JP2004233619A - Optical switch and optical wavelength router - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical switch and an optical wavelength router, with which power consumption is made constant and temperature variation is prevented and which have stable characteristics. <P>SOLUTION: The optical switch is constructed with a quartz type optical waveguide 1. With respect to its construction, an input branching part 2A distributes a light wave inputted from an input waveguide 5 to all of four output waveguides with the same intensity, an output coupling and branching part 3A distributes a light wave inputted to an arbitrary one out of four input waveguides to all of four output waveguides 29-32 with the same intensity and a phase shifter part 4A, interposed between the input branching part 2A and the output coupling and branching part 3A, comprises phase shifter waveguides 11-14, connecting the four output waveguides of the input branching part 2A and the four input waveguides of the output coupling and branching part 3A one to one with one another, and respectively provided with thin film heaters 15-18 to conduct phase modulation. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical switch and an optical wavelength router, which are routing devices used in optical fiber communication.
[0002]
[Prior art]
With the rapid development of optical communication technology, various optical components have been researched and developed. Among them, a waveguide type optical component based on an optical waveguide on a flat substrate occupies the most important position. This is because the waveguide-type optical component has a feature that it can be mass-produced with a precision equal to or less than the light wavelength and with good reproducibility by a photolithography technique and a fine processing technique. In particular, an optical switch (hereinafter, referred to as TOSW) formed on a silica-based optical waveguide and using a thermo-optic effect (hereinafter referred to as TOSW) can realize a large-scale optical switch. In addition, it is excellent in stability and controllability with respect to its temporal change, and research and development are being vigorously promoted.
[0003]
FIG. 15 is a schematic diagram of a conventional tree-type optical switch using TOSW.
In FIG. 15, a 1 × 8 channel (channel) optical switch using the TOSW will be described, and for simplification of description, only parts necessary for the operation will be described.
[0004]
As shown in FIG. 15, the conventional 1 × 8-channel optical switch is configured using a silica-based optical waveguide 101, connected to an input waveguide 102 for receiving a light wave, and connected to the input waveguide 102, and configured using a Mach-Zehnder interferometer. A first-stage switch 103, two connection waveguides 109 and 110 connected to two outputs of the first-stage switch 103, and two second-stage switches (second connection) connected to the connection waveguides 109 and 110, respectively. Stage first switch 111, etc.), four connection waveguides (connection waveguides 113, 114, etc.) connected to two outputs of two second stage switches, respectively, and four connection waveguides respectively connected. It has four third-stage switches (eg, third-stage second switch 115) and eight output waveguides (eg, output waveguides 117, 118) connected to the four third-stage switches. The first-stage switch 103 includes two optical directional couplers 104 and 105, arm waveguides 106 and 107 having the same length sandwiched therebetween, and a thin-film heater 108 disposed above the arm waveguide 106. Be composed. Other second-stage switches and third-stage switches have the same configuration as the first-stage switch 103.
[0005]
Next, the operation of the conventional optical switch will be described. Here, the case of switching to the output waveguide 117 will be described, but the operation principle is the same when switching to another output waveguide.
[0006]
The light wave input from the input waveguide 102 is equally distributed to the arm waveguides 106 and 107 by the optical directional coupler 104 of the first-stage switch 103. When power is not applied to the thin film heater 108 on the arm waveguide 106, the light waves propagated through the arm waveguides 106 and 107 are multiplexed in the optical directional coupler 105 and branched to the connection waveguide 110. When an appropriate electric power is applied to the thin film heater 108 on the arm waveguide 106, the phase difference of the light wave between the arm waveguides 106 and 107 is set to a half wavelength at the wavelength, so that the connection waveguide 109 is formed. Branched to That is, the lightwave input from the input waveguide 102 is switched to the connection waveguide 109 or 110 by the first-stage switch 103.
[0007]
The light wave input to the second-stage first switch 111 via the connection waveguide 109 is switched to the connection waveguide 114 or the connection waveguide 113 by application / non-application of electric power to the thin-film heater 112, and the thin-film When an appropriate power is applied to the heater 112, the connection is switched to the connection waveguide 114. Further, the light wave incident on the third-stage second optical switch 115 via the connection waveguide 114 is switched to the connection waveguide 118 or the connection waveguide 117 by applying / non-applying power to the thin film heater 116. When no power is applied to the thin film heater 116, an optical path can be set to the output waveguide 117, and a desired output to the output waveguide 117 can be obtained.
[0008]
Therefore, in the conventional optical switch shown in FIG. 15, switching from the input waveguide 102 to the output waveguide 117 is realized by applying appropriate power to the thin film heaters 108 and 112.
[0009]
As a conventional optical switch using a tree-type TOSW as shown in FIG. 15, an optical switch of 1 × 128 ch using a silica-based optical waveguide has been reported (see Non-Patent Document 1). In this 1 × 128-channel optical switch, a silica-based optical waveguide having a relative refractive index difference of 1.5% is used, the half-wave power of the thin-film heater is 0.385 W, the average crosstalk is 50.8 dB, and each output waveguide is used. The average loss to the wave path is 3.7 dB, and good characteristics are obtained.
[0010]
However, in an optical switch using a tree-type TOSW, in order to switch to an arbitrary output waveguide, for example, the number of output channels is set to two. ^M In the case where the number of thin film heaters is set, power must be applied to at least 0 thin film heaters and at most M thin film heaters. Specifically, M = 7 (2 ⁷ = 128), the power consumption varies from 0 W to 2.695 W depending on the output channel.
[0011]
As described above, the optical switch using the TOSW based on the silica-based optical waveguide has excellent characteristics and is expected to be applied to a communication system. On the other hand, the power consumption varies depending on the output channel. The following issues are issues for study.
[0012]
FIG. 16 is a diagram illustrating a measurement result of a transient response characteristic of the Mach-Zehnder interferometer using the thermo-optic effect.
As shown in FIG. 16, in the Mach-Zehnder interferometer using the thermo-optic effect, the transient response characteristics of the switching are 4 ms at the rising edge when the light intensity becomes 90% or more, and 5 ms at the falling edge when the light intensity becomes 10% or more. Switching time is required. That is, since the conventional optical switch uses the Mach-Zehnder interferometer utilizing the thermo-optic effect, its operation is limited to about several ms.
[0013]
Meanwhile, in recent wavelength division multiplexing (hereinafter referred to as WDM) communication networks, path control by wavelength, that is, optical wavelength routing is becoming an important technology. In a metro access network, the application of optical wavelength routing makes it possible to construct a highly flexible network, and there is a strong need for such an optical wavelength router.
[0014]
FIG. 17 is a schematic diagram of a conventional optical wavelength router that routes a wavelength multiplexed signal (hereinafter, referred to as a WDM signal).
Here, for the sake of simplicity, an outline of a four-wavelength 1 × 5ch optical wavelength router that routes four WDM signals to five arbitrary spatial paths will be described as an example.
[0015]
As shown in FIG. 17, a conventional optical wavelength router includes an input waveguide 121 for receiving a light wave, a 1 × 4ch input branching array waveguide grating 122 connected to the input waveguide 121, and a connecting waveguide group. A first stage 1 × 2 optical switch group 124 connected to the four outputs of the input demultiplexing arrayed waveguide grating 122 via 123 and a first stage 1 × 2 optical switch group via a connecting waveguide group 125, respectively. And a 5 × 4 × 1ch output multiplexing array waveguide grating 135 connected to one side of the output of each of the optical switches 124 and a first stage 1 × 2 optical switch group 124 via a connecting waveguide group 126. A second stage 1 × 2 optical switch group 127 connected to the other side of the output of each optical switch, and a third stage connected to the output of the second stage 1 × 2 optical switch group 127 via a connection waveguide 128. And a step light switch group 129. The 1st-4x1ch output multiplexing array waveguide grating 131 connected to the output of the 3rd stage 1x2 optical switch group 129 for each corresponding wavelength via the path 130, Wave array waveguide grating 132, 3-4 × 1ch output multiplexing array waveguide grating 133, 4-4 × 1ch output multiplexing array waveguide grating 134, and first to fifth 4 × 1ch output multiplexing Output waveguides 136 to 140 connected to the combined outputs of the arrayed waveguide gratings 131 to 135, respectively.
