JP2014160216A - Mach-zehnder interferometer type wavelength selection switch - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a Mach-Zehnder interferometer type wavelength selection switch capable of reducing the size thereof by integrating wavelength couplers and by increasing the number of output ports.SOLUTION: The Mach-Zehnder interferometer type wavelength selection switch includes: a first array waveguide diffraction grating that has one input port and N output waveguides, which branches a wavelength division multiplex signal to output an optical signal of a wavelength to the respective output waveguides; N of 1×M optical switches that inputs an optical signal which is output from one of the N output waveguides to output the same to either one of M output ports; a Mach-Zehnder interferometer type complex wavelength coupler including plural wavelength couplers that inputs N optical signals which are output from the N of 1×M optical switches to combine the same into N+M-1 outputs; and a second array waveguide diffraction grating that inputs the N optical signals output from the Mach-Zehnder interferometer type complex wavelength coupler into any of the N+M-1 input ports to output the same to the M output ports.

Description

  The present invention relates to a Mach-Zehnder interferometer type wavelength selective switch, and more particularly to a wavelength selective switch that functions as an optical switch in an optical communication network node.

  In recent years, research on wavelength selective switches (WSS) has been actively conducted in the field of optical communication devices. WSS is indispensable for constructing the next generation of Reconfigurable Optical Add-Drop Multiplexer (ROADM) nodes. A device that can selectively output an arbitrary wavelength in an input wavelength division multiplexing (WDM) signal to an arbitrary output port, and is roughly classified into two types. The first is a spatial optical WSS in which a diffraction grating and a planar switching element such as MEMS (Micro Electro Mechanical System) or LCoS (Liquid Crystal on Silicon) are connected by a spatial optical system. Second, integrated WSS based on optical waveguide technology. Spatial optical WSS has become mainstream because it can accommodate more ports and has better optical characteristics than integrated WSS. However, it has the disadvantages of being large and expensive due to the complexity of the manufacturing process. On the other hand, it is difficult for the integrated WSS to accommodate more ports than the spatial optical WSS, but it is advantageous in terms of space saving and cost.

FIG. 1 shows an optical circuit type 1 × 2 wavelength selective switch which is a conventional integrated WSS. The wavelength selective switch 100 receives a wavelength division multiplexed signal including N wavelengths from _one input port IN ₁ and includes a wavelength selected from _two output ports OUT ₁ and OUT _2. Is output. The wavelength selective switch 100 includes an arrayed waveguide grating (AWG) 101 including one input waveguide and N output waveguides, N 1 × 2 optical switches 102, and N−1. 2 × 1 wavelength couplers 103 and AWGs 104 including N + 1 input waveguides and two output waveguides (see, for example, Non-Patent Document 1).

The wavelength division multiplexed signal input to the input port IN ₁ is demultiplexed by the AWG 101 and output waveguides A _{1 to} A _N (A ₁ , A ₂ ,..., A _N from the side closest to the longest arrayed waveguide). ), Optical signals having wavelengths λ _{1 to} λ _N are output. Optical signals of respective wavelengths, 1 × 2 is switched by the optical switch 102 is outputted to one of output waveguides B ₂ output waveguides B ₁ or below the upper side of FIG. Each wavelength coupler 103 is selected by the 1 × 2 optical switch 102 (a) combines optical signals of adjacent wavelengths, (b) passes only optical signals of one wavelength, (c) adjacent wavelengths The above three operations are performed.

It is assumed that the input waveguide of the AWG 104 is H ₁ , H ₂ ,..., H _{N + 1} from the side closest to the longest arrayed waveguide. Due to the symmetry of AWG, for example, when optical signals of wavelengths λ _{1 to} λ _N are incident on the input waveguides H _{2 to} H _{N + 1} , wavelength division multiplexed signals including wavelengths λ _{1 to} λ _N are output. Output to port OUT ₁ . When optical signals having wavelengths λ _{1 to} λ _N are incident on the input waveguides H _{1 to} H _N , wavelength division multiplexed signals including the wavelengths λ _{1 to} λ _N are output to the output port OUT ₂ . In this way, an optical signal having an arbitrary wavelength can be output to either of the output ports OUT ₁ and OUT ₂ .

  However, in the conventional integrated WSS, the number of output ports is as small as two, and the performance is inferior in terms of the number of ports as compared with the spatial optical type WSS.

Yuichiro Ikuma, Takayuki Mizuno, Hiroshi Takahashi, Hiroyuki Tsuda, “Wavelength selective switches using silica optical waveguide,” The Institute Of Electronics, Information And Communication Engineers, OPE2012-125, October 26, 2012

  In the conventional integrated WSS, in order to increase the number M of output ports, the number of ports of the optical switch must be increased and N + M−1 wavelength couplers must be provided, which causes a problem that the circuit becomes large. .

