Wavelength cross-connect device, add-drop device, control device, and optical transmission method

Abstract

A wavelength cross-connect device (20) comprises: an optical branching unit (22a) that causes optical signals extracted for each wavelength by an optical signal extraction unit (21) to branch into a plurality of paths set as a multicast path; an optical amplification unit (22b) that compensates for optical power of the optical signals caused to branch by the optical branching unit (22a); a wavelength conversion unit (24) that converts the wavelengths of the optical signals amplified by the optical amplification unit (22b); and an optical signal multiplexing unit (25) that transmits, to the plurality of paths set as the multicast path, optical signals obtained by multiplexing optical signals outputted from the optical amplification unit (22b) and the wavelength conversion unit (24) and other optical signals inputted thereto.

Description

Wavelength cross-connect device, add-drop device, control device, and optical transmission method

[0001] The present invention relates to a wavelength cross-connect device, an add-drop device, a control device, and an optical transmission method.

[0002] The Innovative Optical and Wireless Network (IOWN) is a network infrastructure that uses optical communication technology to enable high-speed, high-capacity communications. The All Photonics Network (APN) is a key technology for realizing IOWN. Conventional networks (NWs) are hierarchically organized, with optical signals converted to electrical signals at the boundaries of these NWs and then aggregated. In contrast, the APN eliminates the need for electrical termination of optical signals at these NW boundaries, connecting signals directly from the source to the destination as optical signals, enabling low-power, high-quality, high-capacity, and low-latency transmission. In such an IOWN APN, optical paths between users are established using conventional optical transmission equipment by providing unicast transmission technology, which allocates one wavelength between the user and the destination to establish an optical path.

[0003] On the other hand, even when providing broadcast communication services such as TV broadcasting, live streaming, and content delivery in such user-to-user optical path connection services, conventional transmission equipment requires a unicast transmission method in which one wavelength is assigned between each user and each destination, and the optical path is established. This requires a wavelength to be assigned for each destination receiving traffic from the source (each user who views the traffic). This increases the number of wavelengths accommodated in the optical transmission equipment, raising concerns that the costs of establishing optical paths will increase in proportion to service demand. Therefore, a technology to improve the wavelength accommodation efficiency of transmission equipment is needed when performing such broadcast communication to multiple users. Multicast methods are available as a method for achieving broadcast communication from one point to multiple points, and previous studies of multicast methods have all focused on technologies that achieve broadcast transmission through electrical processing. Patent Document 1 proposes a method for achieving broadcast communication in which an optical signal transmitted via an optical path is terminated at the receiver and converted back to an electrical signal, and then the electrical signal is looped back and returned to the transmitter each time, thereby transmitting the same signal to multiple destinations.

[0004] JP 2016-134796 A

[0005] However, when multicast communication is performed using conventional optical transmission equipment, conversion processing between optical signals and electrical signals is required each time a receiving end user receives an optical signal, and therefore a multicast transmission method (optical multicast) or optical transmission equipment that copies (branches) the optical signal itself in the optical layer and transmits it to multiple points, which satisfies the APN concepts of E2E optical connection and low latency, has not been realized.For example, the drop-and-continue method described in Patent Document 1 has a device configuration that realizes multicast after converting the received optical signal into an electrical signal in the transponder, and is not a device configuration that realizes multicast in the optical layer (optical multicast).

[0006] Therefore, a main object of the present invention is to provide optical multicast transmission in which optical signals are branched as they are and transmitted to each point.

[0007] In order to solve the above problems, the optical transmission device of the present invention has the functions of a wavelength cross-connect device and an add-drop device. The wavelength cross-connect device has the optical signal route selection function of conventional optical transmission devices. The add-drop device has the following functions: - The add function multiplexes any optical signals from the transmitters it accommodates and sends the multiplexed signal to the wavelength cross-connect device to be connected. - The drop function demultiplexes some of the WDM (Wavelength Division Multiplexing) signals distributed by the route selection function of the wavelength cross-connect device and sends the demultiplexed signals to the receiver it accommodates. In addition to these functions, the present invention has the following features. The present invention provides a wavelength cross-connect device and an add-drop device that accepts input of optical signals from relay devices that have passed before the device itself and that are set as a multicast path, and is characterized by comprising: an optical signal extraction unit that extracts optical signals from the input optical signals that correspond to wavelengths that are set as the multicast path; an optical branching unit that branches the optical signals for each wavelength extracted by the optical signal extraction unit to multiple routes that are set as the multicast path; an optical amplification unit that compensates for the optical power of the optical signals branched by the optical branching unit; a conversion unit that converts the wavelength of the optical signal amplified by the optical amplification unit to an unused wavelength that is set as the multicast path so that it does not overlap with the wavelengths of other optical signals that pass through an optical signal multiplexing unit that outputs the optical signal; and the optical signal multiplexing unit that transmits an optical signal that is obtained by multiplexing the optical signal output from the optical amplification unit and the conversion unit with other input optical signals to the multiple routes that are set as the multicast path.

