Optical communication system, optical communication device, and optical communication method

Abstract

The present invention provides an optical communication system having a multi-wavelength optical sorting unit. The multi-wavelength optical sorting unit accepts signals of different wavelengths transmitted or received by each of a plurality of subscriber devices that use a single optical fiber for uplink signal output and downlink signal input or that use different optical fibers for uplink signal output and downlink signal input, and sorts and outputs each signal to an output destination route or subscriber device according to wavelength from among a plurality of routes or the plurality of subscriber devices.

Description

Optical communication system, optical communication device, and optical communication method

[0001] The present invention relates to an optical communication system, an optical communication device, and an optical communication method.

[0002] Optical communication devices capable of relaying optical signals according to their destinations while reducing delays have been proposed (see, for example, Patent Document 1). Regarding the number of optical fibers, in access network sections, upstream and downstream signals with different wavelengths are often multiplexed and transmitted using a single optical fiber. However, in relay network sections, the optical fiber for the upstream signal and the optical fiber for the downstream signal are often separate, and the same wavelength is used for the upstream and downstream signals. For this reason, conventional optical communication systems assume subscriber devices that input and output uplink and downlink signals from a single optical fiber, and perform conversion between single-core and two-core transmission using a 1 / 2-core converter (see, for example, Patent Document 2). For example, the 1 / 2-core converter is a WDM (Wavelength Division Multiplex) filter.

[0003] FIG. 8 shows one embodiment of an optical communication system using the technology of Patent Document 2. The optical communication system includes a subscriber device, a 1 / 2 fiber conversion unit, an optical distribution unit, and a WXC (Wavelength Cross Connect) unit. The subscriber device inputs and outputs uplink and downlink signals via a single-core optical fiber. The 1 / 2 fiber conversion unit connects a single-core transmission section in which uplink and downlink signals are transmitted bidirectionally via the same optical fiber with a two-core transmission section in which uplink and downlink signals are transmitted via different optical fibers. The optical distribution unit inputs signals from multiple subscriber devices in the upstream direction, multiplexes signals with the same destination route, and outputs a wavelength-multiplexed signal for each route. The optical distribution unit inputs wavelength-multiplexed signals from multiple routes in the downstream direction and outputs the required signal to each subscriber device.

[0004] The WXC unit is composed of wavelength multiplexing / demultiplexing units for each upstream and downstream path. The wavelength multiplexing / demultiplexing units are, for example, WSSs (Wavelength Selective Switches). In the upstream direction, the WXC unit multiplexes optical signals from each optical distribution unit for each path and outputs the multiplexed signals to the transmission path. In the downstream direction, the WXC unit outputs wavelength-multiplexed signals input from the transmission path to optical distribution units that accommodate destination subscriber devices according to the wavelengths. In addition, if the wavelength of the optical signal of a downstream signal is the wavelength destined for a subscriber device at another base, the WXC unit outputs the signal to a port connected to the wavelength multiplexing / demultiplexing unit of the path destined for that base.

[0005] In the technology of Patent Document 1, the optical distribution unit is composed of an optical SW (switch) and an AWG (Arrayed Waveguide Grating). The AWG multiplexes and demultiplexes wavelengths, and the optical SW switches input and output destinations according to the path. The subscriber device also has an optical transceiver. A wavelength-tunable optical transmitter / receiver can be used as the optical transceiver. In this case, the subscriber device can communicate at any wavelength. The optical transceiver may also be an optical transceiver with an AMCC (Auxiliary Management and Control Channel) function. In this case, the wavelength used can be controlled via a control signal superimposed by the AMCC.

[0006] International Publication No. 2021 / 131001 International Publication No. 2023 / 095226

[0007] In the above-mentioned conventional technology, a 1 / 2 fiber converter is required to accommodate subscriber devices that input and output uplink and downlink signals through a single optical fiber. Since the same number of 1 / 2 fiber converters are required as the number of subscriber devices, this leads to increased costs.

[0008] Furthermore, when accommodating subscriber devices that separately output and input uplink and downlink signals using two optical fibers, a 1 / 2-core converter is not required. Therefore, depending on the type of subscriber device, on-site work such as installing and removing a 1 / 2-core converter is required at the device installation site, which can cause confusion for on-site workers. In addition, it is necessary to select and install a rack to install the 1 / 2-core converter, and depending on the installation location of the optical SW, wiring between racks may also be required, which increases the amount of work required.

[0009] In view of the above circumstances, an object of the present invention is to provide an optical communication system, an optical communication device, and an optical communication method that can accommodate a plurality of subscriber devices that transmit and receive optical signals while reducing the number of devices.

[0010] An optical communication system according to one embodiment of the present invention includes a multi-wavelength optical distribution unit that distributes and outputs signals of different wavelengths transmitted and received by a plurality of subscriber devices, each of which uses a single optical fiber to output upstream signals and input downstream signals, or uses different optical fibers to a route or subscriber device among a plurality of subscriber devices according to the wavelength.

[0011] An optical communication device according to one embodiment of the present invention includes a multi-wavelength optical distribution unit that distributes and outputs signals of different wavelengths transmitted and received by a plurality of subscriber devices, each of which uses a single optical fiber to output upstream signals and input downstream signals, or uses different optical fibers to a route or subscriber device among a plurality of subscriber devices according to the wavelength.