  In addition, in the conventional integrated WSS, the configuration of the 1 × 2 wavelength selective switch does not include the crossed waveguide, whereas the configuration of the 1 × M wavelength selective switch includes many crossed waveguides in the optical circuit. It will end up. In the crossed waveguide, as the crossing angle is smaller, crosstalk occurs between the crossed waveguides, and the characteristics of the propagating optical signal are deteriorated. When a cross waveguide is provided, it is desirable to make the cross angle of the cross waveguide as close to 90 degrees as possible in order to reduce crosstalk.

  An object of the present invention is to increase the number of output ports of an integrated WSS and to reduce the size by integrating Mach-Zehnder interferometer type wavelength couplers.

  In order to achieve the above object, according to the first embodiment, N wavelength division multiplexed signals are inputted from one input port, and M (M is an integer of 3 or more) outputs. A Mach-Zehnder interferometer-type wavelength selective switch for outputting a wavelength division multiplexed signal including a wavelength selected from a port, including the one input port and N output waveguides, wherein the wavelength division multiplexed signal is separated. A first arrayed waveguide diffraction grating that outputs an optical signal of each wavelength to each of the output waveguides and an optical signal output from one of the N output waveguides; N 1 × M optical switches output to any one of the output ports and N optical signals output from the N 1 × M optical switches are input and combined into N + M−1 outputs. Mach-Zehnder interferometer type composite wavelength consisting of multiple wavelength couplers A second arrayed waveguide diffraction which inputs N optical signals output from the coupler and the Mach-Zehnder interferometer-type composite wavelength coupler to any one of N + M−1 input ports and outputs them to M output ports. And a lattice.

  The second embodiment is characterized in that the first arrayed waveguide diffraction grating and the second arrayed waveguide diffraction grating are combined into one arrayed waveguide diffraction grating.

  As described above, according to the present invention, a plurality of Mach-Zehnder interferometer-type wavelength couplers are integrated to form a Mach-Zehnder interferometer-type composite wavelength coupler, thereby reducing the size of the optical circuit and the Mach-Zehnder interferometer. The number M of output ports of the type wavelength selective switch (M is an integer of 3 or more) can be increased.

It is a figure which shows the optical circuit type 1x2 wavelength selective switch which is the conventional integrated WSS. It is a figure which shows the Mach-Zehnder interferometer type | mold wavelength selective switch concerning the 1st Embodiment of this invention. It is a figure for demonstrating the structure of an array waveguide diffraction grating. It is a figure for demonstrating the structure of a 1 * M optical switch. It is a figure which shows the structure of the Mach-Zehnder interferometer type | mold wavelength coupler concerning the 1st Embodiment of this invention. It is a figure which shows the other structure of a Mach-Zehnder interferometer type | mold wavelength coupler. It is a figure for comparing the transmission band of a Mach-Zehnder interferometer type wavelength coupler. It is a figure which shows the structure of a Mach-Zehnder interferometer type composite wavelength coupler. It is a figure which shows the relationship between the stage number of a Mach-Zehnder interferometer, and the number of output ports. It is a figure for demonstrating the mounting method of a Mach-Zehnder interferometer type | mold composite wavelength coupler. It is a figure which shows the Mach-Zehnder interferometer type | mold wavelength selective switch concerning the 2nd Embodiment of this invention. It is a figure which shows the connection method of a 1 * M optical switch and a Mach-Zehnder interferometer type | mold composite wavelength coupler. It is a figure which shows the connection method of a 1 * M optical switch and a Mach-Zehnder interferometer type | mold composite wavelength coupler. It is a figure which shows the Mach-Zehnder interferometer type | mold wavelength selective switch concerning the 3rd Embodiment of this invention. It is a figure which shows the Mach-Zehnder interferometer type | mold wavelength selective switch concerning the 4th Embodiment of this invention.

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

(First embodiment)
FIG. 2 shows a Mach-Zehnder interferometer type wavelength selective switch according to the first embodiment of the present invention. The wavelength selective switch 200 inputs a wavelength division multiplexed signal including N wavelengths (shown in the case of N = 9) from _one input port IN ₁ , and M (M is an integer of 3 or more, FIG output port _{OUT 1,} OUT 2 are shown) in the case of M = 4, ..., and outputs the wavelength division multiplexed signal including a wavelength selected from the OUT _M. The wavelength selective switch 200 includes an input waveguide and N output waveguides A _{1 to} A _N (A ₁ , A ₂ ,..., A _N from the side closest to the longest arrayed waveguide). (First arrayed waveguide diffraction grating), N 1 × M optical switches 202 (referred to as S ₁ , S ₂ ,..., S _N from the side closest to the longest arrayed waveguide of AWG 201), and Mach-Zehnder interference Meter-type composite wavelength coupler (MZC) 203, N + M−1 input waveguides (E ₁ , E ₂ ,..., E _{N + M−1} from the side closest to the longest arrayed waveguide) and M output leads And an AWG 204 (second arrayed waveguide diffraction grating) including a waveguide.

