JP5867233B2 - Station side equipment - Google Patents

Description

  The present invention is used in a network including a station-side device, a branched optical transmission line, and a plurality of branches each including a subscriber-side device connected to a branch destination of the optical transmission line. It relates to the station side device.

  A communication network that connects a building (station) owned by a communication carrier and a subscriber's home is called an access network. In response to the recent increase in communication capacity, optical access networks that enable transmission of an enormous amount of information by using optical communication are becoming mainstream in access networks.

  As one form of the optical access network, there is a passive optical network (PON: Passive Optical Network). The PON includes one station side device (OLT: Optical Line Terminal) provided in the station, a subscriber side device (ONU: Optical Network Unit) provided in each of a plurality of subscriber homes, and an optical splitter. Is done. The OLT and the ONU and the optical splitter are connected by an optical fiber.

  A single-core optical fiber is used for connection between the OLT and the optical splitter. This single-core optical fiber is shared by a plurality of ONUs. The optical splitter is an inexpensive passive element. Thus, PON is excellent in economic efficiency and easy to maintain. For this reason, the introduction of PON is progressing rapidly.

  In PON, signals transmitted from each ONU to the OLT (hereinafter also referred to as upstream optical signals) are combined by an optical splitter and transmitted to the OLT. On the other hand, a signal sent from the OLT to each ONU (hereinafter also referred to as a downstream optical signal) is demultiplexed by the optical splitter and transmitted to each ONU. In order to prevent interference between the upstream optical signal and downstream optical signal, different wavelengths are assigned to the upstream optical signal and downstream optical signal, respectively.

  In PON, various multiplexing techniques are used. The multiplexing technology used in the PON includes time division multiplexing (TDM) technology in which a short interval on the time axis is assigned to each subscriber, wavelength division multiplexing (WDM) in which different wavelengths are assigned to each subscriber (WDM: Wave Division Division Multiplex). And code division multiplexing (CDM) technology that assigns different codes to each subscriber. Among these multiplexing techniques, TDM-PON using TDM is currently most widely used.

  In TDM-PON, TDMA (Time Division Multiple Access) is used. TDMA is a technique in which the OLT manages the transmission timing of each ONU so that upstream optical signals from different ONUs do not collide with each other.

  Usually, in a PON system, one OLT includes one optical transmission line branched and one PON branch including an ONU connected to a branch destination of the optical transmission line (hereinafter, also simply referred to as a branch). I manage. Here, for example, when the number of ONUs included in one branch is small, the OLT is shared by a small number of ONUs. Therefore, when there are few ONUs in a branch, it is desirable that one OLT manages a plurality of branches. Further, when a load is concentrated on a specific OLT, it is preferable that a plurality of OLTs manage one branch.

  Therefore, a PON system (hereinafter also referred to as TDM / WDM-PON) in which a plurality of OLTs manage a plurality of branches by using both TDM and WDM has been proposed.

  In TDM / WDM-PON, the OLT can send a downstream optical signal to different branches by changing the transmission wavelength of the downstream optical signal. The ONU can send an upstream optical signal to a specific OLT by sending an upstream optical signal having a wavelength designated by the OLT. As a result, one OLT can communicate with an ONU included in an arbitrary branch constituting the TDM / WDM-PON.

  Here, in order to change the transmission wavelength of the downstream optical signal, a configuration is known in which the OLT includes a number of light sources corresponding to the number of branches (see, for example, Patent Document 1).

JP 2011-135280 A

  In the configuration of Patent Document 1 described above, the number of light sources included in each OLT increases according to the number of branches, leading to higher costs and a larger apparatus.

  On the other hand, a configuration in which each OLT includes one wavelength variable light source and enables transmission to a plurality of branches is conceivable.

  However, in a configuration in which each OLT includes one wavelength tunable light source, a downstream optical signal cannot be transmitted during wavelength switching by the wavelength tunable light source, leading to a decrease in transmission efficiency.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a station-side device that does not reduce transmission efficiency while suppressing an increase in the scale of the device.

  In order to achieve the above-described object, the station-side device of the present invention used in a network including a station-side device, a plurality of branches, and an optical routing means includes a control unit and N (N Is an integer of 1 or more) and an optical signal processing unit. Each branch includes a branched optical transmission line and a subscriber side device connected to a branch destination of the optical transmission line. The optical routing means has a plurality of optical communication ports divided into a first group connected to the station side device and a second group connected to the optical transmission line, and the optical communication ports of one group The input optical signal is output from the optical communication port of the other group determined according to the wavelength of the optical signal.

  The control unit is a control signal generating unit that generates a downlink control signal for controlling the subscriber side device, a transmission plan generating unit that generates a transmission plan based on information including a destination of the downlink data signal, and a wavelength setting based on the transmission plan Wavelength setting means for generating a signal, and path control means for generating a path switching signal.

  The electrical signal processing unit generates a downstream electrical signal based on the downstream control signal and the downstream data signal.

