Wavelength cross-connect device and wavelength cross-connect method

Abstract

A wavelength cross-connect device (10) includes a WXC unit (20) and a wavelength band switching unit (30). The WXC unit (20) includes input-end WSSs (21a to 21m) and output-end WSSs (22a to 22m) each of which receives wavelength multiplexed signal light obtained by multiplexing optical signals that do not require wavelength band conversion among sets of N optical signals obtained by branching wavelength multiplexed signal light at the input-end WSSs. The wavelength band switching unit (30) is configured to convert the wavelength band of wavelength multiplexed signal light, which is obtained by multiplexing optical signals that require the wavelength band conversion among the N optical signals obtained by branching the wavelength multiplexed signal light at each of the input-end WSSs, into a different wavelength band and to output the wavelength multiplexed signal light after the conversion to one of the output-end WSSs such that the path of the wavelength multiplexed signal light is changed.

Description

Technical Field

[0001] The present invention relates to a wavelength cross-connect device and a wavelength cross-connect method used for multi-band transmission in which wavelength-division multiplexed signal light obtained by multiplexing optical signals in different wavelength bands is transmitted through an optical fiber.

Background Art

[0002] A wavelength cross-connect device used in a multi-band transmission system is an optical node that connects any two paths in an optical network to an optical transmission path composed of one or more optical fibers or a multi-core fiber that transmits wavelength-division multiplexed signal light obtained by multiplexing optical signals in different wavelength bands. In this wavelength cross-connect device, the wavelength-division multiplexed signal light transmitted from the input-side path is output to an arbitrary output-side path via a plurality of WSSs (Wavelength Selective Switches).

[0003] A conventional wavelength cross-connect device first demultiplexes the optical signals in each wavelength band of the wavelength-division multiplexed signal light transmitted in a multi-band for each of the M input-side paths. For example, it demultiplexes the optical signals in the S band, C band, and L band multiplexed in the wavelength-division multiplexed signal light.

[0004] However, each wavelength band is, in order from the short-wavelength side, the S band of 1460 nm to 1530 nm, the C band of 1530 nm to 1565 nm, and the L band of 1565 nm to 1625 nm. Each optical signal in the S band, C band, and L band is assigned to the S band, C band, and L band of the optical fiber as a path during transmission.

[0005] Each of the above-demultiplexed optical signals in the S-band, C-band, and L-band (each wavelength band) is input to each WXC (Wavelength Cross Connect) unit provided for each wavelength band. In each WXC, each wavelength band's optical signal is processed, such as adjusting the attenuation amount, by the WSS of each wavelength band arranged on the input side of the WXC, and is input to the WSS of each wavelength band on the output side that is mesh-connected to the input-side WSS. The input optical signals in the S-band, C-band, and L-band are multiplexed by the output-side WSS, and the wavelength-division multiplexed signal light resulting from this multiplexing is multi-band transmitted to M output-side optical paths.

[0006] As a conventional technique related to this type of wavelength cross-connect device, there is one described in Non-Patent Document 1.

Prior Art Documents

Non-Patent Documents

[0007]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0008] However, in the above-described conventional wavelength cross-connect device, in the configuration of each WXC unit in the S-band, C-band, and L-band, due to the difference in optical characteristics depending on each wavelength band, there are deviations in the transmission performance of the optical signals in the S-band, C-band, and L-band. For example, wavelength-band dependence occurs in the transmission band and optical loss, which are the specifications of the WSS and optical amplifier, and this wavelength-band dependence causes deviations in the transmission performance of optical signals between the S-band, C-band, and L-band. This deviation reduces the utilization efficiency of each wavelength band in the optical network.

[0009] The present invention has been made in view of such circumstances, and an object thereof is to suppress differences in transmission performance of optical signals in different wavelength bands in an optical network and improve the utilization efficiency of each wavelength band in the optical network.

Means for Solving the Problems

[0010] To solve the above problems, the present invention provides Wave a long cross-connect device, Before For each of M optical transmission paths composed of one or a plurality of optical fibers, the wavelength-division multiplexed signal light in which optical signals in different wavelength bands transmitted in a multi-band are multiplexed is branched into N, which is a number larger than M, by M input-side WSSs (Wavelength Selective Switches), and the N-branched wavelength-division multiplexed signal light is subjected to relay processing of changing the direction path through M output-side WSSs mesh-connected to the input-side WSSs and outputting the result. The wavelength cross-connect device Before the input-side WSSs, The a WXC (Wavelength Cross Connect) unit having the output-side WSSs to which wavelength-division multiplexed signal light in which optical signals that do not require wavelength band conversion among the wavelength-division multiplexed signal light branched N times for each input-side WSS are multiplexed is input, Before a wavelength band switching unit that converts the wavelength band of the wavelength-division multiplexed signal light in which optical signals that require wavelength band conversion among the wavelength-division multiplexed signal light branched N times for each input-side WSS are multiplexed into different wavelength bands, changes the direction path, and outputs the result to the output-side WSS , and includes The wavelength band switching unit A first WSS that sequentially selects and outputs one by one a plurality of wavelength-division multiplexed signal lights from the input-side WSS; a wavelength band switching processing unit that outputs a wavelength-division multiplexed signal light in which the wavelength band multiplexed in the wavelength-division multiplexed signal light from the first WSS is converted into a different wavelength band; and a second WSS that branches the wavelength-division multiplexed signal light from the wavelength band switching processing unit and inputs it to each of the output-side WSSs so as to change the path, are provided as a set of configurations The set of configurations is provided in the same number as the number of wavelength-division multiplexed signal lights in which optical signals that require wavelength band conversion among the N-branched wavelength-division multiplexed signal lights for each input-side WSS are multiplexed This and is characterized by the above.

Effects of the Invention

[0011] According to the present invention, it is possible to suppress the difference in the transmission performance of each optical signal in different wavelength bands in an optical network and improve the utilization efficiency of each wavelength band of the optical network.

Brief Description of the Drawings

[0012]

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Best Mode for Carrying Out the Invention

[0013] Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, in all the drawings of this specification, components having corresponding functions are denoted by the same reference numerals, and the description thereof will be omitted as appropriate. <Configuration of Embodiment> FIG. 1 is a block diagram showing the configuration of a wavelength cross-connect device applied to a multi-band transmission system according to an embodiment of the present invention.

[0014] The wavelength cross-connect device 10 shown in FIG. 1 includes a WXC unit 20 and a wavelength band switching unit 30.