[0016]
In the above-described conventional optical wavelength router, the WDM signal input from the input waveguide 121 is wavelength-demultiplexed by the input demultiplexing arrayed waveguide grating 122, and then the demultiplexed light wave is tree-type 1 × for each wavelength. Routed by the two optical switch groups 124, 127, 129, multiplexed by the first to fifth 4 × 1ch output multiplexing array waveguide gratings 131 to 135, and output from any output waveguides 136 to 140 You. Since this optical wavelength router has a tree-type TOSW for each wavelength, it is possible to set an arbitrary output for each wavelength.
[0017]
As an optical wavelength router as shown in FIG. 17, a 1 × 9 channel optical wavelength router has been reported (see Non-Patent Document 2). In this 1x9ch optical wavelength router, it is reported that the 1x2 optical switch is configured by a Mach-Zehnder interferometer by TOSW, the half-wave power of TOSW is 0.45W, and the maximum value of power consumption is 14W. Have been. It is also reported that propagation loss to each output waveguide is 5.4 dB at the maximum and crosstalk is 46 dB at the worst value.
[0018]
In the 1 × 9ch optical wavelength router, the power consumption changes from 0 W to 14 W depending on the setting state of the path. This means that the temperature of the optical waveguide substrate constituting the optical wavelength router fluctuates, and the input demultiplexing array waveguide grating 122 and the first to fifth 5-4 × 1ch output multiplexing array waveguide grating 131 are used. The change in the temperature of the optical waveguide substrate adversely affects the multiplexing / demultiplexing characteristics of 135.
[0019]
FIG. 18 is a diagram showing a change in the output spectrum at the center wavelength of an arbitrary output multiplexing arrayed waveguide grating by applying a temperature change corresponding to the power applied to the TOSW to the substrate in the conventional optical wavelength router. .
Specifically, in the conventional optical wavelength router shown in FIG. 17, the power applied to the TOSW is changed to 0 W, 1.8 W, and 3.6 W, and the 1-1 × 4 output multiplexed array waveguide grating is formed. The change of the output spectrum at the center wavelength of 131 was measured. As shown in FIG. 18, it is found that the center wavelength of the 1-1 × 4 output multiplexed array waveguide grating 131 is shifted by the power applied to the TOSW, and the change of the center wavelength is about 10 GHz / W. . That is, it can be seen that the power originally applied for optical wavelength routing also affects the wavelength demultiplexing characteristics of the arrayed waveguide grating.
[0020]
Further, in the conventional optical wavelength router having the above configuration, since the TOSW is used for path routing, the response speed is limited to about several milliseconds, similarly to the characteristic shown in FIG.
[0021]
[Non-patent document 1]
T. Watanabe, et al, "Silica-based PLC Ix128 Thermo-Optic Switch," Proc. 27 ^th European Conference on Optical Communication, P134-135 Tu. L. 1.2, 2001, Amsterdam.
[Non-patent document 2]
C. R. Doerr, "Silica-Waveguide lx9 waveguide-Selective cross connect," Proc. Optical Fiber Communication, Postdeadline Papers P2-4, FA3-1, 2002, Anaheim.
[0022]
[Problems to be solved by the invention]
As described above, the power consumption of the 1 × Nch optical switch based on the thermo-optic effect using the silica-based optical waveguide varies depending on the output channel to be selected, making it difficult to control the temperature of the entire component. That is, the temperature fluctuation is given to other components having a temperature dependency due to the fluctuation of the power consumption, for example, the array type waveguide grating, which causes the characteristic deterioration.
[0023]
Furthermore, the response characteristics of the optical switch based on the thermo-optic effect using a silica-based optical waveguide are governed by the limitations of the thermo-optic effect, which are on the order of several milliseconds, and hinder application to high-speed applications. That is, the TOSW exhibits extremely excellent performance for applications such as low-speed routing, for example, securing a low-speed transmission line when a transmission line fails, but burst switching that requires a response characteristic on the order of μs is required. It has been difficult to apply the present invention to packet switching that requires response characteristics of the order of ns or ns.
[0024]
SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide an optical switch and an optical wavelength router that can stabilize power consumption, prevent temperature fluctuation, and have stable operation characteristics.
[0025]
[Means for Solving the Problems]
The outlines of the optical switch and the optical wavelength router according to the present invention are as follows.
That is, an optical switch according to the present invention that solves the above problems is configured on a planar lightwave circuit, and includes an input branching unit that branches an input lightwave, and an output branching unit that branches and splits a lightwave. And a phase shifter section which is interposed between the input branch section and the output branch section and modulates the phase of the light wave. The input branch section includes at least one input section input waveguide and N input section output waveguides. And an input section branching means for splitting a light wave input from one input section input waveguide to all of the N input section output waveguides with equal strength. The unit outputs light waves input to any one of the N output unit input waveguides, the N output unit output waveguides, and the N output unit input waveguides to the N output unit output units. Output section branching means for branching to equal strength to all of the waveguides. The phase shifter section includes a phase shifter waveguide that connects the N input section output waveguides and the N output section input waveguides on a one-to-one basis, and phase modulation means provided on each of the phase shifter waveguides. It is characterized by having.
Note that N is an integer greater than 1.
[0026]
An optical wavelength router according to the present invention that solves the above-mentioned problems is configured on a planar lightwave circuit, and includes an input branching unit that branches an input lightwave, and an output branching unit that performs lightwave branching. And a phase shifter section interposed between the input branch section and the output branch section and modulating the phase of the light wave. The input branch section includes at least one input section input waveguide and N input section outputs. A waveguide, and input section branching means for splitting a light wave input from one input section input waveguide into all of the N input section output waveguides with equal strength. The branch unit converts the light waves input to any one of the N output unit input waveguides, the N output unit output waveguides, and the N output unit input waveguides into N output units. Output section branching means for branching to equal strength into all of the output waveguides. The shifter section includes N input connection waveguides connected to the N input section output waveguides, and at least (N-1) 1-input M-output wavelength demultiplexers connected to the input connection waveguides. And at least (N−1) × M phase shifter waveguides connected to the wavelength demultiplexer, and at least (N−1) M-input / one-output wavelength multiplexing connected to the phase shifter waveguide. And N output connection waveguides for connecting the wavelength multiplexer and the N output section input waveguides, and phase modulation means provided in each of the phase shifter waveguides. Features.
Note that N and M are integers larger than 1.
[0027]
Further, in the optical switch or the optical wavelength router, a phase modulator based on a thermo-optic effect or a phase modulator based on an electro-optic effect may be used as a phase modulator.
[0028]
Further, in the above optical switch or optical wavelength router, the input branching section, the output branching section and the phase shifter section may be constituted by a quartz optical waveguide, and the phase modulating means is constituted by lithium niobate. May be composed of a silica-based optical waveguide.
[0029]
In addition, the input unit branching unit may be configured by connecting a 50% coupling optical directional coupler or a 1 × 2 branch multimode interference coupler in multiple stages, and the output unit branching unit may be configured by a 50% coupling multidirectional interference coupler. It may be configured such that a coupled light directional coupler or a 2 × 2 multiplexing / branching multimode interference coupler is connected in multiple stages.
