JP2007288655A - Multi-rate pon system and its station side unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable controlled transmission with terminal units including automatic registration in a multi-rate PON (passive optical network) system having a plurality of transmission rates for terminal units, even when the station side unit does not recognize the transmission rates to which the respective terminal units correspond. <P>SOLUTION: A multi-rate PON system performs transmission in a downstream direction or an upstream direction, or in a two-way direction between a central unit 1 and each of terminal units 2, 3 and 4 at a plurality of transmission rates including a reference rate. The central unit 1 registers the terminal units 3 and 4 having transmission capability of a transmission rate different from the reference rate, and performs control system transmission at the reference rate to recognize the capability of the terminal units 3 and 4, so that main signal transmission with the terminal units 3 and 4 in the downstream or upstream direction or in the two-way direction can be performed at a transmission rate other than the reference rate. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a multi-rate PON system in which communication between a station-side device and a plurality of terminal devices can be performed at a plurality of transmission rates using a time division multiplexing method, and a station-side device used in this system.

A PON system (Passive Optical Network System) is a P2MP (P2MP) in which one station side device (OLT: Optical Line Terminal) and a plurality of user terminal devices (ONU: Optical Network Unit) are connected via a passive element such as an optical coupler. Point To Multipoint) type optical fiber network system. Among these PON systems, GE-PON (Gigabit Ethernet-PON) is an economical implementation of a gigabit class transmission system based on Ethernet (registered trademark) technology. It was established as IEEE 802.3ah ^TM in 2004. This is one of the high-speed optical access methods standardized in June.
In the PON system described above, a TDM (Time Division Multiplexing) method for aligning and transmitting signals for each terminal device is used for the downlink signal transmitted from the station side device to each terminal device. For uplink signals transmitted to the apparatus, a TDMA (Time Division Multiple Access) system is employed in which optical signals are transmitted at correct timing so that the signals do not collide with each other. In order to accurately perform the signal transmission timing in the TDMA system, it is necessary that the clock of the terminal device and the clock of the station side device are accurately synchronized.

For this reason, for example, in the standard based on the IEEE 802.3ah ^TM , the station side device counts the local clock to generate a clock of the station side device (hereinafter referred to as a PON counter), and the transmission clock of the PON downstream signal is the local clock. It is specified that the value of the PON counter at the time of transmission is recorded as a time stamp in the PON control frame transmitted to the terminal device in synchronization with the clock.
Also, as a terminal device, the local clock is synchronized with the clock included in the PON reception signal, the local clock is counted to generate the PON counter of the terminal device, and when the PON control frame is received, Update the PON counter with the indicated time stamp value, transmission permission is indicated by the value of the PON counter, and the terminal device transmits to the PON when its own PON counter is within the specified range, at this time Is synchronized with a local clock (see Non-Patent Document 1).

  In the above standard, regarding the automatic registration of a terminal device, the station side device polls the terminal device for a registration request (specifically, broadcasts a discovery gate which is a kind of transmission permission), and the terminal device issues a registration request. It is also stipulated that registration is made with a registration permission of the station side device and a confirmation response of the terminal device in response to this by transmitting. However, according to the standard, the transmission rate is limited to a case where the transmission rate is fixed at 1.25 Gbps for both uplink and downlink. There are no regulations regarding control communication between the terminal device and each terminal device, such as automatic registration of terminal devices and OAM (Operation Administration and Maintenance).

IEEE Std 802.3ah (registered trademark) -2004 (64. Multipoint MAC Control; 57. Operation Administration and Maintenance)

In the PON system, it is expected that the transmission speed will be further increased in the future, but even if the transmission speed is further increased, it is necessary to introduce a new high-speed service while maintaining the existing service, so that a plurality of transmission rates must coexist. There is. In this case, communication between the station side device and each terminal device is performed at a plurality of transmission rates (hereinafter referred to as multi-rate PON).
As described above, when a terminal device having a high-speed transmission rate that was not initially assumed is newly installed in an existing PON system, what transmission rate can be received for the high-speed terminal device, and / or Since it is unknown at what transmission rate the request is transmitted, control communication including automatic registration of the terminal device cannot be adopted based on the above standard premised on that the transmission rate is fixed. Therefore, in this case, the registration procedure between the station side device and the later high-speed terminal device must be manually performed, and it takes a lot of time to introduce the terminal device corresponding to the high-speed transmission rate. There was a problem.

  In view of such circumstances, the present invention enables control communication with a terminal device including automatic registration even if the station device does not know what transmission rate the terminal device supports. The purpose is to facilitate the high-speed service of the PON system.

  A first invention for achieving the above object is a multi-rate PON system in which downlink, uplink, or bidirectional communication between a station-side device and each terminal device is performed at a plurality of transmission rates including a reference rate. The terminal side device registers the terminal device with respect to the terminal device having communication capability at another transmission rate different from the reference rate, and performs management communication for recognizing the capability of the terminal device at the reference rate. And a second step of performing downlink, uplink, or bidirectional main signal communication with the terminal device at another transmission rate different from the reference rate.

  The PON system described above is based on the premise that each terminal device constituting the system has at least a reference rate reception capability. According to the first invention, in that case, the station side device registers the terminal device and recognizes the capability of the terminal device even for a terminal device having communication capability at another transmission rate different from the reference rate. Management system communication is performed at the reference rate, so even if the station side device does not know what transmission rate the terminal device supports, the terminal device can be automatically registered. And the transmission / reception capability of the terminal device can be known.

