Optical switch unit

Abstract

An optical switch unit is constituted by: a first optical switch having one signal input port for inputting a signal and L signal output ports for outputting a signal; a second optical switch having one signal input port for inputting a signal and M signal output ports for outputting a signal; and a third optical switch having N signal input ports for inputting a signal and one signal output port for outputting a signal. An optical switch unit including at least the first optical switch, the second optical switch, and the third optical switch is integrated. L, M, and N are natural numbers of 2 or greater, and at least one of L, M, and N is a natural number different from the other two.

Description

Optical Switch Unit

[0001] The present disclosure relates to an optical transmission device, and more particularly to an optical switch unit including a plurality of optical switches.

[0002] With the spread of the Internet, the demand for data communication networks is rapidly increasing. To meet this rapidly increasing demand, optical communication networks capable of transmitting large volumes of data with low power consumption are widely deployed in data communication networks. In such optical communication networks, in addition to the function of directly connecting two points, flexible routing can be achieved by using optical transmission equipment that applies optical switches.

[0003] As an example of an optical transmission device that applies such an optical switch, a configuration of an optical transmission device called a CDC-ROADM (Colorless, Directionless, Contentionless-Reconfigurable Optical Add Drop Multiplexer) is widely used (see, for example, Non-Patent Document 1). As another example of an optical transmission device that applies an optical switch, in order to simplify the device configuration of the optical transmission device, a configuration is known in which path switching is performed not only in units of signal wavelengths but also in units of wavelength bands consisting of multiple signal wavelengths (see, for example, Non-Patent Document 2).

[0004] T. Watanabe, K. Suzuki and T. Takahashi: "Silica-based PLC transponder aggregators for colorless, directionless, and contentionless ROADM," Optical Fiber Communication Conference (OFC), Paper OTh3D.1 (2012). O. Moriwaki et al., "Terabit-scale hierarchical compact optical cross-connect system employing PLC devices and optical backplane," 2010 Conference on Optical Fiber Communication (OFC / NFOEC), collocated National Fiber Optic Engineers Conference, Paper PDPC9 (2010).

[0005] In such optical transmission equipment, one possible configuration for increasing the amount of data that can be transmitted over a single optical fiber is to broaden the wavelength band used for transmission. Generally, the wavelength band used for transmission is determined by optical devices that have limitations on the wavelengths that can be used, and in many cases, the wavelength range that can be amplified by an optical amplifier coincides with the wavelength band used for transmission. In this case, broadening the wavelength band used for transmission means using multiple types of optical amplifiers that can be used for different wavelength ranges for optical transmission. Therefore, by including a wavelength group demultiplexer and a wavelength group multiplexer in the optical transmission equipment and matching the wavelength range that can be amplified with the wavelength group, a configuration that facilitates the use of multiple types of optical amplifiers can be achieved.

[0006] However, individual optical switches used in such optical transmission devices are configured such that failure or replacement of the optical switch can affect the signals of all input / output ports. This poses a problem in that when an optical switch fails or is replaced, the process for restoring the switch to its original state becomes complicated. The present disclosure has been made in light of this problem, and relates to an optical switch unit that does not affect the signals of other input / output ports when an optical switch fails or is replaced.

[0007] FIG. 1 is a schematic top view for explaining the concept of an optical switch unit according to an embodiment of the present disclosure; FIG. 2 is a schematic top view of an optical transmission device including the optical switch unit according to the first embodiment; FIG. 3 is a diagram for explaining an example in which optical switches according to the first embodiment are integrated; FIG. 4 is a schematic top view of an optical transmission device including the optical switch unit according to the second embodiment; FIG. 5 is a schematic top view of an optical transmission device including the optical switch unit according to the third embodiment; FIG. 6 is a schematic top view of an optical transmission device including the optical switch unit according to the fourth embodiment; and FIG. 7 is a diagram for explaining a comparative example related to the present embodiment.

[0008] Hereinafter, first, second, and third embodiments of the optical switch unit of the present disclosure (hereinafter also collectively referred to as "the present embodiment") will be described with reference to the drawings. The purpose of the drawings is to explain the configuration, arrangement of each part, action, effect, function, technical concept, etc. of the present embodiment. Therefore, the drawings of the present embodiment are intended to exemplify the invention and do not specifically limit the shape or design.