  The optical signal processing unit includes K (K is an integer equal to or greater than N + 1) wavelength variable light sources, electrical switches, and an optical signal selection unit. Each wavelength variable light source generates a downstream optical signal from the downstream electrical signal by changing the wavelength according to the wavelength setting signal. The electrical switch has P input ports (P is an integer equal to or greater than 1) and K output ports, and switches one path according to a path switching signal to select one of K wavelength variable light sources. Send a downstream electrical signal. The optical signal selection unit has K input ports and Q output ports (Q is an integer of 1 or more), and selects and outputs a downstream optical signal generated by any one of the wavelength tunable light sources.

  According to the station side apparatus of the present invention, N + 1 or more wavelength tunable light sources are provided for N electrical signal processing units. For this reason, in addition to the tunable light source that generates the downstream optical signal to each ONU, there is at least one tunable light source that does not generate the downstream optical signal.

  This station-side device changes the wavelength of the wavelength tunable light source that is on standby based on the transmission plan in advance, and switches the transmission wavelength by switching the electrical switch. Since the switching of the electrical switch can be performed at a higher speed than the wavelength setting in the wavelength tunable light source, it is possible to suppress a decrease in transmission efficiency due to the switching of the wavelength.

It is a schematic block diagram of TDM / WDM-PON. It is a figure which shows the relationship between the station side port of AWGR, a subscriber side port, and a wavelength. It is a schematic block diagram of a 1st station side apparatus. It is a figure which shows a transmission plan. It is a schematic diagram for demonstrating operation | movement of a 1st station side apparatus. It is a schematic block diagram of the 2nd station side apparatus. It is a schematic block diagram of the 3rd station side apparatus. It is a schematic diagram for demonstrating operation | movement of a 3rd station | side apparatus.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the arrangement and connection relationship of each component are merely schematically shown to the extent that the present invention can be understood. In the following, a preferred configuration example of the present invention will be described. However, numerical conditions and the like are merely preferred examples. Therefore, the present invention is not limited to the following embodiments, and many changes or modifications that can achieve the effects of the present invention can be made without departing from the scope of the configuration of the present invention.

(TDM / WDM-PON)
A schematic configuration of the TDM / WDM-PON will be described with reference to FIG. The TDM / WDM-PON 10 includes N (N is an integer of 1 or more) OLTs 100, optical routing means 200, and M (M is an integer of 1 or more) branches 300.

  The OLT 100 and the optical routing unit 200 can be installed in the station, but the optical routing unit 200 may be installed outside the station.

  The branch 300 includes an optical transmission line 700 configured with a single-core optical fiber, an optical splitter 400, and an ONU 500, respectively. The optical transmission line 700 is branched by the optical splitter 400, and the ONU 500 is connected to the branch destination of the optical transmission line 700, respectively. The ONU 500 is installed, for example, in a subscriber's house.

  The OLT 100 and the optical routing means 200 are connected by an optical transmission line 600 constituted by an optical fiber.

  The N OLTs can manage M branches and exchange data with ONUs included in these M branches.

  The OLT 100 is connected to an upper network (NW) 20. The OLT 100 converts the downlink data signal received from the upper NW 20 into a downlink optical signal, and sends it to the user terminal 30 via one of the branches 300. Further, the OLT 100 converts an upstream optical signal received from the user terminal 30 via any one of the branches 300 into an upstream data signal and sends the upstream data signal to the upper NW 20.

  The TDM / WDM-PON 10 includes a host switch (SW) 110 and an integrated control unit 120 in the station. The upper SW 110 sends the downlink data signal to the OLT 100 determined according to the destination of the downlink data signal. Further, the upper SW 110 sends the upstream data signal received from each OLT 100 to the upper NW 20. In addition, the upper SW 110 notifies the integrated control unit 120 of traffic information such as traffic and a destination of a downlink data signal transmitted from the upper NW 20.

  The integrated control unit 120 manages the PON link information of the TDM / WDM-PON 10. The integrated control unit 120 receives information on the ONU registered by the OLT, that is, the ONU with which the PON link is established, from the station-side control unit of each OLT 100, and uses RAM (Random Access Memory) as the PON link information. ) And the like (not shown in the figure). Further, the integrated control unit 120 creates a transmission plan based on the traffic information received from the upper SW 110 and the PON link information. In addition, the integrated control unit 120 generates a wavelength setting signal based on the transmission plan. Further, the integrated control unit 120 generates a routing table and sends it to the upper SW 110. The upper SW 110 sets a route based on the routing table.

  Although FIG. 1 shows a configuration example including four OLTs 100-1 to 4 and four branches 300-1 to 300-4, the number of OLTs 100 and branches 300 is not limited to this. Each of the OLT 100 and the branch 300 may include one or more. When the number of OLTs 100 and branches 300 are both 1, that is, when N = M = 1, it functions as a so-called TDM-PON. In the following description, a configuration example in which at least one of the OLT 100 and the branch 300 is plural will be described.

