JP4490166B2 - Station side equipment - Google Patents

Description

  The present invention relates to a PON (Passive Optical Network) system using Ethernet (registered trademark) technology, and relates to IEEE802. The present invention relates to MPCP (Multipoint Control Protocol) control of a GE-PON (Gigabit Ethernet (registered trademark) PON) system in ah.

  FIG. 7 is a diagram showing a conventional GE-PON system. In the conventional GE-PON system, upstream traffic from a subscriber side device (ONU: Optical Network Unit) to a station side device (OLT: Optical Line Terminal) is burst traffic that each ONU 2 transfers in a time division manner. It has become. In order to accommodate this upstream burst traffic in the OLT 1, a CDR (Clock Data Recovery) corresponding to the burst traffic is required in the OLT 1. Burst traffic-compatible CDRs are generally expensive and complex to control, which increases the development cost for increasing the transfer rate and the number of subscribers, and is accompanied by a high-speed compatible device. Need to be taken in, and the unit price of the equipment becomes high.

In addition, as a system that can easily improve the transfer rate using wavelength division multiplexing (WDM), there are PON systems using a plurality of upper and lower wavelengths (for example, Patent Document 1 and Patent Document 2). FIG. 8 shows the upper and lower multiple wavelength PON systems. When the upper and lower multi-wavelength PON systems are used, the upstream traffic is not burst traffic, and the CDR corresponding to burst traffic and the high-speed compatible device are unnecessary. However, since one wavelength is assigned to each ONU 5 for both upstream and downstream, an ONU equipped with an optical module corresponding to each wavelength is required. That is, when 32 units of ONUs 5 are connected to one system, 32 types of ONUs 5 each having a different optical module mounted are required, resulting in poor productivity and increased cost. In addition, since there are a plurality of types of ONUs 5, it is necessary to determine where to place the ONUs 5 mounted with optical modules corresponding to which wavelengths when laying the system.
Japanese Patent Laid-Open No. 10-247896 JP-A-8-8878 IEEE Draft P802.3ah D3.0

  In the conventional method described above, in order to increase the transfer rate, a high-speed compatible device is required to increase the speed of the conventional GE-PON method, and the unit price of the equipment becomes expensive. In addition, the PON method using a plurality of upper and lower wavelengths requires a plurality of types of ONUs, resulting in poor productivity and increased cost.

  The main object of the present invention is to solve such problems in the conventional system, and without adding a special device or preparing a plurality of types of ONUs, the high-speed GE-PON is provided. Plan

The station-side device according to the present invention is
In a station-side device used in a communication system having a station-side device and a plurality of subscriber-side devices,
First transmission means for transmitting a first reply time signal indicating a first time to a first subscriber side device that receives a signal of a first wavelength;
A second transmission means for transmitting a second reply time signal indicating a second time to a second subscriber side device that receives a signal of the second wavelength;
Receiving means for receiving a return signal from the first subscriber side device and the second subscriber side device;
Based on the reception time of this receiving means, comprises a determining means for determining at which wavelength the subscriber-side device that has made a reply,
When the determination result of the determination means indicates that a reply has been made at the first wavelength, a signal is transmitted by the first transmission means, and a reply has been made at the second wavelength. The second transmission means transmits a signal.

  In the present invention, without adding a special device, using a subscriber unit developed for one wavelength in the upper and lower directions, using a plurality of wavelengths in the downlink transmission line, the transfer speed is increased to increase the communication speed. Can be planned. As a result, the number of subscribers can be increased.

Embodiment 1 FIG.
The present embodiment relates to a PON (Passive Optical Network) system using Ethernet (registered trademark) technology. The present invention relates to MPCP control of a GE-PON system in ah.

  FIG. 1 is a configuration diagram showing the entire system of the present embodiment. LANs (Local Area Networks) 11 and 12 configured by Ethernet (registered trademark) or the like are arranged far away from each other, and these two LANs 11 and 12 are interconnected to a WAN (Wide Area Network) 13. The WAN 13 uses various communication methods and performs communication between connected LANs. A plurality of communication terminals 14 are connected to the LAN 11, and a plurality of communication terminals 15 are connected to the LAN 12. Between the WAN 13 and the LAN 11, an ONU (subscriber side device) 16 that is a termination device of the LAN 11 and an OLT (station side device) 17 that is a termination device of the WAN 13 are provided. Between the WAN 13 and the LAN 12, an ONU (subscriber side device) 18 that is a termination device of the LAN 12 and an OLT (station side device) 19 that is a termination device of the WAN 13 are provided. The ONUs 16 and 18 and the OLTs 17 and 19 function as the PON system of this embodiment.

