JP2006038897A - Waveguide type optical switch unit element and waveguide type matrix optical switch - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a matrix optical switch equipped with a sufficient extinction ratio independent of a fabrication error by suitably combining circuits together in the case in which circuit characteristics vary due to an error produced in the fabrication of the matrix optical switch. <P>SOLUTION: The matrix optical switch comprises an input optical waveguide 11a-11b and an output optical waveguide 12a-12b intersecting with each other, and further a bypass optical waveguide 13a-13b which connects the input and output optical waveguides 11a-11b, 12a-12b to each other, and includes a 1×2 optical switch 18a between the bypass optical waveguide 13a-13b and the input optical waveguide 11a-11b, a 2×1 optical switch 18b between the bypass optical waveguide 13a-13b and the output optical waveguide 12a-12b, and a 1×1 optical gate switch 18c between the 1×2 optical switch 18a and the 2×1 optical switch 18b. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a waveguide type optical switch unit element and a waveguide type matrix optical switch. In particular, the present invention relates to a circuit configuration of a waveguide type optical switch that is resistant to manufacturing errors and excellent in an extinction ratio, and a waveguide type matrix optical switch configured as a unit element.

  Network content is becoming more diverse due to the explosive spread of broadband communications, and with this advancement, communication traffic has increased, and the demand for higher capacity, higher speed and higher functionality for communication networks has been increasing day by day. Yes.

  In recent years, optical communication technology has played an important role in meeting these requirements.

  In conventional optical communication networks, signal processing using optical-electrical and electrical-optical conversion has become the mainstream, but in the future optical signals will not be converted into electrical signals on all communication networks including access networks. It is important to develop an optical communication network that connects signals as they are.

  One of the important components in this optical communication system is an optical switch.

  This is a component that plays a central role in systems that switch (route switching) or route (route setting) optical signals as they are in the light of light. The importance is increasing.

  Various forms of configuring the optical switch have been proposed, including a bulk type, a micro-electro-mechanical systems (MEMS) type, a waveguide type, and the like.

  The bulk type is a mechanically driven optical switch composed of movable prisms, lenses, etc., and has little wavelength dependence and relatively low loss, but it is manufactured by assembling several parts, so the process is complicated. However, there is a problem that mass production and scale-up are difficult.

  Although the MEMS type is mechanically driven, it is composed of a large number of mirror arrays, optical fibers and collimating lenses manufactured by applying semiconductor microfabrication technology, and has low wavelength dependence and low loss. It is a component that is easy to mass-produce and scale up, and is currently under active development.

  The waveguide type, on the other hand, is based on optical waveguides that are manufactured by applying semiconductor microfabrication technology to materials such as glass and polymers in addition to semiconductors. It has many advantages such as excellent stability and easy integration with other waveguide type optical components such as optical fiber mounting and optical multiplexer / demultiplexers and optical filters.

  In particular, an optical switch using the thermo-optic effect of a silica-based optical waveguide fabricated on a silicon substrate has features such as low loss, excellent chemical stability and matching with an optical fiber, and is most practically used. It is one of the advanced optical switches.

  As an optical switch used in an optical communication system such as an optical router, there is a matrix optical switch having a plurality of input / output ports which is an object of the present invention.

  As an example, a conceptual diagram of a 4 × 4 matrix optical switch is shown in FIG.

  This matrix optical switch is composed of four input optical waveguides (1a-1d to 4a-4d) and four output optical waveguides (1c-1b to 4c-4b) intersecting each other, and optical switches are provided at 16 intersections. Two-input two-output optical switches s11 to s44 are arranged as unit elements, and the input optical waveguide and the output optical waveguide intersect with each other, so they are sometimes called crossbar switches.

  Each optical switch unit element is in a cross state as shown in FIG. 8B when not energized (or turned off), and switches to a bar state as shown in FIG. 8C when energized (or turned on). .

  Such a switch has a strictly non-blocking configuration that is not affected by other paths at all (not blocked by other paths) with respect to the path connecting any input optical waveguide and output optical waveguide, and only one switch. The paths are connected by setting S11 to S44 to the bar state.

  FIG. 9 shows a configuration diagram of a waveguide type 4 × 4 matrix optical switch in which the 4 × 4 matrix optical switch shown in FIG. 8 is realized by utilizing the thermo-optic effect of the silica glass optical waveguide.

  The matrix circuit configuration in FIG. 8 is crushed diagonally, and 1 to 4 optical switch unit elements S11 to S44 are arranged in parallel and connected in 7 stages.

  FIG. 10A shows an optical waveguide configuration diagram of a double gate type optical switch unit element (see Patent Document 1) used as the switch unit elements S11 to S44 in FIG. 9, and AA ′ in FIG. A cross-sectional view along the line is shown in FIG.

  These optical waveguides are fabricated on a silicon substrate by a known combination of flame hydrolysis reaction deposition and reactive ion etching techniques.

  That is, the optical switch unit element is basically composed of an input optical waveguide 11a-11b, an output optical waveguide 12a-12b, and a bypass optical waveguide 13a-13b that intersect each other, and the input optical waveguide 11a-11b and the bypass optical waveguide 13a- 13b, and the output optical waveguides 12a-12b and the bypass optical waveguides 13a-13b are close to each other at two locations to form directional couplers 14a, 15a and 14b, 15b. Mach-Zehnder interferometer circuits (shown by broken lines in the figure) 18a and 18b are configured.

  The coupling rates of these directional couplers 14a, 15a and 14b, 15b are designed to be 50% at the signal light wavelength, and the optical path length difference between the two arm optical waveguides of the Mach-Zehnder interferometers 18a, 18b is The optical waveguide length is designed to be one-half of the signal light wavelength, and at least one of these arm optical waveguides is an optical phase shifter for changing the optical path length difference using the thermo-optic effect of silica glass. The thin film heaters 16a and 16b are loaded. When the thin film heaters 16a and 16b are off, the optical switch unit element is in a cross state, and when it is on, it is in a bar state.

  Such a configuration can exhibit sufficient optical characteristics even when a manufacturing error occurs with respect to the coupling ratio of the designed directional couplers 14a, 15a and 14b, 15b.

  That is, in the cross state, when the coupling ratios of the two directional couplers 14a, 15a and 14b, 15b in the first Mach-Zehnder interferometer circuits 18a, 18b are not limited to 50%, The 100% signal light passes through the input optical waveguides 11a-11b, and no optical crosstalk occurs to the bypass optical waveguides 13a-13b.

  However, if the two directional couplers 14a, 15a and 14b, 15b are misaligned, or other factors cause optical crosstalk to the bypass optical waveguides 13a-13b, it is the second Mach-Zehnder. In the interferometer circuits 18a and 18b, almost 100% passes through the bypass optical waveguides 13a-13b by the same principle, and optical crosstalk hardly occurs in the output optical waveguides 11a-11b.

  When the heaters 16a and 16b loaded on the two Mach-Zehnder interferometer circuits 18a and 18 are turned on to cancel the optical path length difference corresponding to the half wavelength of the signal light provided in advance, the signal light is input to the input optical waveguide 11a. -11b is led to the bypass optical waveguide 13a-13b, and is further led from the bypass optical waveguide 13a-13b to the output optical waveguide 11a-11b to be in a bar state.

  In this way, the double gate type optical switch unit element has two Mach-Zehnder interferometer circuits that form a double barrier to suppress optical crosstalk in the cross state. This is a technology that can realize a switch and can improve the practicality of an optical communication system using a matrix optical switch.

  The configuration of the matrix optical switch shown in FIGS. 8 and 9 can be easily selected by arbitrarily selecting the number of input optical waveguides and the number of output optical waveguides. Depending on the path of the waveguide, the number of optical switch unit elements and crossing optical waveguides to pass through varies, so that variations in insertion loss due to the path become a problem.

  FIG. 11 shows the configuration of a new matrix optical switch devised to solve this problem (see Patent Document 2).

  The configuration is an N × N (N is a positive integer) matrix optical switch having the same number of input / output optical waveguides. Here, a configuration of a 4 × 4 switch is shown.