  When there is one OLT 100, that is, when N = 1, a configuration without the upper SW 110 can be provided. Further, if the function of the integrated control unit 120 is configured to be executed by the station side control unit, a configuration without the integrated control unit may be used. In the following description, when a plurality of OLTs 100 are provided in a station, the plurality of OLTs 100, the integrated control unit 120, and the upper SW 110 may be collectively referred to as an integrated OLT.

  The optical routing means 200 is, for example, an arrayed optical waveguide router (AWGR) configured by arranging optical wavelength filters, and has a plurality of optical communication ports that can input and output optical signals.

  The plurality of optical communication ports are divided into a first group connected to the OLT 100 via the optical transmission line 600 and a second group connected to the optical transmission line 700 of the branch 300. The optical routing unit 200 outputs the optical signal input to the optical communication port of one group from the optical communication port of the other group that is determined according to the wavelength of the optical signal.

  In the following description, the optical communication port 220 included in the first group is also referred to as a station-side port 220. The optical communication port 230 included in the second group is also referred to as a subscriber side port 230. In the configuration example shown in FIG. 1, the first to fourth station-side ports 220-1 to 220-4 are connected to the first to fourth OLTs 100-1 to 4 in a one-to-one correspondence. The first to fourth subscriber-side ports 230-1 to 230-4 are connected to the first to fourth branches 300-1 to 300-4 in a one-to-one correspondence.

In AWGR, a wavelength lambda as a reference, the wavelength lambda + n [lambda _FSR apart by an integral multiple of lambda _FSR from lambda is treated as the same wavelength (Here, n is an integer other than 0). This characteristic is called AWGR circulation, and λ _FSR is called free spectrum range. Therefore, in AWGR, when an optical signal having a wavelength satisfying the above relationship is input to an optical communication port in one group, the optical signal is output from the optical communication port in the other group determined by the wavelength λ.

  FIG. 2 shows an example of the relationship between the wavelengths of the upstream and downstream signals and the numbers of the station-side port 220 and the subscriber-side port 230 that are input and output.

In this embodiment, the downstream signal input to the station side port 220 is set to one of λ1 to λ4 as shown in FIG. 2, and the upstream optical signal input to the subscriber side port is λ1. It is set to a value obtained by adding nλ _FSR to each wavelength of ˜λ4.

For example, a downstream signal of wavelength λ1 input to the first station side port 220-1 is output from the first subscriber side port 230-1 and input to the first subscriber side port 230-1. The upstream optical signal having the wavelength λ1 + nλ _FSR is output from the first station-side port 220-1. Also, the downstream signal of wavelength λ2 input to the first station side port 220-1 is output from the second subscriber side port 230-2 and input to the second subscriber side port 230-2. The upstream optical signal of wavelength λ2 + nλ _FSR is output from the first station side port 220-1.

  As described above, the first to fourth station-side ports 220-1 to 220-4 are connected to the first to fourth OLTs 100-1 to 4 in a one-to-one correspondence with each other. The subscriber-side ports 230-1 to 230-4 are connected to the first to fourth branches 300-1 to 300-4 in a one-to-one correspondence. Therefore, each OLT 100 can select one branch of the plurality of branches 300 and transmit the downstream optical signal by changing the wavelength of the downstream optical signal. On the other hand, each ONU 500 can select one of the plurality of OLTs 100 and transmit the upstream optical signal by changing the wavelength of the upstream optical signal.

(Station equipment)
The station side apparatus of the present invention is used in TDM / WDM-PON.

  The station-side apparatus includes a control unit, N (N is an integer of 1 or more) electrical signal processing units, and an optical signal processing unit.

  The control unit includes control signal generation means, transmission plan creation means, wavelength setting means, buffer control means, and path control means. The control signal generating means instructs each ONU to transmit the upstream optical signal and the transmission amount, that is, generates a downstream control signal for controlling each ONU. The transmission plan creation means creates a transmission plan based on traffic information including the destination of the downlink data signal. The wavelength setting means generates a wavelength setting signal based on the transmission plan created by the transmission plan creation means. The buffer control means generates a read instruction signal. The route control means generates a route switching signal.

  The electrical signal processing unit generates a downstream electrical signal based on the downstream control signal generated by the control unit and the downstream data signal received from the upper NW.

  The optical signal processing unit includes K (K is an integer of N + 1 or more) wavelength variable light sources, an electrical switch, and an optical signal selection unit.

  The wavelength tunable light source generates a downstream optical signal having a wavelength set according to the wavelength setting signal from the downstream electrical signal. The wavelength tunable light source is configured to include any suitable electrical / optical conversion means capable of changing the wavelength, such as a TLD (Tunable Laser Diode).

  The electrical switch has P input ports (P is an integer equal to or greater than 1) and K output ports, and switches the path in accordance with a path switching signal to select one of the K wavelength variable light sources. Then, send a downstream electrical signal. The optical signal selection unit has K input ports and Q output ports (Q is an integer of 1 or more), and selects a downstream optical signal generated by one of the K wavelength variable light sources. Output.