[0015] The WXC unit 20 is connected for each of M input paths composed of one or a plurality of optical fibers, and includes M <1×N> WSSs (Wavelength Selective Switches) 21a, 21b,..., 21m to which wavelength-division multiplexed signal lights 1a, 1b,..., 1m that have been multi-band transmitted for each input path are input. Further, it includes M <N×1> WSSs 22a, 22b,..., 22m on the output side that are fully meshed-connected (described later) to the M <1×N> WSSs 21a to 21m on the input side. Note that the <1×N> WSSs 21a to 21m on the input side are also referred to as input-side WSSs 21a to 21m, and the <N×1> WSSs 22a to 22m on the output side are also referred to as output-side WSSs 22a to 22m.

[0016] The WXC unit 20 outputs, to the wavelength band switching unit 30, optical signals that require wavelength band conversion among the optical signals of different wavelength bands multiplexed in the wavelength-division multiplexed signal lights 1a, 1b,..., 1m that have been multi-band transmitted for each of the M input paths by the optical fibers indicated by the symbol Mi, and outputs the optical signals that do not require wavelength band conversion to the output-side WSSs 22a to 22m so that the path is changed.

[0017] However, for each of the wavelength-division multiplexed signal lights 1a to 1m that have been multi-band transmitted for each input path, as shown by 1a<S,C,L>, 1b<S,C,L>, 1m<S,C,L> in FIG. 1, it is assumed that the optical signals in the S band, C band, and L band are multiplexed. N and M have a magnitude relationship of N>M. For example, let N = 5 and M = 4. Also, the output ports of the <N×1> WSSs 22a to 22m on the output side are connected to M output paths indicated by the code Mo that output the wavelength-division multiplexed signal light. Also, the <1×N> WSSs 21a to 21m on the input side may be optical couplers such as 1×N optical fiber couplers.

[0018] Also, it is assumed that the input-side WSSs 21a to 21m are, in order from the top in the figure, the first input-side WSS 21a, the second input-side WSS 21b, and the Mth input-side WSS 21m. The output-side WSSs 22a to 22m are also, in order from the top, the first output-side WSS 22a, the second output-side WSS 22b, and the Mth output-side WSS 22m.

[0019] The full-mesh connection is as follows. That is, in the input-side WSSs 21a to 21m, (M - 1) = 4 - 1 = 3 of the N output ports (N output ports) of the first WSS 21a are connected to the N input ports of the second to Mth WSSs 22b to 22m excluding the first on the output side. In this way, (M - 1) = 3 output ports for each of the input-side WSSs 21a to 21m are connected to (M - 1) = 3 input ports among the N input ports of each of the output-side WSSs 22a to 22m excluding the output-side WSS of the same path as the input-side WSS. By this connection, a path through which the optical signals that do not require the above-described wavelength band conversion are transmitted for path change is configured.

[0020] Also, (N - M + 1) = 5 - 4 + 1 = 2 output ports excluding the (M - 1) = 3 output ports of the first WSS 21a on the input side are connected to the wavelength band switching unit 30. The same connection is made for the second to Mth input-side WSSs 21b to 21m as well.

[0021] Excluding the (M - 1) = 3 input ports of the first WSS22a on the output side, the (N - M + 1) = 2 input ports are connected to the wavelength band switching unit 30. Similarly, the second to M-th output side WSS22b to 22m are also connected in the same way. With these (N - M + 1) connections, the optical signals that require the above-described wavelength band conversion are configured to be transmitted to the wavelength band switching unit 30.

[0022] The input side WSS21a to 21m have the same function and are equipped with a function of N-branching for each of the multi-band (wavelength bands of S-band, C-band, and L-band) wavelength division multiplexed signal lights 1a to 1m. However, the WSS does not perform a simple N-branching by a coupler or the like, but has a function of performing N-branching by outputting each optical signal of the wavelength division multiplexed signal light input from the input port from an arbitrary output port. Taking the first input side WSS21a as an example, the WSS21a branches the wavelength division multiplexed signal light 1a input from one input port and outputs the branched wavelength division multiplexed signal light 1a from N output ports.

[0023] The output side WSS22a to 22m have the same function and are equipped with a function of sequentially selecting the multi-band wavelength division multiplexed signal light. Taking the first output side WSS22a as an example, the WSS22a sequentially selects each wavelength division multiplexed signal light input from N input ports and outputs it from one output port to one output path.

[0024] Next, the wavelength band switching unit 30 converts the optical signals of different wavelength bands multiplexed in the (N - M + 1) wavelength division multiplexed signal lights from the input side WSS21a to 21m into a predetermined wavelength band, further changes the path, and outputs them to the output side WSS22a to 22m.

[0025] The wavelength band switching unit 30 is configured to include the <M×1> WSS25a, 25b on the input side, the wavelength band switching processing units 26a, 26b, and the <1×M> WSS27a, 27b on the output side. The <M×1> WSS25a, 25b on the input side have M M-input ports and one output port. The <1×M> WSS27a, 27b on the output side have one input port and M output ports.

[0026] However, the <M×1> WSSs 25a and 25b on the input side may be optical couplers such as M×1 optical fiber couplers. The <1×M> WSSs 27a and 27b on the output side may be 1×M optical couplers. Also, the <M×1> WSSs 25a and 25b constitute the first WSS described in the claims. The <1×M> WSSs 27a and 27b constitute the second WSS described in the claims.

[0027] Also, the input-side WSS 25a, the wavelength band switching processing unit 26a, and the output-side WSS 27a form a set of configurations. The number of configurations in this set is the same as the number of (N - M + 1) = 2 output ports of the input-side WSS 21a of the WXC unit 20. In this example, there are a first set of configurations and a second set of configurations.

[0028] In the first set of configurations, one of the (N - M + 1) = 2 output ports of the input-side WSS 21a to 21m of the WXC unit 20 is connected to the M input ports of the input-side <M×1> WSS 25a. The output port of the <M×1> WSS 25a is connected to the input port of the wavelength band switching processing unit 26a. The output port of the wavelength band switching processing unit 26a is connected to the input port of the output-side <1×M> WSS 27a.

[0029] <1×M> WSS 27a changes the output path of the optical signal in the wavelength band converted by the wavelength band switching processing unit 26a to one of the M output paths. The M output ports of the <1×M> WSS 27a are connected to one of the (N - M + 1) = 2 input ports of the output-side WSS 22a to 22m of the WXC unit 20. The second set of configurations is also connected in the same way as the first set of configurations.

[0030] <Configuration of the wavelength band switching processing unit> As shown in FIG. 2 by taking the wavelength band switching processing unit 26a as a representative, the wavelength band switching processing units 26a and 26b are configured to include a wavelength band demultiplexing unit 31, a plurality of input-side wavelength band conversion units 32 and 33, a <K×K> WSS 34, a plurality of output-side wavelength band conversion units 35 and 36, and a wavelength band multiplexing unit 37.