[0008] According to the present invention, it is possible to provide optical multicast transmission in which an optical signal is directly branched and transmitted to each point.

[0009] FIG. 1 is a configuration diagram of an optical transmission system according to the present embodiment. FIG. 1 is a configuration diagram showing details of a multicast path setting controller according to the present embodiment. FIG. 2 is a flowchart showing the processing of the multicast path setting controller following FIG. 3 according to the present embodiment. FIG. 3 is a flowchart showing the processing of the multicast path setting controller according to the present embodiment. FIG. 1 is an explanatory diagram of the process of determining whether an available wavelength is pulled through according to the present embodiment. FIG. 2 is a network diagram showing optical transmission devices at each point from the start point to the end point of an optical path according to the present embodiment. FIG. 1 is a configuration diagram showing details of a wavelength cross connect device according to the present embodiment. FIG. 1 is a configuration diagram showing details of a drop-side optical branching and amplifying unit according to the present embodiment. FIG. 1 is an explanatory diagram of a wavelength conversion unit according to the present embodiment. FIG. 1 is a configuration diagram showing details of an add-drop device according to the present embodiment. FIG. 1 is an explanatory diagram showing branching processing of an add signal in a wavelength cross connect device according to the present embodiment. FIG. 1 is an explanatory diagram showing branching processing of a pass signal in a wavelength cross connect device according to the present embodiment. FIG. 1 is an explanatory diagram showing branching processing of a pass signal + drop signal in a wavelength cross connect device according to the present embodiment. FIG. 1 is an explanatory diagram showing branching processing of an add signal in an add-drop device according to the present embodiment. FIG. 1 is an explanatory diagram showing branching processing of a pass signal + drop signal in an add-drop device according to the present embodiment. FIG. 1 is an explanatory diagram showing branching processing of a drop signal in an add-drop device according to the present embodiment.

[0010] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

[0011] 1 is a configuration diagram of an optical transmission system 100. The optical transmission system 100 includes a host device 81, a multicast path setting controller (control device) 70, and an optical transmission device (relay device) 10. The optical transmission device 10 is a relay device that serves as a passing node of a multicast path. A maintenance person 82 receives a request to open a multicast path from the host device 81, such as a network management server, and inputs the start and end point information, passing nodes and route, number of branches, branching rate, and amplification rate to the multicast path setting controller 70 as setting information for a new multicast path.

[0012] The multicast path setting controller 70 determines the following control information by referring to the input setting information for the new multicast path and the topology of the optical network to which multiple optical transmission devices 10 are connected (for example, as illustrated in FIG. 6 ), and sets the control information in each optical transmission device 10: - "Connection port open / close information" indicating which wavelength of an optical signal is to be output from which port of the optical transmission device 10 connected to which path. This connection port open / close information indicates the path to which the optical signal of the multicast path is to be branched. - "Branch ratio" indicating the power ratio of each output signal when each optical branching unit in the optical transmission device 10 branches and outputs the optical signal. - "Amplification ratio" when each optical amplifier unit in the optical transmission device 10 amplifies the optical signal.

[0013] The optical transmission device 10 includes a wavelength cross-connect device 20 for optical transmission between other optical transmission devices 10 and an add-drop device 30 for optical transmission between the transmitters and receivers accommodated by the device itself. The left side of FIG. 1 is the input side, and the right side is the output side. The input side of the wavelength cross-connect device 20 is equipped with transmission paths 11a and 11b, optical amplifiers 41a and 41b, and route selectors 42a and 42b, respectively, for WDM signals from different transmission paths (different direction paths). The optical amplifiers 41a and 41b compensate for the power of the optical signals that have passed through the transmission paths and been attenuated and input to the optical amplifiers 41a and 41b.

[0014] On the output side of the wavelength cross-connect device 20, there are provided, in the order of passage of the optical signal, route selection units 42c and 42d, optical amplification units 41c and 41d, and transmission paths 11c and 11d leading to the next repeater. The optical amplification units 41c and 41d compensate for insertion loss within the device when the signal passes through the route selection units 42a, 42b, 42c, and 42d. Connected to the add-drop device 30 are a transmitter Tx for inputting an add signal added from outside, and a receiver Rx for extracting a drop signal and outputting it to the outside.

[0015] FIG. 2 is a block diagram showing the details of the multicast path setting controller 70. FIGS. 3 and 4 are flowcharts showing the processing of the multicast path setting controller 70. Each component of FIG. 2 will be described below with reference to FIGS. 3 and 4. The multicast path setting controller 70 has an input unit 71, a wavelength setting unit 72, a conversion setting unit 77, a transmission feasibility determination unit 73, a hardware setting control unit 74, a wavelength information DB 75, and a transmission design information DB 76. The input unit 71 receives the following inputs as route information for a newly set multicast path as described in FIG. 1: Selection of start node and end node (S101 in FIG. 3). Route selection of passing nodes (S102). Input of the number of branches, branching rate, and amplification rate for each passing node (S103).