[0030]
Alternatively, the input branching unit may be configured by connecting all or a part of the Mach-Zehnder interferometer having a coupling rate adjusting function in multiple stages, or the output combining / branching unit may include all or a part of the input branching unit. Alternatively, a Mach-Zehnder interferometer having a coupling rate adjusting function may be connected in multiple stages.
[0031]
In addition, the first stage of a multi-stage 50% coupled optical directional coupler or 1 × 2 branch multimode interference coupler, or a multi-stage 50% coupled optical directional coupler or 2 × 2 branch multi-mode coupler At least one of the final stages of the mode interference coupler may be configured using a variable light directional coupler using a Mach-Zehnder interferometer.
[0032]
50% coupled optical directional coupler forming an input branching unit, either a 1 × 2 multimode interference coupler or a Mach-Zehnder interferometer having a coupling rate adjusting function, and 50% coupled optical directional forming an output branching unit Any Mach-Zehnder interferometer using either a coupler, a 2 × 2 branch multi-mode interference coupler or a Mach-Zehnder interferometer having a coupling ratio adjustment function as two combiners is set so that the optical path length difference becomes zero. It may be done.
[0033]
The input section branching means may be constituted by a 1 × N-branch multimode interference optical coupler, and the output section branching means may be constituted by an N × N-branch multimode interference optical coupler.
[0034]
BEST MODE FOR CARRYING OUT THE INVENTION
Some embodiments of the optical switch and the optical wavelength router according to the present invention will be described in detail with reference to the drawings of the following examples. In all the drawings showing the embodiments, those having the same functions are denoted by the same reference numerals, and their repeated description will be omitted.
[0035]
(Example 1)
FIG. 1 is a schematic diagram of an optical switch showing an example of an embodiment according to the present invention. The details of the configuration, operation, and characteristics of an optical switch of 1 × 4 channels (channels) will be described.
[0036]
The 1 × 4ch optical switch of the present embodiment is configured using a planar lightwave circuit such as a quartz optical waveguide 1, and the optical waveguide having a non-refractive index difference of 0.75% is used.
[0037]
As shown in FIG. 1, the 1 × 4ch optical switch according to the present embodiment includes an input branching unit 2A, an output combining / branching unit 3A, and a phase shifter unit 4A.
The input branching unit 2A includes an input waveguide 5 serving as an input unit input waveguide for inputting a light wave, a first-stage optical directional coupler 6 connected to the input waveguide 5 and being a 1 × 2 optical splitter, Connection waveguides 7, 8 connected to the first-stage optical directional coupler 6, and second-stage optical directional coupling connected to the first-stage optical directional coupler 6 via the connection waveguides 7, 8. Vessels 9 and 10. In the input branching section 2A, the light wave input from the input waveguide 5 is equally distributed (with equal intensity) to four input section output waveguides by the second-stage optical directional couplers 9 and 10 serving as input section branching means. Divided).
[0038]
The phase shifter section 4A has four phase shifter waveguides 11, 12, 13, and 14, and thin film heaters 15, 16, 17, and 18 disposed thereon. The four outputs from the input branching unit 2 are connected to the phase shifter waveguides 11, 12, 13, and 14, respectively. Here, a thin film heaters 15 to 18 are used as the phase modulation means to constitute a phase modulator based on the thermo-optic effect.
[0039]
The output branching section 3A has four output section input waveguides, which are connected to the phase shifter waveguides 11, 12, 13, 14 of the phase shifter section 4A. Here, the phase shifter waveguides 11 and 12 are connected to two inputs of a third-stage optical directional coupler 19, and the phase shifter waveguides 13 and 14 are connected to two inputs of a third-stage optical directional coupler 20. Connected to input. One output of the third-stage optical directional coupler 19 and one output of the third-stage optical directional coupler 20 are connected to the two outputs of the fourth-stage optical directional coupler 27 via the connection waveguides 21 and 23. Connected to input. The other output of the third-stage optical directional coupler 19 and the other output of the third-stage optical directional coupler 20 are connected to the fourth-stage optical directional coupler 28 via the connection waveguides 22 and 24. Connected to two inputs. Finally, the fourth-stage optical directional couplers 27 and 28 are connected to output waveguides 29, 30, 31, and 32, which become output section output waveguides. In the output multiplexing / branching unit 3A having the above configuration, the light wave input to any one output unit input waveguide is connected to the third-stage optical directional couplers 19 and 20 constituting the output unit multiplexing / branching means by the connection waveguide. The waveguides 22 to 24, the cross waveguides 25 and 26, and the fourth-stage optical directional couplers 27 and 28 are equally distributed (divided into equal intensities) into four output waveguides 29 to 32.
[0040]
Here, the connecting waveguides 21, 22, 23, and 24 are all set to have the same length, and the intersecting waveguides 25 intersect at the same angle θ as the intersecting angle θ of the connecting waveguides 22 and 23. And 26 are arranged for the connecting waveguides 21 and 24. In this embodiment, the intersection angle θ is set to 30 degrees. By arranging the cross waveguides 25 and 26 at such an angle θ, it is possible to reduce the variation of the loss in each path and improve the extinction ratio.
[0041]
In the optical switch of this embodiment, the second-stage optical directional coupler 9 and the third-stage optical directional coupler 19 are connected, and the second-stage optical directional coupler 10 and the third-stage optical directional coupler 20 are connected. All paths are set to equal length. Also, any paths connecting the first-stage optical directional coupler 6 and the fourth-stage optical directional couplers 27 and 28 are all set to the same length. That is, in the optical switch of the present embodiment, any one of the optical directional couplers constituting the input branching unit 2A and any one of the optical directional couplers constituting the output coupling / branching unit 3A are provided as two coupling / branching units. When an arbitrary Mach-Zehnder interferometer is formed, the optical path length difference is set to be zero.
[0042]
Although the optical switch of this embodiment uses a quartz-based optical waveguide that has low propagation loss and is easy to manufacture, other optical waveguides, for example, a waveguide made of an InP compound or an optical waveguide made of SiON may be used. The same effect can be obtained. Also, in this embodiment, a 3 dB (50%) coupled optical directional coupler is used as a 1 × 2 optical splitter and a 2 × 2 optical splitter, but a 1 × 2 split multimode interference coupler, 2 × 2 The same effect can be obtained by using an optical splitter or an optical splitter configured by connecting multi-branch multi-mode interference couplers in multiple stages. Further, a 1 × N branching multimode interference coupler having an integer N larger than 2 and an N × N branching multimode interference coupler may be used.
[0043]
Next, the operation of the optical switch according to the present embodiment will be described below.
The light wave input from the input waveguide 5 is distributed to the equal power by the input branching unit 2A, and propagates to the phase shifter waveguides 11, 12, 13, and 14. By applying appropriate power to the thin-film heaters 15, 16, 17, and 18, and adjusting the phase states of the light waves in the third-stage optical directional couplers 19 and 20, the third-stage optical directional coupler 19 Can be set to one of the connection waveguides 21 and 22, and the emission from the third-stage optical directional coupler 20 can be set to one of the connection waveguides 23 and 24.
[0044]
Further, while maintaining the phase difference given by the thin film heaters 15 and 16 and the phase difference given by the thin film heaters 17 and 18, the phase difference given by the thin film heaters 15 and 16 and the thin film heaters 17 and 18 is appropriately set, so that The output from the four-stage optical directional couplers 27 and 28 can be set to one of the output waveguides 29, 30, 31, and 32.