[0012] An optical communication method according to one aspect of the present invention includes a distribution step in which signals of different wavelengths transmitted and received by a plurality of subscriber devices, each of which uses a single optical fiber for outputting upstream signals and inputting downstream signals, or uses different optical fibers for outputting upstream signals and inputting downstream signals, are distributed and output to a route or subscriber device among a plurality of routes or a plurality of the subscriber devices according to the wavelength.

[0013] According to the present invention, it is possible to accommodate a plurality of subscriber devices that transmit and receive optical signals while reducing the number of devices.

[0014] FIG. 1 is a configuration diagram of an optical communication system according to a first embodiment. FIG. 2 is a configuration diagram of a multi-wavelength light distribution unit according to the first embodiment. FIG. 3 is a configuration diagram of a multi-wavelength light distribution unit according to the first embodiment. FIG. 4 is a configuration diagram of a multi-wavelength light distribution unit according to the first embodiment. FIG. 5 is a configuration diagram of an optical communication system according to a second embodiment. FIG. 6 is a configuration diagram of an optical communication system according to a third embodiment. FIG. 7 is a configuration diagram of an optical communication system using prior art.

[0015] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that the same parts in the drawings are designated by the same reference numerals, and the description thereof will be omitted.

[0016] (First Embodiment) FIG. 1 is a diagram showing an example of the configuration of an optical communication system 1 according to a first embodiment of the present invention. The optical communication system 1 includes a subscriber device 2, a multi-wavelength optical distribution unit 3, and a WXC unit 4. The subscriber device 2 has a mechanism for multiplexing and demultiplexing upstream and downstream signals to enable transmission and reception of upstream and downstream signals via a single optical fiber connection. In this embodiment, the subscriber device 2 outputs uplink and downstream signals through a single core. Hereinafter, multiple subscriber devices 2 will be referred to as subscriber devices 2-a, 2-b, .... Each subscriber device 2 uses different upstream and downstream wavelengths. The multi-wavelength optical distribution unit 3 is mounted, for example, on an optical communication device.

[0017] The multi-wavelength optical distribution unit 3 has ports 32 that accommodate each subscriber device 2, and ports 37 that correspond to the upstream and downstream of routes #1 to #K (K is an integer equal to or greater than 1). A port 32 and the subscriber device 2 that port 32 accommodates are connected by a single optical fiber that transmits uplink and downlink signals. The port 32 that accommodates subscriber device 2-x (x = a, b, ...) is referred to as 32-x, the port 37 that corresponds to the upstream of route #k (k is an integer equal to or greater than 1 and equal to or less than K) is referred to as port 37u-k, and the port 37 that corresponds to the downstream of route #k is referred to as port 37d-k.

[0018] The port 32-x of the multi-wavelength light distribution unit 3 is assigned a wavelength used for an upstream signal and a wavelength used for a downstream signal by a subscriber device 2-x connected to the port 32-x by an optical fiber. In the upstream direction, the multi-wavelength light distribution unit 3 inputs an upstream signal from the subscriber device 2-x through the port 32-x, and if the upstream signal has a wavelength assigned to the port 32-x, outputs the input upstream signal to the WXC unit 4 from a port 37u-k corresponding to the upstream of a route #k specified by a route assigned to an optical path ending at the subscriber device 2-x. In the downstream direction, the multi-wavelength light distribution unit 3 inputs the downstream signal output by the WXC unit 4 through ports 37d-1 to 37d-K corresponding to the downstream of each of routes #1 to #K. The multi-wavelength light distribution unit 3 outputs the input downstream signal from the port 32-x assigned with the wavelength used by the subscriber device 2-x, which is the destination of the downstream signal, to the optical fiber between the subscriber device 2-x.

[0019] 8 can be used as the WXC unit 4. The WXC unit 4 includes 2×K wavelength multiplexing / demultiplexing units 41. The wavelength multiplexing / demultiplexing unit 41 corresponding to the upstream of the path #k is referred to as wavelength multiplexing / demultiplexing unit 41u-k, and the wavelength multiplexing / demultiplexing unit 41 corresponding to the downstream of the path #k is referred to as wavelength multiplexing / demultiplexing unit 41d-k.

[0020] The wavelength multiplexing / demultiplexing unit 41u-k multiplexes upstream optical signals input from the multi-wavelength optical distribution unit 3 or a wavelength multiplexing / demultiplexing unit 41d different from the wavelength multiplexing / demultiplexing unit 41u-k, and outputs the multiplexed signals to a transmission path connected to the path #k. The wavelength multiplexing / demultiplexing unit 41d-k demultiplexes downstream signals transmitted through the transmission path connected to the path #k, and outputs the demultiplexed downstream signals to the port 37 of the multi-wavelength optical distribution unit 3 associated with the wavelengths. Furthermore, if the wavelength of the downstream signal is a wavelength destined for a subscriber device at another base, the wavelength multiplexing / demultiplexing unit 41d-k outputs the downstream signal to a port connected to the wavelength multiplexing / demultiplexing unit 41u-k' of the path #k' (k' ≠ k, k' is an integer between 1 and K) destined for that base.

[0021] In the optical communication system 1, the multi-wavelength light distribution unit 3 performs 1 / 2 fiber conversion. Therefore, it is not necessary to provide a 1 / 2 fiber conversion unit for each subscriber device 2. When the subscriber device 2 uses a two-core optical fiber, the optical fiber that transmits the upstream signal sent by the subscriber device 2 and the optical fiber that transmits the downstream signal addressed to the subscriber device 2 are connected to different ports 32 of the multi-wavelength light distribution unit 3.