When viewed from the terminal device, the communication with the station side device proceeds in the order of the registration phase, the OAM initial setting phase, and the main signal communication phase, as will be described later in the embodiment. According to the first aspect, communication in the registration phase and the OAM initial setting phase is performed at the reference rate regardless of the difference in transmission / reception capabilities of the terminal device. For this reason, automatic registration based on the reference rate is possible regardless of the number of terminal devices having different transmission rates from the reference rate.
However, for main signal communication in the main signal communication phase, it is desirable that the station-side device performs at a higher transmission rate according to the transmission / reception capability of each terminal device. Therefore, in this case, in the OAM initial setting phase, by causing the station side device to negotiate the transmission rate with each terminal device, in the subsequent main signal communication phase, the multi-rate corresponding to the communication capability of each terminal device. Communication becomes possible.
In the main signal communication phase, main signal communication and management communication for transmission permission (GATE) and transmission request (REPORT) for controlling the main signal communication are performed. The transmission rates of these main signal communication and management communication can be negotiated individually and upstream and downstream in the OAM initial setting phase.

In the first invention, the transmission permission (GATE) and the transmission request (REPORT) are exchanged uniformly at the reference rate, and the station side device collects the transmission requests from all the terminal devices in a concentrated manner. Centralized dynamic bandwidth allocation is performed in which bandwidth allocation is performed in a concentrated manner and transmission permission is transmitted to each terminal device in a concentrated manner.
In this case, in the downlink direction, all transmission permissions are transmitted from the station side apparatus to the terminal apparatus at the reference rate, so there is no need to switch the transmission rate for each transmission permission, and overhead at the time of rate switching can be reduced in this respect. There is an advantage. Also, in the uplink direction, all transmission requests are transmitted from the terminal device to the station side device at the reference rate, so the station side device does not need to switch the reception rate for each transmission request, and reduces overhead during rate switching. There is an advantage that you can.

According to a second invention for achieving the above object, downlink communication from a station-side device to each terminal device is performed at a plurality of transmission rates, and uplink communication from each terminal device to the station-side device is performed. In a multi-rate PON system performed at a single rate, the station side device transmits a registration request transmission permission for each terminal device for each transmission rate, and registers a terminal device that has responded The first step of performing the downlink communication at the transmission rate, and all the downlink communication including the management communication and the main signal communication including the transmission permission to the terminal device after registration and the transmission request from the terminal device. It has the 2nd step performed at the said transmission rate, It is characterized by the above-mentioned.
Alternatively, in a multi-rate PON system in which bidirectional communication between the station-side device and each terminal device is performed at a plurality of transmission rates, the station-side device permits transmission of a registration request to each terminal device at a transmission rate. Including a first step of performing management communication for registering a terminal device that has been transmitted and responded at the transmission rate, a transmission permission for the terminal device after registration, and a transmission request from the terminal device A second step of performing all communication including management communication and main signal communication at the transmission rate is provided.

In the PON system described above, it is assumed that each terminal device can transmit and receive only one transmission rate. Further, it is assumed that the transmittable rate is a single rate (for example, a reference rate) that is the same for all terminal apparatuses and a rate that is equal to the receivable rate.
In one PON system, it is assumed that the transmission rate in the upstream direction is unified and is determined in advance. That is, since the station side device knows at what rate the uplink communication is performed with respect to the transmission permission given to the terminal device, it can prepare for reception. According to the second invention, in that case, the station side device transmits a transmission permission for the registration request for each transmission rate, and performs management communication for registering the terminal device that has responded at the transmission rate. Since it did in this way, even if the station side apparatus does not grasp | ascertain what transmission rate the terminal apparatus supports, recognition of the receiving capability of a terminal apparatus and automatic registration can be performed simultaneously.
When viewed from the terminal device, the communication with the station side device proceeds in the order of the registration phase, the OAM initial setting phase, and the main signal communication phase, as will be described later in the embodiment. According to the second aspect of the invention, all communications are performed at individual transmission rates at which the terminal device has the capability regardless of the phase. Therefore, it is not necessary for the station side apparatus to negotiate the transmission rate with each terminal apparatus in the OAM initial setting phase as described above.

Further, in the second invention, since transmission permission (GATE) and transmission request (REPORT) are exchanged at individual transmission rates, each transmission rate is individually received when a transmission request from each terminal device arrives. It is preferable that the station side apparatus perform the distributed dynamic band allocation that performs band allocation and transmits a transmission permission to the terminal apparatus corresponding to the transmission rate.
In this case, the transmission request is transmitted to the station side device as a series with the upstream main signal, and the transmission permission is transmitted to each terminal device as a series with the downstream main signal, so that the transmission permission and the transmission request are transmitted. Compared to the centralized type that needs to be managed as a whole, overhead can be reduced.