The MZC 203 includes two 1 × 1 wavelength couplers (ie, one through optical waveguide), two 2 (M−2) × 1 wavelength couplers, two 3 (M−1) × 1 wavelength couplers, N -M + 1 4 (M) × 1 wavelength couplers are included. The wavelength couplers are C ₁ , C ₂ ,..., C _{N + M−3} from the side closest to the longest array waveguide of MZC 203. The through optical waveguide on the side closest to the longest arrayed waveguide is C ₀ , and the through optical waveguide on the side closest to the shortest arrayed waveguide is C _{N + M−2} . As a result, N × M inputs from N 1 × M optical switches 202 are input to M types of wavelength couplers of Z × 1 wavelength couplers (Z = 1 to M), and N + M−1 Composite to output.

The configuration of the arrayed waveguide diffraction grating will be described with reference to FIG. The arrayed waveguide diffraction grating includes a first input / output waveguide 301, a first slab waveguide 302, an arrayed waveguide 303, a second slab waveguide 304, and a second input / output waveguide 305. Yes. d ₁ is a waveguide installation interval on the array waveguide side of the first slab waveguide 302, and d ₂ is a waveguide installation interval on the array waveguide side of the second slab waveguide 304. D ₁ is a waveguide installation interval on the input / output waveguide side of the first slab waveguide 302, and D ₂ is a waveguide installation interval on the input / output waveguide side of the second slab waveguide 304. f ₁ is the length of the first slab waveguide 302, and f ₂ is the length of the second slab waveguide 304. It is assumed that the arrayed waveguide diffraction grating satisfies (Equation 1).

When the AWG 204 in FIG. 2 satisfies (Equation 1), the AWG 204 is distributed to the output ports OUT _{1 to} OUT ₄ according to the position of the input waveguide of the AWG 204 from the basic characteristics of the AWG. Therefore, in order to change an optical signal having a certain wavelength, which has been demultiplexed by the AWG 201, from the output port OUT ₁ to the output port OUT ₂ , the input waveguide of the AWG 204 into which this optical signal is incident is designated as 1 in FIG. What is necessary is just to change to the upper input waveguide.

  The configuration of the 1 × M optical switch will be described with reference to FIG. The 1 × M optical switch 202 is configured by combining 2 × 2 symmetric Mach-Zehnder interferometers. The 2 × 2 symmetric Mach-Zehnder interferometer 400a includes two equal-length arm waveguides 402a and 402b that connect between two 2 × 2 couplers 401a and 401b. Is provided with a phase shifter 403 for controlling. The phase shifter 403 is a heater integrated on the optical waveguide circuit, and controls the phase generated in the optical waveguide using the thermo-optic effect of the optical waveguide.

  When there is no phase difference between the arm waveguides 402 a and 402 b, the optical signal input from the input port 404 is output to the cross port 405. When the phase difference between the arm waveguides 402 a and 402 b is π, the input optical signal is output to the bar port 406. Further, 2 × 2 symmetrical Mach-Zehnder interferometers 400b and 400c are cascade-connected to each of the cross port 405 and the bar port 406, thereby switching M outputs (the figure shows the case of M = 4). Can do.

The 1 × M optical switch 202 according to the first embodiment includes N 1 × M optical switches _Sk , and the 1 × M optical switch _Sk includes M (= 4) output ports P _k1 and P _k2. , _..., to any of the _{P kM,} and outputs the light of wavelength λ _k.

The MZC 203 includes two through optical waveguides (C ₀ , C _{N + M−2} ), two 2 (M−2) × 1 wavelength couplers (C ₁ , C _{N + M−3} ), and two three (M−1). ) × 1 wavelength coupler (C ₂ , C _{N + M−4} ), NM + 1 4 (M) × 1 wavelength couplers (C _{3 to} C _{N + M−5} ). The M (= 4) output ports P _k1 , P _k2 ,..., P _kM of the 1 × M optical switch S _k are sequentially connected to wavelength couplers C _k−1 , C _k , C _{k + 1} , C included in the MZC 203, respectively. connected to _{k + 2} . Details of the MZC 203 will be described later.