[0009] (Concept) FIG. 1 is a schematic top view illustrating the concept of the optical switch unit of this embodiment, showing an optical transmission device 100 including three optical switch units 101. Each optical switch unit 101 shown in FIG. 1 includes optical switches 307, 310, and 311 and an optical filter 309. This embodiment is configured by integrating some or all of the optical switches 307, 310, and 311 and the optical filter 309 included in the three optical switch units 101. The optical transmission device 100 further includes a wavelength band demultiplexer 303 and an optical amplifier 304 before and after each optical switch unit 101, and further includes a wavelength cross-connect function unit 308 that connects the inputs and outputs of the optical switches 307 and 311 of each optical switch unit 101. The optical switch units 101, the wavelength band demultiplexer 303, and the optical amplifier 304 realize a circuit that switches paths for each signal wavelength band. Such a configuration will be described below.

[0010] The wavelength band demultiplexer 303 is a demultiplexer that demultiplexes an externally input wavelength-multiplexed signal into optical signals of two or more wavelength bands. The optical amplifier 304 amplifies each of the optical signals of the wavelength bands output from the wavelength band demultiplexer 303. The wavelength cross-connect function unit 308 is a device that relays optical signals in an optical fiber network, switching connection destinations according to the signal output destination and performing signal branching, joining, and the like. The wavelength cross-connect function unit 308 of this embodiment is configured to realize a path control function for optical signals on a wavelength-by-wavelength basis. However, although the optical transmission device 100 of this embodiment includes other circuits having input ports and output ports in addition to the optical switch unit 101, the other circuits are not limited to the wavelength cross-connect function unit 308 and may be any circuits.

[0011] The optical filter 309 may be a variable optical filter whose filter characteristics can be electrically changed, or a fixed optical filter whose filter characteristics are fixed. Examples of variable optical filters include a variable wavelength filter that changes the transmission wavelength of the filter by applying a voltage, and a filter whose filter characteristics are controlled using liquid crystal or MEMS (microelectromechanical systems). Examples of fixed optical filters include a bandpass filter that passes light of a specific wavelength and blocks light of other wavelengths, and a filter that compensates for the wavelength dependence of the gain of the optical amplifier 304 to flatten the gain.

[0012] In particular, the optical filter 309 may be configured by a circuit that changes the loss transmission spectrum by being driven using the thermo-optic effect. Examples of such optical filters include a thermo-optic tunable filter, an optical thermal switch, and a thermo-optic tunable diffraction grating.

[0013] The optical switch unit 101 will now be described. The optical switch 307 included in the optical switch unit 101 is an optical switch having one input port (hereinafter also referred to as "1 input") and L output ports (hereinafter also referred to as "L outputs"). The optical switch 310 is an optical switch with 1 input and M outputs, and the optical switch 311 is an optical switch with N inputs and 1 output.

[0014] 1, the optical transmission device 100 has one input port Pin and one output port Pout (hereinafter collectively referred to as "path"). The input port Pin inputs a wavelength-multiplexed signal from the outside, and the output port Pout outputs a wavelength-multiplexed signal to the outside. However, in this embodiment, any number of input ports Pin and output ports Pout may be arranged in the optical transmission device 100 depending on the design.

[0015] The input port of the optical switch 307 is connected to the output port of the optical amplifier 304. In this embodiment, one of the output ports of the optical switch 307 is connected to the input port of the optical filter 309. The other output port is connected to the wavelength cross-connect function unit 308. The output port of the optical filter 309 is connected to the input port of a 1-input, M-output optical switch 310. The output port of the optical switch 310 is connected to the input port of an N-input, 1-output optical switch 311. Furthermore, the input port of the optical switch 311 is connected to the output port of the wavelength cross-connect function unit 308. The output port of the optical switch 311 is connected to the input port of the wavelength band multiplexer 313. The example shown in FIG. 1 shows the case where L=2 and N=M+1. N is M+1 because the optical transmission device 100 has one wavelength cross-connect function unit 308. N is not limited to M+1, but becomes M+n, where n is the number of output ports of devices other than the optical switch unit 101, such as the wavelength cross-connect function unit 308, added to M. Here, it is preferable that n is the number of output ports of devices other than the optical switch unit 101, such as the wavelength cross-connect function unit 308, be equal to L-1.