[0031] K is the number of wavelength bands, and in this example, K = 3 for the S band, C band, and L band. Note that <K×K> WSS34 constitutes the specific WSS described in the claims. Also, the wavelength band conversion units 32 and 33 on the input side constitute the input side conversion unit described in the claims. The wavelength band conversion units 35 and 36 on the output side constitute the output side conversion unit described in the claims.

[0032] The wavelength band demultiplexing unit 31 demultiplexes the wavelength multiplexed signal light of the S band, C band, and L band input from the <M×1> WSS25a (Fig. 1) on the input side, and outputs each optical signal of the demultiplexed S band, C band, and L band. However, it is assumed that the C band is one wavelength band (specific wavelength band) that <K×K> WSS34 can process. <K×K> WSS34 can only process the optical signal of the specific wavelength band (C band). Therefore, the demultiplexed optical signal of the C band is input to <K×K> WSS34 in its original state.

[0033] The wavelength band conversion unit 32 on the input side of <K×K> WSS34 converts the optical signal of the S band into an optical signal of the C band and outputs it to <K×K> WSS34. The wavelength band conversion unit 33 converts the optical signal of the L band into an optical signal of the C band and outputs it to <K×K> WSS34.

[0034] The wavelength band conversion unit 35 on the output side converts the optical signal of the C band into an optical signal of the S band and outputs it to the wavelength band multiplexing unit 37. The wavelength band conversion unit 36 converts the optical signal of the C band into an optical signal of the L band and outputs it to the wavelength band multiplexing unit 37.

[0035] <K×K> WSS34 plays a role of switching the wavelength band of the optical signal multiplexed in the wavelength multiplexed signal lights 1a to 1m input from the optical transmission path Mi on the input side of the wavelength cross-connect device 10 (Fig. 1) to the wavelength band for transmission to the optical transmission path Mo (Fig. 1) on the output side.

[0036] This <K×K> WSS34 has the same number of input ports and output ports as the number of wavelength bands K = 3 multiplexed in the wavelength-division multiplexed signal light. In the <K×K> WSS34, the optical signals in the C band input from K = 3 input ports are output from K = 3 output ports connected to the wavelength band conversion units 35, 36 that perform conversion to a predetermined wavelength band or the wavelength band multiplexing unit 37.

[0037] For example, the optical signal in the C band input from the second input port of the <K×K> WSS34 is input from the first output port to the wavelength band conversion unit 35, where it is converted into an optical signal in the S band. This example is a conversion process for converting the input optical signal in the C band into an optical signal in the S band and transmitting it to the optical transmission path Mo (Fig. 1) on the output side.

[0038] The wavelength band multiplexing unit 37 multiplexes the optical signals in the S band, C band, and L band to convert them into wavelength-division multiplexed signal light, and outputs the converted wavelength-division multiplexed signal light to the <1×M> WSS27a on the output side shown in Fig. 1.

[0039] The <1×M> WSS27a, 27b output the wavelength-division multiplexed signal light to (N - M + 1) = 2 input ports in the output-side WSS22a~22m.

[0040] Each of the output-side WSS22a~22m changes the path of the wavelength-division multiplexed signal light by sequentially selecting the wavelength-division multiplexed signal light in the S band, C band, and L band input from the N input ports and outputting it to M output paths from the output ports.

[0041] <Operation of the Embodiment> Next, the wavelength cross-connect operation of the wavelength cross-connect device 10 according to this embodiment will be described with reference to the flowchart in Fig. 3.

[0042] In step S1 shown in Fig. 3, the wavelength-division multiplexed signal lights 1a~1m transmitted in a multi-band manner for each of the M input paths shown in Fig. 1 are input to the input ports of the M input-side WSS21a~21m of the WXC unit 20. Note that for each of the wavelength-division multiplexed signal lights 1a~1m, the optical signals in the S band, C band, and L band are multiplexed.

[0043] In step S2, each input-side WSS21a to 21m branches each wavelength-division multiplexed signal light 1a to 1m, and outputs, to the N input ports of the predetermined output-side WSS22a to 22m, the optical signals that do not require wavelength band conversion among the branched wavelength-division multiplexed signal lights. Further, the optical signals that require wavelength band conversion are output to the M input ports of the <M×1> WSS25a, 25b of the wavelength band switching unit 30.

[0044] In step S3, the <M×1> WSS25a, 25b sequentially selects M wavelength-division multiplexed signal lights in which the S band, the C band, and the L band are multiplexed, and outputs them to the wavelength band switching processing units 26a, 26b.

[0045] In step S4, the wavelength band switching processing units 26a, 26b demultiplex the input wavelength-division multiplexed signal lights of the S band, the C band, and the L band in the wavelength band demultiplexing unit 31 shown in FIG. 2, and output each of the demultiplexed optical signals of the S band, the C band, and the L band. At this time, the optical signal of the C band is input to the <K×K> WSS34 in its original state. The optical signal of the S band is output to the wavelength band conversion unit 32, and the optical signal of the L band is output to the wavelength band conversion unit 33.

[0046] In step S5, the wavelength band conversion unit 32 converts the optical signal of the S band into an optical signal of the C band and outputs it to the <K×K> WSS34. The wavelength band conversion unit 33 converts the optical signal of the L band into an optical signal of the C band and outputs it to the <K×K> WSS34. Further, the optical signal of the C band demultiplexed by the wavelength band demultiplexing unit 31 is output to the <K×K> WSS34 without conversion.

[0047] In step S6, the <K×K> WSS34 outputs the optical signals of the C band input from the K (3) input ports from the K output ports required for wavelength band conversion. For example, the optical signal of the C band input from the second input port of the <K×K> WSS34 is output from the first output port to the wavelength band conversion unit 35.

[0048] In step S7, the wavelength band conversion unit 35 converts the optical signal in the C band into an optical signal in the S band and outputs it to the wavelength band multiplexing unit 37. The wavelength band conversion unit 36 converts the optical signal in the C band into an optical signal in the L band and outputs it to the wavelength band multiplexing unit 37. The optical signal in the C band output from the <K×K> WSS 34 other than the above C band is output to the wavelength band multiplexing unit 37 without conversion.

[0049] In step S8, the wavelength band multiplexing unit 37 outputs the wavelength multiplexed signal light obtained by multiplexing the optical signals in the S band, C band, and L band to the input ports of the <1×M> WSSs 27a and 27b shown in FIG. 1.

[0050] In step S9, the <1×M> WSSs 27a and 27b output the wavelength multiplexed signal light to two input ports (predetermined input ports) of (N - M + 1) = 2 among the N input ports of the output side WSSs 22a to 22m on the output side of the WXC unit 20 so that the wavelength multiplexed signal light is changed in the forward path.