The operation of the wavelength selective switch 200 in FIG. 2 will be described. Wavelength division multiplexed signal input to the input port IN ₁ is demultiplexed by AWG201, to each of the output waveguides _A 1 to A _N, the optical signals of respective wavelengths lambda ₁ to [lambda] _N corresponding to subscript outputs Is done. An optical signal of each wavelength is switched to one of M output ports P _k1 , P _k2 ,..., P _kM by a 1 × M optical switch 202, and wavelength couplers C _k−1 and C _k included in the MZC 203 are included. , C _{k + 1} , or C _{k + 2} . Each wavelength coupler included in the MZC 203 combines the optical signals input from the 1 × M optical switch and outputs the combined optical signals to the input waveguides E _{1 to} E _{N + M−1} of the AWG 204.

When the AWGs 201 and 204 satisfy (Equation 1), assuming that light of wavelengths λ _{1 to} λ _N is incident on the input waveguides E _{M to} E _{N + M−1} due to the basic characteristics of the AWG, the wavelength λ ₁ wavelength division multiplexed signal including to [lambda] _N are output to the output port OUT _1. If light of wavelengths λ _{1 to} λ _N is incident on the input waveguides E _{1 to} E _N , a wavelength division multiplexed signal including the wavelengths λ _{1 to} λ _N is output to the output port OUT _M. In this way, assuming that the light of wavelength λ _k guided to the 1 × M optical switch S _k is switched to the output port P _k1 , it is output from the output port OUT _{M of the} AWG 204 via the wavelength coupler of the AWG 203. Is done. Also, assuming that light of wavelength λ _k is switched to output port P _kM , it is output from output port OUT _{1 of} AWG 204.

  In the first embodiment, the optical waveguide circuit constituting the arrayed waveguide diffraction grating and the optical switch includes, for example, a clad layer made of quartz and a core formed on a substrate made of quartz or silicon. In the first embodiment, N = 9 and M = 4, but it is obvious that further enlargement is possible.

(Mach-Zehnder interferometer type wavelength coupler)
FIG. 5 shows the configuration of a Mach-Zehnder interferometer-type wavelength coupler according to the first embodiment of the present invention. The MZC 203 is configured by combining 2 × 2 asymmetric Mach-Zehnder interferometers. As shown in FIG. 5A, the asymmetric Mach-Zehnder interferometer 500 includes two arm waveguides 502a and 502b having different lengths that connect between two 2 × 2 couplers 501a and 501b. Asymmetric Mach-Zehnder interferometer 500, becomes zero phase difference with respect to the wavelength lambda _k between the upper and lower arm waveguides, since it is designed to be π with respect to the wavelength lambda _{k + 1,} the wavelength lambda _k The optical signal is output to the cross port, and the optical signal of wavelength λ _{k + 1} is output to the bar port. Therefore, when optical signals having wavelengths λ _k and λ _{k + 1} are input to different input ports, two optical signals are output from the same output port. If the input and output are interchanged due to the symmetry of input and output in the optical circuit, a wavelength coupler that combines optical signals of different wavelengths is obtained.

The frequency interval at which the output port is switched is determined by the difference ΔL in length between the long arm waveguide and the short arm waveguide. The difference between the two wavelengths to be combined expressed in frequency units is Δν, the speed of light in vacuum is c, and the group index of the waveguide is _ng . ΔL for the frequency interval at which the output port is switched becomes Δν is given by Equation (2).

However, if ΔL represented by Equation (2) is used as it is, the transmission band generally does not match the wavelength to be combined. Therefore, ΔL needs to be slightly increased or decreased from Equation (2). The length of the increment or decrement the L _s. In order to allow the wavelength λ _k to pass through the cross port, the phase difference between the upper and lower arm waveguides need only be 0. Therefore, ΔL ′ satisfying the expression (3) is satisfied, where m is a positive integer. Use. L _s can be 1 wavelength or less at the maximum, and its influence on Δν is sufficiently small.

  A method of configuring a wavelength coupler by combining asymmetric Mach-Zehnder interferometers will be described by taking the case of M = 4 as an example. 5B includes an asymmetric Mach-Zehnder interferometer 500 having a frequency interval of Δν, an asymmetric Mach-Zehnder interferometer 510 having a frequency interval of 2Δν connected to the output port 505 of the asymmetric Mach-Zehnder interferometer 500, and an asymmetric type. And an asymmetric Mach-Zehnder interferometer 520 having a frequency interval of 2Δν connected to the output port 506 of the Mach-Zehnder interferometer 500.

  Next, the operation of the wavelength coupler will be described. Wavelengths λ1 to λ4 having a frequency interval Δν are incident on one input port 504 of the asymmetric Mach-Zehnder interferometer 500. Optical signals with wavelengths λ1 and λ3 are output to an output port 505 that is a cross port with respect to the input port, and optical signals with wavelengths λ2 and λ4 are output to an output port 506 that is a bar port with respect to the input port. Is done. An optical signal with wavelength λ1 and a wavelength λ3 is output from the cross port of the asymmetric Mach-Zehnder interferometer 510, and an optical signal with wavelength λ4 is output from the crossport of the asymmetric Mach-Zehnder interferometer 520, and an optical signal with wavelength λ2 is output from the bar port. .