  As described above, according to the present invention, in the multi-rate PON system in which the terminal apparatus has a plurality of types of transmission rates, the station apparatus knows in advance what transmission rate the terminal apparatus supports. Even without this, since control communication with a terminal device including automatic registration is possible, high-speed service of the PON system can be easily achieved.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[Overall configuration of PON system]
FIG. 1 is a schematic configuration diagram of a multi-rate PON system assumed by the present invention.
In FIG. 1, a station-side device 1 is installed in a telephone station or the like as a central station for a plurality of terminal devices 2, 3, and 4, and each terminal device 2, 3, and 4 is installed in a subscriber house of a PON system. is set up. One optical fiber (main line) 5 is connected to the station side apparatus 1. The optical fiber 5 is branched into a plurality of optical fibers (branch lines) 7, 8, 9 via an optical coupler 6, thereby forming an optical fiber network 10. The terminal devices 2, 3, and 4 are respectively connected to the ends of the branched optical fibers 7, 8, and 9, thereby forming a P2MP PON system. The station side device 1 is connected to the host network 11, and the terminal devices 2, 3, 4 are connected to the respective user networks 12, 13, 14.

In FIG. 1, for the sake of simplicity, a P2MP configuration in which three terminal devices 2, 3, and 4 are connected is illustrated. However, in practice, 32 terminal devices are branched from one optical coupler 6. Can be connected. In addition, FIG. 1 illustrates a topology with only one optical coupler 6, but by arranging a plurality of stages of optical couplers 6 having a small number of branches in a column, it is possible to make terminal devices distributed over a wide area short. It is also possible to connect to the station side device 1 by a fiber.
In this PON system, downstream optical wavelength and upstream optical wavelength are divided and wavelength division multiplexing (WDM) is performed. That is, a laser beam having a single wavelength λ1 is used for uplink communication between the station side device 1 and the terminal devices 2, 3, and 4, and a single wavelength λ2 different from the wavelength λ1 is used for downlink communication. Laser light is used.

Accordingly, a WDM filter is provided between the transmitter / receiver of the PON medium (optical fibers 5, 7, 8, 9) and the station side device 1 and each of the terminal devices 2, 3, 4, and only the wavelength component to be received is provided. The optical signal sent to the receiver and output from the transmitter is multiplexed with the received light via the WDM filter and sent to the optical fibers 5, 7, 8 and 9. The wavelengths λ1 and λ2 can be selected in the range of 1260 nm ≦ λ1 ≦ 1360 and 1480 nm ≦ λ2 ≦ 1500 according to IEEE Std 802.3ah ^™ -2004 Clause 60.
This PON system is a multi-rate PON system in which transmission is performed at a multi-rate in the downlink direction, the uplink direction, or both directions, and each terminal device 2, 3, 4 has the reception capability or the transmission capability or the capability of both transmission and reception. They may be different from each other. In the example of FIG. 1, the maximum information communication rates that can be transmitted and received by the terminal apparatuses 2, 3, and 4 are 1G, 2G, and 10 Gbps, respectively, and a 1 Gbps signal, a 2 Gbps signal, and a 10 Gbps signal are time-division multiplexed. The station side device 1 and each of the terminal devices 2, 3, 4 transmit and receive.
However, the transmission rates in the downlink and uplink directions do not necessarily have to be the same, and there is no need for multi-rate in either direction. For example, a PON system in which downlink is multirate and all uplinks are 1 Gbps may be used.

[Configuration example of station side equipment]
FIG. 2 shows an example of the station side apparatus 1 according to the present invention.
In the station side device 1, the frame sent from the upper network 11 is temporarily stored in the buffer 64 via the receiving unit 60, and then passes through the WDM filter 65 as an optical signal via the PON transmitting unit 63. And transmitted to the optical fiber 5 of the PON. In the PON optical fiber 5, one-fiber bidirectional wavelength multiplexing is performed, and the optical signal transmitted from the PON optical fiber 5 is separated from the transmitted light by the WDM filter 65 and transmitted to the PON receiver 61.
The frames restored in the PON receiving unit 61 are identified as the main signal frame F1 and the management frame F2 by the frame type determination unit 65, and are once sorted and stored in the buffer 62, respectively. Thereafter, the main signal frame F1 is transmitted to the upper network 11 via the transmission unit 66 as data for the user.

On the other hand, the management system frame F 2 is sent to the management system communication processing unit 67. The management frame F2 includes a PON control frame and an OAM frame. The management communication processing unit 67 supervises registration and uplink access control of the terminal devices 2, 3, 4 by exchanging PON control frames with the terminal devices 2, 3, 4. Here, the transmission permission to be given to the terminal devices 2, 3, 4 in the uplink access control is determined by the dynamic band allocation unit 68 in consideration of the requests from the terminal devices 2, 3, 4 and the network operation policy.
The OAM processing unit 69 manages the exchange of OAM frames. The PON control frame and the OAM frame to be transmitted to the terminal devices 2, 3, 4 pass through the buffer 64, the PON transmission unit 63, and the WDM filter 65 and are interrupted between the main signal frames F 1 column. 3 and 4 are transmitted.

The PON transmission unit 63 includes an encoding unit 71 that performs 8B / 10B conversion at a 1G or 2G rate, a 10G encoding unit 72 that performs 64B / 66B conversion at a 10G rate, and an encoding unit 71 and 10G encoding. An E / O conversion unit 73 that converts an electrical binary signal output from any one of the units 72 into an optical on / off signal, and a transmission scheduler 74 are included.
The state of the buffer 64 is managed by the transmission scheduler 74, and this transmission scheduler 74 determines the transmission order of the frames stored in the buffer 64 to the PON. The transmission scheduler 74 recognizes the connection state with the terminal devices 2, 3, 4 and the transmission rate for each of the terminal devices 2, 3, 4 based on the notification from the management communication processing unit 67.