[0022] An example of the configuration of the multi-wavelength optical distribution unit 3 shown in Figure 1 will be described using Figures 2 to 5. Here, the multi-wavelength optical distribution unit 3 will be described as accommodating three uplink and downlink signals transmitted over one core and distributing them in two directions. Since the uplink and downlink signals have different wavelengths, a total of six wavelengths are used. The wavelength of the uplink signal used by subscriber device 2-x with x = a, b, c is λux, and the wavelength of the downlink signal is λdx, with the uplink signal with wavelength λux being the uplink signal P(λux) and the downlink signal with wavelength λdx being the downlink signal P(λdx). Also, since there are two directions, the number of directions K = 2.

[0023] 2 is a diagram showing the configuration of the multi-wavelength light distribution unit 310. The multi-wavelength light distribution unit 310 is used as the multi-wavelength light distribution unit 3 shown in FIG. 1. The multi-wavelength light distribution unit 310 has a 1×N wavelength selective switch 311 and a 1×M wavelength selective switch 315. N is the number of subscriber devices that can be accommodated. M is the number of directions K×2. Subscriber device 2-x transmits an upstream signal P(λux) with a wavelength λux and receives a downstream signal P(λdx) with a wavelength λdx.

[0024] The 1×N wavelength selective switch 311 has N ports 312 and one port 313. One port 312 is connected to one subscriber device 2. In FIG. 2, N=3. The port 312 connected to subscriber device 2-x is referred to as port 312-x. The 1×N wavelength selective switch 311 receives upstream signals from each of the N ports 312 and outputs the received upstream signals to ports 313 according to their wavelengths. The port 313 outputs the wavelength-multiplexed upstream signals to the 1×M wavelength selective switch 315. The 1×N wavelength selective switch 311 also receives wavelength-multiplexed downstream signals from the 1×M wavelength selective switch 315 via port 313, demultiplexes them, and outputs the demultiplexed downstream signals from ports 312 according to their respective wavelengths.

[0025] The 1×M wavelength selective switch 315 distributes input signals to output destinations according to their wavelengths, outputting upstream signals in the direction of the wavelength multiplexing / demultiplexing unit 41 and downstream signals in the direction of the subscriber device 2. Specifically, the 1×M wavelength selective switch 315 has one port 316 and M ports 317. The port 317 corresponding to the upstream of path #k is referred to as port 317u-k, and the port 317 corresponding to the downstream of path #k is referred to as port 317d-k. The 1×M wavelength selective switch 315 receives the upstream wavelength-multiplexed signal output by the 1×N wavelength selective switch 311 from port 316, demultiplexes the input upstream wavelength-multiplexed signal, distributes each upstream signal obtained by demultiplexing the input upstream wavelength-multiplexed signal to a path according to its wavelength, and outputs the result from port 317. In addition, the 1xM wavelength selective switch 315 outputs the downstream signals input from each route corresponding to ports 317d-1 to 317d-K to port 316 according to their wavelengths, and port 316 wavelength-multiplexes the downstream signals and outputs them to the 1xN wavelength selective switch 311.

[0026] As described above, each port 312 of the 1×N wavelength selective switch 311 corresponds to a different subscriber device 2. Port 312-x is assigned the wavelength λux of the upstream signal and the wavelength λdx of the downstream signal of the corresponding subscriber device 2-x. The upstream signal with wavelength λux transmitted by subscriber device 2-x is input to the 1×N wavelength selective switch 311 from port 312-x, and the downstream signal with wavelength λdx destined for subscriber device 2-x is distributed to and output from port 312-x.

[0027] An example of the operation of the multi-wavelength optical distribution unit 310 will be described. The 1×N wavelength selective switch 311 multiplexes the upstream signal P (λ ua) input from port 312-a, the upstream signal P (λ ub) input from port 312-b, and the upstream signal P (λ uc) input from port 312-c, and outputs the multiplexed signals from port 313 to the 1×M wavelength selective switch 315. The 1×M wavelength selective switch 315 receives the multiplexed upstream signal from port 316, outputs the upstream signal P (λ ua) and the upstream signal P (λ ub) to the wavelength multiplexing / demultiplexing unit 41u-1 from port 317u-1 corresponding to path #1, and outputs the upstream signal P (λ uc) to the wavelength multiplexing / demultiplexing unit 41u-2 from port 317u-2 corresponding to path #2.

[0028] The 1×M wavelength selective switch 315 receives the downstream signal P (λda) and downstream signal P (λdb) output by the wavelength multiplexing / demultiplexing unit 41d-1 from port 317d-1 corresponding to path #1, and receives the downstream signal P (λdc) output by the wavelength multiplexing / demultiplexing unit 41d-2 from port 317d-2 corresponding to path #2. Port 316 of the 1×M wavelength selective switch 315 outputs the wavelength-multiplexed downstream signal P (λda), downstream signal P (λdb), and downstream signal P (λdc). The 1×N wavelength selective switch 311 receives the wavelength-multiplexed downstream signal output by the 1×M wavelength selective switch 315 from port 313 and demultiplexes it. The 1×N wavelength selective switch 311 outputs the downstream signal P(λda) from a port 312-a, outputs the downstream signal P(λdb) from a port 312-b, and outputs the downstream signal P(λdc) from a port 312-c.

[0029] Fig. 3 is a diagram showing the configuration of a multi-wavelength light distribution unit 320. The multi-wavelength light distribution unit 320 is used as the multi-wavelength light distribution unit 3 shown in Fig. 1. The multi-wavelength light distribution unit 320 shown in Fig. 3 differs from the multi-wavelength light distribution unit 310 shown in Fig. 2 in that it has a 1xM coupler 325 instead of the 1xM wavelength selection switch 315.