[0045]
FIG. 2 is a diagram showing a relationship between phases given to light waves in each thin-film heater when outputting to each output waveguide.
As shown in FIG. 2, for example, when the light wave incident on the input waveguide 5 is switched to the output waveguide 30, the thin film heaters 15, 16, 17, 18 are supplied with π / 2, π / 2, What is necessary is just to apply the electric power corresponding to the phase shift which becomes pi and 0. Further, since the applied power of the thin-film heater and the phase shift amount of the light wave caused by the thin-film heater are in a proportional relationship, the total sum of the phase shift amounts of the respective thin-film heaters, that is, the total sum of the applied power to each thin-film heater is determined by which output waveguide is selected. It can be seen that even in this case, the power becomes equal.
[0046]
3A and 3B show the static characteristics of the 1 × 4ch optical switch of the present embodiment. FIG. 3A is a graph showing the propagation loss in each output waveguide, and FIG. 5 is a graph illustrating an extinction ratio with another output waveguide when an output is set to an output waveguide 30.
In this measurement, the measurement is performed on monochromatic light having a wavelength of 1550 nm, and the loss is 2.5 dB at the maximum for the output waveguide 30, 2.1 dB at the minimum for the output waveguide 29, and 2.3 dB on average. Good characteristics were obtained. The extinction ratio was 33.4 dB with respect to the output waveguide 29 at the worst value, 35.2 dB with respect to the output waveguide 31 at the best value, and 34.4 dB on average.
[0047]
As described above, according to the optical switch of the present embodiment, it is possible to realize an optical switch in which switching is performed with constant power consumption, the temperature is stabilized, and the switching operation characteristics are stabilized.
[0048]
(Example 2)
FIG. 4 is a schematic diagram of an optical switch showing another example of the embodiment according to the present invention. An optical switch of 1 × 4 ch is taken as an example similarly to the first embodiment, and details of its configuration, operation and characteristics are described. explain.
[0049]
Further, in the present embodiment, the input branching section and the output branching section forming the optical switch are formed using a silica-based optical waveguide as in the first embodiment, and the phase shifter section forming the optical switch is formed of z-type. An optical waveguide having an electro-optic effect phase shifter made of cut traveling wave type titanium diffusion lithium niobate was used.
[0050]
As shown in FIG. 4, the 1 × 4ch optical switch according to the present embodiment is a planar lightwave circuit including an input branching section 2A and an output branching section 3A formed by a quartz optical waveguide 1 and a phase shifter section 4B formed by a lithium niobate waveguide. Consists of
The configurations of the input branching unit 2A and the output combining / branching unit 3A are the same as those in the first embodiment, and a detailed description thereof will be omitted.
[0051]
The input branch unit 2A and the phase shifter unit 4B are connected to the four connection waveguides 51, 52, 53, and 54 from the second-stage optical directional couplers 9 and 10 of the input branch unit 2A at the joint surface 33, respectively. The phase shifter waveguides 40, 41, 42, and 43 arranged in the shifter section 4B are joined so as to match each other. In addition, the output coupling / branching unit 3A and the phase shifter unit 4B also include, on the joint surface 34, the phase shifter waveguides 40, 41, 42, and 43 disposed in the phase shifting unit 4B, and the third stage light of the output coupling / branching unit 3A. The four connecting waveguides 55, 56, 57, 58 to the directional couplers 19, 20 are joined so as to coincide with each other.
[0052]
In the phase shifter unit 4B, electrodes 44a and 44b, 45a and 45b, 46a and 46b, 47a and 47b are provided, respectively, so that an appropriate electric field can be applied to the phase shifter waveguides 40, 41, 42, and 43. Have been. Here, the electrodes 44a and 44b, 45a and 45b, 46a and 46b, 47a and 47b are used as the phase modulating means to constitute a phase modulator based on the electro-optic effect. The amount of phase shift by each electrode is the same as the setting in FIG. 2 in the first embodiment. For example, when switching to the output waveguide 29, π / 2 between the electrodes 44a and 44b, π / 2 between the electrodes 45a and 45b, 0 between the electrodes 46a and 46b, and 0 between the electrodes 47a and 47b. An electric field corresponding to π may be applied.
[0053]
Although the input branch and the output branch are also made of a silica-based optical waveguide in this embodiment from the viewpoint of easy fabrication and low propagation loss, the same effect can be obtained by using an InP compound or a SiON optical waveguide. It is possible to get. Although the phase shifter is made of an optical waveguide made of lithium niobate, the phase shifter is replaced with an optical waveguide capable of realizing a phase shifter having other high-speed response characteristics, for example, a KTP (Potassium Titanyl Phosphate) waveguide having an electro-optical effect. It is possible to obtain the same effect. Further, in the present embodiment, as in the first embodiment, a 3 dB (50%) coupled optical directional coupler is used as a 1 × 2 optical branching device and a 2 × 2 optical combining / branching device. The same effect can be obtained by using an optical splitter or an optical splitter configured by connecting a coupler, a 2 × 2 branching multimode interference coupler, or the like in multiple stages. Further, a 1 × N branching multimode interference coupler having an integer N larger than 2 and an N × N branching multimode interference coupler may be used.
[0054]
FIG. 5 is a diagram illustrating a measurement result of a transient response characteristic of the optical switch according to the present embodiment.
Specifically, in the 1 × 4 channel optical switch of the present embodiment, the transient response characteristics when the light wave from the input waveguide 5 was switched between the output waveguide 29 and the output waveguide 30 were measured. As is clear from FIG. 5, a high-speed transient characteristic of 1 ns can be obtained for both the output up to 90% and the output up to 10%, and very high-speed switching can be realized. Was.
[0055]
6A and 6B show the static characteristics of the 1 × 4ch optical switch of the present embodiment. FIG. 6A is a graph of the propagation loss in each output waveguide, and FIG. It is the graph which showed the extinction ratio with another output waveguide at the time of setting to 30.
In this measurement as well, measurement was performed for monochromatic light having a wavelength of 1550 nm, and the loss was 4.2 dB at the worst value, 3.7 dB at the best value, and 3.9 dB at the average value, and the extinction ratio was 27 dB at the worst value. , The best value was 32.5 dB, and the average value was 29.3 dB, and good characteristics were obtained.
[0056]
As described above, according to the present embodiment, an optical switch that stabilizes the temperature by performing switching with constant power consumption, stabilizes the switching operation characteristics, and performs high-speed switching operation is realized. Thus, the optical switch according to the present embodiment can be applied to a burst switch or a packet switch.
[0057]
(Example 3)
FIG. 7 is a schematic diagram of an optical wavelength router showing an example of an embodiment according to the present invention. The configuration, operation and characteristics of the optical wavelength router of 1 × 4ch-6 waves will be described in detail.
[0058]
The optical wavelength router of the present embodiment is configured on a planar lightwave circuit such as a silica-based optical waveguide 1, and the phase shifter unit of the first embodiment is replaced with a wavelength multiplexer / demultiplexer using an arrayed waveguide grating and a phase shifter array. This constitutes a 1 × 4ch-6-wave optical wavelength router.
[0059]
As shown in FIG. 7, the optical wavelength router according to the present embodiment includes, as input units, an input waveguide 61 for receiving a light wave, an input branch unit 62 connected to the input waveguide 61, and four input branch units 62. And four connection waveguides 63, 64, 65, 66 connected to the outputs, and as output portions, four output waveguides 81, 82, 83, 84, and output waveguides 81, 82, It has an output coupling / branching unit 80 that connects 83 and 84, and connection waveguides 76, 77, 78 and 79 connected to four inputs of the output coupling / branching unit 80. The input branching unit 62 and the output combining / branching unit 80 of the optical wavelength router according to the present embodiment have the same configuration as the input branching unit 2A and the output combining / branching unit 3A according to the first embodiment, and a detailed description is omitted.