[0051] In step S10, each of the output side WSSs 22a to 22m outputs the wavelength multiplexed signal light in the S band, C band, and L band input from the N input ports to M output forward paths from a predetermined output port while sequentially selecting them.

[0052] <Effect of Embodiment> The effect of the wavelength cross-connect device 10 according to the embodiment of the present invention will be described. The wavelength cross-connect device 10 branches the wavelength multiplexed signal lights 1a to 1m in which the optical signals in different wavelength bands (S band, C band, and L band) transmitted in a multi-band are multiplexed into a number N larger than M by the input side WSSs 21a to 21m for each of the M optical transmission paths composed of one or a plurality of optical fibers. Further, relay processing is performed in which the N-branched wavelength multiplexed signal lights are changed in the forward path by the output side WSSs 22a to 22m mesh-connected to the input side WSSs 21a to 21m and output to the output side forward path.

[0053] (1a) The wavelength cross-connect device 10 includes a WXC unit 20 and a wavelength band switching unit 30. The WXC unit 20 includes input-side WSSs 21a to 21m and output-side WSSs 22a to 22m to which a wavelength-division multiplexed signal light in which optical signals that do not require wavelength conversion among the wavelength-division multiplexed signal lights branched into N by the input-side WSSs 21a to 21m are multiplexed is input.

[0054] The wavelength band switching unit 30 is configured to convert the wavelength band of a wavelength-division multiplexed signal light in which optical signals that require wavelength conversion are multiplexed from the wavelength-division multiplexed signal lights branched into N for each of the input-side WSSs 21a to 21m to a different wavelength band, change the routing, and output the result to the output-side WSSs 22a to 22m.

[0055] According to this configuration, the wavelength cross-connect device 10 branches into N the wavelength-division multiplexed signal lights 1a to 1m in which optical signals of different wavelength bands transmitted in a multi-band are multiplexed, by the input-side WSSs 21a to 21m of the WXC unit 20. The wavelength band of a wavelength-division multiplexed signal light in which optical signals that require wavelength conversion are multiplexed from the N-branched wavelength-division multiplexed signal lights is converted to a different wavelength band by the wavelength band switching unit 30, the routing is changed, and the result can be output to the output-side routing Mo on the output side via the output-side WSSs 22a to 22m.

[0056] Therefore, in a multi-band transmission system 40 (FIG. 4) in which a plurality of nodes to which the wavelength cross-connect device 10 is applied are link-connected, wavelength band conversion can be performed in units of links and wavelengths, which will be described later. By this conversion, for example, the wavelength of the free wavelength band of the optical transmission path between nodes 40a and 40b (for example, the wavelength C1 in the C band) can be converted and used by the wavelength cross-connect device 10 on the front side of the section between the nodes 40a and 40b. Since the wavelength of the wavelength free section can be set to be usable in this way, the usage capacity of the network can be improved. That is, the utilization efficiency of the network of the multi-band transmission system can be improved.

[0057] The multi-band transmission system (also referred to as the system) 40 shown in Fig. 4 is configured such that each of the nodes 40a, 40b, 40c, 40d, 40e, 40f as communication devices including a wavelength cross-connect device 10 is connected in a ring shape by optical transmission paths 41a, 41b, 41c, 41d, 41e, 41f made of optical fibers.

[0058] The above-mentioned link unit is a unit of the optical transmission path 41a that connects two adjacent node intervals (for example, nodes 40a and 40b) in the system 40. In other words, it is a unit of two adjacent node intervals.

[0059] In the prior art, for example, when multi-band transmitting optical signals in different wavelength bands in multiple paths via the optical transmission paths 41a, 41b, 41c between nodes 40a - 40b - 40c - 40d with node 40a as the starting point and node 40d as the ending point, the transmission was limited to one wavelength band in one path. Note that the interval between nodes 40a - 40b - 40c - 40d is also referred to as between nodes 40a... 40d.

[0060] For example, when multi-band transmitting optical signals in the S band, C band, and L band between nodes 40a... 40d, path 1 through the optical transmission paths 41a to 41c was limited to transmitting only the optical signal in the S band, path 2 was limited to transmitting only the optical signal in the C band, and path 3 was limited to transmitting only the optical signal in the L band.

[0061] Here, in multi-band transmission, there is a characteristic that power transitions from an optical signal with a shorter wavelength to an optical signal with a longer wavelength. Therefore, in the above example, the transmission of the optical signal in the S band of path 1 has poor transmission performance, the transmission of the optical signal in the C band of path 2 has normal transmission performance, and in many cases, the transmission of the optical signal in the L band of path 3 has good transmission performance. Thus, there was a deviation in transmission performance among paths 1, 2, and 3.

[0062] The transmission performance is also determined depending on parameters such as the transmission band and the loss amount as the performance of devices (optical products) such as optical fibers, and Stimulated Raman Scattering (SRS), which is one of the nonlinear optical effects. The above parameters have strong band dependence. Since the transmission performance depends on the used wavelength band as described above, a deviation occurs between different wavelength bands.

[0063] On the other hand, in the present embodiment, the wavelength cross-connect device 10 can change the wavelength band for each section (link unit) between each node 40a…40d.

[0064] For example, as shown in FIG. 5, in path 1 between nodes 40a-40b-40c-40d, an optical signal in the S band is transmitted in the first section (between nodes 40a-40b), an optical signal in the C band is transmitted in the second section (between nodes 40b-40c), and an optical signal in the L band is transmitted in the third section (between nodes 40c-40d). In path 2, an optical signal in the C band is transmitted in the first section, an optical signal in the L band is transmitted in the second section, and an optical signal in the S band is transmitted in the third section. In path 3, an optical signal in the L band is transmitted in the first section, an optical signal in the S band is transmitted in the second section, and an optical signal in the C band is transmitted in the third section.

[0065] When optical signals in different wavelength bands are transmitted for each of paths 1, 2, and 3 in each section in this way, the transmission performance of different wavelength bands for each of paths 1, 2, and 3 in each section is averaged. By this averaging, the deviation in transmission performance between paths 1 to 3 is suppressed. By suppressing this deviation, the utilization efficiency of the network of the multi-band transmission system can be improved.

[0066] Next, the effect of being able to convert the wavelength band in units of wavelengths will be described. As shown in FIG. 6, it is assumed that the S band of the optical signal is composed of wavelengths S1, S2, S3, the C band is composed of wavelengths C1, C2, C3, and the L band is composed of wavelengths L1, L2, L3.