That is, four input optical waveguides 1a-1d to 4a-4d and four output optical waveguides 1c-1b to 4c-4b are provided, and there are 16 optical switch unit elements S11 to S44 corresponding to N ^2. 9 is a path-independent configuration in which the number of passing optical switch unit elements and crossing optical waveguides is the same in all paths, and the circuit layout of the waveguide type optical switch is also different from the configuration of FIG. Since N parallel optical switch unit elements are connected in N stages (N = 4 in the example in the figure), the configuration in FIG. 9 is 2N−1 stages (2 × 4−1 = 7). However, the circuit length is shortened and propagation loss can be reduced.

  The operation as a matrix optical switch is the same as described above, and a single path is established by driving only one optical switch unit element, which is a strictly non-blocking configuration.

In addition, a waveguide-type matrix optical switch (see Patent Document 3) employing the double gate type described above as an optical switch unit element has been put into practical use, and its usefulness has been demonstrated.
JP-A-6-51354 Japanese Patent Publication No. 6-66982 JP 9-297230 A JP-A-3-267902 JP 2002-162528 A S. Sohma el al. , Electron-Lett., Vol.38. No.3, pp.127-128.2002

  The double gate type optical switch unit element shown in FIG. 10 can realize a sufficient extinction ratio without being affected by variations in coupling ratios when the directional couplers 14a, 15a and 14b, 15b are manufactured.

  However, in actuality, in this configuration, the optical path length difference corresponding to a half wavelength set in advance in the arm optical waveguide of the Mach-Zehnder interferometer causes an error during fabrication, and sufficient extinction cannot be obtained when off (no power). There is a case.

  This is because the phase in the interferometer is shifted. For example, in a thermo-optic type optical switch, the error can be corrected by adjusting the power supplied to the heater to set the two states of cross and bar. Although it is possible, it is necessary to always drive the optical switch even when the optical signal path is not switched at all. This causes problems in system operation such as an increase in power cost and heat radiation design.

  As a countermeasure for this problem, there is a technique for inducing a constant refractive index change by generating a thermal history phenomenon by a local thermal stress applied to the arm optical waveguide (see, for example, Patent Document 4).

  According to this method, the characteristics of all the optical switch unit elements can be made uniform, the switching operation can be performed on and off, and a high extinction ratio can be obtained.

  However, in order to correct manufacturing errors that occur randomly with this technology, it is necessary to inspect all manufactured parts and correct all errors, which is a cause of increased manufacturing time and manufacturing cost. It was.

  The present invention has been made in view of the above-described prior art, and in the case where circuit characteristics fluctuate due to errors that occur during the production of a matrix optical switch, a matrix having a sufficient extinction ratio that does not depend on fabrication errors due to the combination of circuits. This is a technology that realizes optical switches.

  In order to achieve the above object, an optical switch unit element of the present invention includes one input optical waveguide and one output optical waveguide that intersect each other, and a bypass optical waveguide that connects the input optical waveguide and the output optical waveguide. A 1 × 2 optical switch is formed between the bypass optical waveguide and the input optical waveguide, the input optical waveguide being the input section, the input optical waveguide and the bypass optical waveguide being the output section, and the bypass optical waveguide and the output optical waveguide. The 2 × 1 optical switch having the output optical waveguide and the bypass optical waveguide as the input section and the output optical waveguide as the output section is formed between the 1 × 2 optical switch and the 2 × 1 optical switch. It is a 1 × 1 optical gate switch having a part of the waveguide as an input part and an output part.

  The optical switch unit element includes a 1 × 2 optical switch and a 2 × 1 optical switch, at least one of two directional couplers including two adjacent optical waveguides, two arm optical waveguides, and arm optical waveguides By a Mach-Zehnder interferometer type optical switch composed of a phase shifter equipped on one side, or a phase shifter equipped on at least one of two multimode optical couplers and two arm optical waveguides or arm optical waveguides Constructed Mach-Zehnder interferometer type optical switch, Y branch optical waveguide is arranged on the input side of 1 × 2 switch and the output side of 2 × 1 switch, the output side of 1 × 2 switch and the input of 2 × 1 switch A directional coupler comprising two adjacent optical waveguides on the side is arranged, and at least one of the two arm optical waveguides and the arm optical waveguides connecting them. Mach-Zehnder interferometer type optical switch composed of phase shifter equipped on either side, optical switch composed of Y branch type optical waveguide and phase shifter, and directional coupling consisting of two adjacent optical waveguides And an optical switch constituted by a phase shifter mounted on at least one of the optical waveguides.

  The optical switch unit element includes two directional couplers each having a 1 × 1 optical gate switch including two adjacent optical waveguides, regardless of the form of the 1 × 2 optical switch and the 2 × 1 optical switch described above. A Mach-Zehnder interferometer type optical switch comprising two arm optical waveguides or a phase shifter mounted on at least one of the arm optical waveguides, or two multimode optical couplers and two arm optical waveguides; Mach-Zehnder interferometer type optical switch composed of a phase shifter mounted on at least one of the arm optical waveguides, a directional coupling consisting of a Y-branch optical waveguide on the input side and two adjacent optical waveguides on the output side Is installed in at least one of the two arm rice waveguides and arm optical waveguides connecting the Y-branch type optical waveguide and the directional coupler. Mach-Zehnder interferometer type optical switch constituted by a phase shifter, optical switch constituted by a phase shifter equipped in at least one of two Y-branch type optical waveguides, two arm optical waveguides and arm optical waveguides It is characterized in that it is in any form of an optical switch constituted by a directional coupler composed of two adjacent optical waveguides and a phase shifter equipped in at least one of the optical waveguides.

  Further, the matrix optical switch of the present invention has M × N intersections in M (M is a positive integer) input optical waveguides and N (N is a positive integer) output optical waveguides that intersect each other. A waveguide type optical switch unit element is arranged, and the waveguide type optical switch unit element is connected to the input / output optical waveguide.

  Alternatively, the waveguide type optical switch unit elements are arranged in N (N is a positive integer) rows and N columns, and N input optical waveguides of the optical switch unit elements arranged in the first column are used as N input terminals, respectively. Any one of the output optical waveguides N of the optical switch unit elements arranged in the N-th column is set as N output terminals, and an arbitrary output can be obtained by selecting and controlling one appropriate waveguide type optical switch unit element. In all the paths from each input optical waveguide connected to the optical waveguide, the same number of waveguide type optical switch unit elements are always connected. One of the connection forms is the first row (2k− 1) The input optical waveguides and output optical waveguides of the optical switch unit elements arranged in columns (k is an integer, 2 ≦ 2k <N) are the same as the input optical waveguides of the optical switch unit elements arranged in the second row 2k columns. Arranged in 1 row and 2k columns The input optical waveguide and the output optical waveguide of the optical switch unit element respectively connected to the output optical waveguide of the optical switch unit element and arranged in the Nth row (2k−1) column are the (N−1) th when N is an even number. ) Connected to the input optical waveguide of the optical switch unit element arranged in the row 2k column and the output optical waveguide of the optical switch unit element arranged in the Nth row 2k column, respectively, and when N is an odd number, the Nth row 2k column An optical switch unit connected to the input optical waveguide of the arranged optical switch unit element and the output optical waveguide of the optical switch unit element arranged in the (N-1) th row and 2k column, respectively, and arranged in the first row and 2k column The input optical waveguide and the output optical waveguide of the element are the input optical waveguide of the optical switch unit element arranged in the first row (2k + 1) column and the output optical waveguide of the optical switch unit element arranged in the second row (2k + 1) column. Connect each The input optical waveguide and the output optical waveguide of the optical switch unit element arranged in the Nth row and 2k column are the same as the input optical waveguide of the optical switch unit device arranged in the Nth row (2k + 1) column when N is an even number. (N-1) Optical switch unit element connected to output optical waveguide of optical switch unit element arranged in row (2k + 1) column, and arranged in (N-1) th row (2k + 1) column when N is an odd number And the output optical waveguide of the optical switch unit element arranged in the Nth row (2k + 1) column.