[0060]
Further, in connection with the input branching unit 62, the phase shifter unit 4C is connected to the input branching unit 62 via connection waveguides 63, 64, 65, and 66 serving as input connection waveguides. In connection with, the output branching section 80 was connected via connection waveguides 76, 77, 78, 79 serving as output connection waveguides. In the phase shifter unit 4C, the connection waveguides 63, 64, 65, and 66 are connected to 1 × 6 wavelength demultiplexing arrayed waveguide gratings 67, 68, 69, and 70, respectively, serving as wavelength demultiplexers. Waveguides 76, 77, 78, and 79 were connected to 6 × 1 wavelength multiplexing array waveguide gratings 72, 73, 74, and 75, respectively, serving as wavelength multiplexers. The number of 1 × M wavelength demultiplexing array waveguide gratings and M × 1 wavelength multiplexing array waveguide gratings required for the phase shifter unit 4C is at least (N−1) when outputting to N output waveguides. In this embodiment, four 1 × 6 wavelength demultiplexing array waveguide gratings 67 to 70 and four six × 1 wavelength multiplexing arrayed waveguide gratings 72 to 75 were provided. Here, M is the number of WDM signals to be multiplexed / demultiplexed.
[0061]
Each of the 1 × 6 wavelength demultiplexing array waveguide gratings 67, 68, 69, 70 and the 6 × 1 wavelength multiplexing array waveguide gratings 72, 73, 74, 75 is an input-side slab waveguide that diffracts an optical signal. And an output-side slab waveguide, which connects between the input-side slab waveguide and the output-side slab waveguide, and is composed of a plurality of arrayed waveguides having different lengths from each other, all having the same combination. It has a wave characteristic and splits a WDM signal into optical frequencies f1, f2, f3, f4, f5, f6 or multiplexes a light wave with optical frequencies f1, f2, f3, f4, f5, f6 into a WDM signal. It is.
[0062]
Further, the demultiplexing (output) side port of the 1 × 6 wavelength demultiplexing array waveguide grating 67 and the demultiplexing (input) side port of the 6 × 1 wavelength demultiplexing array waveguide grating 72 are connected to the 1 × 6 wavelength demultiplexing array waveguide. The demultiplexing side port of the waveguide grating 68 and the demultiplexing side port of the 6 × 1 wavelength multiplexing array waveguide grating 73, the demultiplexing side port of the 1 × 6 wavelength multiplexing array waveguide grating 69 and the 6 × 1 wavelength multiplexing array The demultiplexing side port of the waveguide grating 74 and the demultiplexing side port of the 1 × 6 wavelength demultiplexing arrayed waveguide grating 70 and the demultiplexing side port of the 6 × 1 wavelength demultiplexing arrayed waveguide grating 75 are provided with a plurality of phase shifter arrays 71. Are connected for each corresponding wavelength. The phase shifter array 71 includes a plurality of phase shifter waveguides and thin film heaters disposed thereon, similarly to the phase shifter unit 4A of the first embodiment. A phase modulator based on the thermo-optic effect is used. The number of the phase shifter waveguides of the phase shifter array 71 necessary for the phase shifter unit 4C is determined by using N output waveguides using a 1 × M wavelength demultiplexing array waveguide grating and an M × 1 wavelength multiplexing array waveguide grating. , It suffices to have at least (N-1) × M. In this embodiment, 24 phase shifter waveguides are provided for four output waveguides. Again, M is the number of WDM signals to be multiplexed / demultiplexed.
[0063]
In the phase shifter unit 4C having the above-described configuration, for example, the light wave input from the connection waveguide 63 to the 1 × 6 wavelength demultiplexing array waveguide grating 67 is transmitted to the 1 × 6 wavelength demultiplexing array waveguide grating 67 demultiplexing side port. The light is demultiplexed for each wavelength, experiences different phase shifts, is further multiplexed by the 6 × 1 wavelength multiplexing array waveguide grating 72, and propagates to the connection waveguide. Similarly, between the connection waveguide 64 and the connection waveguide 77, between the connection waveguide 65 and the connection waveguide 78, and between the connection waveguide 66 and the connection waveguide 79, a phase shift amount different for each wavelength is applied to the phase shifter array. 71. Therefore, the output waveguides for each wavelength can be independently set by the same control as in the first embodiment.
[0064]
Although this embodiment also describes an optical wavelength router constituted by a silica-based optical waveguide, the optical wavelength router according to the present invention does not depend on the material of the optical waveguide, and may be an InP compound optical waveguide or a SiON optical waveguide. The same effect can be obtained by using such an optical waveguide. In this embodiment, an arrayed waveguide grating is used as a wavelength multiplexer / demultiplexer. However, similar effects can be obtained by using a wavelength multiplexer / demultiplexer configured by a lattice filter or a transversal filter.
[0065]
FIG. 8 is a diagram illustrating an example of setting an output waveguide from which light waves of each frequency are output and a phase shifter amount between the connection waveguides at that time in the present embodiment.
In the present embodiment, the demultiplexing frequencies of six waves of the 1 × 6 wavelength demultiplexing array waveguide grating and the 6 × 1 wavelength demultiplexing array waveguide grating are f1 = 192.9 THz, f2 = 193.0 THz, and f3 = 193. 1 THz, f4 = 193.2 THz, f5 = 193.3 THz, f6 = 193.4 THz, and the free spectral range were set to 1600 GHz. As shown in FIG. 8, each splitting frequency is output to a predetermined output waveguide according to the setting of the amount of phase shifter between the connection waveguides. For example, for the splitting frequency f1 = 192.9 THz, the phase shifter between the connecting waveguides 63 and 76 is π / 2, the phase shifter between the connecting waveguides 64 and 77 is π / 2, and the connecting waveguide is π / 2. When the amount of phase shifter between 65 and 78 is set to 0 and the amount of phase shifter between connection waveguides 66 and 79 is set to π, a light wave is output to output waveguide 81.
[0066]
FIG. 9 shows a result of measuring a spectrum in each output waveguide when the amount of the phase shifter is set in FIG.
As can be seen from the graphs of FIGS. 9A, 9B, 9C, and 9D, the output waveguide 81 has frequencies f1 and f5 (see FIG. 9A), and the output waveguide 82 has The frequency f2 is output (see FIG. 9B), the output waveguide 83 outputs the frequencies f3 and f6 (see FIG. 9C), and the output waveguide 84 outputs the frequency f4 (see FIG. 9D). In each frequency, the crosstalk was about 30 dB and the propagation loss was 6.1 dB on average, showing good characteristics.
[0067]
Further, as can be seen from the example of setting the amount of phase shifter shown in FIG. 8, even in the optical wavelength router according to the present invention, when the path is switched for each wavelength, there is a difference in the total power applied to each thin film heater. In addition, the influence of temperature fluctuation on the 1 × 6 wavelength demultiplexing array waveguide gratings 67, 68, 69, 70 and the 6 × 1 wavelength demultiplexing array waveguide gratings 72, 73, 74, 75, that is, Does not cause temperature changes. In this example, the power consumption was 12 W constantly.
[0068]
Further, as described above, the optical wavelength router according to the present invention can set the number of spatial output channels and the number of wavelength channels independently, and can be a flexible optical wavelength router.
[0069]
(Example 4)
FIG. 10 is a schematic diagram of an optical wavelength router showing another example of the embodiment according to the present invention. The details of the configuration, operation, and characteristics of the optical wavelength router of 1 × 4ch-6 waves will be described as an example. I do.