(Configuration of the station side device of the first embodiment)
The OLT 140 according to the first embodiment will be described with reference to FIG. The OLT 140 includes an electric signal processing unit 150 and an optical signal processing unit 170. In the OLT 140 according to the first embodiment, the number N of electric signal processing units 150 is one.

  The electrical signal processing unit 150 includes an interface (I / F) 152, a downstream electrical signal generation unit 154, a buffer 156, an upstream electrical signal processing unit 158, and a station side control unit 160.

  Since the interface 152, the downstream electrical signal generation unit 154, and the upstream electrical signal processing unit 158 can be configured in the same manner as any suitable known OLT, detailed description thereof will be omitted here.

  The interface 152 transmits / receives an upstream data signal and a downstream data signal to / from the upper NW. Further, the interface 152 sends the traffic information to the station side control unit 160 as a control unit.

  The downlink electrical signal generation unit 154 generates a downlink electrical signal based on the downlink data signal received from the interface 152 and the downlink control signal received from the station side control unit 160. The downstream electrical signal is sent to the buffer 156.

  The buffer 156 stores the downstream electrical signal, and in response to the readout instruction signal received from the station-side control unit 160, reads the downstream electrical signal indicated by the readout instruction signal at the timing indicated by the readout instruction signal, and outputs the downstream electrical signal. The signal is read out and sent to the optical signal processing unit 170.

  The upstream electrical signal processor 158 separates the upstream electrical signal received from the optical receiver 172 into an upstream data signal and an upstream control signal. The uplink data signal is sent to the upper NW via the interface 152, and the uplink control signal is sent to the station side control unit 160. The uplink control signal includes, for example, information on the bandwidth requested by each ONU.

  The optical signal processing unit 170 includes a high-speed wavelength variable light source 180, an optical receiving unit 172, and a multiplexing / demultiplexing unit 174.

  In this embodiment, the high-speed wavelength variable light source 180 includes two wavelength variable light sources 184, an electric switch 182, and an optical signal selection unit 186.

  The variable wavelength light source 184 generates a downstream optical signal having a wavelength determined according to the wavelength setting signal from the downstream electrical signal. The wavelength tunable light source is configured to include any suitable electrical / optical conversion means capable of changing the wavelength, such as a TLD (Tunable Laser Diode).

  In this embodiment, the OLT 140 includes more wavelength variable light sources 184 than the number N of electrical signal processing units 150. Here, since N = 1, the number K of tunable light sources 184 included in the high-speed tunable light source 180 is 2. That is, the high-speed wavelength tunable light source 180 includes an operating wavelength tunable light source that generates a downstream optical signal and a standby wavelength tunable light source. The number K of wavelength tunable light sources is not limited to two as long as a standby wavelength tunable light source can be prepared. If there are many wavelength-tunable light sources in the standby state, the scale of the apparatus is increased. In this embodiment, K is set to N + 1, that is, 2.

  The electrical switch 182 switches the path in accordance with the path switching signal, and sends a downstream electrical signal to one of the two wavelength variable light sources 184-1 and 2. The optical signal selection unit 186 has K (two in this case) input ports and Q (here, one) output ports, and two wavelength variable light sources 184-according to the path switching signal. Any configuration may be used as long as the downstream optical signal generated by any one of 1 and 2 is output. For example, the optical signal selection unit 186 can be configured with an optical switch. As in the first embodiment, when the output port is 1, the optical signal selection unit 186 can be configured by an optical multiplexer. In this case, it is not necessary to input a path switching signal to the optical signal selection unit 186. Details of the wavelength changing operation by the high-speed wavelength variable light source 180 will be described later.

  The downstream optical signal generated by the high-speed wavelength variable light source 180 is sent to each branch 300 via the multiplexing / demultiplexing unit 174 and the optical routing means 200.

  The optical receiver 172 converts the upstream optical signal sent through the multiplexing / demultiplexing unit 174 into an upstream electrical signal. The optical receiving unit 172 includes an arbitrary suitable photoelectric conversion element such as a PD (Photo Diode). The PD is set so that at least an upstream optical signal in a wavelength band that can be set by the ONU 500 can be received. The upstream electrical signal is sent to the upstream electrical signal processing unit 158.

The multiplexing / demultiplexing unit 174 transmits the downstream optical signal generated by the high-speed wavelength variable light source 180 to the optical routing unit 200 and transmits the upstream optical signal received from the optical routing unit 200 to the optical receiving unit 172. The multiplexing / demultiplexing unit 174 includes any suitable multiplexer / demultiplexer such as a WDM filter. As already described, in this embodiment, light in a wavelength band of λ1~λ4 the downstream optical signals, also in the upstream optical signal light in the wavelength band λ1 + nλ _FSR ~λ4 + nλ _FSR is used. For this reason, an upstream signal and a downstream signal can be multiplexed and demultiplexed by using a WDM filter.