[0016] If the same unused wavelength exists in all relay devices indicated in the route information of the multicast path, the wavelength setting unit 72 sets the unused wavelength as the wavelength set for the multicast path. Therefore, existing optical paths are registered by wavelength in the wavelength information DB 75. Then, the wavelength setting unit 72 refers to the wavelength information DB 75, and if there is an unused wavelength available for use by all transit nodes of the new multicast path at the time of wavelength setting (Yes in S111), the wavelength setting unit 72 determines that the unused wavelength can be pulled through (newly assigned). Then, the wavelength setting unit 72 registers in the wavelength information DB 75 that the unused wavelength will be assigned to the new multicast path (S114).

[0017] If the same unused wavelength does not exist in all relay devices indicated in the route information of the multicast path, the conversion setting unit 77 configures wavelength conversion of the multicast path so as to use an unused wavelength in each relay device. Therefore, if the wavelength setting unit 72 determines that it is impossible to install an unused wavelength (No in S111), the conversion setting unit 77 refers to the wavelength information DB 75. If a convertible unused wavelength exists at some transit nodes of the new multicast path (Yes in S112), the conversion setting unit 77 registers the wavelength in the wavelength information DB 75 so that the wavelength can be converted to an available wavelength that can be individually used at the transit nodes (S113). On the other hand, if a convertible unused wavelength does not exist (No in S112), the conversion setting unit 77 returns to S102 to prompt the user to re-input the configuration information (route information) of the new multicast path via the input unit 71.

[0018] After the wavelength setting unit 72 or the conversion setting unit 77 sets the wavelength, the transmission feasibility determination unit 73 determines the receiving end Q factor or OSNR (Optical Signal to Noise Ratio) as the transmission quality of the multicast path based on the setting information of the new multicast path (transmission distance, number of branches / branching rate, amplification rate) (S121). The transmission feasibility determination unit 73 also performs a transmission feasibility determination for each optical signal branch in the wavelength cross-connect device 20 and the add / drop device 30. If the transmission quality of the multicast path is equal to or higher than the transmission standard registered in the transmission design information DB 76 (equal to or higher than a predetermined Q-limit or a predetermined minimum receivable OSNR) (Yes in S121), the transmission feasibility determination unit 73 determines that the new multicast path is transmission feasible and sets its detailed parameters (branching rate and amplification rate that are equal to or higher than the Q-limit and the minimum receivable OSNR) (S122).

[0019] On the other hand, if the transmission quality of the multicast path is below the transmission standard (No in S121), the transmission feasibility determination unit 73 determines in S123 that it is below the Q-limit or below the minimum receivable OSNR, and returns the processing to S102 to prompt the user to re-input the setting information (route information) of a new multicast path from the input unit 71.

[0020] The hardware setting control unit 74 sets a multicast path for the optical transmission device in accordance with the route information of the multicast path received by the input unit 71 and the wavelength set by the wavelength setting unit 72 or the conversion setting unit 77. Therefore, for each passing node of the new multicast path that the transmission feasibility determination unit 73 has determined to be transmittable, if the hardware setting control unit 74 determines that transmission is possible through the wavelength cross-connect device 20 (Yes in S131 of FIG. 4), the hardware setting control unit 74 reflects the multicast setting of S122 in the wavelength cross-connect device 20 (S132). On the other hand, if the hardware setting control unit 74 determines that transmission is not possible through the wavelength cross-connect device 20 (No in S131), the hardware setting control unit 74 reflects the multicast setting of S122 in the add-drop device 30 (S133).

[0021] That is, if it is determined that transmission is possible using either the wavelength cross-connect device 20 or the add-drop device 30 within the same transit node, priority is given to using the wavelength cross-connect device 20. As described above, the multicast path setting controller 70 opens a new multicast path by remotely controlling the setting of the hardware of each transit node (S134).

[0022] 5 is an explanatory diagram of the process of determining whether an available wavelength can be pulled (S111). If the same wavelength is available as an available wavelength in a total of nine optical transmission devices 10a to 10i, which are transit nodes of one multicast path, the wavelength setting unit 72 determines that the wavelength can be pulled (Yes in S111).

[0023] 6 is a network diagram showing optical transmission devices 10 at each point from the start point to the end point of an optical path. When the optical transmission device 10A receives an add optical signal (add signal) from a transmitter 91A accommodated therein, it transmits the add signal as a pass signal that branches and continues to the optical transmission devices 10B and 10C. The optical transmission device 10C receives a pass signal from the optical transmission device 10A and branches and transmits the pass signal to the optical transmission devices 10D and 10E. The optical transmission device 10D receives a pass signal from the optical transmission device 10C and transmits the pass signal as a drop signal that terminates (Drops) to the accommodated receivers 92C and 92D.