  FIG. 2 is a configuration diagram of a GE-PON system using a plurality of downlink wavelengths according to the present embodiment, which is a part of FIG. A GE-PON system using multiple downstream wavelengths is a subscriber-system exchange OLT 20 that is a member of the WAN 13, a WDM coupler (signal separation device) 21 that separates the output light from the OLT 20, and a plurality of transmission paths. And a plurality of ONUs 23 connected to the optical couplers 21 and 22 through branch paths. The OLT 20 is the same as the OLTs 17 and 19 in FIG. The ONU 23 is the same as the ONUs 16 and 18 in FIG.

  The GE-PON system using a plurality of downlink wavelengths is a system that increases the number of subscribers accommodated by solving the problems of the prior art and increasing the downlink transfer rate. The GE-PON system using a plurality of downstream wavelengths gives a light receivable wavelength of a PD (Photo Diode) mounted on the reception optical module of the ONU 23 to allow reception of a plurality of wavelengths. Therefore, it is possible to realize a GE-PON system using a plurality of downstream wavelengths, which is a PON system having a plurality of downstream wavelengths and one upstream wavelength. Further, in the GE-PON system using a plurality of downstream wavelengths, there is one type of ONU, and the same equipment as a conventional GE-PON ONU can be used. In FIG. 2, each ONU 23 can receive the wavelengths λd_1 to 3 output from the OLT 20 and can transmit the wavelength of λu. Downlink wavelengths λd_1 to 3 output from the OLT 20 are wavelength-separated by the WDM coupler 21, and only a single wavelength is input to the ONU 23. That is, the ONU actually receives any single wavelength after being separated by the WDM coupler 21, but each ONU also receives an optical signal of any wavelength after being separated by the WDM coupler 21. It can be received.

  In the GE-PON system using a plurality of downlink wavelengths according to the present embodiment, the downlink transfer rate output from the OLT 20 is 1 Gbps × the number of wavelengths because wavelength multiplexing is performed, and the transfer rate can be increased to a multiple of the number of wavelengths. More subscribers can be accommodated in one system. Further, since the vertical transfer rate in each ONU 23 is equivalent to that of the conventional GE-PON system, it is possible to use the conventional GE-PON system ONU.

  In the GE-PON system using a plurality of downlink wavelengths according to the present embodiment, the signal bands provided by one OLT 20 can be shared by a plurality of ONUs 23 by using the optical couplers 21 and 22. Downlink signals in the direction from the OLT 20 toward the ONU 23 are broadcast to all the ONUs 23 belonging to that wavelength for each wavelength transmitted by the OLT 20, and each ONU 23 extracts only information corresponding to itself. Conversely, the upstream signal in the direction from the ONU 23 to the OLT 20 is a time division method in which each ONU 23 sequentially transmits a signal in accordance with a transmission permission signal given from the OLT 20.

  FIG. 3 is a block diagram showing an example of connection and configuration of the OLT 20 and the ONU 23. The OLT 20 includes an MPCP unit 30 that controls the PON system. The MPCP unit 30 includes an MPCP control unit 31 that determines MPCP processing and an MPCP processing unit 32 that generates an MPCP frame to be sent from the OLT 20 to the ONU 23. The MPCP control unit 31 includes a Discovery Window generation calculation processing unit 33 and a wavelength group determination unit (determination unit) 300. The Discovery Window generation calculation processing unit 33 determines the generation period and window width of the Discovery Window. Moreover, the wavelength group determination unit 300 determines the wavelength group of the ONU. As will be described later, each ONU is classified into a plurality of wavelength groups according to the wavelength of the optical signal to be received. The wavelength group determination unit 300 determines a wavelength group belonging to each ONU. Further, the OLT 20 includes a PON termination unit 34 as a communication interface with the ONU 23. The PON termination unit 34 includes a frame transmission unit 35 that transmits the user frame and the MPCP frame generated by the MPCP processing unit 32 toward the ONU 23, and a transmission optical module (first transmission unit or second transmission unit) 37. The transmission optical module 37 converts each frame from the frame transmission unit 35 corresponding to each wavelength from an electrical signal to an optical signal. Further, the PON termination unit 34 is provided with a frame identification unit 36 that separates a frame received from the ONU 23 into an MPCP frame and a user frame, and a burst-compatible CDR so that burst data from the connected ONU 23 can be received. A receiving optical module (receiving means) 38 for converting an optical signal into an electric signal is provided. Also provided is a WDM coupler 39 that multiplexes and separates a plurality of downstream wavelengths and upstream wavelengths. The ONU 23 includes an MPCP unit 40 that controls the PON system. The MPCP unit 40 includes an MPCP control unit 41 that determines MPCP processing, and an MPCP processing unit 42 that generates an MPCP frame to be transmitted from the ONU 23 to the OLT 20. The ONU 23 includes a PON termination unit 43 as a communication interface with the OLT 20. The PON termination unit 43 includes a frame transmission unit 44 that transmits a user frame and an MPCP frame generated by the MPCP processing unit 42 toward the OLT 20, and a frame identification unit 45 that separates a frame received from the OLT 20 into an MPCP frame and a user frame. I have. Also, the PON termination unit 43 is a transmission optical module 46 that converts the frame output from the frame transmission unit 44 from an electrical signal to an optical signal. λd1 to 3) A receiving optical module 47 capable of receiving is provided. Further, a WDM coupler 48 for multiplexing and separating the downstream wavelength and the upstream wavelength is provided.