In addition, the transmission scheduler 74 instructs the 10G encoding unit 72 and the encoding unit 71 which one is to be enabled according to the transmission order determined by itself, and if the encoding unit 71 is to be enabled, 1G Or 2G is instructed. In addition, the transmission scheduler 74 instructs the buffer 64 to extract a frame.
The PON receiver 61 includes an O / E converter 75 that converts an optical on / off signal into an electrical binary signal, a data recovery 76 that restores binary information in synchronization with a 1G or 2G rate, A code synchronization unit 77 that restores a frame by performing 10B / 8B conversion while synchronizing with 8B / 10B code from binary information, 10G-CDR78 that restores binary information in synchronization with the rate of 10G, and its binary information 10G code synchronizer 79 that restores a frame while performing 66B / 64B conversion, and a reception scheduler 80.

  The reception scheduler 80 is notified of the period of arrival of the uplink signal and the signal rate from the management communication processing unit 67. The reception scheduler 67 instructs which one of the recovery system of the data recovery 76 and the code synchronization unit 77 and the recovery system of the 10G-CDR 78 and the 10G-code synchronization unit 79 is valid before the upstream signal arrives. When the former is validated, the reception scheduler 80 further instructs whether to restore information at a rate of 1G or 2G.

[First communication method]
Hereinafter, the communication method of the first embodiment including automatic registration of the terminal devices 2, 3, 4 performed in the multi-rate PON system having the station-side device 1 according to the above configuration will be described with reference to FIGS. 3 and 4. explain.
In this embodiment, PON control communication is performed at a reference rate (1G in this case), and automatic registration of each multi-rate terminal device is performed. In other words, the present embodiment performs multi-rate by performing PON control communication with terminal devices 3 and 4 having other transmission rates (2G and 10G in this case) different from the reference rate all at the reference rate. Access control including automatic registration is performed with each of the terminal devices 2, 3, and 4.

3 and 4, the station side device is described as OLT. Further, in FIG. 3, a terminal device to be newly registered is described as ONU-X, and in FIG. 4, terminal devices having rates of 1G, 2G, and 10G are respectively referred to as ONU-A, ONU-B, and ONU-C. It is described.
FIG. 3 shows steps from registration to main signal communication, focusing on one terminal device among a plurality of multi-rate terminal devices (ONU-A, ONU-B, and ONU-C). It is.

As shown in FIG. 3, first, in the registration phase, the OLT broadcasts a transmission permission frame DGATE (a kind of PON control frame) for polling a registration request.
When the ONU-X, which is a terminal device to be newly registered, receives DGATE, it sends a registration request frame REGREQ (a type of PON control frame) to the OLT within the transmission permission period described in the DGATE. When the OLT accepts an ONU-X registration request, the OLT transmits a registration frame REGISTER (a kind of PON control frame) to the ONU-X.

  Further, the OLT transmits a normal transmission permission frame GATE (a type of PON control frame) to the ONU-X in order to send a registration confirmation frame REGACK (a type of PON control frame) from the ONU-X. As a response to REGISTER, ONU-X sends REGACK during the transmission permission period described in GATE. The OLT receives REGACK and ends the ONU-X registration procedure.

In the OAM initial setting phase subsequent to the registration phase, rate negotiation is performed by exchanging OAM frames in addition to normal initial setting and status confirmation. Here, since the station side apparatus 1 of this embodiment shown in FIG. 2 has 1G, 2G, and 10G transmission / reception capabilities, if the ONU-X has 1G and 2G transmission / reception capabilities, It is reasonable in terms of bandwidth efficiency to perform signal communication with 2G.
Therefore, after the end of the negotiation, data communication after an appropriate time is performed at a 2G rate. However, communication of PON control frames such as GATE and REPORT is performed at the reference rate (1G).

FIG. 4 shows an example of a communication method when ONU-A, ONU-B, and ONU-C having different rates are operating.
As shown in FIG. 4, in this case, a plurality of terminal apparatuses having different transmission rates (in the example shown, ONU-A having 1G transmission / reception capability, ONU-B having 1G / 2G transmission / reception capability, and 1G and 10G Communication is performed between the ONU-C) having transmission and reception capabilities and the OLT.

The uplink bandwidth allocation method in OLT is based on a centralized DBA (Dynamic Bandwidth Allocation) in which REPORTs are collected intensively from all terminal devices, and bandwidth allocation is dynamically performed in consideration of the state of all terminal devices. That is, the OLT continuously transmits GATE to the ONU-A, ONU-B, and ONU-C, and continuously transmits REPORT from the ONU-A, ONU-B, and ONU-C. As described above, since the GATE group is uniformly transmitted at the 1G reference rate, it is not necessary to switch the transmission rate in units of GATE having a frame length of 64 bytes, and overhead during rate switching can be reduced.
Similarly, in the present embodiment, the transmission permission to each terminal device is arranged in consideration of the rate switching overhead in uplink bandwidth allocation. That is, since the REPORT group is transmitted from the ONU-A, ONU-B, and ONU-C at a rate of 1G, it is not necessary to switch the reception rate in the REPORT unit having a frame length of 64 bytes in the OLT, and the rate is switched. Time overhead can be reduced.