[0030] The 1×M coupler 325 receives an upstream multiplexed signal from the 1×N wavelength selective switch 311 and branches it into M signals. The 1×M coupler 325 outputs the branched upstream multiplexed signals to the upstream wavelength multiplexing / demultiplexing units 41u-1 to 41u-K of each route. The 1×M coupler 325 also multiplexes the downstream signals received from the wavelength multiplexing / demultiplexing units 41d-1 to 41d-K, and inputs the multiplexed downstream signal from port 313 of the 1×N wavelength selective switch 311.

[0031] An example of the operation of the multi-wavelength optical distribution unit 320 will be described. The 1×N wavelength selective switch 311 multiplexes an upstream signal P (λua) input from port 312-a, an upstream signal P (λub) input from port 312-b, and an upstream signal P (λuc) input from port 312-c, and outputs the multiplexed upstream signal from port 313 to the 1×M coupler 325. The 1×M coupler 325 branches the upstream multiplexed signal input from the 1×N wavelength selective switch 311, and outputs the branched upstream multiplexed signals to the upstream wavelength multiplexing / demultiplexing unit 41u-1 connected to path #1 and the upstream wavelength multiplexing / demultiplexing unit 41u-2 connected to path #2, respectively.

[0032] Furthermore, the 1×M coupler 325 multiplexes the downstream signal P (λda) and downstream signal P (λdb) input from the downstream wavelength multiplexing / demultiplexing unit 41d-1 connected to path #1 with the downstream signal P (λdc) input from the downstream wavelength multiplexing / demultiplexing unit 41d-2 connected to path #2, and inputs the multiplexed downstream signal to port 313 of the 1×N wavelength selective switch 311. The 1×N wavelength selective switch 311 inputs the multiplexed downstream signal output by the 1×M coupler 325 from port 313 and demultiplexes it. The 1×N wavelength selective switch 311 outputs the downstream signal P (λda) from port 312-a, outputs the downstream signal P (λdb) from port 312-b, and outputs the downstream signal P (λdc) from port 312-c.

[0033] The multi-wavelength optical distribution unit 320 uses a 1xM coupler 325 instead of the 1xM wavelength selection switch 315. In the upstream direction, upstream signals of wavelengths that do not need to be transmitted to each route are also transmitted, but the upper WXC unit 4 performs processing to transmit the necessary wavelengths, so that only the necessary wavelengths can be transmitted to each route.

[0034] Fig. 4 is a diagram showing the configuration of a multi-wavelength light distribution unit 330. The multi-wavelength light distribution unit 330 is used as the multi-wavelength light distribution unit 3 shown in Fig. 1. The multi-wavelength light distribution unit 330 shown in Fig. 4 differs from the multi-wavelength light distribution unit 310 shown in Fig. 2 in that it has a 1xN coupler 331 instead of the 1xN wavelength selection switch 311.

[0035] An example of the operation of the multi-wavelength optical distribution unit 330 will be described. The 1×N coupler 331 multiplexes the upstream signal P (λ ua) input from the subscriber device 2-a, the upstream signal P (λ ub) input from the subscriber device 2-b, and the upstream signal P (λ uc) input from the subscriber device 2-c, and outputs the multiplexed upstream signal to the 1×M wavelength selective switch 315. The 1×M wavelength selective switch 315 receives the multiplexed upstream signal from port 316, outputs the upstream signal P (λ ua) and the upstream signal P (λ ub) to the wavelength multiplexing / demultiplexing unit 41u-1 from port 317u-1 corresponding to path #1, and outputs the upstream signal P (λ uc) to the wavelength multiplexing / demultiplexing unit 41u-2 from port 317u-2 corresponding to path #2.

[0036] The 1×M wavelength selective switch 315 also receives the downstream signal P (λda) and downstream signal P (λdb) output from the wavelength multiplexing / demultiplexing unit 41d-1 through port 317d-1, and receives the downstream signal P (λdc) output from the wavelength multiplexing / demultiplexing unit 41d-2 through port 317d-2. The 1×M wavelength selective switch 315 multiplexes these input downstream signals and outputs a downstream multiplexed signal from port 316. The 1×N coupler 331 branches the downstream multiplexed signal input from the 1×M wavelength selective switch 315, and outputs the branched downstream multiplexed signals to each of the subscriber devices 2-a, 2-b, and 2-c.

[0037] As described above, the multi-wavelength optical distribution unit 330 uses a 1×N coupler 331 instead of the 1×N wavelength selective switch 311. In the downstream direction, downstream signals of undesired wavelengths also arrive at the subscriber device 2. However, by providing a wavelength filter before the receiver of the subscriber device 2, or by performing processing in the receiver of the subscriber device 2 to extract only the desired wavelength, it is possible to extract and transmit only the downstream signal of the desired wavelength.

[0038] Fig. 5 is a diagram showing the configuration of the multi-wavelength light distribution unit 340. The multi-wavelength light distribution unit 340 is used as the multi-wavelength light distribution unit 3 shown in Fig. 1. The multi-wavelength light distribution unit 340 shown in Fig. 5 has a 1xN coupler 331 and a 1xM coupler 325.

