 375 μm in the length of the first slab waveguide 1104 and adjacent to the connection waveguides 1106-1 to 1106-14. This can be realized by setting the interval to d2 = 10 μm and setting the relative values of the waveguide widths of the connection waveguides 1106-1 to 1106-14 at the boundary surface of the slab to values shown in Table 4-2.

  The thermo-optic phase shifters 1110-1 to 1110-14 are one configuration example of the phase shifter unit. The thermo-optic phase shifters 1110-1 to 1110-14 can be phase shifter waveguides in which a waveguide and a thin film heater are stacked. Another configuration example of the phase shifter portion may be a phase shifter waveguide in which a waveguide and a thin film electrode are stacked.

  The output waveguides 1202-1 to 1205-5 are output ports of the optical switch. The second slab waveguide 1204 and the connection waveguides 1206-1 to 1206-14 are configured similarly to the first slab waveguide 1104 and the connection waveguides 1106-1 to 1106-14, respectively. Together, the second slab waveguide 1204 and the connection waveguides 1206-1 to 1206-14 constitute an output multiplexing unit.

Next, the operation of the optical switch shown in FIG. 3 will be described.
The signal light input to the input waveguide 1102 is incident on the first slab input surface of the first slab waveguide 1104 (the surface to which the input waveguide 1102 is connected). In the first slab waveguide 1104, The signal light is branched and coupled to connection waveguides 1106-1 to 1106-14. The relative ratio of the light intensity of the optical signals guided through the connection waveguides 1106-1 to 1106-14 is

It is.

  Each signal light is guided through the connection waveguides 1106-1 to 1106-14 and enters the thermo-optic phase shifters 1110-1 to 1110-14. Each signal light that is independently phase-shifted by the thermo-optic phase shifters 1110-1 to 1110-14 is guided through the connection waveguides 1206-1 to 1206-14 and enters the second slab waveguide 1204. To do.

  Each optical signal incident on the second slab waveguide 1204 forms interference fringes on the second slab waveguide output surface (the surface to which the output waveguide 1202 is connected) by multi-beam interference. At this time, the position where the interference fringes are formed and the light intensity of the interference fringes can be controlled by controlling the amount of phase modulation applied in the thermo-optic phase shifters 1110-1 to 1110-14. Therefore, an optical signal incident on the optical switch can be coupled to a desired output waveguide 1202-1 to 1202-5 with a desired light intensity.

  For example, the optical signals branched into 14 are respectively subjected to phase modulation (the phase is shifted) in the thermo-optic phase shifters 1110-1 to 1110-14, but at this time, the thermo-optic phase shifters 1110-1 to 1110 are shifted. Phase setting (phase distribution) by −14 is 0, α × 2π / N, α × 2 × 2π / N, α × 3 × 2π / N,... Α × (N−1) × 2π / N Set to linear. By setting the phase distribution linearly in this way, the position where the intensity of the interference fringe reaches a peak moves substantially linearly on the output surface of the second slab waveguide. α is a constant and corresponds to an output port from which an optical signal is to be output.

  FIG. 4 shows a calculation result of interference fringes formed on the second slab output surface when the above parameters are used. It can be seen that the side lobe between the adjacent interference fringe positions (X = 65.4 μm) is effectively suppressed.

Example 1
A one-input five-output optical switch based on the first embodiment was fabricated using a silica glass-based PLC having a relative refractive index difference Δ = 1.5% between the core and the clad. When the applied power of the thermo-optic phase shifter was adjusted so that light was output to one of the five output ports, the extinction ratios at the remaining four shut-off output ports were measured, and all were 40 dB or more. It was.

  The first embodiment has described the configuration example of the optical switch when the number of input ports is 1, the number of output ports M is 5, and N = 14. However, the optical switch according to the present invention is not limited to this. The number M of output ports of the optical switch can be set to an arbitrary number of 2 or more. Further, the present invention can be implemented by setting the number of input ports to 2 or more and N to M or more and 3 or more. Furthermore, the present invention can be implemented as a reflection type optical switch described below as a modification of the transmission type optical switch shown in FIG.

(Deformation)
The optical switch shown in FIG. 7 is a schematic diagram of an optical switch with one input and five outputs (one input port and five output ports), similar to the optical switch shown in FIG. That is, FIG. 7 is a schematic diagram of a reflective optical switch when M = 5 and N = 14.