[0067] In the prior art, the setting in one wavelength band was limited to one path for the entire section. However, in the present embodiment, the wavelength cross-connect device 10 can set any wavelength in a different wavelength band for each of paths 1, 2, and 3 for each section of nodes 40a - 40b - 40c - 40d. For example, set the wavelength S1 in the S band for path 1 of the optical transmission line 41a in the section of nodes 40a - 40b, set the wavelength C1 in the C band for path 2 of the optical transmission line 41b in the section of nodes 40b - 40c, and set the wavelength L1 in the L band for path 3 of the optical transmission line 41c in the section of nodes 40c - 40d, and the optical signal can be transmitted at the set wavelengths S1, C1, and L1.

[0068] In the case of the present embodiment where the conversion of the wavelength band is possible in units of wavelengths in this way, the constraint of wavelength continuity in the prior art can be avoided. The wavelength continuity constraint means the necessity of continuous transmission at the same wavelength within one wavelength band for one path between nodes 40a...40d.

[0069] For example, as shown in FIG. 7, assume that wavelengths S1, S2, S3 in the S band, wavelengths C1, C2, C3 in the C band, and wavelengths L1, L2, L3 in the L band are set between each of nodes 40a...40d outside the sections indicated by the five elliptical dashed frames. In this case, in the prior art, due to the wavelength continuity constraint, in the wavelength free section indicated by the elliptical dashed frame, the same wavelength of the same path collides, so the corresponding wavelength cannot be used. For example, in the wavelength free section indicated by the elliptical dashed frame in the C band between nodes 40a - 40b, since the wavelength C2 has already been set between nodes 40b - 40d, the wavelength C2 of the same wavelength that collides with it cannot be set.

[0070] However, in this embodiment, since the wavelength cross-connect device 10 can convert the wavelength band in terms of wavelength, for example, the wavelength C2 shown within the elliptical dashed line frame in the C band between nodes 40a - 40b can be set. Furthermore, the wavelength S2 shown within the elliptical dashed line frame in the S band between nodes 40b - 40c can be set, and the wavelength L2 shown within the elliptical dashed line frame in the L band between nodes 40c - 40d can be set. In this case, the optical signal can be transmitted using the wavelength C2 in the wavelength band C between nodes 40a - 40b, the wavelength S2 in the wavelength band S between nodes 40b - 40c, and the wavelength L2 in the wavelength band L between nodes 40c - 40d.

[0071] By using the available wavelengths indicated by the elliptical dashed line frame in this way, the optical signal can be transmitted while avoiding wavelength collisions, so the usage capacity of the network can be improved. That is, the utilization efficiency of the network of the multi-band transmission system can be improved.

[0072] Furthermore, by such conversion in terms of wavelength of the wavelength band, the capacity constraint due to inter-band stimulated Raman scattering occurring in the S band can also be relaxed.

[0073] <Path Setting Example 1> Here, Path Setting Example 1 will be described with reference to FIG. 8. A path setting device 55 is connected to each of the nodes 40a to 40d. An external terminal device 56 such as a personal computer for performing a path setting order is connected to this path setting device 55. Also, a plurality of arrows W1 indicate wavelength band switching points.

[0074] The path setting device 55 manages the usage status of wavelengths between nodes 40a... 40d. For example, when an order to newly set a path between nodes 40a... 40d is added by the external terminal device 56, since a path cannot be set between nodes 40a... 40d using the same wavelength, the path setting device 55 checks the available state of the wavelength.

[0075] The path setting device 55 gives the instructions described in the following (1) to (4) according to the confirmation of the available state of the wavelength. (1) The path setting device 55 instructs the node 40a to transmit the wavelength C2 in the C band to the node 40b as indicated by the arrow Y11 in order to set an optical path in the optical transmission line 41a. (2) The path setting device 55 instructs the node 40b to switch the C band of the optical signal with the input wavelength C2 to the S band and convert it into an optical signal with the wavelength S2 as indicated by the arrow Y12 in order to set an optical path in the optical transmission line 41b, and then transmit it to the node 40c. (3) The path setting device 55 instructs the node 40c to switch the S band of the optical signal with the input wavelength S2 to the L band and convert it into an optical signal with the wavelength L2 as indicated by the arrow Y13 in order to set an optical path in the optical transmission line 41c, and then transmit it to the node 40d. (4) The path setting device 55 may instruct the node 40d to return to the wavelength S2 in the S band. This is executed when the available wavelength bands are determined at the start point and the end point of the path.

[0076] Next, as shown in FIG. 9, when inter-band stimulated Raman scattering does not occur in the S band, C band, and L band, the optical signal-to-noise ratios {SNR (Signal-to-Noise Ratio) [dB] on the vertical axis} of the S band, C band, and L band are substantially the same as indicated by the broken line 51.

[0077] On the other hand, when inter-band stimulated Raman scattering occurs, the SNR of the S band, C band, and L band decreases as the frequency of the wavelength band increases, in other words, as the wavelength of the wavelength band becomes shorter, as indicated by the solid line 52. The SNR is the worst in the S band. For this reason, as indicated by the broken-line horizontal bar with the reference numeral 54 in FIG. 10, optical signal transmission through the S band cannot be performed between the nodes 40a - 40b - 40c - 40d.

[0078] However, in this embodiment, since the wavelength cross-connect device 10 can convert the wavelength band in terms of wavelength, the wavelengths of different wavelength bands may be set in the wavelength free interval indicated by the elliptical broken line frame as follows. That is, wavelength C3 may be set between nodes 40a - 40b, wavelength S3 may be set between nodes 40b - 40c, and wavelength L3 may be set between nodes 40c - 40d. With this setting, wavelength C3 in wavelength band C is used between nodes 40a - 40b, wavelength S3 in wavelength band S is used between nodes 40b - 40c, and wavelength L3 in wavelength band L is used between nodes 40c - 40d, so that an optical signal can be transmitted while mitigating the influence of inter-band stimulated Raman scattering.

[0079] <Path setting example 2> Here, path setting example 2 will be described with reference to FIG. 11. However, as shown in FIG. 8 above, a path setting device 55 to which an external terminal 56 is connected is connected to each of the nodes 40a to 40d.

[0080] The path setting device 55 manages the usage status of wavelengths between nodes 40a... 40d. For example, when an order to newly set a path between nodes 40a... 40d is added by the external terminal 56, the path setting device 55 checks the free state of the wavelength. In the case of the example in FIG. 11, it is possible to set a path between nodes 40a - 40d with wavelength S3. However, as a setting condition, for example, if it is stipulated that wavelength S3 can be set for up to two consecutive links, a path cannot be set on the optical transmission paths 41a, 41b, 41c with wavelength S3.

