Optical transmission device

Abstract

Provided is an optical transmission device that makes it possible to minimize a detour free path to be prepared in a node configuration on the assumption that a plurality of wavelength ranges are used. An optical transmission device according to the present disclosure comprises: M wavelength group demultiplexers that demultiplex a wavelength multiplexed signal inputted from outside into optical signals of N wavelength groups; an optical amplifier that amplifies each of the demultiplexed optical signals of the wavelength groups; a first optical switch that is connected to an output of the optical amplifier; N(N-1) wavelength group conversion units that each convert, into an optical signal of another wavelength group, an optical signal of a wavelength group outputted from each of (N-1) outputs among outputs of the first optical switch; MN second optical switches that each selectively output one signal among optical signals of wavelength groups outputted from M outputs among the outputs of the first optical switch, and optical signals of wavelength groups from the respective outputs of the wavelength group conversion units; and M wavelength group multiplexers that multiplex the optical signals of the N wavelength groups outputted from the second optical switches.

Description

Optical Transmission Equipment

[0001] The present disclosure relates to an optical transmission device.

[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 that can transmit large amounts of data with low power consumption are being widely constructed.

[0003] Furthermore, optical transmission devices using optical switches can be used in optical communication networks, which enable flexible setting of paths between any number of points in the optical communication network.

[0004] In recent years, as an example of an optical transmission device that applies such an optical switch, a transmission device that uses multiple wavelength bands (e.g., C-band and L-band) for the purpose of transmitting more information through a single optical fiber has begun to be put into practical use (see, for example, non-patent document 1).

[0005] FIG. 1 is a diagram schematically illustrating the basic configuration of a conventional optical transmission device 100. Note that FIG. 1 illustrates, as an example, a case in which there is one input port for wavelength-multiplexed signals input from an external device and one output port for wavelength-multiplexed signals output to an external device. However, this is intended for illustrative purposes only, and the number of input ports and output ports (number of directions) of the optical transmission device 100 may be M (M is an integer equal to or greater than 1). Furthermore, in the optical transmission device 100 having such a configuration, as will be described later, the first optical switch is configured to output the direction of an optical signal of a wavelength group to one of M directions in accordance with a user selection. Note that in FIG. 1, the traveling direction of the optical signal is depicted by an arrow.

[0006] As shown in FIG. 1, optical transmission device 100 capable of connecting optical fibers with up to M directions includes a wavelength group demultiplexer 101 that demultiplexes an externally input wavelength-multiplexed signal into optical signals of N wavelength groups (N is an integer of 2 or more), N optical amplifiers 102a-c that amplify each of the optical signals of the N wavelength groups output from wavelength group demultiplexer 101, N 1-input M-output first optical switches 103a-c connected to the output ports of each of optical amplifiers 102a-c, N M-input 1-output second optical switches 104a-c connected to the output ports of each of first optical switches 103a-c, and a wavelength group multiplexer 105 connected to the output port of second optical switches 104a-c and multiplexing the input N wavelength groups. In addition, in Figure 1, the number N of optical signals of wavelength groups that are demultiplexed by the wavelength group demultiplexer 101 is depicted as 3, but this is intended as an example, and the number N can be set arbitrarily depending on the number of wavelength groups that the wavelength multiplexed signal has.

[0007] When a wavelength-multiplexed signal is input from outside the optical transmission device 100, the externally input wavelength-multiplexed signal is demultiplexed into N wavelength groups (three wavelength groups in the example of FIG. 1 ) by the wavelength group demultiplexer 101 (for example, demultiplexed into S-band, C-band, and L-band). Each of the demultiplexed optical signals of the N wavelength groups is input to a respective optical amplifier 102 a-c configured to be able to amplify the optical signal of that wavelength group. For example, the optical amplifier 102 a is configured to be able to amplify an optical signal of the S-band, the optical amplifier 102 b is configured to be able to amplify an optical signal of the C-band, and the optical amplifier 102 a is configured to be able to amplify an optical signal of the L-band.

[0008] The output ports of the optical amplifiers 102a-c are input to respective 1-input, M-output first optical switches 103a-c for selecting an output route. In the above example, an amplified S-band optical signal is input to the first optical switch 103a, an amplified C-band optical signal is input to the first optical switch 103b, and an amplified L-band optical signal is input to the first optical switch 103c. The optical signals of each wavelength group input to each of the first optical switches 103a-c are output to any of the M routes selected by the user and input to the corresponding second optical switches 104a-c. However, the output ports of each of the first optical switches 103a-c are all connected to respective input ports of different second optical switches 104a-c.