  As shown in FIG. 5B, the area occupied by the wavelength coupler can be reduced by disposing the long arm waveguides of the asymmetric Mach-Zehnder interferometers 510 and 520 so as to face each other on the optical circuit. . Further, by providing the crossed waveguide 530 in the subsequent stage of the asymmetric Mach-Zehnder interferometers 510 and 520, the optical signals having the wavelengths λ1 to λ4 can be output in the order of the subscripts at the output port 540 of the wavelength coupler.

  By connecting the input of the 1 × M optical switch 202 to the output port 540 and connecting the AWG 204 to the input port 504 due to the input / output symmetry in the optical circuit, the optical circuit can function as a wavelength coupler.

With reference to FIG. 6, a description will be given of different combinations of asymmetric Mach-Zehnder interferometers. An asymmetric Mach-Zehnder interferometer 600 with a frequency interval of 2Δν is placed in the preceding stage, and wavelengths λ _{1 to} λ ₄ with a frequency interval of Δν are incident on one input port 604. Optical signals with wavelengths λ ₁ and λ ₂ are output to an output port 605 that is a cross port with respect to the input port, and wavelengths λ ₃ and λ ₄ are output to an output port 606 that is a bar port with respect to the input port. An optical signal is output. Next, an asymmetric Mach-Zehnder interferometer 610 having a frequency interval Δν is connected to the cross port 605, and an asymmetric Mach-Zehnder interferometer 620 having a frequency interval Δν is also connected to the bar port 506. At the output port 640 of the wavelength coupler, optical signals having wavelengths λ _{1 to} λ ₄ can be output in the order of subscripts.

  FIG. 7 shows the transmission band of the wavelength coupler shown in FIG. 5B and the wavelength coupler shown in FIG. FIG. 7 (a) shows the transmittance of the wavelength coupler shown in FIG. 5 (b). The transmission band coincides with the wavelength to be combined, the peak loss is about 0 dB, and the crosstalk is about −40 dB. On the other hand, FIG. 7B shows the transmittance of the wavelength coupler shown in FIG. 6. The transmission band does not match the wavelength to be combined, the peak loss is about 0.5 dB, and the crosstalk is about −12 dB. . Although the wavelength coupler shown in FIG. 5B includes the crossed waveguide 530, the transmission characteristics are superior to the wavelength coupler shown in FIG. In this embodiment, as the Mach-Zehnder interferometer type wavelength coupler, an asymmetric Mach-Zehnder interferometer having a frequency interval of Δν is arranged in the front stage and an asymmetric Mach-Zehnder interferometer having a frequency interval of 2Δν is arranged in the rear stage.

FIG. 8 shows a configuration of a Mach-Zehnder interferometer type composite wavelength coupler (MCZ) applied to the wavelength selective switch 200. Among the wavelength couplers included in the MZC 203, 4 (M) × 1 wavelength couplers C _{3 to} C ₆ are shown. For convenience of explanation, a wavelength coupler that demultiplexes optical signals having different wavelengths will be described. An asymmetric Mach-Zehnder interferometer having a frequency interval of Δν is arranged in the front stage, and an asymmetric Mach-Zehnder interferometer having a frequency interval of 2Δν is arranged in the rear stage. The asymmetric Mach-Zehnder interferometer 801 having an arm waveguide length difference of ΔL ₁ and a frequency interval of Δν receives an optical signal of wavelengths λ _{1 to} λ _N as a cross port. , The even-numbered optical signal of the subscript is output to the bar port. An asymmetric Mach-Zehnder interferometer 802 having an arm waveguide length difference of ΔL ₂ and a frequency interval of 2Δν uses optical signals of wavelengths λ ₁ , λ ₅ , λ ₉ ,... As cross ports and wavelengths λ ₃ , λ ₇ , λ. ₁₁ ,... Are output to the bar port. The asymmetric Mach-Zehnder interferometer 803 having an arm waveguide length difference of ΔL ₃ and a frequency interval of 2Δν uses optical signals of wavelengths λ ₄ , λ ₈ , λ ₁₂ ,... As cross ports and wavelengths λ ₂ , λ ₆ , λ ₁₀ optical signals are output to the bar port. In this way, the remaining 4 (M) × 1 wavelength couplers C _{7 to} C _{N + M-5} can also be configured.

  Such a Mach-Zehnder interferometer type composite wavelength coupler is established in the case of the equation (4).