  In the GE-PON system using a plurality of downlink wavelengths according to the present embodiment, a plurality of wavelengths are used in the downlink transmission path, and ONUs are divided into wavelength groups corresponding to the number of wavelengths according to the input downlink wavelengths. Since the downstream optical signal output from the OLT performs wavelength separation on the transmission path, each ONU group does not receive optical signals of wavelengths other than the downstream optical signal input to the wavelength group to which the ONU group belongs. In FIG. 2, ONUs belonging to the wavelength group of λd_1 do not receive the optical signals of λd_2 and λd_3 due to wavelength separation by the WDM coupler 21. Also, for frames transmitted using optical signals, ONUs belonging to the wavelength group of λd_1 do not receive frames transmitted using λd_2 or λd_3. On the other hand, in the conventional GE-PON system, since the downlink transmission path has one wavelength, all downlink traffic transmitted from the OLT is broadcast to all ONUs.

  The control such as MPCP in the conventional GE-PON system is based on the premise that the downlink control frame is broadcast to all ONUs. However, in this method, as described above, the downlink control frame transferred from the OLT is broadcast only to the ONU group to which the wavelength belongs, and is not broadcast to other ONU groups. Therefore, the conventional GE-PON method is used. This is a problem when a control method such as MPCP control is used.

  In the conventional GE-PON system, when a downlink user frame input to an OLT from a higher-level device is transferred to the corresponding ONU, since the downlink traffic is broadcast to all ONUs, all user frames received by the OLT are transmitted. May be transmitted to the ONU. However, in the GE-PON system using a plurality of downlink wavelengths according to the present embodiment, a frame transmitted using a certain wavelength is broadcasted only to the ONU group to which that wavelength belongs, and received by other groups. Therefore, it is necessary to determine which wavelength is used to transmit the downlink user frame.

  In order to solve the above problem, in the GE-PON system using a plurality of downlink wavelengths according to this embodiment, the OLT needs to recognize which wavelength each ONU belongs to. The OLT can use a control method such as MPCP control of the conventional GE-PON method by transmitting a control frame addressed to each ONU using the recognized wavelength. Furthermore, the OLT can determine which wavelength is used to transmit the downlink user frame to each ONU. In the present embodiment, in order to recognize which wavelength group the ONU belongs to, a Discovery Window / Discovery Gate frame of MPCP control of the GE-PON system is used.

  First, the registration work sequence of the ONU 23 in the conventional GE-PON system will be described with reference to FIG. In the GE-PON system using MPCP control, the ONU registration operation is an operation in which the OLT automatically recognizes an unregistered ONU among the ONUs connected to the OLT and performs registration. Therefore, ONU registration work by OLT is periodically performed. At a certain period, the OLT 20 transmits to all the ONUs 23 to which the Discovery Gate frame 51 that is an MPCP control frame is connected. The Discovery Gate frame 51 includes a GST (Grant Start Time) that is the transmission start time of the Register Request frame 52 that the ONU 23 sends back to the OLT 20. When the ONU 23 newly connected to the system receives the Discovery Gate frame 51, it transmits a Register Request frame 52, which is an MPCP control frame, to the OLT 20 from the time when Random Delay is added to GST. In this registration sequence, the Discovery Window 56 is a reception wait time for the Register Request frame transmitted from the ONU 23 for the OLT 20, and a transmission time for the Register Request frame for the ONU 23. Therefore, the ONU 23 must transmit a Register Request frame so that the Register Request frame reaches the OLT 20 within the range of the Discovery Window 56.