  As another form realized by switching the above input / output relationship, the input light of the optical switch unit element arranged in the first row (2k−1) column (k is an integer, 2 ≦ 2k <N). The waveguide and the output optical waveguide are respectively connected to the input optical waveguide of the optical switch unit element arranged in the first row 2k column and the output optical waveguide of the optical switch unit element arranged in the second row 2k column, and the Nth row ( The input optical waveguide and the output optical waveguide of the optical switch unit element arranged in the (2k-1) column are the same as the (N −)-th input optical waveguide of the optical switch unit element arranged in the Nth row and 2k column when N is an even number. 1) Connect to the output optical waveguide of the optical switch unit element arranged in the row 2k column, respectively, and when N is an odd number, the input optical waveguide and the optical waveguide of the optical switch unit element arranged in the (N-1) th row 2k column Optical array arranged in N rows and 2k columns The optical switch unit element is connected to the output optical waveguide of the switch unit element, and the optical switch unit element arranged in the first row 2k column is arranged in the second row (2k + 1) column. Are connected to the output optical waveguide of the optical switch unit element arranged in the first row (2k + 1) column, respectively, and the input optical waveguide and the output optical waveguide of the optical switch unit element arranged in the Nth row 2k column Are the input optical waveguides of the optical switch unit elements arranged in the (N−1) th row (2k + 1) column and the output optical waveguides of the optical switch unit elements arranged in the Nth row (2k + 1) column when N is an even number. When N is an odd number, the input optical waveguide of the optical switch unit element arranged in the Nth row (2k + 1) column and the output of the optical switch unit element arranged in the (N−1) th row (2k + 1) column Contact to optical waveguide Characterized in that it is.

  For example, as shown in FIG. 1, the quartz glass optical waveguide that is most used at present is manufactured, and the 1 × 2 optical switch, 2 × 1 optical switch, and 1 × 1 optical gate switch in the above-described configuration are used. Both are Mach-Mach, which consists of two directional couplers composed of two optical waveguides close to each other and two arm optical waveguides whose optical path length difference is set to one half of the signal light wavelength. According to the waveguide type optical switch unit element constituted by the Zender interferometer circuit and the thermo-optic phase shifter, the optical path length difference set in advance in the first Mach-Zehnder interferometer circuit constituting the 1 × 2 optical switch When off, the signal light propagating through the input optical waveguide passes through the input optical waveguide as it is regardless of the coupling rate of the directional coupler, and the optical switch unit element is in a cross state.

  Even if a slight light leakage (crosstalk) is generated in the bypass optical waveguide from the first Mach-Zehnder interferometer circuit at the time of OFF, the second Mach-Zehnder interferometer circuit constituting the 2 × 1 optical switch As in the first Mach-Zehnder interferometer circuit, since the signal light passes through the bypass optical waveguide as it is, the ratio of the signal light leaking to the output optical waveguide is very small, and crosstalk to the unconnected output optical waveguide can be suppressed. it can.

  However, in actual optical switch fabrication, in addition to the coupling rate error of the directional coupler, an error may also occur in the optical path length difference set in the Mach-Zehnder interferometer circuit.

  In this case, the optical signal leaks from the input optical waveguide to the bypass optical waveguide when it is off, and further propagates to the output optical waveguide to cause crosstalk.

  Therefore, as described above, in the bypass optical waveguide, one of the third Mach-Zehnder interferometer circuits constituting the 1 × 1 optical gate switch is connected to the bypass optical waveguide on the 1 × 2 optical switch (input) side. By connecting the other optical waveguide to the bypass optical waveguide on the 2 × 1 optical switch (output) side, the gate is cut off, so that the extinction ratio deteriorated due to the manufacturing error is complemented, and the optical switch unit element Overall, a high extinction ratio, that is, low crosstalk is realized.

  When the thermo-optic phase shifter is turned on, an optical signal input to one optical waveguide of each of the first, second, and third Mach-Zehnder interferometer circuits is guided to the other optical waveguide and bypassed from the input optical waveguide. The light propagates from the bypass optical waveguide to the output optical waveguide through the optical waveguide and the 1 × 1 optical gate switch in the open state, and the optical switch unit element enters the bar state, and the input optical waveguide and the output optical waveguide are connected.

  In the configuration as described above, the coupling rate of the directional coupler and the optical path length difference of the Mach-Zehnder interferometer circuit deviate from the set values due to manufacturing errors, and the extinction ratio per Mach-Zehnder interferometer circuit is Even in the case of deterioration, it is not necessary to add a manufacturing process or add an optical switch driving circuit, and it is possible to suppress the increase in crosstalk only by the optical circuit design and realize optical characteristics equivalent to those of the conventional art.

  That is, the present invention is mainly intended to reduce crosstalk caused by manufacturing errors when the optical switch unit element is in a cross state by devising a circuit configuration, and thus constitutes the above-described Mach-Zehnder interferometer circuit. When the optical coupler is a multimode optical coupler, one of the optical couplers is a Y-branch optical waveguide and the other is a directional coupler, or a 1 × 2 optical switch constituting an optical switch unit element or The present invention can also be applied when the 2 × 1 optical switch is a Y-branch type optical switch or a directional coupler type optical switch, and is used as a 1 × 2 switch or a 2 × 1 switch as a 1 × 1 optical gate switch. In addition to the above-mentioned Mach-Zehnder interferometer circuit, light composed of two Y-branch optical waveguides and two arm optical waveguides The present invention can also be applied to an optical switch using one port of a switch or a directional coupler type optical switch.

  In addition, using these optical switch unit elements, a waveguide matrix composed of M (M is a positive integer) input optical waveguides and N (N is a positive integer) output optical waveguides crossing each other. Low crosstalk of the optical switch can be realized.

  Further, these optical switch unit elements are arranged in N rows and N columns for N (N is a positive integer) input optical waveguides and N (N is a positive integer) output optical waveguides. By selecting and controlling the waveguide type optical switch unit element, all the paths from each input optical waveguide connected to any output optical waveguide are connected so as to always pass the same number of waveguide type optical switch unit elements. The crosstalk of the waveguide type matrix optical switch can be reduced.

  An optical switch unit element constituting a matrix optical switch according to the present invention includes an input optical waveguide, an output optical waveguide, and a bypass optical waveguide that intersect each other, and a 1 × 2 optical switch is configured by the input optical waveguide and the bypass optical waveguide, An output optical waveguide and a bypass optical waveguide constitute a 2 × 1 optical switch, and a 1 × 1 optical gate switch is provided in the bypass optical waveguide between the 1 × 2 optical switch and the 2 × 1 optical switch. Optical signal leakage (crosstalk) generated in the output optical waveguide due to manufacturing errors can be suppressed to an extremely low level.

  That is, it is possible to easily provide a matrix optical switch having an excellent extinction ratio while greatly reducing the manufacturing accuracy without requiring correction processing after the manufacturing or an additional drive circuit.

  Various circuit forms such as a Mach-Zehnder interferometer circuit, a Y-branch optical waveguide, and a directional coupler can be used in combination depending on the material forming the optical switch and the optical waveguide characteristics.

  The optical switch unit element of the present invention and the matrix optical switch using the optical switch unit element are very effective means for providing a low-cost and highly practical optical switch device, and require exchange and switching of various optical signals. It is expected to contribute greatly to the development of large-capacity optical communication networks.

  The best mode for carrying out the present invention is Examples 1 to 8 shown below.

  In the following examples, a waveguide-type optical switch using a Mach-Zehnder interferometer circuit type optical switch using a thermo-optic effect as a constituent element of an optical switch, using a silica-based single mode optical waveguide formed on a silicon substrate. The optical switch unit element and the waveguide matrix optical switch will be described.

  This is because this combination is stable and easy to integrate, and it is possible to provide a low-loss optical switch that is excellent in matching with a silica-based optical fiber.

  However, the present invention is not limited to these combinations.

  A schematic configuration of a 4 × 4 matrix optical switch as a first embodiment of the N × N matrix optical switch according to the present invention is shown in FIGS.