[Second communication method]
Next, referring to FIG. 5 and FIG. 6, a communication method according to the second embodiment including automatic registration of terminal devices 2, 3, 4, which is performed in a multirate PON system having the station side device 1 according to the above configuration. Will be explained.
In this embodiment, the transmission / reception capabilities of each of the terminal devices 2, 3, and 4 are fixed to one rate, and the main signal and the PON control communication are communicated without distinction. That is, in the present embodiment, both terminal device 2, 3 and 4 are permitted to transmit the main communication and the management signal communication including the transmission request from the terminal device and the main signal communication other than the management communication. 3 and 4 are performed at individual transmission rates (here, 1G, 2G, and 10G).
In FIGS. 5 and 6, the station side device is also described as OLT. Also, in FIG. 5, a terminal device to be newly registered is described as ONU-X. Also in FIG. 6, terminal devices with rates of 1G, 2G, and 10G are respectively referred to as ONU-A, ONU-B, and ONU- C.

FIG. 5 shows the steps from registration to main signal communication, focusing on one of the multi-rate terminal devices (ONU-A, ONU-B, and ONU-C). It is.
The sequence in this case is the same as the communication method shown in FIG. However, in this embodiment, both downlink communication and uplink communication are performed at a predetermined rate for each terminal device. That is, 1G bidirectional communication is performed in ONU-A, 2G bidirectional communication is performed in ONU-B, and 10G bidirectional communication is performed in ONU-C.

For this reason, in this embodiment, since it is not necessary to negotiate the rate in the OAM initial setting phase, the communication method of FIG. 3 is different in that the control is not performed.
Further, in the communication method shown in FIG. 5, since both downlink communication and uplink communication are performed at a constant rate for each terminal device, when attention is paid to one terminal device (ONU-X shown in FIG. 5), registration is performed. Regardless of the phase, the OAM initial setting phase, and the main signal communication phase, both management communication such as PON control communication and main signal communication that is data transmission / reception are performed at the same rate unique to the terminal device.

FIG. 6 shows an example of a communication method when ONU-A, ONU-B, and ONU-C are operating.
As shown in FIG. 6, in this case as well, a plurality of terminal apparatuses having different transmission rates (in the example shown, ONU-A having 1G transmission / reception capability, ONU-B having 2G transmission / reception capability, and 10G transmission / reception capability). The communication is performed between the ONU-C) and the OLT, but the uplink bandwidth allocation method in the OLT is different from the case of FIG.

That is, the OLT uplink bandwidth allocation method according to the present embodiment is based on the distributed DBA in which bandwidth allocation is performed individually and GATE is transmitted when each REPORT arrives.
In this embodiment, in order to reduce overhead as much as possible, the REPORT is transmitted to the OLT as a series with the upstream main signal (that is, in the same burst as the upstream main signal). This means that the OLT gives a transmission permission so that the main signal and REPORT can be transmitted together. Similarly, GATE is transmitted as a series with downstream main signals to ONU-A, ONU-B, and ONU-C (ie, before and after the downstream main signal or between main signal frame trains with a short interframe gap). ing.

In the example illustrated in FIG. 6, as an initial state, ONU-A, ONU-B, and ONU-C are all unregistered.
In this case, the registration phase is first executed at a rate of 1G, and only the ONU-A can respond to this, and as a result, the ONU-A is registered. Subsequently, communication with ONU-A (including OAM, PON control, and main signal communication) continues at the 1G rate.
Thereafter, a registration phase is executed at a rate of 2G, to which only ONU-B can respond, and as a result, ONU-B is registered. After that, the 1G communication between the OLT and the ONU-A and the 2G communication between the OLT and the ONU-B are continued while being switched.

Thereafter, a registration phase is executed at a rate of 10G, to which only the ONU-C can respond, and as a result, the ONU-C is registered. Thereafter, the 1G communication between the OLT and the ONU-A, the 2G communication between the OLT and the ONU-B, and the 10G communication between the OLT and the ONU-C are continued while being switched.
Thus, even when the rate at which the terminal device can be transmitted and received is limited, operation including automatic registration of each terminal device is possible. In this case, the terminal device can be made inexpensive.

[Downlink signal frame]
FIG. 7 shows an example of a downlink signal frame of a multi-rate PON in the case where management communication such as PON control communication is performed with the reference rate unified (in the case of FIGS. 3 and 4).
As shown in FIG. 7, in this multi-rate PON, a GE-PON with an information communication rate of 1 Gbps / a transmission rate of 1.25 Gbps is used as a base (reference rate), and a signal with an information communication rate of 2 Gbps and a signal with an information communication rate of 10 Gbps are used. Is TDM. In the period of information communication rate 1 Gbps (hereinafter referred to as “1G period”. The same applies to 2G and 10G), the transmission system of GE-PON is basically used. That is, 1 octet of communication information is converted into 10-bit transmission information by 8B / 10B conversion, and a serialized 10-bit string is transmitted as a 1.25 Gbps NRZ signal and an optical on / off signal corresponding thereto.

In such a multi-rate PON, control communication for performing access control in the PON upstream direction is performed according to the GE-PON system. That is, transmission permission for the terminal devices 2, 3, and 4 is indicated by the value of the PON counter. At this time, the synchronization of the PON counter is performed by updating the PON counters of the terminal devices 2, 3, and 4 themselves with the time stamp TS written in the control frame (gate frame) that is intermittently sent within the 1G period. Is called.
In PON, downlink signals are received by all the terminal devices 2, 3, and 4. Depending on the configuration of the receiving circuit, an unexpected rate (2G or 10G in this case) to an expected rate (1G in this case). When switching to, it takes time to synchronize again. Therefore, in the downstream signal frame shown in FIG. 7, the station side device 1 changes the rate to the terminal devices 2, 3, and 4 in order to ensure that ultra-high speed signals that cannot be specified in advance will coexist in the multi-rate PON. It comes to notice.