Here, n is the number of stages of the Mach-Zehnder interferometer constituting the wavelength coupler, 2 ⁿ is the maximum number of output ports of the wavelength selective switch (when two stages of Mach-Zehnder interferometers are connected in n stages, it becomes 2 n), and a is The number of ports is subtracted from the maximum number of output ports of the wavelength selective switch. The number of crossings in the crossing waveguide increases as n increases, with n = 2 and a = 0, 1 with n = 3 and a = 0, n = 4 and 9 with a = 0, n = 5 means 21 pieces.

FIG. 9 shows the relationship between the number of stages of the Mach-Zehnder interferometer and the number of output ports. Since it is desired to realize a wavelength selective switch having three or more output ports, the number of stages of the Mach-Zehnder interferometer is n ≧ 2. In each stage, the number of ports a that can be reduced is determined from the relationship between the difference in arm waveguide length and the frequency interval, and the maximum value of a is amax = 2 ^{(n−1) −1} .

  The Mach-Zehnder interferometer type composite wavelength coupler has an asymmetrical Mach-Zehnder interferometer with a frequency interval of Δν in the front stage and a plurality of asymmetrical arrangement Mach-Zehnder interferometers with a frequency interval of 2Δν in the subsequent stage. As shown in FIG. 9, by selecting the number n and a of Mach-Zehnder interferometers from the relationship between n, a and M, any one of 1 × M (M is an integer of 3 or more) wavelength selective optical switch The number of input ports M can also be configured.

  A more compact mounting method of the Mach-Zehnder interferometer type composite wavelength coupler will be described with reference to FIG. In the adjacent wavelength coupler, the asymmetric Mach-Zehnder interferometers 901a and 901b having the frequency interval Δν of the preceding stage are arranged so that the long arm waveguides face each other, so that the wavelength coupler occupies more than the configuration shown in FIG. The area can be reduced.

(Second Embodiment)
FIG. 11 shows a Mach-Zehnder interferometer-type wavelength selective switch according to the second embodiment of the present invention. The wavelength selective switch 1000 inputs a wavelength division multiplexed signal including N wavelengths (the figure shows a case where N = 9) from _one input port IN ₁ , and M (M ≧ 3, M = integer) , Shows a case where M = 4), and outputs a wavelength division multiplexed signal including wavelengths selected from the output ports OUT ₁ , OUT ₂ ,..., OUT _M. The wavelength selective switch 1000 is a form in which the AWG 201 and the AWG 204 of the Mach-Zehnder interferometer type wavelength coupler 200 of the first embodiment are integrated into one AWG 1001.

The AWG 1001 has one input port IN ₁ and N + M−1 input waveguides corresponding to the input waveguides of the AWG 204 (F ₁ , F ₂ ,..., F from the side closest to the longest arrayed waveguide) _{N + M} ). Also, N output waveguides corresponding to the output waveguides of the AWG 201 and output ports corresponding to the output ports OUT ₁ , OUT ₂ ,..., OUT _M of the AWG 204 (from the side closest to the longest arrayed waveguide) G ₁ , G ₂ ,..., _{GN + M} ). The AWG 1001 satisfies (Equation 1).

When the wavelength division multiplexed signal input to the input port IN ₁ is input to the input waveguide F ₁ , the center wavelength is output to the output waveguide G _{N + M} from the basic characteristics of the AWG. If the wavelengths of light output to the output waveguides G _{M + 1 to} G _{N + M} are λ ₁ to λ _N , respectively, the wavelength λ _N is the center wavelength of the AWG 1001. Therefore, the AWG 1001 selects and designs the longest wavelength among the wavelength division multiplexed signals as the center wavelength.

The operation of the wavelength selective switch 1000 in FIG. 11 will be described. The wavelength division multiplexed signal input to the input port IN ₁ is demultiplexed by the AWG 1001, and optical signals of the respective wavelengths (λ _{1 to} λ _N ) are output to the output waveguides G _{M + 1 to} G _{N + M.} An optical signal of each wavelength is switched to one of output ports P _k1 , P _k2 ,..., P _kM by a 1 × M optical switch (S _k ) 202, and wavelength couplers C _k−1 , C included in the MZC 203. It is output to any one of _k , C _{k + 1} , and C _{k + 2} . Each wavelength coupler included in the MZC 203 combines the optical signals input from the 1 × M optical switch and outputs them to the input waveguides F _{2 to} F _{N + M} of the AWG 1001.

From the basic characteristics of the AWG, if light of wavelengths λ _{1 to} λ _N is incident on the input waveguides F _{M + 1 to} F _{N + M} , wavelength division multiplexed signals including wavelengths λ _{1 to} λ _N are output to the output port OUT ₁ . Is done. If light of wavelengths λ _{1 to} λ _N is incident on the input waveguides F _{2 to} F _{N + 1} , a wavelength division multiplexed signal including the wavelengths λ _{1 to} λ _N is output to the output port OUT _M. If the light of wavelength λ _k guided to the 1 × M optical switch S _k is switched to the output port P _k1 in this way, the light is output from the output port OUT _{M of the} AWG 1001 via the wavelength coupler of the MZC 203. Is done. Also, assuming that light of wavelength λ _k is switched to output port P _kM , it is output from output port OUT _{1 of} AWG 1001.