[0016] The natural number M is determined by the number of directions of the optical transmission device 100. If the number of directions is X, then the number of output ports M of the optical switch 310 should be equal to or greater than X. Here, the number of directions M of the optical transmission device 100 may be three: an input port, an output port that outputs a signal to another optical transmission device, and an output port that returns the output signal to itself (the optical transmission device 100). Furthermore, if the signal is not returned to itself, the minimum number of directions of the optical transmission device 100 is X-1, which is one less. Therefore, in the example shown in FIG. 1, L = 2, M = 2, and N = 3 (2 + 1).

[0017] In this embodiment, of the three natural numbers L, M, and N, for example, if the number of output ports of the optical switch 310 is set to M and the number of input ports N of the optical switch 311 is set to N=M+1, then when L and M are equal, at least one of M, L, and N (here, M) will be different from the other two. Also, when L and M are different, all of L, M, and N will be different from each other. The number M of routes in the optical transmission device 100 is arbitrary, and in this embodiment, at least one of the natural numbers L, M, and N will be different from the other two, regardless of the number of routes M. However, in this embodiment, N is greater than L and M in all cases.

[0018] When a wavelength-multiplexed signal is input from outside the optical transmission device 100, the wavelength-multiplexed signal is demultiplexed into two or more wavelength bands by the wavelength band demultiplexer 303. Each of the demultiplexed optical signals in the wavelength bands is input to an optical amplifier 304 configured to be capable of amplifying the optical signal in the wavelength band, and amplified. As a combination of wavelength band and optical amplifier 304 configuration, for example, if the wavelength band is the C band, the optical amplifier 304 may be a C-band EDFA or a C-band lumped Raman amplifier. If the wavelength band is the L band, the optical amplifier 304 may be an L-band EDFA or an L-band lumped Raman amplifier. Furthermore, if the wavelength band is the S band, the optical amplifier 304 may be a thulium-doped fiber amplifier (TDFA) or an S-band lumped Raman amplifier. Note that, although three optical amplifiers 304 are provided in the example shown in FIG. 1 , this embodiment is not limited to this example, and any optical amplifiers 304 may be used. The wavelength ranges that the optical amplifiers 304 can amplify may differ from one another.

[0019] The optical signals of the wavelength bands amplified by the optical amplifiers 304 are input to the corresponding optical switches 307. The optical switches 307 input the input optical signals of the wavelength bands to either the wavelength cross-connect function unit 308 or the optical filter 309, depending on the user's selection. In other words, the optical switches 307 are configured so that the user can select (control) whether the amplified optical signals of the wavelength bands are propagated to the wavelength cross-connect function unit 308 or the optical filter 309.

[0020] The optical filter 309 amplifies the optical signal of the input wavelength band and inputs it to the input port of the optical switch 310. The output port of the optical switch 310 is connected to the input port of the optical switch 311 or the output port of the wavelength cross-connect function unit 308. Therefore, the optical switch 311 is configured so that the user can select (control) and output either the optical signal that has passed through the wavelength cross-connect function unit 308 or the optical signal that has been input from a desired input route and passed through the optical filter 309, out of the optical signals of the corresponding wavelength band. Each output port of the optical switch 311 is connected to the input port of the wavelength band multiplexer 313. The wavelength band multiplexer 313 multiplexes and outputs optical signals of multiple wavelength bands.

[0021] As described above, the optical transmission device 100 of this embodiment is provided with optical switch units 101a, 101b, and 101c, each for a different wavelength band. Therefore, because each optical switch unit that processes a wavelength band is independent, replacing one optical switch unit does not affect the processing of the optical switch units for other wavelength bands. Furthermore, because the device for one path from the input port Pin to the output port Pout is independent from the devices for other paths, replacing one device for one path does not affect the processing of the devices for other paths. Furthermore, even when signals do not pass through the wavelength cross-connect function unit 308, which performs routing control on a wavelength-by-wavelength basis, the optical filter 309 can perform optical adjustments for individual signals. Therefore, the optical switch circuit of this embodiment is capable of performing optical adjustments, such as optical level adjustments, for individual signals when routing control is performed on a wavelength-by-wavelength basis.