  FIG. 11 is a logical configuration of a matrix optical switch, and FIG. 1 is a configuration diagram of an optical switch unit element as a component thereof.

  1A is a circuit configuration plan view of an optical switch unit element according to the present invention, and FIG. 1B is a cross-sectional view taken along line B-B ′ shown in FIG.

  As described above, the matrix optical switch shown in FIG. 11 adopts a path-independent configuration in which the number of passing optical switch unit elements does not depend on the path, and 4 × 4 = 16 optical switch unit elements are 4 in number. The configuration is arranged in four rows and columns.

  As shown in FIG. 1, the optical switch unit element according to the present embodiment is formed on a silicon substrate 1 and has an input optical waveguide 11a-11b and an output optical waveguide 12a-12b that are embedded in a silica-based glass clad 2. Are basically the bypass optical waveguides 13a-13b disposed in the vicinity thereof.

  A part of the bypass optical waveguides 13a-13b is formed close to the input optical waveguide 11a-11b at a distance of several μm at two locations to form two directional couplers 14a and 15a, and a Mach is formed between the two optical waveguides. A zender interferometer circuit (1 × 2 optical switch) 18a is formed.

  The coupling ratio of the directional couplers 14a and 15a is designed to be 50% by adjusting the interval and the length of the optical waveguide in the coupling portion.

  The optical waveguide serving as the arm portion of the Mach-Zehnder interferometer circuit 18a has an effective optical path length on the bypass optical waveguide 13a-13b side with respect to the input optical waveguide 11a-11b side (1.55 μm in the first embodiment). ), I.e. 0.775 μm.

  Further, as shown in FIG. 1B, a thin film heater 16a as an optical phase shifter using a thermo-optic effect is formed on the surface of the arm optical waveguide with the clad layer 2 on the side of the input optical waveguide 11a-11b having a short effective optical path length. Is loaded.

  Similarly, another part of the bypass optical waveguides 13a-13b is adjacent to the output optical waveguides 12a-12b at two locations to form two directional couplers 14b and 15b, and a Mach between the two optical waveguides is formed. A zender interferometer circuit (2 × 1 optical switch) 18b is formed.

  The coupling ratio of the directional couplers 14b and 15b is designed to be 50%. The arm optical waveguide of the Mach-Zehnder interferometer circuit has an effective optical path length on the bypass optical waveguide 13a-13b side of the output optical waveguide 12a-12b. It is designed to be longer than one half of the signal light wavelength (1.55 μm in the first embodiment), that is, 0.775 μm.

  A thin film heater 16b as an optical phase shifter utilizing a thermo-optic effect is loaded on the surface of the arm optical waveguide in the cladding layer 2 on the output optical waveguide 12a-12b side having a short effective optical path length.

  Further, another part of the bypass optical waveguides 13a to 13b between the two Mach-Zehnder interferometer circuits 18a and 18b includes two directional couplings in which the two interference optical waveguides 17a and 17b are close to each other. 14c and 15c are formed and connected to a Mach-Zehnder interferometer circuit (1 × 1 optical gate switch) 18c formed between two optical waveguides.

  The coupling ratio of the directional couplers 14c and 15c is designed to be 50%. The arm optical waveguide of the Mach-Zehnder interferometer circuit 18c is configured such that one optical waveguide 17b is connected to the other optical waveguide 17a side. It is designed to be a half of the light wavelength (1.55 μm in the first embodiment), that is, 0.775 μm.

  A thin film heater 16c as an optical phase shifter utilizing a thermo-optic effect is loaded on the surface of the arm optical waveguide in the clad layer 2 on the optical waveguide 17a side having a short effective optical path length.

  The input optical waveguides 11a-11b and the output optical waveguides 12a-12b intersect each other, and intersect each other at an intersecting portion 19 at an angle θ at which crosstalk and radiation loss can be ignored.

  The signal light input from the end point 11a of the optical waveguide when the thin film heaters 16a, 16b, and 16c are off (no energization) propagates through the optical waveguide 11a-11b in the Mach-Zehnder interferometer circuit 18a and passes through the optical waveguide 12a- The signal is output to the optical waveguide end 11b beyond the intersection 19 with 12b.

  Further, the signal light input from the end point 12a of the optical waveguide passes through the optical waveguide 12a-12b in the Mach-Zehnder interferometer circuit 18b through the intersection 19 with the optical waveguide 11a-11b and passes through the optical waveguide end. To 12b.

  That is, in the matrix optical switch, the operation when the optical switch unit element is off is connected to the cross path.

  At this time, even when the coupling ratios of the directional couplers 14a, 15a, 14b, and 15b in the input side 1 × 2 switch 18a and the output side 2 × 1 switch 18b deviate from 50% of the design values, Since the effective optical path length difference between the two arm optical waveguides of the Zender interferometer circuit is set to one half of the signal light wavelength, it does not pass through the propagating optical waveguide and shift to the other optical waveguide. Therefore, a high extinction ratio can be realized in principle.

  Also, optical power that does not contribute to interference is generated due to the effects of higher-order modes due to defects and errors during operation of the optical waveguide, and the 1 × 2 switch 18a slightly changes from the input optical waveguide 11a-11b to the bypass optical waveguide 13a-13b. Even if light leakage (crosstalk) occurs, the 2 × 1 switch 18b in the subsequent stage can obtain the same extinction characteristic, so that crosstalk to the output optical waveguides 12a-12b can be suppressed.

  Further, even when the crosstalk occurs due to the difference in the effective optical path length set in the arm optical waveguide of the Mach-Zehnder interferometer circuit due to a design or manufacturing error, the 1 × 2 switch 18a and 2 × Crosstalk generated in the 1 × 2 switch 18a is cut off by the 1 × 1 gate switch 18c connected to the bypass optical waveguides 13a-13b between the 1 switches 18b.

  Even if slight crosstalk passes through the gate due to the influence of the higher-order mode as described above, propagation to the output optical waveguides 12a-12b can be prevented by the 2 × 1 switch 18b. A high extinction ratio can be realized.

  Here, it should be emphasized as a feature of the present invention that even if the operating point of the optical switch fluctuates due to a design or manufacturing error and the crosstalk characteristics deteriorate or become nonuniform, a new correction after the manufacturing is performed. It is possible to alleviate the characteristic deterioration only by design ingenuity without requiring an additional drive circuit for processing and offset operation.

  Therefore, the configuration of the optical switch is not limited to the Mach-Zehnder interferometer circuit as described above, and is configured by an optical switch unit element including a Y-branch optical waveguide, a multimode coupler, or a directional coupler as a constituent element, and the optical switch unit element. The same effect can be obtained in the waveguide matrix optical switch.

  When the thin film heaters 16a, 16b and 16c are turned on (energized) in conjunction with each other and appropriate power is applied, the arm optical waveguides in the three Mach-Zehnder interferometer circuits 18a, 18b and 18c are effective. The optical path length difference becomes zero due to the thermo-optic effect, and an optical signal input to one optical waveguide is guided to the other optical waveguide and propagates.

  That is, the optical signal input from the optical waveguide end 11a in the 1 × 2 optical switch 18a is guided to the bypass optical waveguide 13a-13b, and output from the optical waveguide 17b connected to the input side in the 1 × 1 optical gate switch 18c. The 2 × 1 optical switch 18b guides the bypass optical waveguide 13a-13b to the output optical waveguide 12a-12b and finally outputs it to the optical waveguide end 12b.

  As a result, the optical switch unit elements are connected to the bar path, and the input optical waveguide and the output optical waveguide are connected in the matrix optical switch.

  In the ON state, when the coupling ratio of the directional couplers 14a, 15a, 14b, 15b, 14c, and 15c is deviated from 50%, the signal light input from the optical waveguide end 11a is 100% in the 1 × 2 optical switch 18a. The signal light component that is not guided to the bypass optical waveguides 13a to 13b and leaks to the optical waveguides 11a to 11b propagates to the optical waveguide end 11b through the intersection 19.