In this case, the terminal devices 2, 3, and 4 can be prepared so as to mask a reception signal in an unexpected rate period (see the mask circuit 17 in FIG. 8) or to quickly reproduce data of a reception target rate. As shown in FIG. 7, a notice of rate change can be made by notifying each terminal device 2, 3 and 4 in a special sequence (Ca / Cb / Lh / Ll) of 1G period.
Ca / Cb is a special code indicating the start of a special sequence for rate notice and the type of rate. Lh / Ll represents a period during which the rate is changed. In this communication procedure, the 1G period is basically used, and after the rate period other than 1G, the period is temporarily returned to the 1G period. That is, it is assumed that all the terminal devices 2, 3, and 4 have at least a 1G signal reception capability.

  In the joining procedure of the terminal devices 2, 3, and 4, first, the signal of 1G period is restored, and the PON counter is synchronized so that it can be received without exception during the 1G period while tracing the rate change notice. Thereafter, similar to the GE-PON registration procedure, registration of the terminal devices 2, 3, and 4 and link establishment are triggered by sending a registration request according to the discovery gate. Further, by exchanging OAM information, the station side apparatus 1 recognizes a rate that the terminal apparatuses 2, 3, and 4 can receive. All communications required so far are performed in the 1G period. Thereafter, when the station-side device 1 transmits a downlink user frame to the terminal devices 2, 3, and 4, an optimal transmission rate is selected.

[Configuration example of terminal device (part 1)]
FIG. 8 shows an example of the PON interface unit of the terminal device 100 that can constitute the multi-rate PON system (FIG. 1) of the present invention.
The terminal device 100 shown in FIG. 8 can join the multi-rate PON system of the present invention shown in FIG. 1, but can receive only a reference signal (information communication rate 1G) for downlink signals (for 1G). ) Used as 2.
The optical signal received from the PON is converted into an electric signal by the receiver 16 and input to the mask circuit 17. The mask circuit 17 masks a signal (in this case, 2G and 10G signals) at a rate that the terminal device 100 does not receive. The output of the mask circuit 2 is input to a subsequent CDR (Clock Data Recovery) 18 to recover the clock and data.

A code synchronization circuit 19 is connected to the subsequent stage of the CDR 18. This circuit 19 detects the boundary of the 8B / 10B code from the restored clock and data, cuts out the 8B / 10B code, performs 10B / 8B conversion, and restores the frame. At this time, the rate change notice expressed by the special symbol of the 8B / 10B code is interpreted, and an instruction to mask the signal of the rate not to be received is sent to the mask circuit 17.
This mask is for preventing the CDR 18 from malfunctioning due to an unexpected signal. That is, the mask circuit 17 is for preventing the internal state of the CDR 18 from being abnormal due to an unexpected ultra-high-speed signal and increasing the resynchronization time after switching to the expected signal.

The extracted frame is input to the frame type classification circuit 20 at the subsequent stage of the code synchronization circuit 19, and the PON control frame and the other frames are separated. Among these, the PON control frame is sent to the control frame processing circuit 22 through the time stamp extraction circuit 21. The time stamp extraction circuit 21 reads the time stamp TS and sends the stamp TS to the PON time control circuit 23 and the drift determination circuit 26.
The clock that is the basis of the transmission unit of the PON interface according to the first embodiment is generated by the voltage controlled crystal oscillator 25 made of, for example, VCXO. In GE-PON, since the PON counter is 32-bit information having a resolution of 16-bit time (= 16 ns), in this embodiment, the VCXO 25 has a center frequency of 125 MHz.

The PON time control circuit 23 increments the PON counter based on the basic clock generated by the VCXO 25, and updates the value of the PON counter when the time stamp TS is sent from the extraction circuit 21. That is, the PON time control circuit 23 has a 33-bit counter that is incremented by the basic clock, and outputs the upper 32 bits as a PON counter.
The updated information of the PON counter is sent to the drift determination circuit 26 and the transmission control circuit 27, respectively. The drift determination circuit 26 determines a difference between the type stamp TS and the PON counter before update at the time when the type stamp TS is sent, and outputs an alarm as an unexpected difference as an abnormality of the PON system. In addition, the drift determination circuit 26 corrects the variable frequency of the VCXO 25 in a direction in which the deviation is reduced, and adjusts the basic clock generated by the VCXO 25. The frequency control of the general VCXO 25 is performed by changing the analog voltage level of the control input.

On the other hand, the upstream frame is once buffered in the upstream buffer 28, and then sequentially extracted based on the instruction of the transmission control circuit 27 and sent to the encoding circuit 29. The encoding circuit 29 serializes the transmission frame after 8B / 10B encoding, and sends it to the transmitter 30 as a 1-bit NRZ signal. In this embodiment, since the reference transmission rate is 1.25 GHz, the serialization is performed in synchronization with a transmission clock of 1.25 GHz. The transmission clock is generated by the clock multiplier circuit 31 based on the basic clock.
Based on the light emission instruction signal from the transmission control circuit 27, the transmitter 30 converts the input NRZ signal into a light on / off signal. The uplink transmission signal in this embodiment is only a 1.25 Gbps signal based on GE-PON.