[0039] An example of the operation of the multi-wavelength optical distribution unit 340 will be described. The 1×N coupler 331 multiplexes the upstream signal P (λua) input from the subscriber device 2-a, the upstream signal P (λub) input from the subscriber device 2-b, and the upstream signal P (λuc) input from the subscriber device 2-c, and outputs the multiplexed upstream signal to the 1×M coupler 325. The 1×M coupler 325 branches the upstream multiplexed signal input from the 1×N coupler 331, and outputs the branched upstream multiplexed signal to the upstream wavelength multiplexing / demultiplexing unit 41u-1 of path #1 and the upstream wavelength multiplexing / demultiplexing unit 41u-2 of path #2.

[0040] The 1×M coupler 325 also inputs a downstream multiplexed signal obtained by multiplexing the downstream signal P (λda) and downstream signal P (λdb) input from the wavelength multiplexing / demultiplexing unit 41d-1 with the downstream signal P (λdc) input from the wavelength multiplexing / demultiplexing unit 41d-2 to the 1×N coupler 331. The 1×N coupler 331 branches the downstream multiplexed signal input from the 1×M coupler 325, and outputs the branched downstream multiplexed signals to each of the subscriber devices 2-a, 2-b, and 2-c.

[0041] The multi-wavelength light distribution unit 340 uses both of the two wavelength selective switches as couplers, and has the characteristics of both the multi-wavelength light distribution unit 320 and the multi-wavelength light distribution unit 330 .

[0042] (Second Embodiment) When multiplexing uplink and downlink signals into a single fiber, the uplink and downlink signals typically have different wavelengths. In this case, the multi-wavelength optical distribution unit configured as shown in Figures 2 to 5 can accommodate only one signal of a single wavelength. This is because if a wavelength assigned as an uplink / downlink wavelength to one subscriber device is assigned as a downlink / uplink wavelength to another subscriber device accommodated in the same multi-wavelength optical distribution unit, wavelength collisions will occur within the multi-wavelength optical distribution unit. Therefore, the number of subscriber devices that can actually be accommodated by the multi-wavelength optical distribution unit is half the number of available wavelength resources. Furthermore, in this optical communication system, the number of wavelengths that can be added to a single wavelength multiplexing / demultiplexing unit (uplink) connected to a certain path and the number of wavelengths that can be dropped from a single wavelength multiplexing / demultiplexing unit (downlink) connected to the same path are half the number of signals that can actually be added / dropped.

[0043] Therefore, in the second embodiment, at least two or more multi-wavelength optical distribution units are installed. The wavelength of an upstream signal assigned to a certain subscriber unit is used as the wavelength of a downstream signal for a subscriber unit accommodated in a multi-wavelength optical distribution unit that does not accommodate that subscriber unit. Similarly, the wavelength of a downstream signal assigned to a certain subscriber unit is used as the wavelength of an upstream signal for a subscriber unit accommodated in a multi-wavelength optical distribution unit that does not accommodate that subscriber unit.

[0044] Fig. 6 is a diagram showing an example of the configuration of an optical communication system 11 according to the second embodiment. The optical communication system 11 has subscriber devices 2-a, 2-b, 2-c, and 2-d, a plurality of multi-wavelength light distribution units 3, and a WXC unit 4. Fig. 6 shows an example in which the number of multi-wavelength light distribution units 3 is two. The two multi-wavelength light distribution units 3 are referred to as multi-wavelength light distribution units 3-1 and 3-2.

[0045] The multi-wavelength optical distribution unit 3-1 accommodates subscriber devices 2-a and 2-b, while the multi-wavelength optical distribution unit 3-2 accommodates subscriber devices 2-c and 2-d. The multi-wavelength optical distribution unit 3-1 assigns λ1 as the wavelength of the upstream signal and λ2 as the wavelength of the downstream signal to subscriber device 2-a. The multi-wavelength optical distribution unit 3-2 then assigns λ2 as the wavelength of the upstream signal and λ1 as the wavelength of the downstream signal to subscriber device 2-c. The same is true for subscriber devices 2-b and 2-d. That is, the multi-wavelength optical distribution unit 3-1 assigns λ3 as the wavelength of the upstream signal and λ4 as the wavelength of the downstream signal to subscriber device 2-b, while the multi-wavelength optical distribution unit 3-2 assigns λ4 as the wavelength of the upstream signal and λ3 as the wavelength of the downstream signal to subscriber device 2d. As a result, even when using the multi-wavelength optical distribution unit 3, it is possible to accommodate without halving the number of wavelengths available for either the upstream or downstream in the optical communication system 11. In other words, the number of subscriber devices that can actually be accommodated when viewed by the multi-wavelength optical distribution unit 3 alone remains half the number of available wavelength resources, but in the optical communication system 11, the number of wavelengths that can be added to one wavelength multiplexing / demultiplexing unit (upstream) connected to a certain path and the number of wavelengths that can be dropped from one wavelength multiplexing / demultiplexing unit (downstream) connected to the same path can be made equal in number of signals that can actually be added / dropped.

[0046] A specific example of the operation of the optical communication system 11 will be described. Here, it is assumed that the upstream signals of subscriber device 2-a and subscriber device 2-c are transferred to route #k. The multi-wavelength optical distribution unit 3-1 receives the upstream signal P (λ1) output from subscriber device 2-a via port 32 and outputs the upstream signal P (λ1) from port 37-k to a wavelength multiplexing / demultiplexing unit 41u-k connected to route #k. The multi-wavelength optical distribution unit 3-2 receives the upstream signal P (λ2) output from subscriber device 2-c via port 32 and outputs the upstream signal P (λ2) from port 37-k to a wavelength multiplexing / demultiplexing unit 41u-k connected to route #k. The wavelength multiplexing / demultiplexing unit 41u-k multiplexes the upstream signal P (λ1) and the upstream signal P (λ2) and outputs the multiplexed signal to a transmission path connected to route #k.