  However, since this leaked component is eventually output to the optical waveguide ends 1d, 2d, 3d and 4d which are not used in FIG. 4, although there is a slight loss increase in the optical switch unit element, it is quenched as a matrix optical switch. There is no degradation of the ratio.

  Further, when the difference in effective optical path length of one-half of the signal light wavelength set in the arm optical waveguides of the three Mach-Zehnder interferometer circuits 18a, 18b and 18c deviates from the design, the respective interferometers If the operating point at is set appropriately, there is no problem.

  Alternatively, in the system design, when it becomes necessary to control the matrix optical switch with a single power supply or several power supplies, each optical switch unit element cannot be driven at an optimum operating point. The loss increase is negligible.

As shown in FIGS. 1A and 1B, the 4 × 4 matrix optical switch in Example 1 is a clad formed of quartz glass on a silicon substrate 1 having a thickness of 1 mm and a diameter of 4 inches. the single mode optical waveguide layer 2 and the buried type, produced by a combination of reactive ion etching techniques and deposition techniques SiCl ₄ or GeC1 ₄ silica glass film using a flame hydrolysis reaction of raw material gas, such as a thin film Heaters 16a, 16b and 16c and electrodes for power supply (not shown) were produced on the surface of the clad layer 2 by vacuum deposition and patterning.
The core size of the manufactured optical waveguide was 4.5 μm × 4.5 μm, and the relative refractive index difference Δ with the cladding layer 2 was 1.5%.

  The 4 × 4 matrix optical switch in the first embodiment is formed by using this optical waveguide and combining a linear optical waveguide and a curved optical waveguide having a bending radius of 2 mm.

  The angle θ of the crossed optical waveguide at the optical switch unit element and the portion connecting them is set to 40 degrees.

  The Mach-Zehnder interferometer circuits 18a, 18b and 18c in the optical switch unit element were set so that the effective optical path length difference of the arm optical waveguide was 0.775 μm, which is a half of the signal light wavelength 1.55 μm.

  Considering that the refractive index of quartz glass is 1.45, the actual difference in arm optical waveguide length is 0.775 μm / 1.45 = 0.534 μm.

  The thin film heaters 16a, 16b, and 16c formed on the surface of the clad layer 2 as phase shifters by the thermo-optic effect have a thickness of 0.1 μm, a width of 30 μm, and a length of 1 mm.

  The total length of the optical switch unit element of Example 1 constituted by the three Mach-Zehnder interferometer circuits 18a, 18b and 18c and the crossed optical waveguide was 11 mm.

  The chip size of the 4 × 4 matrix optical switch formed by combining the optical switch unit elements is 10 mm × 80 mm.

  After this 4 × 4 matrix optical switch chip was cut out by a dicing saw, a heat radiating plate was attached to the lower part of the silicon substrate 1, and a single mode optical fiber array was connected to the input / output optical waveguide end.

  The power switch terminal of the optical switch chip was electrically connected to an external electric wiring board provided with an electrical connector, and the module was completed.

  By connecting a power source to the electrical connector and appropriately selecting the thin film heaters 16a, 16b, and 16c to be fed, the operation of the optical switch for arbitrarily switching and connecting between the ports of 4 inputs and 4 outputs was confirmed.

  Since the power supplied to the three thin film heaters 16a, 16b, and 16c loaded on the optical switch unit element that is turned on to connect an arbitrary input / output port was 0.4 W, each light The power consumption of the switch unit elements is 1.2 W, and the total power consumption is about 4.8 W because the entire 4 × 4 matrix optical switch has four optical switch unit elements that are driven simultaneously.

  The insertion loss including the optical fiber connection loss from the input optical waveguide end to the output optical waveguide end of the matrix optical switch was about 2 dB, and the extinction ratio of the entire matrix optical switch was 60 dB or more.

  In particular, the extinction ratio is greatly different even when the coupling ratio of the directional coupler is greatly deviated to about 50% ± 10% due to a manufacturing error, and the set effective optical path length difference is deviated by 10 to 20% with respect to the set 0.775 μm. It showed excellent extinction characteristics and showed that the matrix optical switch according to the present invention is very resistant to manufacturing errors.

  For comparison, a crossbar type 4 × 4 matrix optical switch constituted by four input / output optical waveguides crossing each other as shown in FIG. 2 was also manufactured.

  The specifications of the optical waveguide used are the same as those of the above path-independent 4 × 4 matrix optical switch.

  The 4 × 4 matrix optical switch according to this example has a configuration in which seven stages of optical switch groups are integrated, and the chip size including electrodes for power supply is 10 mm × 130 mm.

  When a heat sink and an optical fiber array were attached to form a module and the optical characteristics were measured, the insertion loss of the matrix optical switch was 1 to 3 dB and the extinction ratio was 60 dB or more.

  The power consumption of the entire matrix optical switch was 4.8W.

  As described above, by adopting the optical switch unit element in the present invention, excellent extinction characteristics that are strong against manufacturing errors are shown regardless of the configuration of the matrix optical switch.

  FIG. 2 shows a configuration of a 4 × 8 matrix optical switch as an embodiment of an M × N (M and N are different positive integers) matrix optical switch according to the present invention.

  In the figure, 1a-1d, 2a-2d to 4a-4d are input optical waveguides, 1c-1b, 2c-2b to 8c-8b are output optical waveguides, and 4 × 8 = 32 intersections are optical switch units. Elements S11 to S48 are arranged.

  The specifications of the optical waveguide used in this example, the method of manufacturing the chip, and the module are the same as those of the 4 × 4 matrix optical switch in Example 1.

  In contrast to the first embodiment, the matrix optical switch of the present embodiment is characterized in that the number of input / output optical waveguides is different. The matrix configuration was a crossbar type.

  This configuration is suitable for realizing an M × N matrix optical switch in that an arbitrary number of input / output optical waveguides can be selected, and each group of 1 to 4 optical switch unit elements is connected in 11 stages.

  FIG. 3 shows an outline of a circuit layout diagram on the substrate of the 4 × 8 matrix optical switch of this embodiment.

  As shown in FIG. 3, all 11-stage optical switch unit element groups from the input optical waveguide bundle 70a to the output optical waveguide bundle 70b are appropriately connected to the curved optical waveguide and the linear optical waveguide bent at 90 degrees, The arrangement is characterized in that it is designed so that the overall length of the circuit is as short as possible and the overall size is reduced.

  Here, the specification of the optical waveguide used in this example is that the relative refractive index difference Δ between the clad and the core is 1.5%, and the single mode optical fiber connected to the optical waveguide is a spot of the optical signal propagating through the core. Since there is a difference in size, there is a problem that coupling loss occurs.

  Therefore, in this embodiment, a spot size conversion optical waveguide having a tapered structure (not shown, see Patent Document 5) is adopted near the end face of the input / output optical waveguide, thereby reducing the coupling loss with the single mode optical fiber, The insertion loss of the entire matrix optical switch chip is kept low.

  The 4 × 8 matrix optical switch of this example was fabricated on a 1 mm thick silicon substrate, and the chip size including the power supply terminal and the electrical wiring was 65 mm × 70 mm.

  The circuit configuration, design specifications, and module manufacturing method of the optical switch unit elements S11 to S48 are the same as in the first embodiment.

  By connecting a power source to the electrical connector and appropriately selecting the heater to be fed, the operation of the optical switch for arbitrarily switching and connecting between the ports of 4 inputs and 8 outputs was confirmed.

  Since the power supplied to the three thin film heaters 16a, 16b, and 16c loaded on the optical switch unit element that is turned on to connect an arbitrary input / output port was 0.4 W, each light The power consumption of the switch unit elements is 1.2 W, and the total power consumption is about 4.8 W because the entire 4 × 8 matrix optical switch has four optical switch unit elements that are driven simultaneously.

  The insertion loss including the optical fiber connection loss from the input optical waveguide end to the output optical waveguide end of the matrix optical switch was 4 dB or less, and a very low loss value was obtained.

  Further, the extinction ratio of the entire matrix optical switch showed an excellent value of 60 dB or more even when a post-manufacturing difference in directional coupler and effective optical path length occurred.