[0022] First Embodiment FIG. 2 is a schematic top view of an optical transmission device 300 including an optical switch unit 301 according to a first embodiment. In the first embodiment, the integrated components of the switch unit 301 are shown in white, and the other components are shown in gray. As shown in FIG. 2, the optical switch unit 301 is integrated to include one 1-input, L-output optical switch 307, one 1-input, M-output optical switch 310, and one N-input, 1-output optical switch 311. Note that while FIG. 2 shows one optical switch unit 301, the first embodiment may also include two more optical switch units 301 using the other optical switches 307, 310, and 311.

[0023] Here, L, M, and N are all natural numbers greater than or equal to 2, and at least one of the natural numbers L, M, and N is different from the other two. That is, the optical switch unit 301 of the first embodiment is different from a configuration in which three optical switches of the same configuration are integrated. Here, the natural numbers L, M, and N are greater than or equal to 2, for example, L=2, M=the number of directions in the optical transmission device, and N=the number of directions in the optical transmission device+1.

[0024] The optical transmission device 300 of the first embodiment does not loop back the output signal, so the number of routes is M = 2. With this configuration, as shown in Fig. 2, the main part of the optical transmission device 300 can be configured to have one input / output for connection with the wavelength cross-connect function unit 308 for each route and each wavelength band, and to output the input signal of the wavelength band to any port. Here, the "integration" of the first embodiment will be described.

[0025] 3 is a diagram illustrating an example of integrating the optical switch of the first embodiment shown in FIG. 3 shows an example in which an optical switch is formed using a Mach-Zehnder optical waveguide on a substrate 701. In this example, a planar lightwave circuit (PLC) is configured that includes optical switches 307, 310, and 311. In the first embodiment, for example, the substrate 701 is a quartz-based substrate, and the optical switches 307, 310, and 311 are integrated on the substrate 701 to configure a quartz-based planar lightwave circuit.

[0026] When the optical switches 307, 310, and 311 are integrated without the optical filter 309 between the optical switches 307 and 310, the optical fiber f is drawn out from the optical switch 307 to the outside of the planar lightwave circuit, connected to the optical filter 309 via the optical fiber f, and also connected to the output of the optical filter 309 via the optical fiber f drawn out from the input port of the optical switch 310, thereby realizing the optical switch unit 101. The first embodiment, which includes the optical filter 309 externally, can optically adjust the optical signal in wavelength units while controlling the path of the optical signal in wavelength band units.

[0027] The first embodiment described above corresponds to a switch function for one wavelength band of one input / output path among the components of the optical transmission device 300, so even if an optical switch fails, the impact is limited to one path and one wavelength band. With this configuration, it is possible to minimize the scope of the impact of a failure and replace only the failed optical switch while maintaining the communication function of the non-failed paths.

[0028] Since the integrated optical switch corresponds to a switch function for one wavelength band, the operating wavelength band of the optical switch may be optimized for one specific wavelength band, and optical switches optimized for each wavelength band may be provided for each wavelength band used in the optical transmission device 300. Alternatively, the operating wavelength band of the optical switch may be set to cover all wavelength bands used in the optical transmission device 300, so that the optical switch can be used in any wavelength band.

[0029] Second Embodiment Fig. 4 is a schematic top view of an optical transmission device 400 including an optical switch unit 401 according to a second embodiment. In the second embodiment, the integrated configuration is shown in white in Fig. 4, and other configurations are shown in gray. In the second embodiment, as shown in Fig. 4, three 1-input, L-output optical switches 307, three 1-input, M-output optical switches 310, and three N-input, 1-output optical switches 311 constitute the optical switch unit 401, and multiple optical switches are integrated together.

[0030] In the second embodiment, the optical switch unit 401 is also configured by integrating a plurality of units u1 (for example, A units), each of which is an optical switch 307, 310, or 311. The integrated optical switch unit 401 of the second embodiment corresponds to the switch function for A wavelength bands, and may be optimized according to the wavelength band of signals that transmit the operating wavelength band of the optical switch 307, etc. Furthermore, the operating wavelength band of the optical switch unit 401 may be configured to cover all wavelength bands used in the optical transmission device 400, so that it can be used in any wavelength band.