[0024] The optical transmission device 10E receives a passing signal from the optical transmission device 10C and transmits the passing signal as a drop signal to the accommodated receiver 92A, as well as to the optical transmission device 10F. Here, the arrows from the optical transmission device 10E to the optical transmission device 10F in FIG. 6 are dashed lines, while the arrows between the other optical transmission devices are solid lines. The difference in the arrows is due to the difference between the wavelength λ2 used for the optical signal from the optical transmission device 10E to the optical transmission device 10F and the wavelength λ1 used for the other optical signals (e.g., from the optical transmission device 10A to the optical transmission device 10C). The optical transmission device 10F receives a passing signal from the optical transmission device 10E and transmits the passing signal as a drop signal to the accommodated receiver 92A. The optical signal passing route described above in FIG. 6 is set as new multicast path setting information (route information) by the hardware setting control unit 74 of the multicast path setting controller 70.

[0025] 7 is a configuration diagram showing the details of the wavelength cross-connect device 20. The wavelength cross-connect device 20 has path selection units 42a, 42b, 42c, and 42d, an optical signal extraction unit 21, a drop-side optical branching and amplification unit 22, an add-side optical branching and amplification unit 23, a wavelength conversion unit (conversion unit) 24, and optical signal multiplexing units 25 and 26, thereby realizing multicast point-to-multipoint connection communication. The optical signal extraction unit 21 extracts the following optical signals based on the wavelength of the optical signal input from the path selection unit 42a: - Extracts optical signals of the multicast path and outputs them to the drop-side optical branching and amplification unit 22. - Outputs optical signals other than those of the multicast path to the optical signal multiplexing unit 25.

[0026] Although not shown, a processing unit similar to the optical signal extraction unit 21 may also be provided between the route selection unit 42b and the optical signal multiplexing unit 26. The optical signal multiplexing units 25 and 26 receive input of a multicast signal that has been branched and whose optical power has been guaranteed, multiplex it with other signals bound for the next relay device, and output the result to the route selection units 42c and 42d.

[0027] The drop-side optical branching and amplifying unit 22 outputs a drop signal to the receiver Rx to the add-drop device 30 and branches a pass signal to the other optical transmission device 10 to the optical signal multiplexing unit 25. Furthermore, the drop-side optical branching and amplifying unit 22 amplifies the optical signal to compensate for attenuation due to branching (power compensation). The add-side optical branching and amplifying unit 23 branches the add signal from the transmitter Tx to the optical signal multiplexing units 25 and 26 and outputs it as a pass signal. Furthermore, the add-side optical branching and amplifying unit 23 amplifies the optical signal to compensate for attenuation due to branching. The wavelength conversion unit 24 converts the wavelength of the input optical signal as necessary to prevent wavelength collisions between the optical signals multiplexed by the optical signal multiplexing units 25 and 26, and then outputs the converted optical signal to the optical signal multiplexing units 25 and 26. In other words, when multiplexing the branched optical signals, if the same wavelength exists in the signals on the opposite-direction multiplexing side, the wavelength conversion unit 24 avoids wavelength collisions by converting the wavelength to an unused wavelength.

[0028] The wavelength cross-connect device 20 described above in Figure 7 accepts input of optical signals from relay devices that have passed before it and are set as part of a multicast path. The wavelength cross-connect device 20 extracts multicast signals from the optical transmission device, branches the optical signals, compensates for their optical power, and multiplexes other signals traveling in different directions. This allows multicast transmission from one point to multiple points by copying the same optical signal without electrical conversion when multicast transmission is performed within the optical transmission device.

[0029] That is, the wavelength cross-connect device 20 executes the following procedures. (Procedure 1A) The optical signal extractor 21 extracts, from the input optical signals, optical signals corresponding to wavelengths set as multicast paths. That is, the optical signal extractor 21 extracts wavelength signals to be multicast from wavelength-multiplexed signals (hereinafter referred to as WDM signals) transmitted from the previous node and divided into various paths, or from signals transmitted from a transmitter and passed through an add-drop device. (Procedure 2A) The optical branching unit 22a of the drop-side optical branching and amplifying unit 22 branches the optical signals for each wavelength extracted by the optical signal extracting unit 21 into multiple paths set as multicast paths. (Procedure 3A) The optical amplifying unit 22b of the drop-side optical branching and amplifying unit 22 compensates for the optical power of the optical signal attenuated by the branching by the optical branching unit 22a.