  The configuration of an 8 × 8 matrix optical switch according to the present invention is shown in FIG.

  In this embodiment, a path-independent configuration is adopted, and the circuit layout on the optical switch chip is arranged so that the optical switch unit element group is folded by appropriately connecting the curved optical waveguide and the linear optical waveguide as in the second embodiment. However, the circuit length and the overall size are designed to be small.

  FIG. 5 shows the circuit configuration and structure of the optical switch unit element employed in this example.

  5A is a plan view of the optical switch unit element, FIG. 5B is a cross-sectional view taken along the line CC ′ shown in FIG. 5A, and FIG. 5C is a line segment. It is sectional drawing cut along DD '.

  As shown in FIG. 5, in this embodiment, heat insulation grooves 20a, 20b and 20c are formed at three locations along the arm optical waveguide portions of the Mach-Zehnder interferometer circuits 18a, 18b and 18c, respectively. The configuration is the same as the circuit configuration of the optical switch unit element shown in FIG.

  The heat insulating groove structure employed in this embodiment suppresses the heat generated from the thin film heaters 16a, 16b and 16c from diffusing in the horizontal direction of the substrate by the heat insulating grooves 20a, 20b and 20c, and efficiently increases the temperature of the core. Therefore, the refractive index can be changed, which is a very effective technique for reducing the power consumption of the thermo-optic optical switch (see Non-Patent Document 1).

  In this example, by adjusting the distance between the heat insulating grooves and the thickness of the cladding layer 2, the power required for switching the optical path was 0.1 W, which is 25% of the conventional value for each thin film heater.

  Further, by forming the heat insulating grooves 20a, 20b, and 20c, the propagation of heat to the adjacent optical waveguide can be cut off, so that the interval between the waveguides can be reduced, and the optical circuit can be miniaturized.

  Specifically, it has become possible to reduce the distance to less than half the conventional waveguide interval.

  The 8 × 8 matrix optical switch produced in this example was produced with the same specifications as the optical waveguides in Examples 1 and 2, and the spot size conversion optical waveguide used in Example 2 was also adopted.

  The heat insulating grooves 20a, 20b and 20c were formed by a reactive ion etching technique.

  The size of the switch chip fabricated on a silicon substrate with a thickness of 1 mm is 50 mm x 50 mm, and the area ratio of an 8 x 8 matrix optical switch that has been conventionally fabricated with an optical waveguide of 0.75% Δ can be reduced to about half. It was realized.

  A module is manufactured through the same steps as in the first and second embodiments, and a power source is connected to the electrical connector to appropriately select a heater to be fed, thereby arbitrarily switching and connecting between 8 input and 8 output ports. The optical switch operation was confirmed.

  The power consumption of each optical switch unit element is 0.3 W, and since the entire 8 × 8 matrix optical switch simultaneously drives eight optical switch unit elements, the total power consumption is as low as about 2.4 W. It was power consumption.

  The insertion loss including the optical fiber connection loss from the input optical waveguide end to the output optical waveguide end of the matrix optical switch was about 5 dB.

  Further, the extinction ratio of the entire matrix optical switch showed an excellent value of 60 dB or more even when a post-manufacturing difference in directional coupler and effective optical path length occurred.

  As described above, in the first to third embodiments of the present invention, the 1 × 1 optical gate switch 18c constituting the optical switch unit element has a diagonal angle of the Mach-Zehnder interferometer circuit in order to prioritize the extinction ratio as shown in FIG. In the part connected to the optical waveguides 17b to 17a, the circuit fabrication error is small, and when design circuit symmetry is important, both the input side and the output side of the 1 × 1 optical gate switch 18c are used. It is possible to obtain the same effect by connecting to the optical waveguide 17a.

  However, when the coupling rate error of the directional coupler is large, a sufficient extinction ratio may not be obtained, so it is necessary to appropriately determine a design guideline according to the application and situation.

  Further, in Examples 1 to 3, the case where the signal light wavelength is 1.55 μm was dealt with. However, according to the configuration method of the present invention, it is obvious that the present invention can also be applied to the case where the signal light wavelength is 1.3 μm. Therefore, an appropriate design can be performed depending on the wavelength band to be used.

  In the first to third embodiments, an optical switch unit element based on a Mach-Zehnder interferometer circuit including two directional couplers is used, but the elements forming the Mach-Zehnder interferometer are, for example, A multi-mode optical coupler or a Y-branch optical waveguide may be used.

  That is, as means for obtaining the intended effect, the circuit configuration indicates that various combinations are possible, and these are shown below by examples.

  In the optical switch unit element of the 8 × 8 matrix optical switch shown in FIG. 4, the input side of the 1 × 1 optical gate switch is connected to the optical waveguide 17a in FIG. 1, and the output side is similarly connected to the optical waveguide 17a. This is an embodiment relating to an 8 × 8 matrix optical switch module having a new circuit configuration.

  That is, as shown in FIG. 12, the fourth embodiment is a modification of the first embodiment. Normally, the Mach-Zehnder interferometer circuit is connected to the cross (conducted by connecting the input and output) in order to increase the extinction ratio. In this example, only the middle 1 × 1 optical gate switch 18c is connected to the through (where the waveguide is connected to the input and the output is the same).

  However, when the thin film heater 16c is off (no power supply), the difference between the effective optical path lengths of the arm optical waveguides 17a and 17b becomes 0, and when the thin film heater 16c is on (energization), the effective optical path lengths of the arm optical waveguides 17a and 17b. The difference is set to 0.775 μm, which is a half of the signal light wavelength of 1.55 μm.

  In the case of the first embodiment shown in FIG. 1, the 1 × 1 optical gate switch 18c is used when the symmetry of the circuit design is to be kept as much as possible compared to the directional coupler 14c having an asymmetric design. Example 4 is effective.

  Other circuit configurations, layouts, and manufacturing methods are the same as those in the third embodiment.

  The 8 × 8 matrix optical switch module manufactured in the present embodiment arbitrarily switches and connects between 8 input and 8 output ports by connecting a power source to an electrical connector and appropriately selecting a heater to be fed. The optical switch operation was confirmed.

  The power consumption and insertion loss were the same as in Example 3, and the extinction ratio of the entire matrix optical switch was 55 dB or more.

  Although the extinction ratio is slightly inferior to that of the third embodiment, the circuit has good symmetry in terms of design, so that the manufacturing error is small. In particular, the uniformity of insertion loss is the difference between the maximum and the minimum loss in the third embodiment. There were some exceeding 1 dB, but it was improved to about 0.5 dB.

  Optical coupling of the Mach-Zehnder interferometer circuit constituting the 1 × 2 optical switch, 2 × 1 optical switch, and 1 × 1 optical gate switch for the optical switch unit element of the 8 × 8 matrix optical switch shown in FIG. It is the Example regarding the 8 * 8 matrix optical switch module of the new circuit structure which consists of the form which used the multi-mode optical coupler as the unit part.

Other circuit configurations, layouts, and manufacturing methods are the same as those in the third embodiment.
The 8 × 8 matrix optical switch module manufactured in the present embodiment arbitrarily switches and connects between 8 input and 8 output ports by connecting a power source to an electrical connector and appropriately selecting a heater to be fed. The optical switch operation was confirmed.

  The power consumption was the same as in Example 3, and the insertion loss was slightly high, about 7 dB.

  The extinction ratio of the entire matrix optical switch was excellent at 60 dB or more.

  Although the insertion loss was somewhat high, the coupling ratio uniformity of the optical coupler was good, and the circuit was slightly reduced. This was an effective means for reducing the size of the device and increasing the uniformity of the insertion loss.

  4 is an input side optical coupler of a Mach-Zehnder interferometer circuit constituting a 1 × 2 optical switch, and a Mach-Zehnder constituting a 2 × 1 optical switch. The output side optical coupler of the interferometer circuit The input side optical coupler of the Mach-Zehnder interferometer circuit constituting the 1 × 1 optical gate switch is a Y-branch type optical waveguide, and the other is a directional coupler. This is an embodiment relating to an 8 × 8 matrix optical switch module having a new circuit configuration.