  The optical switch shown in FIG. 7 includes a first slab waveguide 1104 connected to five input / output waveguides 1302-1 to 1302-1 and 14 thermo-optic phases, which are respectively fabricated on a silica-based optical waveguide 1100. Shifters 1110-1 to 1110-14, 14 connection waveguides 1106-1 to 1106-14 connecting the first slab waveguide 1104 and the thermo-optic phase shifters 1110-1 to 1110-14 are provided. A mirror 1304 is provided at the end of the quartz-based optical waveguide 1100 (the end side different from the end where the connection waveguides 1106-1 to 1106-14 of the thermo-optic phase shifters 1110-1 to 1110-14 are connected).

  Of the input / output waveguides 1302-1 to 1302-5, the input / output waveguide 1302-3 is an input / output waveguide to which a circulator (not shown) is connected, and constitutes an input port and an output port. The input / output waveguides 1302-1, 1302-2, 1302-4 and 1302-5 constitute an output port.

  The first slab waveguide 1104 and the connection waveguides 1106-1 to 1106-14 constitute an input branching unit, similar to the optical switch shown in FIG. 3. Further, the first slab waveguide 1104 and the connection waveguides 1106-1 to 1106-14 constitute an output multiplexing unit.

  In the optical switch of FIG. 7, the signal light input to the input / output waveguide 1302-3 is input to the first slab input surface (input / output waveguide 1302) of the first slab waveguide 1104 similarly to the optical switch shown in FIG. 3. And is branched into 14 signal lights in the first slab waveguide 1104, phase shifted independently by the thermo-optic phase shifters 1110-1 to 1110-14, and reflected by the mirror 1304. The optical path is inverted, guided through the thermo-optic phase shifter 1110 and the connecting waveguide 1106, and incident again on the first slab waveguide.

  Each optical signal incident on the first slab waveguide 1204 forms interference fringes on the first slab waveguide output surface (that is, the same surface as the first slab input surface) by multi-beam interference. Similar to the optical switch shown in FIG. 3, by controlling the phase modulation amount, the position where the interference fringes are formed and the light intensity of the interference fringes can be controlled. Therefore, the optical signal incident on the optical switch can be coupled to the desired input / output waveguides 1302-1 to 1202-5 with the desired light intensity.

(Second Embodiment)
FIG. 5 shows a wavelength selective switch having one input and two outputs (one input port and two output ports (that is, M = 2)) according to the present embodiment, where N = 6. FIG. In FIG. 5, the horizontal direction of the signal light emission end face of the substrate of the silica-based optical waveguide 2100 is x, the vertical direction is y, and the traveling direction of the light wave (signal light), that is, the optical axis is z.

  The wavelength selective switch shown in FIG. 5 includes a quartz optical waveguide 2100, cylindrical lenses 2200-1 to 2200-6, condenser lenses 2300-1 to 2300-6, and phase modulators 2400-1 to 2400-6. Is provided.

  The silica-based optical waveguide 2100 includes a first slab waveguide 2104 connected to two input / output waveguides 2102-1 to 2102-2, and six arrayed-waveguide diffractions, which are respectively formed on a quartz-based substrate. It includes gratings 2110-1 to 2110-6, and six connection waveguides 2106-1 to 2106-6 that connect the first slab waveguide 2104 and the arrayed waveguide diffraction gratings 2110-1 to 2110-6. Each arrayed waveguide diffraction grating 2110 includes a second slab waveguide 2112 connected to one connection waveguide 2106 and an arrayed waveguide 2114 connected to the second slab waveguide 2112.

  Of the input / output waveguides 2102-1 to 2102-2, the input / output waveguide 2102-1 is an input / output waveguide to which a circulator (not shown) is connected, and constitutes an input port and an output port. The input / output waveguide 2102-2 constitutes an output port.

  The first slab waveguide 2104 constitutes an input branching unit. The connection waveguides 2106-1 to 2106-6 constitute an input unit output waveguide. Both the first slab waveguide 2104 and the connection waveguides 2106-1 to 2106-6 constitute an input branching unit. The first slab waveguide 2104 constitutes an output merging / branching means. The connection waveguides 2106-1 to 2106-6 constitute an output unit input waveguide. The first slab waveguide 2104 and the connection waveguides 2106-1 to 2106-6 constitute an output multiplexing unit.