[0009] The second optical switches 104a-c are provided at each of the M output ports of the optical transmission device 100. As described above, the optical transmission device 100 is configured so that a user can select which of the M second optical switches 104a-c an optical signal of each wavelength group transmitted from each of the first optical switches 103a-c is input to. The output port of each of the second optical switches 104a-c is connected to an input port of a wavelength group multiplexer 105 provided at each of the M output ports. The wavelength group multiplexer 105 has the function of multiplexing and outputting optical signals of N wavelength groups.

[0010] The optical transmission device 100 having such a configuration has a function of routing wavelength-multiplexed signals bundled as wavelength groups as control units. Furthermore, the optical transmission device 100 can also be equipped with other functions, such as routing control functions on a wavelength-by-wavelength basis, a signal insertion / removal function, and a function for reducing the signal level deviation between wavelength-multiplexed signals. However, the optical transmission device 100 can be said to be the most basic node configuration when multiple wavelength bands are used.

[0011] In a basic node configuration that assumes the use of multiple wavelength bands, such as the optical transmission device 100, the unit of route control is a coarse unit called a wavelength group, as described above. In such a network, if a failure occurs and signals need to be transferred to a detour route, it is necessary to prepare a wideband free route for detour. However, since the free detour routes that must be prepared are a factor in increasing the system's costs, there is a desire to minimize the number of such routes implemented.

[0012] In order to minimize such empty detour paths, it is effective to convert the wavelength group to which the optical signal belongs to another wavelength group, thereby increasing the flexibility of detour route selection. One method for converting the wavelength group of an optical signal is to receive the optical signal of one wavelength group using a receiver and then retransmit the received optical signal of the wavelength group as it is using another wavelength group. However, this method requires the same number of receivers and transmitters as the number of signal wavelengths in the wavelength group, which results in high costs and high power consumption.

[0013] S. Yamamoto, H. Taniguchi, Y. Kisaka, S. Camatel, Y. Ma, D. Ogawa, K. Hadama, M. Fukutoku, T. Goh, and K. Suzuki: “First demonstration of a C+L band CDC-ROADM with a simple node configuration using multiband switching devices,” Optics Express, Vol. 29, No. 22, pp. 36353-36365, (2021)

[0014] The present disclosure has been made in consideration of the above-mentioned problems, and its purpose is to provide an optical transmission device that minimizes the number of available detour paths that need to be prepared in a node configuration that assumes the use of multiple wavelength bands.

[0015] In response to the above-described problems, the present disclosure provides an optical transmission device configured to be connectable to a maximum of M degrees (M is an integer of 1 or more), the optical transmission device including M wavelength group demultiplexers that demultiplex a wavelength-multiplexed signal input from an external source into optical signals of N wavelength groups (N is an integer of 2 or more), M optical amplifiers that amplify each of the demultiplexed optical signals of the N wavelength groups, M first optical switches with one input and (M+N-1) outputs that are connected to the output ports of each of the M optical amplifiers, and M input / M output N(N-1) first optical switches that wavelength group convert each of the optical signals of the wavelength groups output from each of the (N-1) output ports of the (M+N-1) output ports of the first optical switches into optical signals of another wavelength group. an optical transmission device comprising: 1) wavelength group conversion units; MN second optical switches with (M+N-1) input / 1 output that selectively output one signal from among the optical signals of the wavelength group output from M output ports out of the (M+N-1) output ports of the first optical switch and the N-1 optical signals wavelength group converted from the output ports of the wavelength group conversion units; and M wavelength group multiplexers that multiplex the optical signals of the N wavelength groups output from the second optical switches; and an optical transmission device configured so that the optical signals of the wavelength group that are output from the M output ports out of the (M+N-1) outputs of the first optical switch and that are not guided to the wavelength group conversion units are all input to different second optical switches.

[0016] 1 is a diagram illustrating a schematic basic configuration of an optical transmission device 100 according to a conventional technique; FIG. 2 is a diagram illustrating a conceptual configuration of an optical transmission device 200 according to the present disclosure; and FIG. 3 is a diagram illustrating a conceptual configuration of an optical transmission device 300 according to another example of the present disclosure.