  Other circuit configurations, layouts, and manufacturing methods are the same as those in the third embodiment.

  The 8 × 8 matrix optical switch module manufactured in the present embodiment arbitrarily switches and connects between 8 input and 8 output ports by connecting a power source to an electrical connector and appropriately selecting a heater to be fed. The optical switch operation was confirmed.

  The power consumption was the same as in Example 3, and the insertion loss was about 6 dB.

  The extinction ratio of the entire matrix optical switch was excellent at 60 dB or more.

  By making one of the optical couplers constituting the Mach-Zehnder interferometer circuit a Y-branch type optical waveguide, the manufacturing error of the coupling rate is improved, and the uniformity of the insertion loss is the same as that of the third embodiment. Improved.

  As described above, in Examples 1 to 6, the circuit configuration in the optical coupler portion of the three Mach-Zehnder interferometer circuits constituting the optical switch unit element is the same, but the required optical specifications. The same effect can be obtained even if the optical switch unit element is configured by arbitrarily combining any of the Mach-Zehnder interferometer circuits described in the first to sixth embodiments according to the scale of the optical switch circuit, the circuit layout, and the like. Is obtained.

  In Examples 1 to 6, matrix optical switches based on quartz glass on a silicon substrate have been described. However, other materials that can constitute an optical switch using a Mach-Zehnder interferometer circuit, such as polymer optical waveguides and ions The present invention can also be applied to a diffusion optical waveguide, a lithium niobate-based optical waveguide provided with a phase shifter using an electro-optic effect, and the like.

  In the first to sixth embodiments, the optical switch unit element including the Mach-Zehnder interferometer circuit and the matrix optical switch configured by the optical switch unit element have been described. It will be described again that the same effect can be obtained even with a waveguide, a multimode coupler or a directional coupler.

  FIG. 6 shows an outline of an optical switch unit element using a polymer optical waveguide 32 produced on a silicon substrate 1 as an example and having a Y-branch optical waveguide 30 and a thermo-optic phase shifter 31 as elements.

  6A is a circuit plan view, FIG. 6B is a cross-sectional view taken along line E-E ′ in FIG. 6A, and FIG. 6C is a cross-sectional view taken along line F-F ′.

  That is, the polymer optical waveguide 32 fabricated on the silicon substrate 1 constitutes an input optical waveguide and an output optical waveguide that intersect with each other, and a bypass optical waveguide disposed in the vicinity thereof.

  The bypass optical waveguide and the input optical waveguide form a Y-branch optical waveguide 30 and a 1 × 2 optical switch is configured by a thermo-optic phase shifter 31 mounted thereon, and the bypass optical waveguide and the output optical waveguide are Y-branched The 2 × 1 optical switch is formed by the optical optical phase shifter 31 formed on the optical waveguide 30 and further provided on one of the two Y-branch optical waveguides 30 and the two arm waveguides therebetween. The thermo-optic phase shifter 31 thus configured constitutes a 1 × 1 optical gate switch.

  That is, as in Example 1, a 4 × 4 matrix optical switch was fabricated by combining optical switch unit elements in a path-independent configuration, and optical characteristics were examined, and an extinction ratio of 60 dB or more was obtained.

  In addition, a lithium niobate-based optical waveguide can produce a waveguide type optical switch based on an electro-optic effect.

  In this case, a directional coupler is used as a circuit element, and path switching is performed by applying an electric field between two adjacent waveguides.

  FIG. 7 shows an outline of an optical switch unit element using a lithium niobate-based optical waveguide according to Example 8 of the present invention.

  7A is a circuit plan view, FIG. 7B is a cross-sectional view taken along line G-G ′ in FIG. 7A, and FIG. 7C is a cross-sectional view taken along line H-H ′.

  As shown in FIG. 7, the optical switch unit element according to this example includes an input waveguide and an output waveguide that intersect with each other by a lithium niobate-based optical waveguide core 44 manufactured on a lithium niobate-based substrate 40. And a bypass waveguide in the vicinity thereof and covered with an insulating film 45.

  The bypass optical waveguide and the input optical waveguide form a directional coupler 41, and a 1 × 2 optical switch is configured by the electric field applying electrodes 43a and 43b provided on the two adjacent waveguides. And the output optical waveguide form a directional coupler 41 and electric field applying electrodes 43a and 43b mounted on the two adjacent waveguides constitute a 2 × 1 optical switch. The 1 × 1 optical gate switch is configured by the electric field applying electrodes 43a and 43b mounted on the two waveguides and the two adjacent waveguides.

  That is, as in Example 1, a 4 × 4 matrix optical switch was fabricated by combining optical switch unit elements in a path-independent configuration, and optical characteristics were examined, and an extinction ratio of 60 dB or more was obtained.

  Of course, the optical switch unit element can be configured by arbitrarily combining these circuit elements, and the same effect can be obtained by using any combination.

  As described above, the waveguide type optical switch unit element of the present invention is characterized in that a 1 × 1 gate switch 18c is added to a conventional 2 × 2 switch as shown in FIG. The waveguide-type matrix optical switch according to the invention is characterized in that the matrix optical switch is configured with the waveguide-type optical switch unit element as a constituent unit.

  The present invention can be widely used as an optical switch used in an optical communication system such as an optical router.

It is the top view and sectional drawing which show the structure of the optical switch unit element provided with the 1x2 optical switch in Example 1 of this invention, a 2x1 optical switch, and a 1x1 optical switch. It is a whole top view which shows the structure of the 4x8 matrix optical switch in Example 2 of this invention. It is a top view which shows the outline of the circuit arrangement | positioning of the 4x8 matrix optical switch chip in Example 2 of this invention. It is a whole top view which shows the structure of the 8x8 matrix optical switch in Example 3 of this invention. It is the top view and sectional drawing which show the structure of the optical switch unit element which has a 1x2 optical switch in Example 3 of this invention, a 2x1 optical switch, and a 1x1 optical switch, and has a heat insulation groove | channel structure. It is a top view of the optical switch unit element which used the Y branch optical waveguide which is one Embodiment of this invention as a component. It is a top view of the optical switch unit element which used the directional coupler which is one Embodiment of this invention as a component. It is a whole top view which shows an example of the basic composition of a 4x4 matrix optical switch, and a figure explaining the operation state of each optical switch unit element. FIG. 2 is an overall plan view of a waveguide type 4 × 4 matrix optical switch in which the 4 × 4 matrix optical switch of FIG. It is the top view and sectional drawing of the conventional double gate type | mold optical switch unit element. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an overall plan view showing a configuration of a path-independent configuration 4 × 4 matrix optical switch that is a form of Example 1; It is a top view which shows the structure of the optical switch unit element provided with the 1x2 optical switch in Example 4 of this invention, a 2x1 optical switch, and a 1x1 optical switch.

Explanation of symbols

1a-1d, 2a-2d to 8a-8d Input optical waveguide 1c-1b, 2c-2b to 8c-8b Output optical waveguide 1 Silicon substrate 2 Clad layer 11a-11b Input optical waveguide 12a-12b Output optical waveguide 13a-13b Bypass Optical waveguides 14a, 14b, 14c, 15a, 15b, 15c Directional couplers 16a, 16b, 16c Thin film heater (thermo-optic phase shifter)
17a, 17b Optical waveguides 18a, 18b, 18c forming a Mach-Zehnder interferometer circuit as a 1 × 1 optical gate switch Mach-Zehnder interferometer circuit 19 Optical waveguide intersections 20a, 20b, 20c Adiabatic groove 30 Y branch optical waveguide 31 Thin film heater (thermo-optic phase shifter)
32 Polymer optical waveguide 40 Lithium niobate substrate 41 Directional coupler (1 × 2 switch or 2 × 1 switch)
42 Directional coupler (1 x 1 switch)
43a Electric field application electrode 43b Electric field application electrode 44 Lithium niobate optical waveguide core 45 Insulating film 70a Input optical waveguide bundle 70b Output optical waveguide bundle

Claims (14)