(Operation of the station side device of the first embodiment)
With reference to FIG.4 and FIG.5, operation | movement of the station side apparatus of 1st Embodiment is demonstrated. FIG. 4 is a diagram showing a transmission plan. FIG. 5 is a schematic diagram for explaining the operation of the first station-side device. 5A to 5G show the horizontal axis taking time. FIG. 5A shows a downlink data signal received from the upper NW. FIG. 5B shows a transmission plan similar to that shown in FIG. FIGS. 5C and 5D show wavelength switching in the first and second wavelength variable light sources 184-1 and 2, respectively. FIG. 5E shows the output of the high speed wavelength variable light source 180. FIGS. 5F and 5G show transmission efficiencies for the example and the comparative example, respectively.

  The OLT 140 buffers the downlink electrical signal generated based on the downlink data signal and the downlink control signal received from the upper NW for a certain period of time. Here, it is assumed that the downstream electrical signals applied to the first to fourth branches 300-1 to 4 are buffered in the order of A1, A4, A2, A1, A3, A2, and A3 (FIG. 5A )). Here, the downlink electrical signal addressed to the nth branch is An.

  The transmission plan creation means of the control unit generates a transmission plan based on the buffered downlink electrical signal. Here, the downstream optical signal from time t0 to t1 is addressed to the first branch 300-1, the downstream optical signal from time t1 to t2 is addressed to the second branch 300-2, and the downstream from time t2 to t3 is transmitted. The optical signal is addressed to the third branch 300-3, and the downstream optical signal from time t3 to t4 is addressed to the fourth branch 300-4 (FIG. 5B).

  When the AWGR described with reference to FIG. 2 is used, the transmission wavelengths addressed to the first to fourth branches 300-1 to 300-4 are λ1 to λ4, respectively.

  In each wavelength variable light source 184, the time required to change the wavelength is represented by Δt.

  In this case, the first wavelength tunable light source 184-1 starts changing to the wavelength λ1 at time t0-Δt. At time t0, the downstream electrical signal is read from the buffer 156 and sent to the high-speed wavelength variable light source 180, and the electrical switch 182 is switched to send the downstream electrical signal to the first wavelength variable light source 184-1. From time t0 to time t1, the downstream optical signal generated by the first wavelength tunable light source 184-1 is output. At this time, the second wavelength tunable light source 184-2 is in a standby state.

  The second variable wavelength light source 184-2 in the standby state starts changing to the wavelength λ2 at time t1−Δt. At time t1, the electrical switch 182 is switched to send the downstream electrical signal to the second wavelength variable light source 184-2. From time t1 to time t2, the downstream optical signal generated by the second wavelength tunable light source 184-2 is output. At this time, the first wavelength tunable light source 184-1 is in a standby state (FIG. 5C).

  The first variable wavelength light source 184-1 in the standby state starts changing to the wavelength λ3 at time t2−Δt. At time t2, the electrical switch is switched to send the downstream electrical signal to the first wavelength tunable light source 184-1. From time t2 to time t3, the downstream optical signal generated by the first wavelength tunable light source 184-1 is output. At this time, the second variable wavelength light source 184-2 enters a standby state (FIG. 5D).

  The second variable wavelength light source 184-2 in the standby state starts changing to the wavelength λ4 at time t3-Δt. At time t3, the electrical switch is switched to send the downstream electrical signal to the second wavelength tunable light source 184-2. From time t3 to time t4, the downstream optical signal generated by the second variable wavelength light source 184-2 is output. At this time, the first wavelength variable light source 184-1 is in a standby state.

  According to this configuration, the loss for the wavelength switching time in the wavelength tunable light source can be suppressed by using the two wavelength tunable light sources 184-1 and 2 (FIG. 5F). That is, the transmission efficiency can be improved as compared with the case where one wavelength variable light source is used (FIG. 5G). Moreover, the enlargement of the apparatus can be suppressed as compared with the case where four light sources are used.

  Here, the case where K is 2 and the other wavelength variable light source is in the standby state while the downstream optical signal is generated by one wavelength variable light source has been described, but the present invention is not limited to this. For example, when the ratio of the wavelength switching time at the wavelength tunable light source to the transmission period at one wavelength is large, K may be made larger than 2 and a plurality of wavelength tunable light sources may be set in the standby state.

(Station-side device of the second embodiment)
The OLT 142 of the second embodiment will be described with reference to FIG.

  The OLT of the first embodiment includes one electric signal processing unit 150. On the other hand, the OLT of the second embodiment is an integrated OLT 142 including two or more sets of the electric signal processing unit 150 and the optical signal processing unit 170. Further, the integrated OLT 142 of this embodiment includes a host switch 110 and an integrated control unit 120.

  Each set of the electric signal processing unit 150 and the optical signal processing unit 170 can be configured similarly to the electric signal processing unit 150 and the optical signal processing unit 170 in the OLT of the first embodiment, and functions in the same manner. That is, each set of the electric signal processing unit 150 and the optical signal processing unit 170 has a function as an OLT.