[0017] Various embodiments of the present disclosure will be described in detail below with reference to the drawings. The same or similar reference numerals indicate the same or similar elements, and redundant description may be omitted. Materials and numerical values ​​are for illustrative purposes only and are not intended to limit the technical scope of the present disclosure. The following description is an example, and some configurations may be omitted or modified, or additional configurations may be added, as long as they do not deviate from the gist of one embodiment of the present disclosure.

[0018] 2 is a conceptual diagram illustrating the configuration of an optical transmission device 200 according to the present disclosure. The optical transmission device 200 is configured to be connectable to a maximum of M optical fibers (M is an integer of 1 or greater), and includes M wavelength group demultiplexers that demultiplex an externally input wavelength-multiplexed signal into optical signals of N wavelength groups (N is an integer of 2 or greater), MN optical amplifiers that amplify each of the demultiplexed optical signals of the N wavelength groups, MN first optical switches with one input and (M+N−1) outputs connected to the output ports of each of the MN optical amplifiers, and MN first optical switches with one input and (M+N−1) outputs that amplify each of the (M+N−1) output ports of the first optical switches. The optical switch includes N(N-1) wavelength group converters with M inputs and M outputs that wavelength group convert each of the output optical signals of the wavelength group into an optical signal of another wavelength group; MN second optical switches with (M+N-1) inputs and 1 output that selectively output one signal from the optical signals of the wavelength group from M output ports out of the (M+N-1) output ports of the first optical switch and the wavelength group converted optical signals of the N-1 wavelength groups from the output port of the wavelength group converter; and M wavelength group multiplexers that multiplex the optical signals of the N wavelength groups output from the second optical switches.

[0019] In addition, Figure 2 depicts a configuration in which the number of paths M of the optical transmission device 200 is 2 and the number of wavelength bands N demultiplexed by each of the wavelength group demultiplexers 201a-b is 3, but this is intended as an example, and the number of paths M and the number of wavelength bands N demultiplexed may be set to any number depending on the design.

[0020] In the following description, M will be taken to represent the number of paths in the optical transmission device, and N will be taken to represent the number of wavelength groups demultiplexed by the wavelength group demultiplexer.

[0021] When a wavelength-multiplexed signal is input from outside the optical transmission device 200, the externally input wavelength-multiplexed signal is demultiplexed into N wavelength groups by the wavelength group demultiplexers 201a-b. For example, each of the wavelength group demultiplexers 201a-b can be configured to demultiplex the externally input wavelength-multiplexed signal into three wavelength groups: S band (wavelength 1460-1530 nm band), C band (wavelength 1530-1565 nm band), and L band (wavelength 1565-1625 nm band). In FIG. 2, the path of the S-band optical signal is illustrated by a black (dark) solid line, the path of the C-band optical signal is illustrated by a gray (light) solid line, and the path of the L-band optical signal is illustrated by a black (dark) dashed line.

[0022] Each of the optical signals of the demultiplexed wavelength groups (for example, three wavelength groups of S band, C band, and L band) is input to optical amplifiers 202a1-3, 202b1-3, which are configured to be able to amplify the optical signals of the corresponding wavelength group. Examples of combinations of wavelength groups and optical amplifiers 202a1-3, 202b1-3 settings include a case where the wavelength group is the S band and optical amplifiers 202a1, 202b1 are thulium-doped fiber amplifiers (TDFAs) or S-band lumped Raman amplifiers, a case where the wavelength group is the C band and optical amplifiers 202a2, 202b2 are C-band EDFAs or C-band lumped Raman amplifiers, and a case where the wavelength group is the L band and optical amplifiers 202a3, 202b3 are L-band EDFAs or L-band lumped Raman amplifiers.

[0023] The wavelength ranges that the optical amplifiers 202a1-3 and 202b1-3 can amplify may all be different from each other.

[0024] The output ports of the optical amplifiers 202a1-3 and 202b1-3 are connected to the first optical switches 203a1-3 and 203b1-3, each with one input and (M+N-1) output, which select either an output route or one of the wavelength group converters 204a-f, each of which is provided for a combination of wavelength groups before and after conversion, and which converts the output wavelength group optical signal to the pre-conversion wavelength group. Of the output ports of each of the first optical switches 203a1-3 and 203b1-3, M output ports are connected to one of the second optical switches 205a1-3 and 205b1-3, each with (M+N-1) inputs and one output, which is set to a predetermined wavelength group. Optical signals of wavelength groups transmitted through this route do not pass through the wavelength group converters 204a-f, which will be described later, and are therefore guided to the predetermined second optical switches 205a1-3 and 205b1-3 without wavelength group conversion. For example, the first optical switches 203a1, b1 can be configured so that an amplified S-band optical signal is output from one of M output ports of each of the first optical switches 203a1, b1, and input to one of the second optical switches 205a1, 205b1 set as the S-band without being wavelength group converted.