[0047] Furthermore, the wavelength multiplexing / demultiplexing unit 41d-k connected to the path #k receives the downstream signal P(λ2) and the downstream signal P(λ1), and outputs the downstream signal P(λ2) to the port 37-k of the multi-wavelength optical distribution unit 3-1 according to the wavelength, and outputs the downstream signal P(λ1) to the port 37-k of the multi-wavelength optical distribution unit 3-2 according to the wavelength λ1. The multi-wavelength optical distribution unit 3-1 outputs the downstream signal P(λ2) received from the port 37-k to the subscriber device 2-a from the port 32 connected to the subscriber device that is the destination of the downstream signal. The multi-wavelength optical distribution unit 3-2 outputs the downstream signal P(λ1) received from the port 37-k to the subscriber device 2-c from the port 32 connected to the subscriber device that is the destination of the downstream signal.

[0048] According to the second embodiment, by installing a plurality of multi-wavelength optical distribution units, it is possible to prevent the number of subscriber devices that can actually be accommodated from being halved compared to the number of wavelengths available in the optical communication system.

[0049] (Third Embodiment) The multi-wavelength optical distribution unit can accommodate both subscriber devices that input and output uplink signals through a single-core optical fiber (hereinafter referred to as a single-core subscriber device) and subscriber devices that output and input uplink signals separately using a two-core optical fiber (hereinafter referred to as a two-core subscriber device). Here, in two-core subscriber devices, uplink and downlink signals often have the same wavelength. The multi-wavelength optical distribution unit configured as shown in Figures 2 to 5 cannot accommodate multiple signals of the same wavelength throughout all signals, regardless of whether they are upstream or downstream signals. This is because wavelength collisions occur within the multi-wavelength optical distribution unit. Therefore, in order for this optical communication system to accommodate two-core subscriber devices, a separate device for optical distribution is required. In this case, the connection destination must be changed depending on whether the subscriber device is one-core or two-core, which complicates on-site installation work.

[0050] FIG. 7 is a diagram showing an example of the configuration of an optical communication system 12 according to a third embodiment. In FIG. 7, components identical to those in the optical communication system 1 according to the first embodiment shown in FIG. 1 are designated by the same reference numerals, and their description will be omitted. In the optical communication system 12 according to the third embodiment shown in FIG. 7, the WXC unit 4 is connected to the optical distribution units 6u and 6d in addition to the multi-wavelength optical distribution unit 3. An optical SW 5 is provided between the subscriber device 2 and the multi-wavelength optical distribution unit 3, the optical distribution unit 6u, and the optical distribution unit 6d. The subscriber device 2 is a single-core or dual-core subscriber device. The optical distribution unit 6u is an upstream optical distribution unit similar to the upstream optical distribution unit included in a conventional optical communication system, and the optical distribution unit 6d is a downstream optical distribution unit similar to the downstream optical distribution unit included in a conventional optical communication system. The optical distribution unit 6u receives upstream signals from multiple subscriber devices 2 and wavelength-multiplexes the upstream signals having the same destination route. The optical distribution unit 6u multiplexes upstream signals destined for path #k and outputs the multiplexed signals to the wavelength multiplexing / demultiplexing unit 41u-k. The optical distribution unit 6d outputs signals required for each subscriber device 2 from the downstream wavelength-multiplexed signals input from the wavelength multiplexing / demultiplexing units 41u-1 to 41u-K to the optical SW 5.

[0051] Regardless of whether the destination subscriber device 2 is a single-core or two-core subscriber device, the on-site worker first physically connects the optical fiber to be connected to the subscriber device 2 to the optical SW 5. Then, during device authentication and registration, for example, to open an optical path with the subscriber device 2 as an end point, the on-site worker declares whether the subscriber device 2 is a single-core or two-core subscriber device. Based on this declared information, a control device (not shown) controls the optical SW 5 so that if the subscriber device 2 is a single-core subscriber device, the optical fiber from the subscriber device is connected to the multi-wavelength optical distribution unit 3, and if the subscriber device 2 is a two-core subscriber device, the upstream optical fiber is connected to the upstream optical distribution unit 6u and the downstream optical fiber is connected to the downstream optical distribution unit 6d. In the example of Figure 7, to accommodate a two-core subscriber device 2, the subscriber device 2 is connected to the same optical distribution units 6u and 6d as in the past. However, if the upstream and downstream wavelengths are different, the subscriber device 2 may be connected to the multi-wavelength optical distribution unit 3 instead of the optical distribution units 6u and 6d.

[0052] A specific example of the operation of the optical communication system 12 will be described. It is assumed that the subscriber device 2-a has one core and the subscriber device 2-b has two cores. The subscriber device 2-a uses wavelength λua for the upstream and wavelength λda for the downstream. The subscriber device 2-b uses wavelength λb for both the upstream and downstream. Here, it is assumed that the communication destination of the subscriber devices 2-a and 2-b is route #k.

[0053] The optical SW 5 inputs the upstream signal P(λua) received from the subscriber device 2-a to a port 32 of the multi-wavelength optical distribution unit 3 corresponding to the wavelength λua. The multi-wavelength optical distribution unit 3 outputs the upstream signal P(λua) input from the port 32 to a wavelength multiplexing / demultiplexing unit 41u-k of the WXC unit 4 from a port 37u-k corresponding to the upstream of the path #k specified by the wavelength λua.