[0081] Therefore, the path setting device 55 gives the instructions described in the following (1) to (4) according to the confirmation of the free state of the wavelength. (1) The path setting device 55 instructs node 40a to transmit an optical signal of wavelength S3 in the S band to node 40b as indicated by arrow Y21 in order to set an optical path on the optical transmission path 41a. (2) The path setting device 55 instructs node 40b to transmit the input optical signal of wavelength S3 as it is to node 40c as indicated by arrow Y21 in order to set an optical path on the optical transmission path 41b. (3) The path setting device 55 switches the S band of the input optical signal with wavelength S3 to the L band in order to set an optical path in the optical transmission path 41c for the node 40c, converts it into an optical signal with wavelength L3 as indicated by the arrow Y22, and instructs to transmit it to the node 40d. (4) The path setting device 55 may instruct the node 40d to return to the wavelength S2 in the S band. This is executed when the available wavelength bands are determined at the start point and end point of the path.

[0082] As described above, since the influence of the inter-band induced Raman can be mitigated and an optical signal can be transmitted between the nodes 40a...40d, the capacity constraint due to the inter-band induced Raman scattering can also be mitigated. Therefore, the usage capacity of the network in the multi-band transmission system can be improved, and the utilization efficiency of the network can be improved.

[0083] That is, generally, the network efficiency decreases from the state of 100% due to the wavelength continuity constraint, and further decreases due to the capacity constraint caused by the influence of the inter-band induced Raman scattering. However, according to the wavelength cross-connect device 10 of the present embodiment, the decrease in the network efficiency can be suppressed.

[0084] (2a) The wavelength band switching unit 30 includes an <M×1> WSS 25a as a first WSS that sequentially selects and outputs a plurality of wavelength-division multiplexed signal lights from the input-side WSSs 21a to 21m one by one. Further, it includes a wavelength band switching processing unit 26a that outputs wavelength-division multiplexed signal light in which the wavelength band multiplexed in the wavelength-division multiplexed signal light from the <M×1> WSS 25a is converted into a different wavelength band. Furthermore, it includes a <1×M> WSS 27a as a second WSS that branches the wavelength-division multiplexed signal light from the wavelength band switching processing unit 26a and inputs it to each of the output-side WSSs 22a to 22m so as to change the direction of the path.

[0085] The above <M×1> WSS 25a, wavelength band switching processing unit 26a, and <1×M> WSS 27a are provided as a set of configurations. The set of configurations is configured to have the same number as the number of wavelength-division multiplexed signal lights in which the optical signals that require wavelength band conversion among the N-branched wavelength-division multiplexed signal lights for each of the input-side WSSs 21a to 21m are multiplexed.

[0086] According to this configuration, when it is desired to increase the traffic of the wavelength-division multiplexed signal light transmitted in multiple bands and increase the number of wavelength band switches in the wavelength band switching unit 30, it can be easily increased by increasing it in one set of constituent units.

[0087] (3a) The wavelength band switching processing units 26a and 26b are configured to include a wavelength band demultiplexing unit 31, wavelength band conversion units 32 and 33 as input-side conversion units, a <K×K> WSS 34 as a specific WSS, wavelength band conversion units 35 and 36 as output-side conversion units, and a wavelength band multiplexing unit 37.

[0088] The wavelength band demultiplexing unit 31 demultiplexes and outputs optical signals of different wavelength bands multiplexed in the wavelength-division multiplexed signal light from the <M×1> WSSs 25a and 25b as the first WSSs on the input side.

[0089] The wavelength band conversion units 32 and 33 as the input-side conversion units convert optical signals of wavelength bands other than a predetermined specific wavelength band among the optical signals of different wavelength bands demultiplexed by the wavelength band demultiplexing unit 31 into optical signals of the specific wavelength band.

[0090] <K×K> WSS 34 has the same number of input ports and output ports as the number of demultiplexing in the wavelength band demultiplexing unit 31, can process only a specific wavelength band, and outputs from the output port so as to convert the specific wavelength band converted by the wavelength band conversion units 32 and 33 input from the input port, or the specific wavelength band within the different wavelength bands demultiplexed above, into a predetermined wavelength band.

[0091] The wavelength band conversion units 35 and 36 as the output-side conversion units convert the optical signals of the specific wavelength band output from the output port into optical signals of a predetermined wavelength band. The wavelength band multiplexing unit 37 multiplexes each optical signal of a different wavelength band from the wavelength band conversion units 35 and 36 into wavelength-division multiplexed signal light and outputs it to the <1×M> WSSs 27a and 27b as the second WSSs.

[0092] According to this configuration, by the <K×K> WSS 34, a specific wavelength band converted by the wavelength band conversion units 32 and 33 on the input side, or a specific wavelength band within different wavelength bands demultiplexed by the wavelength band demultiplexing unit 31, is output from the output port so as to be converted into a predetermined wavelength band. In this way, with one <K×K> WSS 34, each optical signal in different wavelength bands can be converted into an optical signal in a predetermined wavelength band, so that the wavelength band switching processing units 26a and 26b can be miniaturized.

[0093] <Other configurations of the wavelength band switching processing unit> The wavelength band switching processing units 26a and 26b may be configured as shown in FIG. 12, representing the wavelength band switching processing unit 26a, in addition to the configuration shown in FIG. 2.

[0094] The wavelength band switching processing unit 26a shown in FIG. 12 includes a <1×P> WSS 61, P wavelength band conversion units 62a, 62b, 62c, 62d, 62e, and 62f, and a <P×1> WSS 63. P is the same number as the number of output ports of the <1×P> WSS 61, the number of input ports of the <P×1> WSS 63, and the number of wavelength band conversion units 62a to 62f.

[0095] However, either one of the <1×P> WSS 61 and the <P×1> WSS 63 may be an optical coupler such as a 1×P or P×1 optical fiber coupler. Note that the <1×P> WSS 61 constitutes the third WSS described in the claims. The <P×1> WSS 63 constitutes the fourth WSS described in the claims.

[0096] The <1×P> WSS 61 branches P each of the optical signals in the S band, C band, and L band of different wavelength bands multiplexed in the wavelength division multiplexed signal light input from the <M×1> WSS 25a (FIG. 1). This P-branching is performed including a predetermined number of optical signals in the same wavelength band. In this example, the optical signals in the S band, C band, and L band are P-branched including two each as follows. That is, the optical signals in the S band are output to the wavelength band conversion units 62a and 62b, the optical signals in the C band are output to the wavelength band conversion units 62c and 62d, and the optical signals in the L band are output to the wavelength band conversion units 62e and 62d.