[0070]
The optical wavelength router according to the present embodiment includes an optical branching unit 92 having an input branching unit 62 and a 1 × 6 wavelength branching array waveguide grating group 86, an output branching unit 80 and a 6 × 1 wavelength combining array waveguide. An optical multiplexing / demultiplexing unit 93 having a lattice group 87 is constituted by a quartz-based optical waveguide, and a phase shifter array unit 94 is constituted by an optical waveguide of z-Cut traveling wave type titanium diffusion lithium niobate. . That is, it corresponds to the optical wavelength router shown in the third embodiment in which the phase shifter of the thermo-optic effect configured using the thin film heater is replaced with the phase shifter of the electro-optic effect using the lithium niobate optical waveguide.
[0071]
Specifically, as shown in FIG. 10, in the optical wavelength router according to the present embodiment, the optical branching unit 92 includes an input waveguide 61 for receiving a light wave, and an input branching unit 62 connected to the input waveguide 61. And a connecting waveguide group 85 connected to the output of the input branching unit 62, and a 1 × 6 wavelength demultiplexing arrayed waveguide grating group 86 connected to the connecting waveguide group 85. The input branching unit 62 has the same configuration as that of the input branching unit 2A of the first embodiment, and the 1 × 6 wavelength demultiplexing array waveguide grating group 86 includes the 1 × 6 wavelength demultiplexing array waveguide shown in the third embodiment. Waveguide gratings 67, 68, 69, and 70 consist of four arrayed waveguide gratings of the same design.
[0072]
The optical multiplexing / demultiplexing unit 93 is connected to the output waveguides 81, 82, 83, 84, the output multiplexing / branching unit 80 connected to the output waveguides 81, 82, 83, 84, and the input of the output multiplexing / branching unit 80. The connection waveguide group 88 includes a 6 × 1 wavelength multiplexing array waveguide grating group 87 connected to the connection waveguide group 88. The output multiplexing / branching unit 80 has the same configuration as that of the output multiplexing / branching unit 3A of the first embodiment. It comprises four arrayed waveguide gratings of the same design as the arrayed waveguide gratings 72, 73, 74, 75.
[0073]
In the phase shifter array unit 94, in connection with the optical demultiplexing unit 92, the optical waveguide from the optical demultiplexing unit 92 and the optical waveguide of the phase shifter array group 89 of the phase shifter array unit 94 are connected so that they respectively match at the joint surface 90. did. Similarly, in the connection with the optical multiplexing / demultiplexing unit 93, the optical waveguide from the optical multiplexing / demultiplexing unit 93 and the optical waveguide of the phase shifter array group 89 of the phase shifter array unit 94 are connected so as to be aligned at the joint surface 91.
[0074]
Further, each demultiplexing (output) side port of the 1 × 6 wavelength demultiplexing arrayed waveguide grating group 86 and each demultiplexing (input) side port of the 6 × 1 wavelength demultiplexing arrayed waveguide grating group 87 are phase-shifted. The respective wavelengths are connected via a shifter array group 89. The phase shifter array group 89 is configured by arranging a plurality of phase shifter waveguides made of lithium niobate and two electrodes provided for the phase shifter waveguides, similarly to the phase shifter unit 4B of the second embodiment. A phase modulator based on the electro-optic effect is configured by using these electrodes as a phase modulation means.
[0075]
In this embodiment, the quartz-based optical waveguide was used from the viewpoint that the optical demultiplexing unit and the optical multiplexing / demultiplexing unit were easy to produce and the propagation loss was low. However, the same applies when an InP compound or a SiON optical waveguide was used. It is possible to get the effect. Further, although the phase shifter array is made of an optical waveguide made of lithium niobate, the same effect can be obtained by replacing it with an optical waveguide capable of realizing a phase shifter having other high-speed response characteristics, for example, a KTP waveguide having an electro-optical effect. It is possible. In this embodiment, an arrayed waveguide grating is used as a wavelength multiplexer / demultiplexer. However, similar effects can be obtained by using a wavelength multiplexer / demultiplexer configured by a lattice filter or a transversal filter.
[0076]
FIG. 11 shows the measurement results of the output spectrum before and after switching the optical frequency in the output waveguide of the optical wavelength router of the present embodiment.
As shown in FIGS. 11A and 11B, in the initial state (before switching), the light waves having the optical frequency f3 = 193.1 THz and the optical frequency f6 = 193.4 THz are supplied to the output waveguide 83 and the optical frequency f4. The lightwave of 193.2 THz is output to the output waveguide 84. In this state, when the lightwave of the optical frequency f6 is switched to the output waveguide 84, only the lightwave of the optical frequency f3 = 193.1 THz is output to the output waveguide 83, as shown in FIGS. A light wave having an optical frequency f6 = 193.4 THz is output to the output waveguide 84 in addition to the optical frequency f4 = 193.2 THz, which indicates that a predetermined optical frequency has been routed to the predetermined output waveguide. At this time, good characteristics such as an extinction ratio of 32 dB and a loss of 8 dB were obtained for each channel.
[0077]
FIG. 12 shows a measurement result of a transient response characteristic when the output of the light wave of the optical frequency f6 is switched from the output waveguide 83 to the output waveguide 84.
As can be seen from FIG. 12, the response time is as fast as 1 ns for both rising and falling of the output from each output waveguide, and it is understood that high-speed optical wavelength routing is realized.
[0078]
(Example 5)
FIG. 13 is a schematic diagram of an optical switch showing still another example of the embodiment according to the present invention. The details of the configuration, operation, and characteristics of a 1 × 4 channel (channel) optical switch will be described as an example. I do.
[0079]
As shown in FIG. 13, the 1 × 4ch optical switch of the present embodiment is also configured using a planar lightwave circuit such as a silica-based optical waveguide 1, and includes an input branching section 2B, an output branching section 3B, and a phase It is composed of a shifter section 4A.
The input branching section 2B includes an input waveguide 5 serving as an input section input waveguide for inputting light waves, an optical directional coupler 95, 96 connected to the input waveguide 5, and phase shifters 97, 98 sandwiched therebetween. Directional coupler 99 using a Mach-Zehnder interferometer composed of:, connecting waveguides 7 and 8 connected to the variable directional coupler 99, and a second-stage optical directional coupler connected to the connecting waveguides 7 and 8 9 and 10, and four input output waveguides connected to two outputs of the second-stage optical directional couplers 9 and 10, respectively. In the input branching unit 2B, the light wave incident from the input waveguide 5 is first branched to the connection waveguides 7 and 8 by the variable directional coupler 99, and the light wave from the connection waveguide 7 is further converted to the phase shifter unit 4A. The light wave from the connection waveguide 8 to the phase shifter waveguides 11 and 12 is branched to the phase shifter waveguides 13 and 14. Here, a variable directional coupler 99 by a Mach-Zehnder interferometer having a coupling rate adjusting means is incorporated as an input section branching means in front of the second-stage optical directional couplers 9 and 10 so that an appropriate coupling rate can be obtained. (Branch ratio) is set so that the output can be appropriately output to each output waveguide (see FIG. 14 for details).
[0080]
The phase shifter section 4A has the same configuration as that shown in the first embodiment, and has four phase shifter waveguides 11 to 14 and thin film heaters 15 to 18 disposed thereon. are doing. The four outputs from the input branching unit 2B are connected to the phase shifter waveguides 11 to 14, respectively, and independently control the phases of the light waves propagating through each phase shifter waveguide using the thin film heaters 15 to 18. Can control.