  The OLT 20 that has received the Register Request frame 52 transmits to the ONU 23 that has transmitted the Register Request frame 52 a Register frame 53 that is an MPCP control frame that indicates connection permission and a Gate frame 54 that includes frame transmission permission information. The ONU 23 that has received the Register frame 53 and the Gate frame 54 transmits a Register ACK frame 55 indicating completion of registration work based on the frame transmission permission information included in the Gate frame 54. When the OLT 20 receives the Register ACK frame 55, the registration work for the newly connected ONU 23 is completed. Further, in the GE-PON system using multiple downlink wavelengths according to the present embodiment, the Discovery Gate frame 51 transmitted from the OLT 20 needs to be transmitted to all the connected ONUs 23. The Discovery Gate frame 51 is transmitted.

  Next, a description will be given of a method in which the OLT 20 according to the present embodiment recognizes which wavelength group of the downstream wavelength the ONU 23 belongs to using a registration work sequence of the ONU 23 in the conventional GE-PON system. FIG. 4 is a part of a registration work sequence of the ONU 23 in the conventional GE-PON system of FIG. 9 and represents a method in which the OLT 20 recognizes a wavelength group to which the ONU 23 belongs. In the present embodiment, the Discovery Window set in the upstream band by the OLT 20 is provided with an independent time for each downstream wavelength (Discovery Window_λd_1, Discovery Window_λd_2, Discovery Window_λd_3 in the figure). The OLT 20 calculates a GST (Grant Start Time) (first time or second time) (GST1, GST2, GST3 in the figure) from the Discovery Window set for each wavelength, and a Discovery Gate including the GST for each downstream wavelength. A frame (first reply time signal or second reply time signal) is transmitted. The Discovery Window for each wavelength is set by the Discovery Window generation calculation processing unit 33.

  When the OLT 20 receives a Register Request frame (return signal) in a Discovery Window set for a certain wavelength, the OLT 20 recognizes the ONU that has transmitted the Register Request frame as an ONU belonging to that wavelength. In FIG. 4, the Discovery Gate frame corresponding to “Discovery Window_λd_1” is “Discovery Gate_λd1”, and the frame includes “GST1” calculated from “Discovery Window_λd_1”. The ONU_X belonging to the downstream wavelength λd_1 receives “Discovery Gate_λd1”, which is a Discovery Gate frame transmitted from the OLT, and adds the Random Delay (maximum delay time) to the time of “GST1” included in the frame To transmit a Register Request frame. The OLT 20 receives the Register Request frame from the ONU_X at “Discovery Window_λd_1”, and recognizes that the ONU_X is an ONU belonging to the wavelength group of the downstream wavelength λd_1. Similarly, the OLT 20 receives the Register Request frame transmitted from the ONU_Y and ONU_Z during the Discovery Window set for each wavelength, and the ONU_Y belongs to the wavelength group of the downstream wavelength λd_2, and the ONU_Z belongs to the wavelength group of the downstream wavelength λd_3. Recognize.

  In the above method, the Discovery Window set for each wavelength is periodically set to automatically recognize a newly connected ONU. Therefore, the Discovery Gate frame corresponding to the Discovery Window is periodically transmitted from the OLT 20 to the ONU 23. When the OLT 20 receives a Register Request frame during Discovery Window, the OLT 20 recognizes that the unregistered ONU 23 is connected to the system, performs the ONU 23 registration work by the above method, and further recognizes the wavelength group to which the ONU 23 belongs. If the OLT 20 does not receive the Register Request frame during the Discovery Window, it is determined that there is no newly connected ONU 23 in the downstream wavelength corresponding to the Discovery Window.

  5 and 6 are flowcharts showing the processing described with reference to FIG. FIG. 5 is a flowchart showing processing on the OLT 20 side, and FIG. 6 is a flowchart showing processing on the ONU 23 side.

  In FIG. 5, first, the OLT 20 generates a Discovery Gate frame in which GST is set for each of λd_1 to λd_3 (S501), multiplexes the Discovery Gate frames for each wavelength, and transmits them to the ONU 23 (S502). Thereafter, it is confirmed whether or not a Register Request frame has been received from the ONU (S503). If it has not been received, the process ends. If it has been received, the process proceeds to S504. Next, it is determined which wavelength group the Discovery Window of the received Register Request frame matches with the Discovery Window (S504), and which wavelength group of λd_1 to λd_3 the ONU that is the transmission source of the Register Request frame belongs to Is determined (S505 to S507). Thereafter, a Register frame and a Gate frame are transmitted to the ONU (S508), and a Register ACK frame is received as a response from the ONU (S509), and the registration process is terminated.