[0025] On the other hand, (N-1) output ports of each of the first optical switches 203a1-3 and 203b1-3 are connected to wavelength group converters 204a-f configured to convert optical signals of one wavelength group input from the first optical switches 203a1-3 and 203b1-3 into another wavelength group. For example, the first optical switches 203a1 and 203b1 may be configured so that an amplified S-band optical signal is output from one of the (N-1) output ports of each of the first optical switches 203a1 and 203b1 and input to wavelength group converter 204a configured to convert the S-band into the C-band or wavelength group converter 204b configured to convert the S-band into the L-band.

[0026] As described above, each of the (N-1) input (N-1) output wavelength group converters 204a-f is configured to convert optical signals of a wavelength group output from (N-1) output ports of each of the first optical switches 203a1-3 and 203b1-3 into another wavelength group. Each output port of the wavelength group converters 204a-f is connected to one of the second optical switches 205a1-3 and 205b1-3 corresponding to the optical signals of the converted wavelength group. For example, the wavelength group converter 204a may be configured to output an optical signal output from one of the (N-1) output ports of each of the first optical switches 203a1 and 203b1, converted from the S band to the C band, to one of the second optical switches 205a2 and 205b2 set as the C band.

[0027] Each of the wavelength group converters 204a-f may be any known device that performs wavelength band conversion on an optical signal of an input wavelength group. For example, each of the wavelength group converters 204a-f may be a wavelength conversion element configured to perform wavelength conversion based on second-order nonlinear optical effects (sum frequency generation (SFG), difference frequency generation (DFG), second harmonic generation (SFG)) using periodically poled lithium niobate (PPLN). In another example, each of the wavelength group converters 204a-f may be a highly nonlinear fiber.

[0028] The output ports of the second optical switches 205a1-3 and 205b1-3 are connected to the input ports of the wavelength group multiplexers 206a-b, respectively. Each of the wavelength group multiplexers 206a-b has the function of multiplexing optical signals of multiple wavelength groups and outputting the multiplexed signal.

[0029] The optical transmission device 200 having the above configuration is configured so that the optical signals of the wavelength groups output from each of the first optical switches 203a1-3 and 203b1-3 are ultimately input to different second optical switches 205a1-3 and 205b1-3. The second optical switches 205a1-3 and 205b1-3 are provided for each output port of the optical transmission device 200, and are configured so that the user can select either the input route or one of the wavelength group conversion units 204a-f provided for each wavelength group before conversion.

[0030] In the optical transmission device 200 according to the present disclosure having such a configuration, when an optical signal of a wavelength group is sent in each of the first optical switches 203a1-3, 203b1-3 toward one of the wavelength group converters 204a-f corresponding to conversion to a target wavelength group, the optical signal of the wavelength group is converted to the target wavelength group, and a route can be set to send the optical signal of the wavelength group toward one of the appropriate second optical switches 205a1-3, 205b1-3 so that it can be sent from a desired output route of the optical transmission device 200. Therefore, in a node configuration using multiple wavelength bands, it is possible to set optical routes that pass through different wavelength bands, and by utilizing this, it is possible to convert an optical signal of any wavelength group while minimizing the number of available detour routes that need to be prepared.

[0031] Furthermore, if the condition that there is no return to the input route is accepted, the number of output ports of each of the first optical switches 203a1-3, 203b1-3 and the number of input ports of each of the second optical switches 205a1-3, 205b1-3 can also be (M+N-2) since the number of route options is reduced by one.

[0032] Furthermore, in practice, in most cases, the optical transmission device 200 operates two sets of wavelength-band optical signal paths, an outbound path and a return path. From this perspective, in the optical transmission device 200, it is desirable that the wavelength-band converters 204a-f are configured to include pairs of wavelength bands before and after conversion of the optical signal to be converted. For example, if the wavelength-band converters 204a-f include the wavelength-band converter 204a configured to convert an S-band optical signal into a C-band optical signal, it is desirable that the wavelength-band converters 204a-f also include, as their counterpart, the wavelength-band converter 204c configured to convert a C-band optical signal into an S-band optical signal.