[0031] The integrated optical switch unit 401 corresponds to the switch function for A wavelength bands of one input / output route among the components of the optical transmission device 400, so even if an optical switch fails, the impact is limited to one route and A wavelength bands. Therefore, the second embodiment minimizes the scope of the impact in the event of a failure and can replace the failed optical switch while maintaining the communication function of the non-failed routes.

[0032] Third Embodiment Fig. 5 is a schematic top view of an optical transmission device 500 including an optical switch unit 501 according to a third embodiment. In Fig. 5, the integrated configuration of the optical switch unit 501 is shown in white, and other configurations are shown in gray. Note that although Fig. 5 shows one optical switch unit 501, in the third embodiment, two more optical switch units 501 may be configured using other optical switches 307, 310, and 311 and an optical filter 309.

[0033] 5, in the third embodiment, one 1-input, L-output optical switch 307, one 1-input, M-output optical switch 310, one N-input, 1-output optical switch 311, and one optical filter 309 are integrated to form an optical switch unit 501. Note that while Fig. 5 shows one optical switch unit 501, in the third embodiment, two more optical switch units 501 may be formed using other optical switches 307, 310, 311 and optical filters 309.

[0034] The optical switch unit 501 including the optical filter 309 corresponds to a switch function for one wavelength band. Therefore, the optical switch unit 501 can optimize the operating wavelength band of the optical switch 307 including the optical filter 309, etc., to one specific wavelength band. The optical transmission device 500 may be provided with optical filters 309 optimized for each wavelength band used. As another embodiment, the operating wavelength bands of the optical switch 307, etc. may be set to cover all wavelength bands used in the optical transmission device 500, so that the optical switch unit 501 including the optical filter 309 can be used in any wavelength band.

[0035] In the third embodiment, the optical wiring between the optical switch 307 and the optical filter 309 and the optical wiring between the optical filter 309 and the optical switch 310 are also integrated, which is expected to have the effect of reducing the number of optical wirings in the optical transmission device 500. Furthermore, since the third embodiment also integrates the optical filter 309, it is possible to simplify the maintenance and repair of the configuration that can optically adjust the optical signal in wavelength units while controlling the path of the optical signal in wavelength band units.

[0036] In the optical switch units 301 and 401 that do not include the optical filter 309 described above, the order of connection of the optical switch 307 and the optical filter 309 is arbitrary and can be changed. However, in the third embodiment in which the optical switch 307, the optical switch 310, and the optical filter 309 are integrally integrated, the order of the optical switch 307, the optical filter 309, and the optical switch 310 along the light propagation direction is fixed at the time of designing the integrated circuit and cannot be changed.

[0037] Furthermore, in the third embodiment, as described above, the optical switches 307, 310, and 311 and the optical filter 309 are integrated on the substrate 701 to form a silica-based planar lightwave circuit. Furthermore, in the third embodiment, an optical filter utilizing the thermo-optic effect is used as the optical filter 309. With this configuration, it is possible to fabricate the optical switches 307, 310, and 311 and the optical filter 309 as a silica-based planar lightwave circuit, and an optical switch unit suitable for integration can be provided. For example, if a filter using a diffraction grating that propagates light in free space is used as the optical filter, it is difficult to integrate the optical filter with the optical switch.

[0038] 6 is a schematic top view of an optical transmission device 600 including an optical switch unit 601 according to a fourth embodiment. In FIG. 6, the integrated configuration of the optical switch unit 601 is shown in white, and other configurations are shown in gray. In the fourth embodiment, as shown in FIG. 6, the optical switch unit 601 is configured by integrating one 1-input, L-output optical switch 307, one optical filter 309, and one 1-input, M-output optical switch 310, with one optical filter 309 being a unit u2, and a plurality of units u2 (e.g., A units) are integrated.

[0039] The optical switch unit 601 corresponds to a switch function for A wavelength bands of one input / output path. Therefore, in the optical transmission device 600 equipped with the optical switch unit 601, even if an optical switch including an optical filter fails, the impact is limited to one path and A wavelength bands. In such an optical transmission device 600, the scope of the impact in the event of a failure is minimized, and the failed optical switch unit can be replaced while maintaining the communication function of the non-failed paths.