  In the configuration example shown in FIG. 6, N is 4, and each optical signal processing unit includes two variable wavelength light sources, so K is 8.

  According to this configuration, not only one OLT can manage a plurality of branches, but also a plurality of OLTs can manage one branch. Since the operation of each OLT is the same as the operation in the station side device of the first embodiment, the description is omitted here.

(Station side apparatus of the third embodiment)
With reference to FIG. 7, the integrated OLT 144 according to the third embodiment will be described. In the integrated OLT 144 of the third embodiment, the number N of electric signal processing units 150 is two or more.

  The OLT 144 includes N electrical signal processing units 150 and one optical signal processing unit 171. Since the configuration and function of the electric signal processing unit 150 are the same as those in the first embodiment, description thereof is omitted.

  The optical signal processing unit 171 includes a high-speed wavelength variable light source, an optical receiving unit, and a multiplexing / demultiplexing unit. The optical signal processing unit 171 includes one high-speed wavelength variable light source 181, N optical receiving units 172, and N multiplexing / demultiplexing units 174. The optical signal processing unit 171, in particular, the high-speed wavelength variable light source 181 is shared by the N electrical signal processing units 150. Therefore, the single multiplexing / demultiplexing unit, the optical receiving unit connected thereto, and the shared high-speed wavelength variable light source 181 function in the same manner as the optical signal processing unit 170 of the first embodiment.

  The number of wavelength tunable light sources 184 is provided more than the number N of electrical signal processing units 150. In other words, an tunable light source in an operating state that generates a downstream optical signal and a tunable light source in a standby state are provided. Here, a case where the number N of the electrical signal processing units 150 is 2 and the number K of wavelength tunable light sources is 3 will be described. The number K of wavelength tunable light sources is not limited to N + 1 as long as a wavelength tunable light source in a standby state can be prepared, that is, N + 1 or more. If there are many wavelength-tunable light sources in the standby state, the scale of the apparatus will increase, so K is preferably set to N + 1. On the other hand, when the transmission period at one wavelength is shorter than the wavelength switching time at the wavelength tunable light source, K may be set larger than N + 1 and a plurality of wavelength tunable light sources may be set in a standby state.

  The electrical switch 182 having P (here, 2) input ports and K (here, 3) output ports switches the path according to the path switching signal, and performs two electrical signal processing. The downstream electrical signal received from the unit is sent to different wavelength variable light sources. The optical signal selection unit 188 has K (here, 3) input ports and Q (here, 2) output ports, and outputs a downstream optical signal. The optical signal selection unit 188 switches the path according to the path switching signal, and the downstream optical signal generated by any of the three wavelength variable light sources 184-1 to 184-3 is output to any of the two output ports. Any configuration can be used. In this embodiment, the optical signal selection unit 188 can be configured by an optical switch. The optical switch switches the path of the optical signal according to a path switching signal including the same information as the electrical switch. For example, the downstream electrical signal received from the first electrical signal processing unit 150-1 is converted into a downstream optical signal by any wavelength variable light source, and then sent to the first multiplexing / demultiplexing unit 174-1. The optical switch sets the path.

  The operation of changing the wavelength in the high-speed wavelength variable light source 181 will be described later.

  The downstream optical signal generated by the high-speed wavelength variable light source 181 is sent to each branch 300 via the multiplexing / demultiplexing unit 174 and the optical routing means 200.

(Operation of the station side device of the third embodiment)
With reference to FIG. 8, the operation of the station-side device of the third embodiment will be described. FIG. 8 is a schematic diagram for explaining the operation of the third station-side device. 8A to 8G show the horizontal axis taking time. FIGS. 8A and 8B show transmission plans of the first and second electric signal processing units, respectively. FIGS. 8C to 8E show wavelength switching in the first to third wavelength variable light sources 184-1 to 184-3, respectively. FIGS. 8F and 8G show outputs from the first and second output ports of the high-speed wavelength variable light source 181, respectively.

  Each OLT buffers the downlink electrical signal generated based on the downlink data signal and the downlink control signal received from the upper network for a certain period of time.

  The station-side control unit creates a transmission plan based on the destination of the buffered downlink electrical signal. Here, the downstream electrical signals A1 and A2 addressed to the first and second branches 300-1 and 2 are buffered to the first OLT, and the downstream electrical signals A1 and A2 are addressed to the third and fourth branches 300-3 and 4 Assume that electrical signals A3 and A4 are buffered in the second OLT.

  The transmission plan creation means of the control unit generates a transmission plan based on the buffered downlink electrical signal. Here, in the first OLT, the downstream optical signal from time t0 to t1 is addressed to the first branch 300-1, and the downstream optical signal from time t1 to t3 is addressed to the second branch 300-2. In the second OLT, the downstream optical signal from time t0 to t2 is addressed to the third branch 300-3, and the downstream optical signal from time t2 to t3 is addressed to the fourth branch 300-4.