  The control frame processing circuit 22 interprets the received PON control frame and performs predetermined processing. Particularly for a normal gate frame, the transmission start time and transmission duration (see FIG. 2) included in the frame are extracted and sent to the transmission control circuit 27. The transmission control circuit 27 instructs the transmitter 30 to emit light when the PON counter reaches the transmission start time, and continues the light emission instruction until the transmission duration time elapses. At this time, prior to the light emission instruction, the upstream buffer 28 is instructed to extract the transmission frame.

  According to the terminal device 100 having the PON interface unit shown in FIG. 8 described above, the time lag between the time stamp TS and the PON counter is small when the time stamp TS included in the control frame of the downlink signal is sent. Thus, since the frequency of the basic clock for driving the PON counter is adjusted and the transmission timing of the upstream signal is determined based on the adjusted PON counter, the station side apparatus 1 and the terminal apparatuses 2 and 3 , 4 can be accurately synchronized with the PON counter of the terminal device 1 when used in the PON system of FIG. For this reason, it is possible to efficiently transmit the uplink signals from the terminal apparatuses 2, 3, and 4 without colliding.

On the other hand, the time stamp TS written in the PON control frame is likely to slightly fluctuate depending on the implementation of the station-side device 1, and within a prescribed range (for example, in the GE-PON ONU). Is recognized as 12 units of blur for a resolution of 16 ns). Therefore, even if the basic clock is adjusted based on the time stamp TS in which such blur is assumed, the basic clock cannot be made more accurate than the accuracy of the time stamp TS.
Therefore, instead of multiplying the basic clock to generate a transmission clock, as shown by a broken line in FIG. 8, the basic clock generator 32 and the VCXO 25, which is a basic clock generator, are separately provided by the transmission clock generator 32. Alternatively, a transmission clock unique to the terminal device 100 generated independently may be adopted.

In this case, it is the same that the transmission start timing becomes accurate, and the transmission clock is generated by the individual transmission clock generator 32 that does not refer to the time stamp TS, so that it is not affected by the jitter of the time stamp TS. A transmission clock is obtained, and an upstream signal that is less prone to receive errors can be transmitted.
For the same reason, it is preferable to add a function to the drift determination circuit 26 to determine the time stamp TS to be used as a reference based on the history of blurring of the past time stamp TS.

For example, the frequency control of the VCXO 25 may be based on the history of the deviation between the time stamp TS and the PON counter in addition to making the deviation immediately between the time stamp TS. Specifically, the influence of blur included in each time stamp TS is reduced by a filter that averages past deviations, and the frequency control of the VCXO 25 is performed.
Similarly, in updating the PON counter, the time stamp TS at that time may not be used as it is, but based on a history of deviation between the time stamp TS and the PON counter. Alternatively, in a PON counter update or VCXO 25 frequency control, a certain range of deviation or unique deviation may be ignored.

The drift determination circuit 26 may be digital or analog. However, since the deviation between the time stamp PS and the PON counter is a digital quantity, a circuit for obtaining an appropriate voltage level based on the deviation quantity is a digital circuit (processor and processor). Including those based on a program). In this case, a digital voltage level may be converted into an analog signal by a DA converter and supplied to the VCXO 25.
Further, the mask circuit 17 may not be provided when a necessary synchronization time is provided in the transmission rate switching sequence or depending on the configuration of the CDR 18 (for example, by an oversampling method described later. In this case, the CDR 18 outputs a clock. But only data recovery.)

Further, in order to recover information at a rate other than 1G, necessary ones of the mask circuit 17, the CDR 18, and the code synchronization circuit 19 may be provided separately and exclusively. In the terminal device 100 of FIG. 8, the VCXO 25 is used as an oscillator, but this can be replaced with a voltage controlled oscillator (VCO).
Further, in the present embodiment, the 1.25 Gbps transmission method is based on the GE-PON transmission method, and the 2.5 Gbps transmission rate is obtained by doubling GE-PON. The transmission rate of 10 Gbps is based on the transmission system of 10 Gbit Ethernet.

[Configuration example of terminal device (part 2)]
FIG. 9 shows an example of the PON interface unit of another terminal device 200 that can constitute the multi-rate PON system (FIG. 1) of the present invention.
The terminal device 200 shown in FIG. 9 is a terminal device that can receive rates of 1G, 2G, and 10G in the downlink direction. Therefore, this terminal device 200 can be used as all the terminal devices 2, 3 and 4 for 1G, 2G and 10G as well as being able to join the multi-rate PON system of the present invention shown in FIG. Further, since all the rates can be received, the mask circuit 17 employed in the terminal device 100 of FIG. 8 is not provided.

In the following description regarding the terminal device 200 of FIG. 9, it is assumed that one specific rate signal specified from the plurality of rates is a high rate signal having an information communication rate of 10 Gbps, and the information communication rate is The 1 G and 2 Gbps low rate signals are assumed to be other rate signals than the specific rate signal.
In addition, since the 8B / 10B code is encoded when the information communication rate is 1G and 2 Gbps, the baud rate in this case is 1.25 Gbps and 2.5 bps, and when the information communication rate is 10 G, the 64b / 66b code is used. In this case, the baud rate is 10.3125 Gbps. However, in this specification, even when the baud rate is 10.3125 Gbps, the description after the decimal point is omitted and 10 G is described.
Since the basic configuration of terminal apparatus 200 shown in FIG. 9 is substantially the same as that of terminal apparatus 100 shown in FIG. 8, the description of the same parts will not be repeated.