[0097] The wavelength band conversion unit 62a converts the S band into an optical signal in the C band, and the wavelength band conversion unit 62b converts the S band into an optical signal in the L band and outputs it to the input port of the <P×1> WSS63. The wavelength band conversion unit 62c converts the C band into an optical signal in the S band, and the wavelength band conversion unit 62d converts the C band into an optical signal in the L band and outputs it to the input port of the <P×1> WSS63. The wavelength band conversion unit 62e converts the L band into an optical signal in the S band, and the wavelength band conversion unit 62f converts the L band into an optical signal in the C band and outputs it to the input port of the <P×1> WSS63.

[0098] The <P×1> WSS63 multiplexes two S bands, C bands, and L bands input to P input ports and outputs the wavelength multiplexed signal light to the <1×M> WSS27a shown in FIG. 1.

[0099] According to this configuration, with the wavelength band switching processing units 26a and 26b having a simple configuration, different wavelength bands multiplexed in the wavelength multiplexed signal light from the WXC unit 20 can be converted into optical signals in other different wavelength bands.

[0100] In addition to the above, in the wavelength band switching processing unit 26a shown in FIG. 2 or FIG. 12, a WSS that can handle at least two or more wavelength bands may be used. For example, instead of the WSS34 that can process the S band, C band, and L band shown in FIG. 2, a configuration may be made by combining one WSS for the S band and one WSS for the C band and L band. Also, when using the E band, S band, C band, and L band, a configuration may be made by providing a WSS for the E band and S band and a WSS for the C band and L band. That is, a configuration that can process four wavelength bands in half may be made.

[0101] <Effect> (1) A wavelength cross-connect device, wherein the wavelength cross-connect device branches, for each of M optical transmission paths composed of one or a plurality of optical fibers, a wavelength-division multiplexed signal light in which optical signals in different wavelength bands transmitted in a multi-band are multiplexed, into N, a number larger than M, by M input-side WSSs (Wavelength Selective Switches), and performs a relay process of changing the routing of the N-branched wavelength-division multiplexed signal light and outputting it through M output-side WSSs mesh-connected to the input-side WSSs, and has a WXC (Wavelength Cross Connect) unit including the input-side WSS and the output-side WSS to which a wavelength-division multiplexed signal light in which optical signals that do not require wavelength band conversion among the wavelength-division multiplexed signal lights N-branched for each input-side WSS are multiplexed is input, and a wavelength band switching unit that converts the wavelength band of a wavelength-division multiplexed signal light in which optical signals that require wavelength band conversion are multiplexed from the wavelength-division multiplexed signal lights N-branched for each input-side WSS into a different wavelength band, changes the routing, and outputs it to the output-side WSS. The wavelength cross-connect device is characterized by the above configuration.

[0102] According to this configuration, the wavelength cross-connect device branches the wavelength-division multiplexed signal light in which optical signals in different wavelength bands transmitted in a multi-band are multiplexed, into N by the input-side WSS of the WXC unit. The wavelength band of the wavelength-division multiplexed signal light in which optical signals that require wavelength band conversion are multiplexed from the N-branched wavelength-division multiplexed signal lights can be converted into a different wavelength band by the wavelength band switching unit, the routing can be changed, and it can be output to the output-side routing through the output-side WSS.

[0103] Therefore, in a multi-band transmission system in which a plurality of nodes to which the wavelength cross-connect device is applied are link-connected (optically transmission path-connected), the wavelength band can be converted in units of links and wavelengths. By this conversion, the wavelength (for example, wavelength C1 in the C band) of the free wavelength band of the optical transmission path in the node section can be converted by the wavelength cross-connect device on the front side of the node section and used. Since the wavelength of the wavelength free section can be set to be usable in this way, the usage capacity of the network can be improved. That is, the utilization efficiency of the network of the multi-band transmission system can be improved.

[0104] (2) The wavelength band switching unit includes a first WSS that sequentially selects and outputs a plurality of wavelength division multiplexed signal lights from the input-side WSS one by one, a wavelength band switching processing unit that outputs wavelength division multiplexed signal lights in which the wavelength bands multiplexed in the wavelength division multiplexed signal lights from the first WSS are converted into different wavelength bands, and a second WSS that branches the wavelength division multiplexed signal lights from the wavelength band switching processing unit and inputs them to each output-side WSS so as to change the path. One set of configurations is provided, and the number of sets of the one set of configurations is the same as the number of wavelength division multiplexed signal lights in which optical signals that require wavelength band conversion among the N-branched wavelength division multiplexed signal lights for each input-side WSS are multiplexed. The wavelength cross-connect device according to (1) above, characterized in that.

[0105] According to this configuration, when the traffic of the wavelength division multiplexed signal light transmitted in the multi-band increases and it is desired to increase the number of wavelength band switches in the wavelength band switching unit, it can be easily increased by increasing it in units of one set of configurations.

[0106] (3) The wavelength band switching processing unit includes a wavelength band demultiplexing unit that demultiplexes and outputs optical signals in different wavelength bands multiplexed in the wavelength division multiplexed signal lights from the first WSS, an input-side conversion unit that converts optical signals in wavelength bands other than a predetermined specific wavelength band among the demultiplexed optical signals in different wavelength bands into optical signals in the specific wavelength band, has the same number of input ports and output ports as the number of demultiplexing, can process only the specific wavelength band, and outputs from the output port so as to convert the specific wavelength band converted by the input-side conversion unit input from the input port or the specific wavelength band in the demultiplexed different wavelength bands into a predetermined wavelength band. A specific WSS, an output-side conversion unit that converts the optical signal in the specific wavelength band output from the output port into an optical signal in a predetermined wavelength band, and a wavelength band multiplexing unit that multiplexes each optical signal in a different wavelength band from the output-side conversion unit into a wavelength division multiplexed signal light and outputs it to the second WSS. The wavelength cross-connect device according to (2) above, characterized in that it is provided.

[0107] According to this configuration, a specific wavelength band converted by the input-side conversion unit or a specific wavelength band within different wavelength bands demultiplexed by the wavelength band demultiplexing unit by a specific WSS is output from the output port so as to be converted into a predetermined wavelength band. In this way, since each optical signal in different wavelength bands can be converted into an optical signal in a predetermined wavelength band by one specific WSS, the wavelength band switching processing unit can be miniaturized.

[0108] (4) The wavelength band switching processing unit includes: a third WSS that demultiplexes different wavelength bands multiplexed in the wavelength multiplexed signal light from the first WSS and includes a predetermined number of optical signals in the same wavelength band; a wavelength band conversion unit that converts the optical signals in the wavelength bands demultiplexed by the third WSS into optical signals in different wavelength bands, and the number of the wavelength band conversion units is the same as the number of the demultiplexing; and a fourth WSS that multiplexes the optical signals in each wavelength band converted by the wavelength band conversion unit to convert them into wavelength multiplexed signal light and outputs the wavelength multiplexed signal light to the second WSS. The wavelength cross-connect device according to (2) above is characterized by being configured in this way.