[0081]
The output branching section 3B has four output section input waveguides, which are connected to the phase shifter waveguides 11 to 14 of the phase shifter section 4A. The phase shifter waveguides 11 and 12 are connected to two inputs of a third-stage optical directional coupler 19, and the phase shifter waveguides 13 and 14 are connected to two inputs of a third-stage optical directional coupler 20. Is done. One output of the third-stage optical directional coupler 19 and one output of the third-stage optical directional coupler 20 are connected to two outputs of the fourth-stage optical directional coupler 27 via the connection waveguides 21 and 23. Connected to input. The other output of the third-stage optical directional coupler 19 and the other output of the third-stage optical directional coupler 20 are connected to the fourth-stage optical directional coupler 28 via the connection waveguides 22 and 24. Connected to two inputs. Finally, the fourth-stage optical directional couplers 27, 28 are connected to output waveguides 29, 30, 31, 32, which are output section output waveguides. Here, the output unit combining / branching means includes third-stage optical directional couplers 19 and 20, connecting waveguides 22 to 24, and fourth-stage optical directional couplers 27 and 28.
[0082]
In the output multiplexing / branching unit 3B, the light waves from the phase shifter waveguides 11 and 12 are multiplexed by the third-stage optical directional coupler 19, and are coupled to one of the connection waveguides 21 and 22. The light waves from 14 are multiplexed by the third-stage optical directional coupler 20 and propagate to one of the connection waveguides 23 and 24. Therefore, when the light wave from the third-stage directional coupler 19 is propagated to the connection waveguide 21 and the light wave from the third-stage directional coupler 20 is propagated to the connection waveguide 23, the light wave is transmitted in the fourth-stage direction. The light propagates to the sexual coupler 27 and is emitted to one of the output waveguides 29 and 30. When the light wave from the third-stage directional coupler 19 is propagated to the connection waveguide 22 and the light wave from the third-stage directional coupler 20 is propagated to the connection waveguide 24, the light wave is transmitted in the fourth-stage direction. The light propagates to the sexual coupler 28 and is emitted to one of the output waveguides 31 and 32.
[0083]
In the optical switches according to the present invention described in the first and second embodiments, if the branching ratio of each optical directional coupler deviates from 1: 1, the extinction ratio is deteriorated. Therefore, as a countermeasure, in the present embodiment, the first-stage splitter is a variable splitter, that is, a variable directional coupler 99 using a Mach-Zehnder interferometer. The operation characteristics of the optical switch having such a configuration will be described with reference to FIG.
[0084]
FIG. 14 shows the calculation of the branching ratio of the variable optical directional coupler and the output power at each output waveguide when the branching ratio of each optical directional coupler is not 1: 1 in the optical switch of this embodiment. This is the result.
Here, in the optical switch shown in FIG. 13, the branching ratio of each of the optical directional couplers 9, 10, 19, 20, 27, 28, 95, and 96 is intentionally given an error from 1: 1. Simulate characteristic degradation due to unpredictable process errors that can occur during fabrication. Specifically, the branching ratio is set to 55:45, the path is set to the output waveguide 30, and the output power of each output waveguide 29, 30, 31, 32 with respect to the branching ratio of the variable optical directional coupler 99 is set. Calculated.
[0085]
As can be seen from FIG. 14, when all the optical directional couplers 9, 10, 19, 20, 27, 28, 95, 96 and the variable optical directional coupler 99 have the same 55:45 branching ratio, the output The crosstalk of about −25 dB can be ensured for the waveguides 31 and 32, while the crosstalk of −21 dB can only be ensured for the output waveguide 29. This corresponds to the occurrence of a manufacturing deviation in the optical directional coupler in the optical switch without the variable optical directional coupler shown in the first embodiment.
[0086]
On the other hand, when the first-stage optical directional coupler is the variable optical directional coupler 99 and the coupling ratio is set from 41% to 51%, the crosstalk to the output waveguides 31 and 32 changes by approximately -25 dB. On the other hand, the crosstalk to the output waveguide 29 can be reduced to -25 dB or less. This is because, in the optical switch shown in FIG. 13, in the outermost Mach-Zehnder interferometer constituted by the variable optical directional coupler 99 and the optical directional coupler 27, the connection guide to the optical directional coupler 27 is obtained. This is because the intensity of the light wave propagating through the wave paths 21 and 23 can be realized by setting the branching ratio of the variable light directional coupler 99 so as to match the coupling ratio of the light directional coupler 27. Therefore, at least one of the first stage of the multi-stage input branching unit 2B or the last stage of the multi-stage output branching unit 3B is configured using a variable optical directional coupler by a Mach-Zehnder interferometer. Further, the input branching unit may be configured by connecting a Mach-Zehnder interferometer having a coupling ratio adjusting function in multiple stages, and the output combining / branching unit may be configured by connecting a Mach-Zehnder interferometer having a coupling ratio adjusting function in multiple stages. May be configured by connecting to In particular, when only the first stage of the input section branching means is a variable optical directional coupler as in this embodiment, the number of adjustment points can be reduced, and the crosstalk performance can be efficiently improved.
[0087]
In the optical switch of the present embodiment, the number of phase shifters and the amount of power supply are increased as compared with the optical switch of the first embodiment, but the power applied to the phase shifters 97 and 98 constituting the variable optical directional coupler is In the case of a situation, the power is very small corresponding to the manufacturing deviation of the optical directional coupler 27. Therefore, the advantage of the present invention is that the constant power consumption characteristic, which is one of the effects of the present invention, is not significantly impaired. Rather, the provision of only one variable optical directional coupler improves crosstalk, which is the main performance of the optical switch. This contributes to improving the yield of devices.
[0088]
【The invention's effect】
The outline of the effects of the present invention is as follows.
That is, according to the present invention, the power consumption of the 1 × Nch optical switch utilizing the thermo-optic effect can be kept constant regardless of the setting state of the output path. Therefore, in other optical circuit components, for example, in an optical wavelength routing device realized by combining an optical switch with an arrayed waveguide grating or the like, even if the other optical circuit components have temperature-dependent optical characteristics. Even if the switching operation to any output waveguide is performed, the operation can be accurately performed without affecting the characteristics.
[0089]
In addition, according to the present invention, high-speed optical switching is possible by replacing the thermo-optical phase shifter with a high-speed phase shifter, for example, a phase shifter using an optical waveguide such as lithium niobate that can use the electro-optical effect. It becomes. This is due to the feature that the optical switch according to the present invention has a configuration in which the phase shifters are arranged in a line unlike the tree type optical switch and the tap type optical switch.
[0090]
Further, according to the present invention, the phase shifter of the optical switch is replaced by a wavelength demultiplexer having the number of switch channels, a phase shifter having the number of switch channels × the number of wavelengths, and a wavelength multiplexer having the number of switch channels. Thus, it is possible to realize an optical wavelength router in which power consumption does not fluctuate in setting an arbitrary wavelength path, that is, in which characteristics of the wavelength multiplexer / demultiplexer do not fluctuate.
[0091]
Further, according to the present invention, the phase shifter section of the optical switch is replaced with a wavelength splitter having the number of switch channels, a high-speed phase shifter having the number of switch channels × the number of wavelengths, and a wavelength multiplexer having the number of switch channels. This enables high-speed optical wavelength routing.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of an optical switch according to a first embodiment of the present invention.
FIG. 2 is a diagram showing a relationship between phases given to light waves in each thin film heater when the light is output to each output waveguide of the optical switch according to the first embodiment.
FIG. 3A is a graph of propagation loss in each output waveguide of the optical switch according to the first embodiment,
(B) is a graph showing the extinction ratio with another output waveguide when the output is set to the output waveguide 30.
FIG. 4 is a schematic view of an optical switch according to a second embodiment of the present invention.