[0040] The optical switch unit 601 including the optical filter 309 supports a switch function for A wavelength bands, and therefore may be provided by optimizing the operating wavelength band of the optical switch including the optical filter 309 for the wavelength band of signals that transmit the operating wavelength band of the optical switch including the optical filter 309. As another provision method, the operating wavelength band of the optical switch including the optical filter 309 may be set to cover all wavelength bands used in the optical transmission device 600, so that the provided optical switch including the optical filter 309 can be used in any wavelength band with the same design.

[0041] (Comparative Example) Next, an optical transmission device serving as a comparative example will be described to explain the effects of the optical switch unit of the embodiment described above. Fig. 7 is a diagram showing the conceptual configuration of a known optical transmission device 200. The optical transmission device 200 has a configuration in which the path switching unit is not only for each signal wavelength, but also for each wavelength band consisting of multiple signal wavelengths. As shown in FIG. 7, the optical transmission device 200 includes P 1-input, Q-output wavelength band demultiplexers 210-1 to P (where P and Q are integers greater than or equal to 2), P Q-input, 1-output wavelength band multiplexers 220-1 to P, Q (P+R)-input, (P+R)-output optical switches 230-1 to Q (where Q is an integer greater than or equal to 2) provided for each wavelength band, R 1-input, S-output wavelength demultiplexers 240-q-1 to 240-q-R provided for the qth wavelength band optical signals (where q is an integer greater than or equal to 1 and less than or equal to Q) output from the optical switches 230-1 to Q, R S-input, 1-output wavelength multiplexers 250-q-1 to 250-q-R provided for the qth wavelength band, and Q×S 2R-input, 2R-output optical switches 260-1 to Q×S provided for each wavelength. 7 shows an example in which P = 2, Q = 5, S = 8, R = 2, and q = 1. In addition, in Fig. 1, the number of wavelengths of optical signals per fiber propagating through each transmission path (optical fiber) is shown in the speech bubble block.

[0042] An optical signal multiplexed with Q×S (5×8=40 in FIG. 7 ) different wavelengths is input from the outside to one of wavelength band demultiplexers 210-1 to 210-P (waveband demultiplexers 210-1 to 210-2 in FIG. 7 ) as an input optical signal to optical transmission device 200. Each of wavelength band demultiplexers 210-1 to 210-2 demultiplexes the optical signal multiplexed with Q×S=40 different wavelengths into optical signals of Q=5 different wavelength bands into which S=8 different wavelengths are multiplexed, and outputs the demultiplexed optical signals of Q=5 different wavelength bands from different ports. That is, the input signal light input to optical transmission device 200 is input to one of wavelength band demultiplexers 210-1 to 210-2 and demultiplexed into optical signals multiplexed with S=8 different wavelengths. Each of the demultiplexed optical signals of the five different wavelength bands is input to optical switches 230-1 to 230-Q (optical switches 230-1 to 230-5 in FIG. 7 ) via a transmission path.

[0043] Optical switches 230-1 to 230-5 are optical switches provided one for each optical signal in five wavelength bands. Each of optical switches 230-1 to 230-5 has (P + R) (in FIG. 7, 2 + 2 = 4) input ports, of which P = 2 input ports are connected to output ports of wavelength band demultiplexers 210-1 to 210-2 that output optical signals in the corresponding wavelength bands. For example, the first output port of wavelength band demultiplexer 210-1 is connected to the input port of optical switch 230-1, and the fifth output port of wavelength band demultiplexer 210-1 is connected to 230-5. Similarly, the first output port of wavelength band demultiplexer 210-2 is connected to the input port of optical switch 230-1, and the fifth output port of wavelength band demultiplexer 210-2 is connected to 230-5. Then, in each of optical switches 230-1 to 230-5, the optical signal in the input wavelength band is output from an arbitrary output port. The connection relationships of the remaining R input ports (that is, not connected to 210-1 to 210-Q) of the optical switches 230-1 to 230-Q will be described later.