[0033] As yet another example, the optical transmission device according to the present disclosure may further include an optical amplifier and / or a wavelength deviation correction unit connected to each output port of the wavelength group conversion unit.

[0034] 3 is a conceptual diagram illustrating the configuration of an optical transmission device 300 according to another example of the present disclosure. As illustrated in FIG. 3, the optical transmission device 300 further includes wavelength deviation correction units 301a1-a3 and 301b1-b3 arranged on the output side of the optical amplifiers 202a1-3 and 202b1-3, respectively. Note that while FIG. 3 depicts a configuration in which the wavelength deviation correction units 301a1-a3 and 301b1-b3 are arranged only on the output side of the optical amplifiers 202a1-3 and 202b1-3, the wavelength deviation correction units may be arranged on the output side of the wavelength group converters 204a-f, or may be arranged on the output sides of both the optical amplifiers 202a1-3 and 202b1-3 and the wavelength group converters 204a-f.

[0035] The outputs of the optical amplifiers 202a1-3, 202b1-3 and wavelength group converters 204a-f may have wavelength deviations in the output light levels. The wavelength deviation correction units 301a1-a3, 301b1-b3 have the function of correcting such wavelength deviations. The wavelength deviation correction units 301a1-a3, 301b1-b3 may be optical functional devices for individually performing optical adjustments according to wavelength, and may be, for example, filters that equalize the wavelength dependency of light intensity.

[0036] Even with the optical transmission device 300 having such a configuration, in a node configuration using multiple wavelength bands, it is possible to convert optical signals of any wavelength group while minimizing the number of available detour paths that need to be prepared. Furthermore, as described above, the optical transmission device 300 can compensate for wavelength deviations in the outputs of the optical amplifiers 202a1-3, 202b1-3 and wavelength group converters 204a-f, and therefore can transmit optical signals of higher quality wavelength groups (with less wavelength deviation).

[0037] As described above, the optical transmission device according to the present disclosure can function as a signal wavelength group conversion device while minimizing the number of available detour paths that need to be prepared in a node configuration that assumes the use of multiple wavelength bands. Such an optical transmission device is expected to be put to practical use as a device that forms detour paths at low cost in optical transmission devices that can transmit vast amounts of data compared to conventional technologies.

Claims

1. An optical transmission device configured to be connectable to a maximum of M degrees (M is an integer of 1 or greater), comprising: M wavelength group demultiplexers that demultiplex an externally input wavelength-multiplexed signal into optical signals of N wavelength groups (N is an integer of 2 or greater); MN optical amplifiers that amplify each of the demultiplexed optical signals of the N wavelength groups; MN first optical switches with 1 input and (M+N-1) outputs connected to the output ports of each of the MN optical amplifiers; and N(N-1) wavelength group conversion units with M inputs and M outputs that wavelength group convert each of the optical signals of the wavelength group output from each of (N-1) output ports out of the (M+N-1) output ports of the first optical switch into an optical signal of another wavelength group. an optical transmission device comprising: MN second optical switches with (M+N-1) input / 1 output that selectively output one signal from among the optical signals of the wavelength group output from M output ports out of the (M+N-1) output ports of the first optical switch and the N-1 optical signals of the wavelength group that have been wavelength group converted from the output port of the wavelength group conversion unit; and M wavelength group multiplexers that multiplex the optical signals of the N wavelength groups output from the second optical switches; wherein the optical transmission device is configured so that the optical signals of the wavelength group that are output from the M output ports out of the (M+N-1) outputs of the first optical switch and that are not guided to the wavelength group conversion unit are all input to different second optical switches.

2. The optical transmission device according to claim 1, wherein the wavelength group converter is configured to include pairs of wavelength bands before and after conversion of the optical signal to be converted.

3. The optical transmission device according to claim 1, further comprising a wavelength deviation correction unit arranged on the output side of each of the optical amplifiers, on the output side of each of the wavelength group conversion units, or on the output side of both each of the optical amplifiers and each of the wavelength group conversion units.

4. The optical transmission device according to claim 1, wherein the wavelength group conversion section is either a wavelength conversion element configured to perform wavelength conversion based on the second-order nonlinear optical effect using periodically poled lithium niobate, or a highly nonlinear fiber.

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