  When the AWGR described with reference to FIG. 2 is used, the transmission wavelengths addressed to the first to fourth branches 300-1 to 300-4 are λ1 to λ4, respectively.

  In the wavelength tunable light source, the time required to change the wavelength is Δt.

  In this case, the first wavelength tunable light source starts changing to the wavelength λ1 at time t0−Δt. At time t0, the downstream electrical signal is read from the buffer of the first OLT and sent to the high-speed wavelength variable light source, and the electrical switch is switched so that the downstream electrical signal from the first electrical signal processing unit 150-1 is The light is sent to the first variable wavelength light source 184-1. Until time t1, the downstream optical signal generated by the first wavelength tunable light source 184-1 is sent to the first multiplexing / demultiplexing unit 174-1.

  The third wavelength tunable light source 184-3 starts changing to the wavelength λ2 at time t0−Δt. At time t0, the downstream electrical signal is read from the second OLT buffer and sent to the high-speed wavelength variable light source 181, and the electrical switch 182 is switched to transmit the downstream electrical signal from the second electrical signal processing unit 150-2. Are sent to the third variable wavelength light source 184-3. Until time t1, the downstream optical signal generated by the third variable wavelength light source 184-3 is sent to the second multiplexing / demultiplexing unit 174-2. At this time, the second wavelength tunable light source 184-2 is in a standby state.

  The second variable wavelength light source 184-2 in the standby state starts changing to the wavelength λ2 at time t1−Δt. At time t1, the electrical switch 182 is switched to send the downstream electrical signal from the first electrical signal processing unit 150-1 to the second wavelength variable light source 184-2. Until time t2, the downstream optical signal generated by the second variable wavelength light source 184-2 is sent to the first multiplexing / demultiplexing unit 174-1. At this time, the first wavelength variable light source 184-1 is in a standby state.

  The first variable wavelength light source 184-1 in the standby state starts changing to the wavelength λ3 at time t2−Δt. At time t2, the electrical switch is switched to send the downstream electrical signal from the second electrical signal processing unit 150-2 to the first wavelength variable light source 184-1. Until time t3, the downstream optical signal generated by the second variable wavelength light source 184-2 is sent to the second multiplexing / demultiplexing unit 174-2. At this time, the third variable wavelength light source 184-3 is in a standby state.

  According to this configuration, when changing the wavelength of the downstream optical signal based on the downstream electrical signal from the two electrical signal processing units, the loss for the wavelength switching time in the wavelength tunable light source is suppressed by using the three wavelength variable light sources. can do. That is, the transmission efficiency can be improved compared to the case where one wavelength variable light source is used.

  Moreover, in the station side apparatus of 1st and 2nd embodiment, although at least 2 variable wavelength light sources are provided with respect to each of an electric signal processing part, according to the station side apparatus of 3rd Embodiment, it is N pieces. It suffices to provide at least N + 1 variable wavelength light sources for the electrical signal processing unit. For this reason, compared with the station side apparatus of 1st and 2nd embodiment, the enlargement of an apparatus can be suppressed further.

(Subscriber equipment)
The subscriber side device used in the TDM / WDM-PON including the station side device of the first to third embodiments is used in the TDM-PON except that the transmission wavelength and the reception wavelength are variable. A similar configuration can be adopted.

  In order to make the transmission wavelength variable, a wavelength variable light source such as TLD may be used as a light source for generating an upstream optical signal in the subscriber side apparatus. In addition, the band of the receiver that receives the downstream optical signal at the subscriber-side apparatus may include the wavelength set for the downstream optical signal.

  In TDM / WDM-PON, downstream optical signals having different wavelengths are transmitted from a plurality of OLTs to one branch. For this reason, since each ONU does not receive an optical signal from an OLT other than the OLT with which the PON link is established, a wavelength tunable filter can be provided on the OLT side of the optical receiver.

  Setting of the wavelength of the wavelength tunable light source and the wavelength tunable filter is performed by an instruction from a subscriber side control unit provided in the subscriber side device. In each of the above-described embodiments, TDM / WDM-PON has been described. However, the present invention is not limited to this. The station side apparatus of the present invention can also be used in a network that performs wavelength division multiplexing such as WDM-PON.