[0044] Waveband multiplexers 220-1 to 220-P (waveband multiplexers 220-1 to 220-2 in FIG. 7) are connected to the output ports of the optical switches 230-1 to 230-5, and have the function of multiplexing optical signals of wavelength bands output from the optical switches 230-1 to 230-5 and outputting the multiplexed signals to the outside via a transmission path. Of the (P+R) output ports of the optical switches 230-1 to 230-5, P=2 output ports are connected to input ports of the wavelengthband multiplexers 220-1 to 220-2 that input signals of the corresponding wavelength bands. For example, the first output port of the optical switch 230-1 is connected to the input port of the wavelengthband multiplexer 220-1, and the second output port is connected to the input port of the wavelengthband multiplexer 220-2. Similarly, the first output port of the optical switch 230-5 is connected to the input port of the wavelengthband multiplexer 220-1, and the second output port is connected to the input port of the wavelengthband multiplexer 220-2. The optical signals of the wavelength bands output from the two output ports of the optical switches 230-1 to 230-5 are multiplexed by the wavelength band multiplexers 220-1 and 220-2, respectively, and output to the outside.

[0045] Each of optical switches 230-1 to 230-5 further includes R (2 in FIG. 7) output ports that are not connected to wavelength band multiplexers 220-1 to 220-2. Here, assuming q=1, and focusing on optical switch 230-1, which inputs and outputs optical signals in the first wavelength band, the R=2 output ports of optical switch 230-1 are input to wavelength demultiplexers 240-q-1 to q-R (wavelength demultiplexers 240-1-1 to 1-2 in FIG. 7), each with 1 input and S outputs (1 input, 8 outputs in FIG. 7). Each of wavelength demultiplexers 240-1-1 to 1-2 has the function of outputting S=8 wavelengths that make up the q=1 wavelength band from a different port. Similarly, when q=2, the R=2 output ports of switch 230-2 are input to wavelength demultiplexers 240-2-1 to 2-2 (not shown), each with 1 input and 8 outputs.

[0046] Optical switches 260-1 to 260-40 are 2R input / 2R output (4 input / 4 output in FIG. 7 ) optical switches, each provided for a wavelength demultiplexed by wavelength demultiplexers 240-q-1 to q-R, with R=2 input ports connected to output ports of wavelength demultiplexers 240-q-1 to 240-q-R that output optical signals of the corresponding wavelengths. For example, the output ports of wavelength demultiplexers 240-1-1 to 240-1-2 are input to optical switches 260-1 to 260-8, as shown in FIG. 7 . Similarly, wavelength demultiplexers 240-2-1 to 2-2 (not shown) are connected to optical switches 260-9 to 260-16.

[0047] Each of optical switches 230-1 to 230-5 further includes R (2 in FIG. 7) input ports that are not connected to wavelength band demultiplexers 210-1 to 210-2. Now, assuming q=1, focusing on optical switch 230-1, which inputs and outputs optical signals in the first wavelength band, the R input ports of optical switch 230-1 are connected to output ports of wavelength multiplexers 250-q-1 to 250-q-R (250-1-1 to 250-1-2 in FIG. 7), each with S inputs and 1 output (8 inputs and 1 output in FIG. 7). Wavelength multiplexers 250-1-1 to 250-1-2 have the function of multiplexing optical signals having different wavelengths and outputting optical signals in S=8 wavelength bands. The optical signals having different wavelengths are optical signals propagated from the R=8 output ports of optical switches 260-1 to 260-8. That is, the output ports of optical switches 260-1 to 260-8 are connected to the input ports of wavelength multiplexers 250-1-1 to 250-1-2. Similarly, the output ports of optical switches 260-9 to 260-16 are connected to the input ports of wavelength multiplexers 250-2-1 to 250-2-2 (not shown).

[0048] Each of the optical switches 260-1 to 260-40 further includes R=2 output ports that are not connected to the wavelength multiplexers 250-q-1 to 250-q-R. These output ports are connected to a group of optical signal receivers. Furthermore, the optical switches 260-1 to 260-40 further include R=2 input ports that are not connected to the wavelength demultiplexers 240-q-1 to 240-q-R. These input ports are connected to a group of optical signal transmitters. Note that FIG. 7 depicts a configuration in which the optical switch 260-1 is connected to the group of receivers and the group of transmitters by two optical fibers each (in other words, the group of receivers is composed of two receivers, and the group of transmitters is composed of two transmitters), but this is for illustrative purposes only, and any number of receivers and transmitters may be installed depending on the design.