  The input branch portion has an optical electric field amplitude that passes through the i-th waveguide among the six connection waveguides 2106-1 to 2106-6 and is coupled to the input / output waveguide 2102-1 and the output waveguide 2102-2. Relative ratio is

Is set or configured to be Specifically, the intensity ratio when the light intensity passing through the end connection waveguide 2106-1 or 2106-6 is set to 1 is set to Table 5-1. When the values in Table 5-1 are converted to the case where the light intensity passing through the central connection waveguide 2106-3 or 2106-4 is 1, the result is as shown in Table 5-2.

  As shown in Table 6-1, the light intensity ratio as shown in Tables 5-1 and 5-2 is such that the length of the first slab waveguide 2104 is 362 μm and the connection waveguides 2106-1 to 2106-6 are adjacent to each other. This can be realized by setting the interval to d2 = 15 μm and setting the relative values of the waveguide widths of the connection waveguides 2106-1 to 2106-6 at the slab boundary surface to the values shown in Table 6-2.

  The arrayed waveguide diffraction gratings 2110-1 to 2110-6 constitute wavelength separation means for separating an input light wave into light waves of L wavelengths. L is the number of wavelengths of the optical signal (light wave) multiplexed on the wavelength multiplexed optical signal input to the wavelength selective switch.

  The cylindrical lenses 2200-1 to 2200-6 are arranged at different ends of the array waveguides 211-1 to 211-6 from the second slab waveguide 2112, and are wavelength-separated from the arrayed waveguides 211-14 to 211-6. Each of the emitted optical signals acts so as to enter the condenser lens 2300 without spreading in the direction perpendicular to the quartz substrate surface (y direction).

  The condensing lenses 2300-1 to 2300-6 condense the wavelength-separated optical signals on the phase modulators 2400-1 to 2400-6.

  The phase modulators 2400-1 to 2400-6 give arbitrary phase shifts to the wavelength-separated optical signals, and the condenser lenses 2300-1 to 2300-6 and the cylindrical lenses 2200-1 to 2200-6 are added. And a phase control element that reflects so as to be coupled to the arrayed waveguides 2114-1 to 2114-6. For example, the phase modulator 2400 can be configured using a device using a refractive index modulation element typified by liquid crystal arranged in the x direction, for example, a device called LCOS (Liquid Crystal on Silicon). The LCOS is a reflection type device in which liquid crystal elements (cells) of at least the number of optical signals separated in wavelength are arranged on the surface of a silicon substrate. Each liquid crystal element (cell) acts as a phase control element to give a phase difference to an incident optical signal and to reverse the optical path. For example, an optical signal having a certain wavelength branched to N from a wavelength-multiplexed signal is condensed on different phase control elements (liquid crystal elements (cells)) constituting the phase modulator 2400 and subjected to phase modulation. At this time, the phase setting (phase distribution) by the phase control element constituting the phase modulator 2400 is 0, α × 2π / N, α × 2 × 2π / N, α × 3 × 2π / N,... Α × It is set linearly as (N-1) × 2π / N. Thus, by setting the phase distribution to be linear, the position where the intensity of the interference fringes reaches a peak moves substantially linearly on the input / output surface (surface on the input / output waveguide 2102 side) of the first slab waveguide. . Here, α is a constant and corresponds to an output port for outputting an optical signal having a certain wavelength. Furthermore, routing (wavelength selection) for each wavelength is possible by making separate phase control elements (liquid crystal elements (cells)) correspond to each wavelength.

  The input / output waveguide 2102, the first slab waveguide 2104, and the connection waveguide 2106 constitute a switching unit. The arrayed waveguide grating 2110, the cylindrical lens 2200, and the condenser lens 2300 constitute a spectroscopic unit. The phase modulator 2400 constitutes a phase modulation unit.

  FIG. 6 shows a calculation result of interference fringes formed on the first slab input / output surface when the above parameters are used. It can be seen that the side lobe between the adjacent interference fringe positions (x = 26.3 μm) is effectively suppressed.

Next, the operation of the wavelength selective switch according to the present invention shown in FIG. 5 will be described.
The signal light multiplexed with a plurality of wavelengths is guided through an input / output waveguide 2102-1 that also serves as an input / output, and the first slab input / output surface of the first slab waveguide 2104 (the input / output waveguide 2102-1 is connected). The first slab waveguide 2104 is branched into six signal lights and coupled to connection waveguides 2106-1 to 2106-6. The relative ratio of the light intensity of the optical signals guided through the connection waveguides 2106-1 to 2106-6 is

It is.