  According to this embodiment, the number of output ports of the arrayed waveguide grating type wavelength selective switch can be increased, and the circuit can be reduced in size by replacing a plurality of wavelength couplers with one AWG. be able to.

(Installation method of optical waveguide)
A connection method between the 1 × M optical switch and the Mach-Zehnder interferometer-type composite wavelength coupler will be described with reference to FIGS. In the wavelength selective switch of FIG. 11, the optical signal of each wavelength is switched to one of the output ports P _k1 , P _k2 ,..., P _kM by a 1 × M optical switch (S _k ) 1202 and included in the MZC 1203. It is output to _{one of the} wavelength couplers C _k−1 , C _k , C _{k + 1} , C _{k + 2} . The minimum waveguide interval of the output ports P _k1 , P _k2 ,..., P _kM is set to p and equal intervals. The minimum waveguide interval between two adjacent 1 × M optical switches 1202 is s. Similarly, the minimum waveguide interval of the input port of the MZC 1203 is set to p and equal intervals. Let s be the minimum waveguide interval between two adjacent MZCs 1203.

In FIG. 13, the input ports of the wavelength couplers C _k−1 , C _k , C _{k + 1} , and C _{k + 2} are U1, U2, U3, and U4. 1 × M optical switch (S _k ) 1202 The output port P _k1 is connected to the input port U4 of the wavelength coupler C _k-1 of the MZC 1203, the output port P _k2 is connected to the input port U3 of the wavelength coupler C _k , and the output Connect port P _k3 to input port U2 of wavelength coupler C _{k + 1} ,
The output port P _kM is connected to the input port U1 of the wavelength coupler C _{k + 2} . The four optical waveguides connected in this way are symmetrical with respect to the x-axis passing through the center of the output port of the 1 × M optical switch (S _k ) 1202.

  As one example, when s = 1700 μm, p = 50 μm, and the bending radius of the optical waveguide R = 3000 μm,

And θ1 = about 90 °. At this time, θ2 = about 70 °. One optical waveguide intersects with the other three optical waveguides. However, as shown in FIG. 12, the intersection angle with the two optical waveguides is set to 90 degrees, and the other one optical waveguide is intersected. The optical waveguide can be installed so that the crossing angle of the waveguide approaches 90 degrees.

(Third embodiment)
FIG. 14 shows a Mach-Zehnder interferometer-type wavelength selective switch according to the third embodiment of the present invention. In the first embodiment shown in FIG. 2, a Mach-Zehnder interferometer type composite wavelength coupler (MZC) including four types of wavelength couplers is used. In the third embodiment, the MZC 1303 is configured using only one type of 4 (M) × 1 wavelength coupler. That is, the MZC 1303 is configured by only N + M−1 M × 1 wavelength couplers.

  M corresponding to two 1 × 1 wavelength couplers (ie, one through optical waveguide), two 2 (M−2) × 1 wavelength couplers, and two 3 (M−1) × 1 wavelength couplers In the × 1 wavelength coupler, a part of the input port is not connected to the output port of the 1 × M optical switch 202. As a result, the transmission characteristics in the wavelength coupler are the same regardless of which path the optical signal propagates, so that the insertion loss can be made uniform.

(Fourth embodiment)
FIG. 15 shows a Mach-Zehnder interferometer-type wavelength selective switch according to the fourth embodiment of the present invention. In the second embodiment shown in FIG. 11, a Mach-Zehnder interferometer type composite wavelength coupler (MZC) including four types of wavelength couplers is used. In the fourth embodiment, the MZC 1403 is configured using only one type of 4 (M) × 1 wavelength coupler. That is, the MZC 1403 is configured by only N + M−1 M × 1 wavelength couplers. As a result, the transmission characteristics in the wavelength coupler are the same regardless of which path the optical signal propagates, so that the insertion loss can be made uniform.

  According to the present embodiment, the number of output ports of the wavelength selective switch can be increased, and the Mach-Zehnder interferometer type wavelength coupler can be integrated and downsized. Further, by appropriately arranging the optical switch and the wavelength coupler, the crossing angle of the crossing waveguide can be as close to 90 degrees as possible, and crosstalk in the crossing direction at the crossing of the waveguide can be reduced.