[0049] The optical transmission device 200 having such a configuration is configured so that, after an input optical signal (wavelength multiplexed signal) input from a transmission path is demultiplexed into wavelength band units, it can be selected, by the routing settings of the optical switches 230-1 to 230-Q, whether the input optical signal is selected and input to wavelength band multiplexers 220-1 to 220-P and multiplexed before being output to the outside, or whether the input is selected and input to wavelength demultiplexers 240-q-1 to 240-q-R and demultiplexed into wavelength units. Furthermore, the optical transmission device 200 selects, by the routing settings of the optical switches 260-1 to 260-Q×S, whether the optical signals demultiplexed by wavelength by wavelength demultiplexers 240-q-1 to 240-q-R are selected and received by a selected optical signal receiver, or whether the optical signals are selected and input to wavelength multiplexers 250-q-1 to 250-q-R and a wavelength band signal is generated.

[0050] Furthermore, the optical transmission device 200 is configured so that an optical signal output from a transmitter is selectively input to wavelength multiplexers 250-q-1 to 250-q-R by the routing settings of optical switches 260-1 to 260-Q×S, and a wavelength band signal can be generated. Similarly, the optical transmission device 200 is configured so that a wavelength band signal generated by wavelength multiplexers 250-q-1 to 250-q-R is selectively input to wavelength band multiplexers 220-1 to 220-P by the routing settings of optical switches 230-1 to 230-Q, and is multiplexed and then output to the outside.

[0051] In this optical transmission device 200, it is clear that the optical switches 230-1 to 230-Q can affect the signals at all input / output ports when they are replaced due to a failure. Furthermore, when routing control is performed on a wavelength band basis, it is difficult to perform optical adjustments such as optical level adjustments for individual signals.

[0052] In contrast, the optical switch unit of this embodiment is suitable for application to optical transmission equipment that can easily accommodate multiple types of optical amplifiers with different amplifiable wavelength ranges. In particular, it is possible to limit the input / output ports that may be affected when a failure or replacement occurs. Furthermore, because optical filters are provided between optical switches, optical adjustments such as optical level adjustments can be performed on individual wavelength-based signals, even when routing control is performed on a wavelength group basis. Therefore, this embodiment is expected to be put into practical use as an optical transmission device that can transmit vast amounts of data compared to known technologies.

[0053] 300, 400, 500, 600 Optical transmission device 301, 401, 501, 601 Optical switch unit 303 Wavelength band demultiplexer 304 Optical amplifier 307, 310, 311 Optical switch 308 Wavelength cross-connect function unit 309 Optical filter 313 Wavelength band multiplexer 701 Substrate 702 Optical waveguide

Claims

1. An optical switch unit comprising: a first optical switch having one signal input port for inputting a signal and L signal output ports for outputting a signal; a second optical switch having one signal input port for inputting a signal and M signal output ports for outputting a signal; and a third optical switch having N signal input ports for inputting a signal and one signal output port for outputting a signal, wherein an optical switch unit including at least the first optical switch, the second optical switch, and the third optical switch is integrated, and L, M, and N are natural numbers greater than or equal to 2, and at least one of L, M, and N is a natural number different from the other two.

2. The optical switch unit according to claim 1, wherein the first optical switch, the second optical switch and the third optical switch are defined as a unit, and a plurality of such units are integrated.

3. The optical switch unit according to claim 1, further comprising an optical filter connecting the signal output port of the first optical switch and the signal input port of the second optical switch, wherein the optical switch unit is integrated with the optical filter.

4. The optical switch unit according to claim 3, wherein the first optical switch, the second optical switch and the third optical switch integrated together with the optical filter are defined as a unit, and a plurality of such units are integrated.

5. The optical switch unit according to claim 3 or 4, wherein the optical filter is driven using the thermo-optic effect.

6. The optical switch unit according to any one of claims 1 to 4, wherein the optical switch unit is configured by a silica-based planar lightwave circuit.

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