  Each signal light is guided through the connection waveguides 2106-1 to 2106-6 and enters the arrayed waveguide gratings 2110-1 to 2110-6. The signal light that has been guided through the connection waveguide 2106-1 and entered the arrayed waveguide grating 2110-1 is wavelength-separated by being guided through the second slab waveguide 21112-1 and the arrayed waveguide 21114-1. Then, the light is emitted from the quartz optical waveguide 2100 at a predetermined angle. Similarly, the signal light guided through the connection waveguide 2106-2 is also wavelength-separated and emitted from the silica-based optical waveguide 2100 at an angle different from that of the signal light guided through the connection waveguide 2106-1. Similarly, the signal light guided through the connection waveguides 2106-3 to 2106-6 is also wavelength-separated and emitted from the silica-based optical waveguide 2100 at different angles.

  Each of the optical signals having a plurality of wavelengths separated by the arrayed waveguide gratings 2110-1 to 2110-6 is transmitted through the cylindrical lenses 2200-1 to 2200-6 and the condenser lenses 2300-1 to 2300-6. Then, the light enters the phase modulators 2400-1 to 2400-6 and is phase-shifted by the phase modulator 2400-1, and the optical path is inverted by reflection.

  The optical signals of the respective wavelengths whose optical paths are inverted by being phase-shifted in the phase modulator 2400 are transmitted through the condenser lens 2300 and the cylindrical lens 2200 and coupled to the arrayed waveguide grating 2110. For example, the optical signals of the respective wavelengths guided through the connection waveguide 2106-1 before the optical path is inverted are wavelength-synthesized in the arrayed waveguide grating 2110-1 after the optical path is inverted, and then again connected to the connection waveguide 2106. −1 and incident on the first slab waveguide 2104. After guiding the connection waveguides 2106-2 to 26-2-6, the phase modulators 2400-2 to 2400-6 are given phase shifts, and the optical signals of the respective wavelengths whose optical paths are reversed are similarly connected again to the connection waveguides 2106-6. 2 to 6 and enters the first slab waveguide 2104.

  A certain wavelength component of the optical signal incident on the first slab waveguide 2104 again forms interference fringes on the input / output surface of the first slab waveguide due to multibeam interference. At this time, the position where the interference fringes are formed and the light intensity of the interference fringes can be controlled by controlling the amount of phase modulation applied in the phase modulators 2400-1 to 2400-6. Therefore, the desired wavelength component of the optical signal incident on the wavelength selective switch can be coupled to the desired input / output waveguides 2102-1 to 2102-2 with the desired light intensity.

  In the present embodiment, all of the connection waveguides 2106-1 to 2106-6 are connected to the arrayed waveguide grating 2110, but any one of them may not be connected to the arrayed waveguide grating 2110. That is, the length of the connection waveguide 2106 not connected to the arrayed waveguide grating 2110 is made equal to the waveguide length of the arrayed waveguide grating 2110, and the light guided through the connected waveguide 2106 not connected to the arrayed waveguide grating 2110 You may comprise so that the phase modulation amount with respect to the optical signal which guides another array waveguide grating 2110 may be determined on the basis of a signal.

(Example 2)
A 1-input 2-output wavelength selective switch (wavelength) using a silica glass PLC with a relative refractive index difference Δ = 1.5% between the core and the clad and a reflective liquid crystal phase modulator array Number L = 40). As a result of measuring the extinction ratio of each wavelength selection switch for each wavelength, all were 40 dB or more.

  The second embodiment has described the case where the number of input ports is 1, the number of output ports M is 2, and N = 6. However, the wavelength selective switch according to the present invention is not limited to this. The number M of output ports of the wavelength selective switch can be an arbitrary number of 2 or more. Further, the present invention can be implemented by setting the number of input ports to 2 or more and N to M or more and 3 or more. Furthermore, the present invention can also be implemented as a transmission type wavelength selective switch described below as a modification of the reflection type wavelength selective switch shown in FIG.

(Deformation)
The wavelength selective switch shown in FIG. 8 is a schematic diagram of an optical switch with one input and two outputs (one input port and two output ports), similar to the optical switch shown in FIG. That is, FIG. 8 is a schematic diagram of a reflection type wavelength selective switch when M = 2 and N = 6.