[0054] Meanwhile, the optical SW5 receives an upstream signal P(λb) from the optical fiber transmitting the upstream signal of the subscriber device 2-b and inputs it to the optical distribution unit 6u according to the wavelength λb. The optical distribution unit 6u outputs the input upstream signal P(λb) to a wavelength multiplexing / demultiplexing unit 41u-k of the WXC unit 4 specified by the wavelength λb. The wavelength multiplexing / demultiplexing unit 41u-k multiplexes the upstream signal P(λua) input from the multi-wavelength optical distribution unit 3, the upstream signal P(λb) input from the optical distribution unit 6u, and an upstream optical signal input from a different wavelength multiplexing / demultiplexing unit 41d, and outputs the multiplexed signal to a transmission path connected to the path #k.

[0055] The wavelength multiplexing / demultiplexing unit 41d-k demultiplexes the downstream signal input from path #k. The wavelength multiplexing / demultiplexing unit 41d-k inputs the demultiplexed downstream signal P(λda) to port 37d-k of the multi-wavelength optical distribution unit 3 corresponding to wavelength λua, and inputs the demultiplexed downstream signal P(λb) to the optical distribution unit 6d corresponding to wavelength λb. The multi-wavelength optical distribution unit 3 outputs the input downstream signal P(λda) to the optical SW5, and the optical distribution unit 6d outputs the input downstream signal P(λb) to the optical SW5. The optical SW5 outputs the downstream signal P(λda) from a port connected to subscriber device 2-a according to the wavelength, and outputs the downstream signal P(λb) from a port connected to the optical fiber for downstream signal transmission of subscriber device 2-b according to the wavelength.

[0056] In this way, by providing an optical SW5 between the subscriber device 2 and the multi-wavelength optical distribution unit 3 and the optical distribution units 6u and 6d, it becomes possible to simultaneously accommodate subscriber devices 2 that transmit uplink and downlink signals over one core and subscriber devices 2 that transmit over two cores without complicating the work of on-site workers.

[0057] According to the above-described embodiment, the optical communication system includes a multi-wavelength light distribution unit. The multi-wavelength light distribution unit may be provided in, for example, an optical communication device. The multi-wavelength light distribution unit distributes and outputs signals of different wavelengths transmitted and received by multiple subscriber devices that input upstream signals and output downstream signals using a single optical fiber, or that output upstream signals and input downstream signals using different optical fibers, to a route or subscriber device among multiple routes or multiple subscriber devices according to the wavelength of the signal.

[0058] The signals of different wavelengths are upstream signals transmitted by a subscriber device and downstream signals received by the subscriber device. The multi-wavelength optical distribution unit has multiple ports. The multi-wavelength optical distribution unit outputs upstream signals transmitted from a subscriber device and input from a port assigned with a wavelength used by the subscriber device to a forwarding destination path according to the port from which the upstream signal was input and the wavelength of the upstream signal. The multi-wavelength optical distribution unit also outputs downstream signals received by a subscriber device from a port assigned with a wavelength used by the subscriber device that is the destination of the downstream signal.

[0059] The optical communication system may further include a multiplexing unit provided for each of a plurality of paths and a demultiplexing unit provided for each of a plurality of paths. For example, the multiplexing units correspond to wavelength multiplexing / demultiplexing units 41u-1 to 41u-K, and the demultiplexing units correspond to wavelength multiplexing / demultiplexing units 41d-1 to 41d-K. The multiplexing units multiplex and output upstream signals distributed to the corresponding paths. The demultiplexing units output downstream signals received from the corresponding paths to the multi-wavelength optical distribution unit or the multiplexing unit according to the wavelength. The multi-wavelength optical distribution unit outputs the upstream signals to the multiplexing unit corresponding to the path to which they are to be transferred, and inputs downstream signals received by the subscriber devices from each of the plurality of demultiplexing units.

[0060] The optical communication system may have a plurality of multi-wavelength optical distribution units. In this case, the wavelength of an upstream signal transmitted by a subscriber device may be the same as the wavelength of a downstream signal received by a subscriber device accommodated in a multi-wavelength optical distribution unit different from the multi-wavelength optical distribution unit accommodating that subscriber device.

[0061] The multi-wavelength light distribution unit may further include an upstream light distribution unit, a downstream light distribution unit, and an optical switch. The upstream light distribution unit receives upstream signals and multiplexes and outputs the received upstream signals for each path according to their wavelengths. The downstream light distribution unit receives downstream signals of the same wavelength as the upstream signals received by the upstream light distribution unit and distributes the received downstream signals to subscriber devices according to their wavelengths. The optical switch outputs upstream signals transmitted from subscriber devices that use one optical fiber to output upstream signals and input downstream signals, to the multi-wavelength light distribution unit, and outputs upstream signals transmitted from subscriber devices that use different optical fibers to output upstream signals and input downstream signals, to the upstream light distribution unit. The optical switch also distributes downstream signals distributed to subscriber devices by the multi-wavelength light distribution unit or the downstream light distribution unit to optical fibers connected to the subscriber devices according to their wavelengths, and transmits them.