10 TDM / WDM-PON
20 Upper network (upper NW)
30 user terminals
100, 140 Station side equipment (OLT)
110 Host switch (Host SW)
120 Integrated control unit 142, 144 Integrated OLT
150 Electric Signal Processing Unit 152 Interface (I / F)
154 Downstream electrical signal generation unit 156 Buffer 158 Upstream electrical signal processing unit 160 Station side control unit 170 Optical signal processing unit 172 Optical reception unit 174 Multiplexing / demultiplexing unit 180, 181 High-speed wavelength variable light source 182 Electrical switch 184 Wavelength variable light source (TLD)
186, 188 Optical signal selector 200 Optical routing means (AWGR)
220 Optical communication port (station side port)
230 Optical communication port (subscriber side port)
300 branch 400 optical splitter 500 subscriber unit (ONU)
600, 700 Optical transmission line

Claims (10)

A station side device,
A plurality of branches each including a branched optical transmission line and a subscriber side device connected to a branch destination of the optical transmission line;
It has a plurality of optical communication ports divided into a first group connected to the station side device and a second group connected to the optical transmission line, and is input to the optical communication port of one group A station-side device used in a network including an optical routing unit configured to output an optical signal from an optical communication port of the other group, which is determined according to the wavelength of the optical signal,
A control unit, N (N is an integer of 1 or more) electrical signal processing unit, and an optical signal processing unit,
The controller is
Control signal generating means for generating a downlink control signal for controlling the subscriber side device;
A transmission plan creation means for creating a transmission plan based on information including the destination of the downlink data signal;
Wavelength setting means for generating a wavelength setting signal based on the transmission plan, and path control means for generating a path switching signal,
The electrical signal processing unit generates a downlink electrical signal based on the downlink control signal and the downlink data signal,
The optical signal processor is
K (K is an integer equal to or greater than N + 1) wavelength tunable light sources that generate a downstream optical signal from the downstream electrical signal by changing the wavelength according to the wavelength setting signal;
It has P input ports (P is an integer equal to or greater than 1) and K output ports, and switches the path according to the path switching signal to be one of the K wavelength variable light sources. An electrical switch for sending the downstream electrical signal, and K input ports and Q output ports (Q is an integer equal to or greater than 1), and generated by one of the K wavelength variable light sources. A station-side device comprising an optical signal selector that selects and outputs a downstream optical signal.   The KN wavelength tunable light sources are standby wavelength tunable light sources, and the standby wavelength tunable light sources correspond to the timing at which the downstream electrical signal is sent to the optical signal processing unit based on the transmission plan. The wavelength is set in advance
The station-side apparatus according to claim 1, wherein: The number N of the electric signal processing unit, the number P of input ports of said electrical switch, and, according to claim 1 or 2 number Q output port of the optical signal selector is characterized in that both 1 Station side equipment. The number N of the electrical signal processing units is 2 or more,
The control unit includes a routing table generating means for generating a routing table,
An upper switch is provided on the upper network side of the electric signal processing unit to select and send any one of the N electric signal processing units for the downlink data signal received from the upper network based on the routing table. The station side apparatus according to claim 1 or 2 . The control unit is divided into an integrated control unit and a station side control unit provided in a one-to-one correspondence with the electrical signal processing unit,
The integrated control unit, the routing table generating unit, said transmission plan creation means, with said wavelength control means及beauty electric switch control means,
The station-side apparatus according to claim 4 , wherein the station-side control unit includes the control signal generation unit. N optical signal processing units are provided one-to-one with N electrical signal processing units,
Line terminal according to claim 4 or 5, characterized in that the number P and the number Q of the output ports of the optical signal selector input port of the electrical switch is both 1. Line terminal according to claim 4 or 5 number P and the number Q of the output port of said input ports is equal to or equal to the number N of the electric signal processing unit. The control unit further includes buffer control means for generating a read instruction signal,
The electrical signal processing unit stores the downstream electrical signal, reads the downstream electrical signal instructed by the readout instruction signal at a timing instructed by the readout instruction signal in response to the readout instruction signal, and outputs the optical signal line terminal according to any one of claims 1 to 7, characterized in that a buffer for sending to the signal processing unit. A station side device,
A branched optical transmission line, and a subscriber side device connected to a branch destination of the optical transmission line;
A station-side device used in a network including
A control unit, N (N is an integer of 1 or more) electrical signal processing unit, and an optical signal processing unit,
The controller is
Control signal generating means for generating a downlink control signal for controlling the subscriber side device;
A transmission plan creation means for creating a transmission plan based on information including the destination of the downlink data signal;
Wavelength setting means for generating a wavelength setting signal based on the transmission plan, and path control means for generating a path switching signal,
The electrical signal processing unit generates a downlink electrical signal based on the downlink control signal and the downlink data signal,
The optical signal processor is
K (K is an integer equal to or greater than N + 1) wavelength tunable light sources that generate a downstream optical signal from the downstream electrical signal by changing the wavelength according to the wavelength setting signal;
It has P input ports (P is an integer equal to or greater than 1) and K output ports, and switches the path according to the path switching signal to be one of the K wavelength variable light sources. An electrical switch for sending the downstream electrical signal, and K input ports and Q output ports (Q is an integer equal to or greater than 1), and generated by one of the K wavelength variable light sources. A station-side device comprising an optical signal selector that selects and outputs a downstream optical signal.   The KN wavelength tunable light sources are standby wavelength tunable light sources, and the standby wavelength tunable light sources correspond to the timing at which the downstream electrical signal is sent to the optical signal processing unit based on the transmission plan. The wavelength is set in advance
The station apparatus according to claim 9, wherein:

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