  The wavelength selective switch shown in FIG. 8 includes a quartz optical waveguide 2100, cylindrical lenses 2200-1 to 2200-6, condenser lenses 2300-1 to 2300-6, and phase modulators 2400-1 to 2400-6. , Condenser lenses 3300-1 to 3300-6, cylindrical lenses 3200-1 to 3200-6, and a quartz-based optical waveguide 3100.

  The silica-based optical waveguide 2100 is the same as the silica-based optical waveguide 2100 shown in FIG. 5 except that it includes one input waveguide 2102 that constitutes an input port.

  The first slab waveguide 2104 and the connection waveguides 2106-1 to 2106-6 constitute an input branching unit. The input branch portion passes through the i-th waveguide among the six connection waveguides 2106-1 to 2106-6, and is relative to the optical electric field amplitude coupled to the output waveguide 3102-1 and the output waveguide 3102-2. Ratio

Is set or configured to be

  The cylindrical lenses 2200-1 to 2200-6 and the condenser lenses 2300-1 to 2300-6 also operate in the same manner as the cylindrical lens 2200 and the condenser lens 2300 shown in FIG.

  The phase modulator 2400 includes a phase control element that applies an arbitrary phase shift to each wavelength-separated optical signal and transmits the optical signal.

  The condensing lenses 3300-1 to 3300-6 and the cylindrical lenses 3200-1 to 3200-6 receive the optical signals that have been phase-shifted by the phase modulators 2400-1 to 2400-6 in the quartz-based optical waveguide 3100. It acts to couple to the two-array waveguides 3114-1 to 3114-6.

  The silica-based optical waveguide 3100 is the same as the silica-based optical waveguide 2100 shown in FIG. 5 except that it includes two output waveguides 3102-1 and 3102-2 that constitute an output port. The third slab waveguides 3112-1 to 3112-6 correspond to the second slab waveguides 2112-1 to 2112-6, respectively, the fourth slab waveguide 3104 corresponds to the first slab waveguide 2104, and the second array The waveguides 3114-1 to 3114-6 correspond to the arrayed waveguides 2114-1 to 2114-6, respectively, and the second connection waveguides 3106-1 to 3106-6 correspond to the connection waveguides 2106-1 to 2106-6, respectively. Correspond.

  The second arrayed waveguides 3114-1 to 3114-6 and the third slab waveguides 3112-1 to 3112-6 constitute second arrayed-waveguide gratings 3110-1 to 3110-6, and incident light of each wavelength. The signals are combined and coupled to the second connection waveguides 3106-1 to 3106-6.

  The second connection waveguides 3106-1 to 3106-6 and the fourth slab waveguide 3104 constitute an output multiplexing unit. The output multiplexing unit passes through the i-th waveguide among the six second connection waveguides 3106-1 to 3106-6 and is coupled to the output waveguide 3102-1 and the output waveguide 3102-2. The relative amplitude ratio is

Is set or configured to be

  A certain wavelength component of the optical signal incident on the fourth slab waveguide 3104 is interference fringes on the output surface of the fourth slab waveguide 3104 (the surface to which the output waveguides 3102-1 and 3102-2 are connected) due to multibeam interference. Form. At this time, the position where the interference fringes are formed and the light intensity of the interference fringes can be controlled by controlling the amount of phase modulation applied in the phase modulators 2400-1 to 2400-6. Therefore, the desired wavelength component of the optical signal incident on the wavelength selective switch can be coupled to the desired output waveguides 3102-1 to 1032-2 with the desired light intensity.

  The output waveguides 3102-1 and 3102-2 constitute an output port and output the optical signal from the fourth slab waveguide 3104.

  In each of the embodiments and modifications described above, the input port and the output port can be reversed and used as an optical switch or wavelength selective switch with M inputs and one output.