[0030] (Procedure 4A) The wavelength converter 24 converts the wavelength of the optical signal amplified by the optical amplifier 22b to an unused wavelength set as a multicast path so that it does not overlap with the wavelengths of other optical signals passing through the optical signal combiner 25 that outputs the optical signal. In other words, the wavelength converter 24 converts the wavelength of the optical signal output from the drop-side optical branching and amplifying unit 22 to the optical signal combiner 25, 26 as necessary to a wavelength different from the wavelengths of other optical signals passing through the optical signal combiner 25, 26. (Procedure 5A) The optical signal combiner 25, 26 combines the optical signal output from the optical amplifier 22b and the wavelength converter 24 with other input optical signals, and transmits the combined optical signal to multiple paths set as multicast paths. In other words, the optical signal combiner 25, 26 combines the optical signal output in (Procedure 3A) or (Procedure 4A) with other input WDM signals, and transmits the combined optical signal to the next relay device.

[0031] FIG. 8 is a configuration diagram showing the details of the drop-side optical branching and amplifying unit 22. The optical branching unit 22a is a device that branches the optical signal extracted by the optical signal extracting unit 21 into multiple paths. FIG. 8 illustrates examples of branching destinations, such as a wavelength conversion unit 24, an optical signal multiplexing unit 25, and an add-drop device 30. The optical amplifying unit 22b compensates for the optical power attenuated by the branching of the optical branching unit 22a. The add-side optical branching and amplifying unit 23 also has a configuration similar to the drop-side optical branching and amplifying unit 22 described above. However, the optical signal input to the add-side optical branching and amplifying unit 23 is replaced from the optical signal extracted by the optical signal extracting unit 21 with the optical signal input by the add-drop device 30.

[0032] FIG. 9 is an explanatory diagram of the wavelength conversion unit 24. Consider a case where an optical signal from an optical path P1 using wavelength λ1 is branched to two branch destinations (route selection units 42c and 42d) in the drop-side optical branching and amplification unit 22. An optical path P2 using wavelength λ1 is also input to the optical signal multiplexing unit 26. Therefore, if the wavelength of the optical path P1 using wavelength λ1 were output to the optical signal multiplexing unit 26 as is, a collision would occur because the optical paths P1 and P2 use the same wavelength λ1 in the optical signal multiplexing unit 26. Therefore, the wavelength conversion unit 24 converts the wavelength of the optical path P1 using wavelength λ1 to wavelength λ2 and outputs the converted wavelength to the optical signal multiplexing unit 26. As a result, the optical paths P1 and P2 use different wavelengths λ1 and λ2 in the optical signal multiplexing unit 26, thereby avoiding collision. The setting information regarding which wavelength of optical signal each wavelength conversion unit 24 converts to which wavelength is registered in the wavelength information DB 75, and is set in each wavelength conversion unit 24 by the hardware setting control unit 74 of the multicast path setting controller 70.

[0033] 10 is a configuration diagram showing the details of the add-drop device 30. The add-drop device 30 has a demultiplexing unit (optical signal extraction unit) 31, a drop-side optical branching and amplification unit 32, an add-side optical branching and amplification unit 33, an optical signal multiplexing unit 34, and a wavelength conversion unit (conversion unit) 35, and thereby realizes multicast point-to-multipoint connection communication, similar to the wavelength cross-connect device 20. Similar to the optical signal extraction unit 21, the demultiplexing unit 31 demultiplexes (extracts) the following optical signals by wavelength based on the wavelength components of the optical signal having multiple wavelengths input from the route selection unit 42b: - Extracts optical signals of the multicast path and outputs them to the drop-side optical branching and amplification unit 32. - Outputs optical signals other than those of the multicast path to the receiver Rx.

[0034] The drop-side optical branching and amplifying unit 32, like the drop-side optical branching and amplifying unit 22 in FIG. 8, includes an optical branching unit 32a that branches drop signals to multiple receivers Rx and an optical amplifier 32b that amplifies optical signals to compensate for attenuation due to branching. The add-side optical branching and amplifying unit 33, like the add-side optical branching and amplifying unit 23, includes an optical branching unit 33a that branches add signals from a transmitter Tx toward multiple route selection units 42c and 42d and an optical amplifier 33b that amplifies optical signals to compensate for attenuation due to branching. The optical signal multiplexing unit 34, like the optical signal multiplexing units 25 and 26, multiplexes optical signals input from the transmitter Tx, the add-side optical branching and amplifying unit 33, and the wavelength conversion unit 35, and outputs the multiplexed signal to the route selection units 42c and 42d. The optical signal multiplexing units 25, 26, and 34 function as WDM units that perform wavelength multiplexing. Similar to the wavelength conversion unit 24 in FIG. 9 , the wavelength conversion unit 35 converts the wavelength of the input optical signal as necessary to prevent wavelength collisions between the optical signals multiplexed in the optical signal multiplexing unit 34, and then outputs the converted optical signal to the optical signal multiplexing unit 34.