FIG. 5 is a graph illustrating a measurement result of a transient response characteristic of the optical switch according to the second embodiment.
FIG. 6A is a graph of a propagation loss in each output waveguide of the optical switch according to the second embodiment,
(B) is a graph showing the extinction ratio with another output waveguide when the output is set to the output waveguide 30.
FIG. 7 is a schematic diagram of an optical wavelength router according to a third embodiment of the present invention.
FIG. 8 is a diagram illustrating an example of setting an output waveguide from which light waves of each frequency are output and a phase shifter amount between connection waveguides at that time in the optical wavelength router according to the third embodiment.
FIG. 9 is a graph showing a spectrum measured at each output waveguide when the amount of phase shifter is set in FIG. 8 in the optical wavelength router according to the third embodiment.
FIG. 10 is a schematic diagram of an optical wavelength router according to a fourth embodiment of the present invention.
FIG. 11 is a graph showing measured output spectra before and after switching the optical frequency in the output waveguide of the optical wavelength router according to the fourth embodiment.
FIG. 12 is a graph showing a measurement result of a transient response characteristic when the output of a light wave having a predetermined optical frequency is switched to a different output waveguide in the optical wavelength router according to the fourth embodiment.
FIG. 13 is a schematic view of an optical switch according to a fifth embodiment of the present invention.
FIG. 14 is a diagram illustrating calculation of the branching ratio of the variable optical directional coupler and the output power of each output waveguide when the branching ratio of each optical directional coupler is not 1: 1 in the optical switch according to the fifth embodiment. It is a figure showing a result.
FIG. 15 is a schematic diagram of a conventional 1 × 8ch tree type optical switch using TOSW.
FIG. 16 is a graph showing a measurement result of a transient response characteristic of a Mach-Zehnder interferometer using a thermo-optic effect.
FIG. 17 is a schematic diagram of a conventional optical wavelength router for routing a wavelength division multiplexed signal.
FIG. 18 is a graph showing a change in the output spectrum at the center wavelength of the output multiplexed arrayed waveguide grating when a temperature change corresponding to the power applied to the TOSW is applied to the substrate in the conventional optical wavelength router.
[Explanation of symbols]
1 Silica-based optical waveguide
2A input branch
3A output branching section
4A phase shifter
5 Input waveguide
6. First-stage optical directional coupler
7,8 Connecting waveguide
9, 10 Second-stage optical directional coupler
11-14 Phase shifter waveguide
15-18 Thin film heater
19, 20 Third-stage optical directional coupler
21-24 connecting waveguide
25, 26 cross waveguide
27, 28 Fourth-stage optical directional coupler
29-32 Output waveguide

Claims (14)

In an optical switch configured on a plane lightwave circuit,
An input branching unit for branching an input lightwave, an output branching unit for branching the lightwave, and a phase shifter unit sandwiched between the input branching unit and the output branching unit and modulating a phase of the lightwave. Consisting of
The input branch unit includes at least one input unit input waveguide, N input unit output waveguides, and a light wave input from one input unit input waveguide, and outputs the N input unit output waveguides. Having an input section branching means for branching to equal strength to all of the waveguides,
The output combining / branching unit converts the lightwave input to any one of the N output unit input waveguides, the N output unit output waveguides, and the N output unit input waveguides into N Output section branching means for branching to equal strength to all of the output section output waveguides of the book,
The phase shifter section is provided in each of the phase shifter waveguides that connect the N input section output waveguides and the N output section input waveguides on a one-to-one basis, and the phase shifter waveguides. An optical switch comprising: a phase modulation unit. In an optical wavelength router configured on a plane lightwave circuit,
An input branching unit for branching an input lightwave, an output branching unit for branching the lightwave, and a phase shifter unit sandwiched between the input branching unit and the output branching unit and modulating a phase of the lightwave. Consisting of
The input branch unit includes at least one input unit input waveguide, N input unit output waveguides, and a light wave input from one input unit input waveguide, and outputs the N input unit output waveguides. Having an input section branching means for branching to equal strength to all of the waveguides,
The output combining / branching unit converts the lightwave input to any one of the N output unit input waveguides, the N output unit output waveguides, and the N output unit input waveguides into N Output section branching means for branching to equal strength to all of the output section output waveguides of the book,
The phase shifter unit includes at least (N) input connection waveguides connected to the N input unit output waveguides, and at least one input and M outputs connected to the input connection waveguide. N-1) wavelength demultiplexers, connected to the wavelength demultiplexer, at least (N-1) × M phase shifter waveguides, connected to the phase shifter waveguide, and M inputs And at least (N-1) wavelength multiplexers having one output, and N output connection waveguides connecting the wavelength multiplexer and the N output section input waveguides; An optical wavelength router comprising: a phase shifter provided in each of the phase shifter waveguides. 3. The optical wavelength router according to claim 1, wherein a phase modulator based on a thermo-optic effect is used as the phase modulating means. 3. The optical switch according to claim 1, wherein the phase modulator includes a phase modulator based on an electro-optic effect. 4. The optical switch according to claim 1, wherein the input branching unit, the output combining / branching unit, and the phase shifter unit are configured by a silica-based optical waveguide. 5. Optical wavelength router as described. The optical switch according to claim 1, wherein the phase modulation unit is made of lithium niobate, or the optical wavelength router according to claim 2 or 4. The input section branching means is configured by connecting a 50% coupling optical directional coupler or a 1x2 branch multi-mode interference coupler in multiple stages. 7. The optical switch according to claim 6, or the optical wavelength router according to claim 2 and claim 3. 4. The output section multiplexing / branching means is configured by connecting a 50% coupling optical directional coupler or a 2 × 2 multiplexing / branching multimode interference coupler in multiple stages. The optical switch according to any one of claims 1 to 6, or the optical wavelength router according to any one of claims 2 and 3 to 6. 7. The input unit branching unit according to claim 1, wherein a Mach-Zehnder interferometer having a coupling ratio adjusting function is configured in a multi-stage connection. An optical switch or an optical wavelength router according to any one of claims 2 and 3 to 6. 7. The output unit combining / branching unit according to claim 1, wherein a Mach-Zehnder interferometer having a coupling rate adjusting function is configured by being connected in multiple stages. 7. The optical wavelength router according to claim 2, or the optical wavelength router according to claim 3. The first stage of the multi-stage 50% coupled optical directional coupler or the 1 × 2 branch multimode interference coupler, or the multi-stage 50% coupled optical directional coupler or the 2 × 2 branch. 9. The optical switch according to claim 7, wherein at least one of the last stages of the multi-mode interference coupler is configured using a variable optical directional coupler using a Mach-Zehnder interferometer. The optical wavelength router according to claim 8. Either a 50% coupled optical directional coupler constituting the input branching unit, a 1 × 2 branch multimode interference coupler or a Mach-Zehnder interferometer having a coupling ratio adjusting function, and a 50% coupled light constituting the output combining / branching unit An arbitrary Mach-Zehnder interferometer using either a directional coupler, a 2 × 2 branch multi-mode interference coupler or a Mach-Zehnder interferometer having a coupling ratio adjustment function as two couplers has an optical path length difference of zero. The optical switch according to any one of claims 7 to 11, or the optical wavelength router according to any one of claims 7 to 11, wherein: 7. The optical switch or claim according to claim 1, wherein said input section branching means is constituted by a 1 × N branching multi-mode interference optical coupler. 7. The optical wavelength router according to claim 2, and any one of claims 3 to 6. 7. The optical switch or claim according to claim 1, wherein said output unit combining / branching means is constituted by an N.times.N branch multimode interference optical coupler. 7. The optical wavelength router according to claim 2, and any one of claims 3 to 6.

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