DESCRIPTION OF SYMBOLS 100 Quartz-type optical waveguide 200-1 to 200-14 Cylindrical lens 300-1 to 300-14 Condensing lens 400-1 to 400-14 Phase modulator 102-1 to 102-5 Input / output waveguide 104 First slab guide Waveguide 110-1 to 110-14 Array waveguide diffraction grating 106-1 to 106-14 Connection waveguide 112 Second slab waveguide 114-1 to 114-14 Array waveguide 1100, 2100, 3100 Silica-based optical waveguide 1102 Input Waveguide 1202-1 to 1202-5 Output waveguide 1104 First slab waveguide 1204 Second slab waveguide 1106-1 to 1106-14, 1206-1 to 1206-14 Connection waveguide 1110-1 to 1110-14 Heat Optical phase shifter 2102-1 to 2102-2 Input / output waveguide 2104 First slab waveguide 2112-1 to 2112-6 2nd slab waveguide 2200-1 to 2200-6, 3200-1 to 3200-6 Cylindrical lens 2300-1 to 2300-6, 3300-1 to 3300-6 Condensing lens 2400-1 ˜2400-6 Phase modulator 1302-1 to 1302-5 Input / output waveguide 1304 Mirror 3102-1 to 3102-2 Output waveguide 2110-1 to 2110-6, 3110-1 to 3110-6 Array waveguide diffraction grating 2106-1 to 2106-6, 3106-1 to 3106-6 Connection waveguide 3112-1 to 3112-6 Third slab waveguide 3104 Fourth slab waveguide

Claims (4)

An input port;
N is an integer greater than or equal to 3, and an input branching unit that branches N light waves input to the input port;
A phase shifter for modulating the phase of each of the branched light waves;
An optical switch comprising: M is an integer not less than 2 and not more than N; and an output multiplexing unit that multiplexes the optical waves modulated in phase and outputs them to M output ports,
The input branching unit is formed on a planar lightwave circuit, the input branching means for branching the lightwave input from the input port into N pieces, and the N number of input part outputs through which the branched N lightwaves are guided. With a waveguide,
The input branching means is a slab waveguide, and the light wave from the input port is incident from the center of the incident surface, and the output surface is moved to the position of the output surface where the N input output waveguides are connected at equal intervals. It is configured to be optically coupled with higher light intensity at the center of
The output multiplexing unit is a slab waveguide, and the light waves whose phase is modulated are incident on the incident surface at equal intervals, and the output surface is positioned at the position of the emission surface where the M output ports are connected at equal intervals. It is configured to be optically coupled with higher light intensity at the center of
The input branching means and the input section output waveguide are relative to the electric field amplitude of the light wave guided through the i-th input section output waveguide of the N input section output waveguides and coupled to the output port. Ratio

An optical switch characterized by being configured as follows.   2. The optical switch according to claim 1, wherein the phase shifter unit is configured by a reflection type phase modulator, and the input branching unit and the output multiplexing unit are the same optical circuit. An input port;
N is an integer greater than or equal to 3, and an input branching unit that branches N light waves input to the input port;
A phase shifter for modulating the phase of each of the branched light waves;
A wavelength selective switch comprising: M, an integer of 2 or more and N or less; and an output multiplexer that combines the modulated light waves and outputs them to M output ports,
The input branch portion is formed on a planar lightwave circuit,
Input branching means for branching the light wave input from the input port into N pieces;
N input output waveguides through which the branched N light waves are respectively guided;
And at least (N-1) wavelength separation means, each connected to one of the N input section output waveguides, for separating an input light wave into light waves of L wavelengths,
The input branching means is a slab waveguide, and the light wave from the input port is incident from the center of the incident surface, and the output surface is moved to the position of the output surface where the N input output waveguides are connected at equal intervals. It is configured to be optically coupled with higher light intensity at the center of
The output multiplexing unit is a slab waveguide, and the light waves whose phase is modulated are incident on the incident surface at equal intervals, and the output surface is positioned at the position of the emission surface where the M output ports are connected at equal intervals. It is configured to be optically coupled with higher light intensity at the center of
The output multiplexing unit is formed on a planar lightwave circuit,
At least (N-1) wavelength multiplexing means for wavelength multiplexing optical waves separated into L wavelengths and modulated in phase;
N output waveguides to which N light waves whose phases are modulated are coupled;
Output merging / branching means connected to the output input waveguide and outputting the input light wave to the M output ports;
The input branching unit and the input unit output waveguide, and the output combining unit and the output unit input waveguide are the i-th input unit among the N input unit output waveguides and the output unit input waveguides. The relative ratio of the electric field amplitude of the light wave passing through the output waveguide and the output portion input waveguide and coupled to the output port is

A wavelength selective switch characterized by being configured as follows. 4. The wavelength selective switch according to claim 3, wherein the phase shifter unit includes a reflection type phase modulator, and the input branching unit and the output multiplexing unit are the same optical circuit.

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