[0109] According to this configuration, with a wavelength band switching processing unit having a simple configuration, different wavelength bands multiplexed in the wavelength multiplexed signal light from the WXC unit can be converted into optical signals in other different wavelength bands.

[0110] In addition, regarding specific configurations, appropriate changes can be made as appropriate without departing from the gist of the present invention.

Explanation of Reference Numerals

[0111] 10 Wavelength cross-connect device 20 WXC unit 21a~21m <1×N>WSS (input-side WSS) 22a~22m <N×1>WSS (output-side WSS) 30 Wavelength band switching unit 25a,25b <M×1>WSS (first WSS) 26a,26b Wavelength band switching processing unit 27a,27b <1×M>WSS (second WSS) 31 Wavelength band demultiplexing unit 32,33 Wavelength band conversion unit (input-side conversion unit) 34 <K×K> WSS (specific WSS) 35, 36 Wavelength band conversion unit (output side conversion unit) 37 Wavelength band multiplexing unit 61 <1×P> WSS (third WSS) 62a~62f Wavelength band conversion unit 63 <P×1> WSS (fourth WSS)

Claims

1. A wavelength cross-connect device, for each of M optical transmission paths composed of one or more optical fibers, the wavelength multiplexed signal light in which each optical signal in different wavelength bands transmitted by multi-band transmission is multiplexed is branched into N, which is a number larger than M, by M input-side WSSs (Wavelength Selective Switches), and the N-branched wavelength multiplexed signal light is subjected to relay processing of changing the path and outputting it through M output-side WSSs mesh-connected to the input-side WSSs, the wavelength cross-connect device, a WXC (Wavelength Cross Connect) unit having the input-side WSS and the output-side WSS to which the wavelength multiplexed signal light in which optical signals that do not require wavelength band conversion among the wavelength multiplexed signal lights N-branched for each input-side WSS is input, a wavelength band switching unit that converts the wavelength band of the wavelength multiplexed signal light in which optical signals that require wavelength band conversion are multiplexed from the wavelength multiplexed signal light N-branched for each input-side WSS into different wavelength bands, changes the path, and outputs it to the output-side WSS, the wavelength band switching unit, comprises a first WSS that sequentially selects and outputs a plurality of wavelength multiplexed signal lights from the input-side WSS one by one, a wavelength band switching processing unit that outputs the wavelength multiplexed signal light in which the wavelength band multiplexed in the wavelength multiplexed signal light from the first WSS is converted into a different wavelength band, and a second WSS that branches the wavelength multiplexed signal light from the wavelength band switching processing unit and inputs it to each output-side WSS so as to change the path, as a set configuration, the number of sets of the set configuration is the same as the number of the wavelength multiplexed signal lights in which optical signals that require wavelength band conversion among the N-branched wavelength multiplexed signal lights for each input-side WSS are multiplexed A wavelength cross-connect device characterized by the above.

2. The wavelength band switching processing unit, a wavelength band demultiplexing unit that demultiplexes and outputs optical signals in different wavelength bands multiplexed in the wavelength multiplexed signal light from the first WSS, an input-side conversion unit that converts optical signals in wavelength bands other than a predetermined specific wavelength band among the demultiplexed optical signals in different wavelength bands into optical signals in the specific wavelength band, It has the same number of input ports and output ports as the number of demultiplexed waves, can process only the specific wavelength band, and outputs from the output port to convert the specific wavelength band converted by the input-side conversion unit input from the input port or the specific wavelength band within the different wavelength bands obtained by demultiplexing into a predetermined wavelength band. A specific WSS; An output-side conversion unit that converts an optical signal of a specific wavelength band output from the output port into an optical signal of a predetermined wavelength band; It includes a wavelength-band multiplexing unit that multiplexes each optical signal of different wavelength bands from the output-side conversion unit into a wavelength-division multiplexed signal light and outputs it to the second WSS. The wavelength cross-connect device according to claim 1, characterized in that.

3. The wavelength-band switching processing unit A third WSS that branches different wavelength bands multiplexed in the wavelength-division multiplexed signal light from the first WSS to include a predetermined number of optical signals of the same wavelength band; The same number of wavelength-band conversion units as the number of branches that convert the optical signals of the wavelength bands branched by the third WSS into optical signals of different wavelength bands; It is configured to include a fourth WSS that multiplexes the optical signals of each wavelength band converted by the wavelength-band conversion unit into wavelength-division multiplexed signal light and outputs it to the second WSS. The wavelength cross-connect device according to claim 1, characterized in that.

4. A wavelength cross-connect method by a wavelength cross-connect device, For each of the M optical transmission paths composed of one or more optical fibers, the wavelength-division multiplexed signal light in which each optical signal of different wavelength bands transmitted in a multi-band is multiplexed is branched by M input-side WSSs (Wavelength Selective Switch) into a number N larger than M, and the N-branched wavelength-division multiplexed signal light is relayed through M output-side WSSs mesh-connected to the input-side WSS to change the path and output. The processing is being performed, The wavelength cross-connect device has a WXC (Wavelength Cross Connect) unit and a wavelength-band switching unit. The WXC unit executes a step of outputting the wavelength-division multiplexed signal light in which optical signals that do not require wavelength-band conversion among the wavelength-division multiplexed signal light branched N times for each input-side WSS are multiplexed to the output-side WSS. The wavelength-band switching unit executes a step of converting the wavelength band of the wavelength-division multiplexed signal light in which optical signals that require wavelength-band conversion are multiplexed from the wavelength-division multiplexed signal light branched N times for each input-side WSS into different wavelength bands and changing the path and outputting it to the output-side WSS. The wavelength band switching unit performs, as a set of configurations, a first step of sequentially selecting and outputting each of a plurality of wavelength-division multiplexed signal lights from the input-side WSS one by one, a second step of outputting a wavelength-division multiplexed signal light obtained by converting a wavelength band multiplexed in the wavelength-division multiplexed signal light output from the first step into a different wavelength band, and a third step of branching the wavelength-division multiplexed signal light output in the second step and inputting it to each of the output-side WSSs so as to change the optical path, where the number of sets of configurations is the same as the number of wavelength-division multiplexed signal lights in which optical signals requiring wavelength band conversion among the N-branched wavelength-division multiplexed signal lights for each of the input-side WSSs are multiplexed. A wavelength cross-connect method characterized by the above.

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