One input optical waveguide and one output optical waveguide intersecting each other, and further, a bypass optical waveguide connecting the input optical waveguide and the output optical waveguide, and between the bypass optical waveguide and the input optical waveguide The 1 × 2 optical switch having the input optical waveguide as an input portion and the input optical waveguide and the bypass optical waveguide as an output portion, and the output optical waveguide between the bypass optical waveguide and the output optical waveguide And a 2 × 1 optical switch having the bypass optical waveguide as an input unit and the output optical waveguide as an output unit, and the bypass optical waveguide between the 1 × 2 optical switch and the 2 × 1 optical switch as an input unit and 1. A waveguide type optical switch unit element comprising a 1 × 1 optical gate switch as an output unit. The 1 × 2 optical switch and the 2 × 1 optical switch are equipped with at least one of two directional couplers composed of two adjacent optical waveguides and two arm optical waveguides or arm optical waveguides. 2. The waveguide type optical switch unit element according to claim 1, wherein the optical element is a Mach-Zehnder interferometer type optical switch constituted by a shifter. The 1 × 2 optical switch and the 2 × 1 optical switch are configured by two multimode optical couplers, two arm optical waveguides, and a phase shifter provided in at least one of the arm optical waveguides. The waveguide type optical switch unit element according to claim 1, wherein the waveguide type optical switch unit element is a Zehnder interferometer type optical switch. A Y-branch type optical waveguide on the input side of the 1 × 2 optical switch and the output side of the 2 × 1 optical switch, and two proximity on the output side of the 1 × 2 optical switch and the input side of the 2 × 1 optical switch A Mach formed by arranging a directional coupler composed of an optical waveguide and a phase shifter provided in at least one of two arm optical waveguides connecting the Y-branch optical waveguide and the directional coupler. The waveguide type optical switch unit element according to claim 1, wherein the waveguide type optical switch unit element is a Zehnder interferometer type optical switch. 2. The waveguide type optical switch unit element according to claim 1, wherein each of the 1 × 2 optical switch and the 2 × 1 optical switch is an optical switch having a configuration equipped with a Y-branch optical waveguide and a phase shifter. . The 1 × 2 optical switch and the 2 × 1 optical switch are optical switches configured by a directional coupler including two adjacent optical waveguides and a phase shifter provided in at least one of the optical waveguides. The waveguide-type optical switch unit element according to claim 1. The 1 × 1 optical gate switch is composed of two directional couplers composed of two adjacent optical waveguides, two arm optical waveguides, and a phase shifter provided in at least one of the arm optical waveguides. 7. A waveguide type optical switch unit element according to claim 1, wherein the waveguide type optical switch unit element is a Zehnder interferometer type optical switch. Mach-Zehnder interferometer type optical switch in which the 1 × 1 optical gate switch is constituted by a phase shifter provided in at least one of two multimode optical couplers, two arm optical waveguides, and arm optical waveguides The waveguide type optical switch unit element according to claim 1, 2, 3, 4, 5, or 6. A directional coupler consisting of a Y-branch optical waveguide on the input side of the 1 × 1 optical gate switch and two adjacent optical waveguides on the output side is arranged to connect the Y-branch optical waveguide and the directional coupler 2. A Mach-Zehnder interferometer type optical switch configured by a phase shifter provided in at least one of the arm optical waveguide and the arm optical waveguide. 7. The waveguide type optical switch unit element according to 6. The 1 × 1 optical gate switch is an optical switch configured by a phase shifter provided in at least one of two Y-branch optical waveguides, two arm optical waveguides, and arm optical waveguides. The waveguide type optical switch unit element according to claim 1, 2, 3, 4, 5, or 6. The 1 × 1 optical gate switch is an optical switch including a directional coupler including two adjacent optical waveguides and a phase shifter provided in at least one of the optical waveguides. Item 7. The waveguide type optical switch unit element according to Item 1, 2, 3, 4, 5, or 6. The waveguide according to claim 1, wherein M × N intersections in M (M is a positive integer) input optical waveguides and N (N is a positive integer) output optical waveguides intersecting each other. A waveguide-type matrix optical switch comprising: a type optical switch unit element; and the waveguide type optical switch unit element connected to the input / output optical waveguide. 12. The waveguide type optical switch unit elements according to claim 1 are arranged in N (N is a positive integer) rows and N columns, and N input optical waveguides of the optical switch unit elements arranged in the first column are respectively provided. N input terminals, N output optical waveguides of the optical switch unit elements arranged in the Nth column are respectively N output terminals, and the first row (2k−1) columns (k is an integer, 2 ≦ 2k) The input optical waveguide and the output optical waveguide of the optical switch unit element arranged in <N) are the optical waveguide unit of the optical switch unit element arranged in the second row 2k column and the optical switch unit arranged in the first row 2k column. The input optical waveguide and the output optical waveguide of the optical switch unit element respectively connected to the output optical waveguide of the element and arranged in the Nth row (2k-1) column are the (N-1) th row 2k when N is an even number. Input optical waveguide and Nth row of optical switch unit elements arranged in columns Connected to the output optical waveguides of the optical switch unit elements arranged in the k columns, respectively, and when N is an odd number, the input optical waveguides of the optical switch unit elements arranged in the Nth row and 2k columns and the (N-1) th row 2k The input optical waveguides and the output optical waveguides of the optical switch unit elements arranged in the first row 2k columns are arranged in the first row (2k + 1) columns, respectively connected to the output optical waveguides of the optical switch unit elements arranged in the columns. Connected to the input optical waveguide of the optical switch unit element and the output optical waveguide of the optical switch unit element arranged in the second row (2k + 1) column, respectively, and the input light of the optical switch unit element arranged in the Nth row 2k column When N is an even number, the waveguide and the output optical waveguide are input optical waveguides of optical switch unit elements arranged in the Nth row (2k + 1) column and optical switch units arranged in the (N−1) th row (2k + 1) column. Device exit Input optical waveguide of optical switch unit element arranged in (N−1) th row (2k + 1) column and optical switch unit element arranged in Nth row (2k + 1) column when connected to the optical waveguide and N is an odd number A waveguide-type matrix optical switch, characterized in that it is connected to an output optical waveguide. 12. The waveguide type optical switch unit elements according to claim 1 are arranged in N (N is a positive integer) rows and N columns, and N input optical waveguides of the optical switch unit elements arranged in the first column are respectively provided. N input terminals, N output optical waveguides of the optical switch unit elements arranged in the Nth column are respectively N output terminals, and the first row (2k−1) columns (k is an integer, 2 ≦ 2k) <N) The input optical waveguide and the output optical waveguide of the optical switch unit element arranged in <N) are the input optical waveguide of the optical switch unit element arranged in the first row 2k column and the optical switch unit arranged in the second row 2k column. The input optical waveguide and the output optical waveguide of the optical switch unit element respectively connected to the output optical waveguide of the element and arranged in the Nth row (2k-1) column are arranged in the Nth row and 2k column when N is an even number. Input optical waveguide of the optical switch unit element and the (N-1) th row Connected to the output optical waveguides of the optical switch unit elements arranged in the k columns, respectively, and when N is an odd number, the input optical waveguides of the optical switch unit elements arranged in the (N−1) th row and 2k columns and the Nth row 2k The input optical waveguide and the output optical waveguide of the optical switch unit element arranged in the first row 2k column are arranged in the second row (2k + 1) column, respectively connected to the output optical waveguide of the optical switch unit element arranged in the column. Connected to the input optical waveguide of the optical switch unit element and the output optical waveguide of the optical switch unit element arranged in the first row (2k + 1) column, respectively, and the input light of the optical switch unit element arranged in the Nth row 2k column When N is an even number, the waveguide and the output optical waveguide are input optical waveguides of optical switch unit elements arranged in the (N−1) th row (2k + 1) column and optical switch units arranged in the Nth row (2k + 1) column. Device exit Input optical waveguide of optical switch unit element arranged in Nth row (2k + 1) column and optical switch unit element arranged in (N-1) th row (2k + 1) column when connected to optical waveguide and N is odd A waveguide-type matrix optical switch, characterized in that it is connected to an output optical waveguide.

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