[0062] The multi-wavelength optical distribution unit may include a first multiplexing unit and a second multiplexing unit. The first multiplexing unit outputs an upstream multiplexed signal obtained by multiplexing upstream signals transmitted from each of a plurality of subscriber devices. Furthermore, the first multiplexing unit receives a downstream multiplexed signal and performs a process of dividing the received downstream multiplexed signal into downstream signals to be distributed to destination subscriber devices and outputting the resulting downstream signals, or receives a downstream multiplexed signal and performs a process of branching the received downstream multiplexed signal to be output to a plurality of subscriber devices. The second multiplexing unit receives a downstream signal from each of a plurality of paths and outputs a downstream multiplexed signal obtained by multiplexing the received downstream signals to the first multiplexing unit.

[0063] Although an embodiment of the present invention has been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and includes designs within the scope of the gist of the present invention.

[0064] 1 Optical communication system 2-a, 2-b, 2-c, 2-d Subscriber equipment 3, 3-1, 3-2, 310, 320, 330, 340 Multi-wavelength optical distribution unit 4 WXC unit 6u, 6d Optical distribution unit 32, 32-a, 32-b, 312-a to 312-c, 313, 316, 317-1 to 317-2 Ports 41u-1 to 41u-K, 41d-1 to 41d-K Wavelength multiplexing / demultiplexing unit 311 1×N wavelength selection switch 316 1×M wavelength selection switch 325 1×M coupler 335 1×N coupler

Claims

1. An optical communication system comprising a multi-wavelength optical distribution unit which distributes and outputs signals of different wavelengths transmitted and received by a plurality of subscriber devices, each of which uses a single optical fiber for outputting upstream signals and inputting downstream signals, or uses different optical fibers for outputting upstream signals and inputting downstream signals, to a plurality of routes or a plurality of said subscriber devices according to the wavelength.

2. The optical communications system of claim 1, wherein the multi-wavelength optical distribution unit has a plurality of ports, and distributes each of the signals of different wavelengths so that an upstream signal transmitted from the subscriber device and input from the port assigned with a wavelength used by the subscriber device is output to the port through which the upstream signal was input and to the forwarding destination according to the wavelength of the upstream signal, and a downstream signal received by the subscriber device is output from the port assigned with a wavelength used by the subscriber device that is the destination of the downstream signal.

3. An optical communications system as described in claim 2, further comprising: a plurality of multiplexing units provided for each of the plurality of routes, which multiplex and output upstream signals distributed to the corresponding routes; and a separation unit provided for each of the plurality of routes, which outputs downstream signals received from the corresponding routes to the multi-wavelength optical distribution unit or the multiplexing unit depending on the wavelength, wherein the multi-wavelength optical distribution unit outputs the upstream signals to the multiplexing unit corresponding to the route to which they are to be forwarded, and inputs the downstream signals received by the subscriber equipment from each of the plurality of separation units.

4. The optical communications system of claim 2, wherein the optical communications system has a plurality of the multi-wavelength optical distribution units, and the wavelength of the upstream signal transmitted by the subscriber device is the same as the wavelength of the downstream signal received by a subscriber device accommodated in a multi-wavelength optical distribution unit different from the multi-wavelength optical distribution unit in which the subscriber device is accommodated.

5. The optical communications system of claim 2, further comprising: an upstream optical distribution unit that receives upstream signals and multiplexes and outputs the received upstream signals for each path according to the wavelength; a downstream optical distribution unit that receives downstream signals of the same wavelength as the upstream signals received by the upstream optical distribution unit and distributes the received downstream signals to the subscriber devices according to the wavelength; and an optical switch that performs the process of outputting the upstream signal transmitted by the subscriber device which outputs the upstream signal and inputs the downstream signal using a single optical fiber to the multi-wavelength optical distribution unit and outputting the upstream signal transmitted by the subscriber device which outputs the upstream signal and inputs the downstream signal using a different optical fiber to the upstream optical distribution unit; and distributing and transmitting the downstream signals distributed to the subscriber devices by the multi-wavelength optical distribution unit or the downstream optical distribution unit according to the wavelength to the optical fiber connected to the subscriber device.

6. The optical communication system of claim 2, wherein the multi-wavelength optical distribution unit comprises: a first multiplexing unit that performs the process of outputting an upstream multiplexed signal obtained by multiplexing the upstream signals transmitted from each of the multiple subscriber devices, and the process of inputting a downstream multiplexed signal and distributing and outputting the obtained downstream signals to the destination subscriber devices, or the process of inputting a downstream multiplexed signal and branching the input downstream multiplexed signal and outputting it to the multiple subscriber devices; and a second multiplexing unit that performs the process of demultiplexing the upstream multiplexed signal output from the first multiplexing unit and distributing and outputting the obtained upstream signals to the destination paths, or the process of branching the upstream multiplexed signal output from the first multiplexing unit and outputting it to the multiple paths, and the process of receiving the downstream signals from each of the multiple paths and outputting the downstream multiplexed signal obtained by multiplexing the received downstream signals to the first multiplexing unit.

7. An optical communications device comprising a multi-wavelength optical distribution unit which distributes and outputs signals of different wavelengths transmitted and received by a plurality of subscriber devices, in which an upstream signal is output and a downstream signal is input through a single optical fiber, or an upstream signal is output and a downstream signal is input through different optical fibers, to a plurality of routes or a plurality of said subscriber devices according to the wavelength.

8. An optical communication method comprising: a distribution step of distributing and outputting signals of different wavelengths transmitted and received by a plurality of subscriber devices, in which an upstream signal is output and a downstream signal is input through a single optical fiber, or an upstream signal is output and a downstream signal is input through different optical fibers, to a plurality of routes or a plurality of said subscriber devices according to the wavelength.

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