[0035] The add-drop device 30 described above in Figure 10 relays optical signals to devices at the start and end points of a multicast path. The add-drop device 30 extracts multicast signals in the optical transmission device, branches the optical signals, compensates for their optical power, and multiplexes other signals traveling in different directions. This allows optical multicast transmission from one point to multiple points by copying the same optical signal without electrical conversion when multicast communication is performed within the optical transmission device.

[0036] That is, the add-drop device 30 executes the following procedures. (Procedure 1B) The demultiplexing unit 31 demultiplexes and extracts optical signals corresponding to wavelengths set as multicast paths from among the WDM signals input from the path selection unit. That is, the demultiplexing unit 31 demultiplexes and extracts wavelength signals to be multicast from among the WDM signals passing through the add-drop device 30. (Procedure 2B) The optical branching unit 32a of the drop-side optical branching and amplifying unit 32 branches the optical signals for each wavelength extracted by the demultiplexing unit 31 to multiple paths set as multicast paths. (Procedure 3B) The optical amplifying unit 32b of the drop-side optical branching and amplifying unit 32 compensates for the optical power of the optical signal attenuated by the branching of the optical branching unit 32a.

[0037] (Step 4B) The wavelength converter 35 converts the wavelength of the optical signal output from the drop-side optical branching and amplifying unit 32 or the add-side optical branching and amplifying unit 33 to an unused wavelength set as a multicast path so that the wavelength does not overlap with the wavelengths of other optical signals passing through the optical signal multiplexing unit 34 that outputs that optical signal. (Step 5B) The optical signal multiplexing unit 34 multiplexes the optical signals output from the optical amplifier 33b and the wavelength converter 35 with other input optical signals, and transmits the resulting optical signal to multiple routes set as multicast paths. In other words, the optical signal multiplexing unit 34 multiplexes the optical signals input from the drop-side optical branching and amplifying unit 32, the add-side optical branching and amplifying unit 33, the wavelength converter 35, and the transmitter Tx, and transmits the multiplexed signal to the next repeater or terminates it at the accommodated receiver Rx.

[0038] 11 to 16, variations regarding which processing unit performs branching processing for each type of signal, i.e., add signal, pass signal, and drop signal, will be described. First, FIGS. 11 to 13 correspond to the case where it is determined that transmission is possible through the wavelength cross-connect device 20 (Yes in S131 in FIG. 4). FIG. 11 is an explanatory diagram showing branching processing of an add signal performed by the wavelength cross-connect device 20. The add-side optical branching and amplifying unit 23 of the wavelength cross-connect device 20 branches the add signal input from the transmitter Tx and outputs it to the optical signal multiplexing units 25 and 26. This example is applied to the optical transmission device 10A in FIG. 6.

[0039] 12 is an explanatory diagram illustrating branching processing of a passing signal in the wavelength cross-connect device 20. The drop-side optical branching and amplifying unit 22 of the wavelength cross-connect device 20 branches the passing signal input from the optical signal extracting unit 21 and outputs the branched signal to the optical signal multiplexing units 25 and 26. This example is applied to the optical transmission device 10C in FIG.

[0040] 13 is an explanatory diagram illustrating branching processing of a pass signal and a drop signal in the wavelength cross-connect device 20. The drop-side optical branching and amplifying unit 22 of the wavelength cross-connect device 20 branches the pass signal input from the optical signal extracting unit 21 and outputs it as a drop signal (termination signal) to the receiver Rx and a pass signal (extended signal) to the optical signal multiplexing unit 25. This example is applied to the optical transmission device 10E in FIG. 6.

[0041] 14 to 16 correspond to cases where transmission is not possible through the wavelength cross-connect device 20 (No in S131) ​​but is possible through the add-drop device 30. Fig. 14 is an explanatory diagram showing the branching process of the add signal performed by the add-drop device 30. The add-side optical branching and amplifying unit 33 of the add-drop device 30 branches the add signal input from the transmitter Tx and outputs it to the path selecting units 42c and 42d. This example is applied to the optical transmission device 10A in Fig. 6.

[0042] 15 is an explanatory diagram illustrating the branching process of a pass signal and a drop signal performed by the add-drop device 30. The drop-side optical branching and amplifying unit 32 of the add-drop device 30 branches the pass signal input from the path selection unit 42a and outputs it as a drop signal (termination signal) to the receiver Rx and a pass signal (extended signal) to the path selection unit 42c. This example is applied to the optical transmission device 10E in FIG. 6.

[0043] 16 is an explanatory diagram illustrating the branching process of a drop signal in the add-drop device 30. The drop-side optical branching and amplifying unit 32 of the add-drop device 30 branches the passing signal input from the path selecting unit 42a and outputs the branched signals to separate receivers Rx. This example is applied to the optical transmission device 10D in FIG. 6.