100, 200, 1000, 1300, 1400 Wavelength selective switch 101, 104, 201, 204, 601, 1001 AWG
102, 202, 1202 1 × 2 optical switch 103 wavelength coupler 203, 1203, 1303, 1403 Mach-Zehnder interferometer type composite wavelength coupler (MZC)
301 First Input / Output Waveguide 302 First Slab Waveguide 303 Array Waveguide 304 Second Slab Waveguide 305 Second Input / Output Waveguide 400 Symmetric Mach-Zehnder Interferometer 401,501 2 × 2 Coupler 402,502 Arm waveguide 403 Phase shifter 404, 504, 604 Input port 405, 505, 605 Cross port 406, 506, 606 Bar port 500, 510, 520, 600, 610, 620, 801-803, 901-903 Asymmetrical Mach-Zehnder interference Total 530 Cross waveguide 540,640 Output port

Claims (9)

Mach-Zehnder interferometer type wavelength selection that inputs N wavelength division multiplexing signals from one input port and outputs wavelength division multiplexing signals including wavelengths selected from M (M is an integer of 3 or more) output ports A switch,
First array waveguide diffraction including the one input port and N output waveguides, demultiplexing the wavelength division multiplexed signal, and outputting an optical signal of each wavelength to each of the output waveguides Lattice,
N 1 × M optical switches that receive an optical signal output from one of the N output waveguides and output to one of the M output ports;
A Mach-Zehnder interferometer-type composite wavelength coupler comprising a plurality of wavelength couplers for inputting N optical signals output from the N 1 × M optical switches and combining them into N + M−1 outputs;
A second arrayed waveguide grating for inputting N optical signals output from the Mach-Zehnder interferometer-type composite wavelength coupler to any one of N + M−1 input ports and outputting the output to M output ports; A Mach-Zehnder interferometer type wavelength selective switch characterized by comprising. Mach-Zehnder interferometer type wavelength selection that inputs N wavelength division multiplexing signals from one input port and outputs wavelength division multiplexing signals including wavelengths selected from M (M is an integer of 3 or more) output ports A switch,
Third array waveguide diffraction including the one input port and N output waveguides, demultiplexing the wavelength division multiplexed signal, and outputting an optical signal of each wavelength to each of the output waveguides Lattice,
N 1 × M optical switches that receive an optical signal output from one of the N output waveguides and output to one of the M output ports;
A Mach-Zehnder interferometer type composite wavelength coupler comprising a plurality of wavelength couplers for inputting N optical signals output from the N 1 × M optical switches and combining them into N + M−1 outputs,
The third arrayed waveguide diffraction grating includes an input waveguide for inputting N optical signals output from the Mach-Zehnder interferometer-type composite wavelength coupler to any of N + M−1 input ports and M outputs. A Mach-Zehnder interferometer-type wavelength selective switch, further comprising a port, and outputting the N optical signals to the M output ports.   3. The Mach-Zehnder interferometer-type wavelength selective switch according to claim 1, wherein the 1 × M optical switch is configured by cascading 2 × 2-symmetric Mach-Zehnder interferometers. The Mach-Zehnder interferometer-type composite wavelength coupler is M types of wavelength couplers of Z × 1 wavelength couplers (Z = 1 to M), and includes N + M−2th N + M−1 wavelength couplers,
Each of the M output ports of the kth 1 × M optical switch is connected to the input waveguide of the k−1, k, k + 1,..., k + M−2nd wavelength coupler. The Mach-Zehnder interferometer-type wavelength selective switch according to claim 1 or 2.   5. The Mach-Zehnder interferometer-type wavelength selective switch according to claim 4, wherein the Z × 1 wavelength coupler includes an asymmetric Mach-Zehnder interferometer. The Mach-Zehnder interferometer-type composite wavelength coupler includes N + M−1 M × 1 wavelength couplers,
Each of the M output ports of the kth 1 × M optical switch is connected to the input waveguide of the k−1, k, k + 1,..., k + M−2nd wavelength coupler. The Mach-Zehnder interferometer-type wavelength selective switch according to claim 1 or 2.   The Mach-Zehnder interferometer-type wavelength selective switch according to claim 6, wherein the M × 1 wavelength coupler includes an asymmetric Mach-Zehnder interferometer.   6. The asymmetric Mach-Zehnder interferometer, wherein an asymmetric Mach-Zehnder interferometer having a frequency interval of Δν is connected to a front stage, and a plurality of asymmetric arrangement Mach-Zehnder interferors having a frequency interval of 2Δν are cascade-connected to the rear stage. 8. A Mach-Zehnder interferometer-type wavelength selective switch according to 7. As for the number M of the output ports, n is the number of stages of the Mach-Zehnder interferometer constituting the wavelength coupler, and a is the number of ports subtracted from the maximum number of output ports of the wavelength selective switch.

The Mach-Zehnder interferometer-type wavelength selective switch according to claim 8, wherein:

Images