In FIG. 6, the ONU 23 determines whether or not a Discover Gate frame has been received from the OLT 20 (S601), and if received, determines whether or not the Discover Gate frame has been received for the first time (S602). . If it is the first reception, that is, if it is an ONU newly connected to the system, the Discovery Window is calculated from the GST and Random Delay set in the Discover Gate frame (S603), and the Register Request is set in the Discovery Window. The frame is transmitted to the OLT (S604). Thereafter, a Register frame and a Gate frame are received from the OLT (S605), a Register ACK frame is transmitted as a response (S606), and the process ends.
In this manner, the OLT 20 can recognize which wavelength group of the downstream wavelength the ONU 23 belongs to by the above method. Based on this recognition, the OLT 20 can determine which wavelength should be used to transmit the MPCP frame and the user frame.

  As described above, in the communication system according to the present embodiment, a plurality of wavelengths are used for the downlink transmission line by using the subscriber apparatus developed for one wavelength above and below without adding a special device. GE-PON can be speeded up by increasing the transfer rate. As a result, the number of subscribers can be increased. Furthermore, since each subscriber unit is configured to receive the wavelength that can be delivered to other terminals, the subscriber unit can be mass-produced uniformly and manufacturing costs can be reduced. Can do.

  In the communication system according to the present embodiment, a different Discovery Window is provided for each wavelength group, and it is determined in which wavelength group the Discovery Request frame, which is a response to the Discovery Gate frame, is received. Thus, it can be determined to which wavelength group the newly connected ONU belongs.

  In the above description, in the GE-PON system, optical signals with a plurality of wavelengths are used for downlink communication. However, the communication system to be applied is not limited to the GE-PON system, and may be a communication system using signals with a plurality of wavelengths. Any system is applicable.

It is a block diagram which shows the structural example of the whole system which concerns on this Embodiment. It is the figure which showed the structural example of the GE-PON system using the downlink multiple wavelength which concerns on this Embodiment. It is a block diagram showing the structural example of OLT and ONU which concern on this Embodiment. It is a figure which shows the ONU registration sequence example which concerns on this Embodiment. It is a flowchart figure which shows the operation example of OLT which concerns on this Embodiment. It is a flowchart figure which shows the operation example of ONU which concerns on this Embodiment. It is the figure which showed the conventional GE-PON system. It is the figure which showed the conventional upper and lower multiple wavelength PON system. It is a figure which shows the sequence of the registration work of the conventional ONU.

Explanation of symbols

  11 LAN, 12 LAN, 13 WAN, 14 terminals, 15 terminals, 16 ONU, 18 ONU, 17 OLT, 19 OLT, 20 OLT, 21 WDM coupler, 22 spectral coupler, 23 ONU, 30 MPCP section, 31 MPCP control section, 32 MPCP processing unit, 33 Discovery Window generation calculation processing unit, 34 PON termination unit, 35 frame transmission unit, 36 frame identification unit, 37 transmission optical module, 38 reception optical module, 39 WDM coupler, 40 MPCP unit, 41 MPCP control unit 42 MPCP processing unit, 43 PON termination unit, 44 frame transmission unit, 45 frame identification unit, 46 transmission optical module, 47 reception optical module, 48 WDM coupler, 51 Discovery Gate frame, 52 Regis er Request frame, 53 Register frame, 54 Gate frame, 55 Register ACK frame, 56 Discovery Window, 300 wavelength group judgment unit.

Claims (3)

In a station-side device used in a communication system having a station-side device and a plurality of subscriber-side devices,
First transmission means for transmitting a first reply time signal indicating a first time to a first subscriber side device that belongs to the first wavelength group and receives a signal of the first wavelength;
A second transmitting means for transmitting a second reply time signal indicating a second time to a second subscriber side device belonging to the second wavelength group and receiving a signal of the second wavelength;
Receiving means for receiving a reply signal for either the first reply time signal or the second reply time signal from any of the subscriber side devices;
Based on the reception time of the reception unit, a station-side apparatus according to claim Rukoto comprises determination means for determining one of whether belongs the subscriber unit first wavelength group and the second wavelength group subjected to reply. The judging means is
Whether or not the reception time of the receiving means is earlier than the time obtained by adding the maximum delay time that can occur in the first subscriber-side device set in advance to the first time, The station apparatus according to claim 1, wherein it is determined whether or not it belongs to the first wavelength group . The station side device
If the determination result of the determination means indicates that the subscriber side device that has sent the reply belongs to the first wavelength group, the first transmission means sends a signal to the subscriber side device that has sent the reply, 2. A signal is transmitted by the second transmission means to a subscriber side device that has sent a reply when the subscriber side device that has performed the transmission indicates that it belongs to the second wavelength group. Or the station side apparatus of 2.

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