[0044] FIG. 17 is a hardware configuration diagram of the optical transmission device 10. The optical transmission device 10 is configured as a computer 900 having a CPU 901, a RAM 902, a ROM 903, a HDD 904, a communication I / F 905, an input / output I / F 906, and a media I / F 907. The communication I / F 905 is connected to an external communication device 915. The input / output I / F 906 is connected to an input / output device 916. The media I / F 907 reads and writes data from a recording medium 917. Furthermore, the CPU 901 controls each unit by executing a program (optical transmission program) loaded into the RAM 902. This program (also called an application, or an app for short) can be distributed via a communication line or recorded on a recording medium 917 such as a USB memory.

[0045] [Effect] The present invention is a wavelength cross-connect device 20 that receives input of optical signals from relay devices that have passed before it and that are set as multicast paths, and is characterized by comprising: an optical signal extraction unit 21 that extracts, from the input optical signals, optical signals that correspond to wavelengths that are set as multicast paths; an optical branching unit 22a that branches the optical signals for each wavelength extracted by the optical signal extraction unit 21 to a plurality of routes that are set as multicast paths; an optical amplification unit 22b that compensates for the optical power of the optical signals branched by the optical branching unit 22a; a wavelength conversion unit 24 that converts the wavelength of the optical signal amplified by the optical amplification unit 22b to an unused wavelength that is set as the multicast path so that the wavelength does not overlap with the wavelengths of other optical signals that pass through the optical signal multiplexing unit 25 that outputs the optical signal; and an optical signal multiplexing unit 25 that transmits an optical signal obtained by multiplexing the optical signal output from the optical amplification unit 22b and the wavelength conversion unit 24 with other input optical signals to a plurality of routes that are set as multicast paths. Furthermore, the wavelength cross-connect device 20 has the function of a wavelength cross-connect device having the path selection function of an optical signal that is possessed by conventional optical transmission devices.

[0046] This allows the wavelength cross-connect device 20 to transmit the same signal as an optical signal to multiple points. Therefore, compared to a configuration in which one wavelength is assigned between one user and one terminal based on the path construction of a conventional optical transmission device and a unicast transmission method is used to communicate an optical path, the number of wavelengths required can be reduced, which improves wavelength accommodation efficiency and enables reductions in the cost and power consumption of the device.

[0047] The present invention provides an add-drop device 30 that relays optical signals to devices at the start or end of a multicast path, comprising: a demultiplexing unit 31 that extracts optical signals corresponding to wavelengths set as multicast paths from among input optical signals; an optical branching unit 33a that branches the optical signals for each wavelength extracted by the demultiplexing unit 31 to multiple routes set as multicast paths; an optical amplifier 33b that compensates for the optical power of the optical signals branched by the optical branching unit 33a; a wavelength conversion unit 35 that converts the wavelength of the optical signal amplified by the optical amplifier 33b to an unused wavelength set as the multicast path so as not to overlap with the wavelengths of other optical signals passing through an optical signal multiplexing unit 34 that outputs the optical signal; and an optical signal multiplexing unit 34 that transmits an optical signal obtained by multiplexing the optical signal output from the optical amplifier 33b and the wavelength conversion unit 35 with other input optical signals to the multiple routes set as multicast paths. Furthermore, the add-drop device 30 has the following functions. The add function multiplexes any optical signal from the transmitters it accommodates and sends the multiplexed signal to the wavelength cross-connect device it connects to. The drop function demultiplexes some of the WDM signals that have been distributed by the route selection function of the wavelength cross-connect device and sends the demultiplexed signals to the receiver it accommodates.

[0048] This allows the add / drop device 30 to transmit the same signal as an optical signal to multiple points. Therefore, compared to a configuration in which one wavelength is assigned between one user and one terminal based on the path construction of conventional optical transmission devices and a unicast transmission method is used to communicate an optical path, the number of wavelengths required can be reduced, improving wavelength accommodation efficiency and realizing reductions in the cost and power consumption of the device.

[0049] The present invention is a multicast path setting controller 70 that sets a multicast path for a conventional optical transmission device that branches an optical signal to multiple paths, and is characterized by comprising: an input unit 71 that receives input of route information for a multicast path to be newly set; a wavelength setting unit 72 that, if the same unused wavelength exists in all repeater devices indicated in the route information for the multicast path, sets the unused wavelength as the wavelength set for the multicast path; a conversion setting unit 77 that, if the same unused wavelength does not exist in all repeater devices indicated in the route information for the multicast path, sets wavelength conversion for the multicast path so that an unused wavelength in each repeater device is used; and a hardware setting control unit 74 that sets the multicast path for the optical transmission device in accordance with the route information for the multicast path received by the input unit 71 and the wavelength set by the wavelength setting unit 72 or the conversion setting unit 77.

[0050] This allows the multicast path setting controller 70 to set each optical transmission device so that the same signal can be transmitted to multiple points as an optical signal. Therefore, compared to a configuration in which one wavelength is assigned between one user and one terminal based on the path construction of a conventional optical transmission device and a unicast transmission method is used to communicate an optical path, the number of wavelengths required can be reduced, improving wavelength accommodation efficiency and realizing reductions in device costs and power consumption.

[0051] REFERENCE SIGNS LIST 10 Optical transmission device (relay device) 20 Wavelength cross-connect device 21 Optical signal extraction unit 22 Drop side optical branching and amplification unit 22a Optical branching unit 22b Optical amplification unit 23 Add side optical branching and amplification unit 24 Wavelength conversion unit (conversion unit) 25, 26 Optical signal multiplexing unit 30 Add / drop device 31 Demultiplexing unit (optical signal extraction unit) 32 Drop side optical branching and amplification unit 32a Optical branching unit 32b Optical amplification unit 33 Add side optical branching and amplification unit 33a Optical branching unit 33b Optical amplification unit 34 Optical signal multiplexing unit 35 Wavelength conversion unit (conversion unit) 70 Multicast path setting controller (control device) 71 Input unit 72 Wavelength setting unit 77 Conversion setting unit 73 Transmission possibility determination unit 74 Hardware setting control unit 75 Wavelength information DB 76 Transmission design information DB 100 Optical transmission system

Claims

1. A wavelength cross-connect device that receives an optical signal from a relay device that has passed before itself and is set as a multicast path, the wavelength cross-connect device comprising: - an optical signal extraction unit that extracts an optical signal corresponding to the wavelength set as the multicast path from the input optical signals; - an optical branching unit that branches the optical signals of different wavelengths extracted by the optical signal extraction unit into a plurality of downstream paths set as the multicast path; - an optical amplification unit that compensates for the optical power of the optical signals branched by the optical branching unit; - a conversion unit that converts the wavelength of the optical signals amplified by the optical amplification unit to an unused wavelength set as the multicast path so as not to overlap with the wavelengths of other optical signals passing through an optical signal multiplexing unit that outputs the optical signals; and - the optical signal multiplexing unit that multiplexes the optical signals output from the optical amplification unit and the conversion unit and other input optical signals and transmits the multiplexed optical signals to a plurality of downstream paths set as the multicast path.

2. An add-drop device that relays an optical signal to a device at the start or end of a multicast path, the add-drop device comprising: - an optical signal extraction unit that extracts an optical signal corresponding to the wavelength set as the multicast path from the input optical signals; - an optical branching unit that branches the optical signals of different wavelengths extracted by the optical signal extraction unit into a plurality of downstream paths set as the multicast path; - an optical amplification unit that compensates for the optical power of the optical signals branched by the optical branching unit; - a conversion unit that converts the wavelength of the optical signals amplified by the optical amplification unit to an unused wavelength set as the multicast path so as not to overlap with the wavelengths of other optical signals passing through an optical signal multiplexing unit that outputs the optical signals; and - the optical signal multiplexing unit that multiplexes the optical signals output from the optical amplification unit and the conversion unit and other input optical signals and transmits the multiplexed optical signals to a plurality of downstream paths set as the multicast path.

3. A control device for setting a multicast path for an optical transmission device that branches an optical signal into a plurality of paths, the control device comprising: an input unit that receives an input of path information of the multicast path to be newly set; a wavelength setting unit that, when the same unused wavelength exists in all relay devices indicated by the path information of the multicast path, sets the unused wavelength as the wavelength set for the multicast path; a conversion setting unit that, when the same unused wavelength does not exist in all relay devices indicated by the path information of the multicast path, sets wavelength conversion of the multicast path so as to use the unused wavelength of each relay device; and a hardware setting control unit that sets the multicast path for the optical transmission device according to the path information of the multicast path received by the input unit and the wavelength set by the wavelength setting unit or the conversion setting unit. A control device characterized by that.

4. An optical transmission method by a control device for setting a multicast path for an optical transmission device that branches an optical signal into a plurality of paths, the control device comprising: an input unit, a wavelength setting unit, a conversion setting unit, and a hardware setting control unit, the input unit receiving an input of path information of the multicast path to be newly set, the wavelength setting unit setting the unused wavelength as the wavelength set for the multicast path when the same unused wavelength exists in all relay devices indicated by the path information of the multicast path, the conversion setting unit setting wavelength conversion of the multicast path so as to use the unused wavelength of each relay device when the same unused wavelength does not exist in all relay devices indicated by the path information of the multicast path, and the hardware setting control unit setting the multicast path for the optical transmission device according to the path information of the multicast path received by the input unit and the wavelength set by the wavelength setting unit or the conversion setting unit. An optical transmission method characterized by that.