The downstream optical signal received from the optical fiber is converted into an electrical signal by the receiver 16. At the subsequent stage of the receiver 16, a low-rate data recovery 35 and a 10G-CDR 36 that is a high-rate clock data recovery are connected.
Among them, the 10G-CDR 36 restores a 10 Gbps clock and data from the input signal, and the data recovery 35 restores 1.25 Gbps or 2.5 Gbps data from the input signal.

FIG. 10 shows a specific example of the data recovery 35 for low rate (for other rate signal) adopted by the terminal device 200 of FIG.
This data recovery 35 samples the input signal consisting of a downstream signal in parallel with a multi-phase clock whose product of the number of phases corresponds to a high rate (and in this case, equivalent to 10 GHz), and thereby converts the low rate signal from the input signal. This is comprised of oversampling data recovery for restoring data, and the transmission rate is determined by the number of change points of values sampled in parallel by the multiphase clock.

That is, in FIG. 10, the input signal is sampled in parallel by a total of eight flip-flops (hereinafter abbreviated as FF) 37, and one of them is selected by the phase selection circuit 38 and output. . The sampling clocks of the eight FFs 37 are given in an arrangement in which the phases are sequentially shifted by 90 degrees based on a 2.5 GHz four-phase clock. Two FFs 37 are driven with one phase.
The eight sampled signals are input to the rate determination unit 39, and the rate of the input signal is determined from the choices of “1G”, “2G”, or “10G” from the frequency with which the same value continues, and the type is output. .

In the terminal device 200, the rate determination performed by the rate determination unit 39 is performed by examining the number of change points of values appearing in the sampled 1.6 ns interval. At this time, the change point constituted by the sampling result of the last phase of the immediately preceding sampling section and the sampling result of the first phase of the current sampling section is also counted.
That is, 1G when the section where the change point is almost 1 or less continues, 2G when the section where the case of 2 occurs almost frequently is 2 or less, and 2G when the section occurs at a considerable frequency (for example, a continuous change (for example, This means that the sampling results of the adjacent three phases are 101 or 010.) When the section where the occurrence occurs continues, it is determined as 10G. However, there may be a section in which neither can be determined.

In parallel with this, the rate determination unit 39 determines the phase (optimum phase) located in the middle of the change point, and notifies the phase selection circuit 38 of it. When the rate is 1G, there is only one optimum of the eight phases, but when the rate is 2G, there can be two.
In this way, one of the phases is selected, and the phase is also selected in the subsequent sections (it is desirable to move to a closer phase according to the phase shift, but not to the other optimum phase). . Alternatively, when the rate is 2G, four adjacent phases may be selected as the selection range, and the optimum phase may be determined from the selected range.

The phase selection circuit 38 obtains a clock supply from the multiphase clock generator 40, and resamples and outputs the selected sampling result with a clock of a predetermined phase so as to be synchronized with the circuit of the next stage.
Returning to FIG. 2, a low-rate code synchronization circuit 41 is disposed following the data recovery 35. When the rate type is 2G, the circuit 41 detects the boundary of the 8B / 10B code from the bit sequence of the data recovery result, cuts out the 8B / 10B code, performs 10B / 8B conversion, and cuts out the frame. When the rate type is 1G, the code synchronization processing is performed with a clock divided by two compared to the case of 2G.

The 10G-CDR 36 restores 10 Gbps data and a clock from an input signal in a 10G period. FIG. 11 shows a specific example of 10G-CDR 36 that is clock data recovery for high rate (for a specific rate signal) that is adopted by the terminal device ONU1 of the present embodiment.
As shown in FIG. 11, the 10G-CDR 36 of this embodiment is a CDR based on a known PLL system, and a first phase comparator 42 that compares the phase of an input signal that is a downstream signal and the output of an oscillator, A second phase comparator 43 is provided for comparing the phase of the output of the frequency divider 47 that reduces the oscillator output to a frequency having a predetermined frequency division ratio and the reference clock signal. One of the outputs of the comparators 42 and 43 is selected, and the selected phase comparators 42 and 43, the loop filter 44, and the VCO (oscillator) 45 constitute a PLL.

That is, the first phase comparator 42 compares the phases of the VCO output and the input signal, whereas the second phase comparator 43 matches the reference clock from the reference clock generator 46 and the frequency of this clock. As described above, the phase of the VCO output is compared with the signal obtained by frequency division by the frequency divider 47. This frequency-divided signal is also input to the frequency comparison circuit 48, and it is determined whether or not the frequency difference is within a predetermined range (inconsistency if not within the range). The reference clock generator 47 generates a reference clock signal at a frequency corresponding to the frequency division ratio of the frequency divider 47 with respect to the high rate signal (10G).
The output of the frequency comparison circuit 48 and the rate type output of the rate determination unit 39 are connected to a changeover switch (switching means) 52 comprising an OR gate. The changeover switch 52 selects the second phase comparator 43 for the PLL loop when the frequency in the frequency comparison circuit 48 does not match or the rate determination result in the rate determination unit 39 is other than the 10G period.

That is, when the rate type is 10G, the external reset of the changeover switch 52 is canceled and # 1 is selected, and the 10G-CDR 36 functions as for 10G. On the other hand, when the rate type is 1G or 2G, the external reset of the changeover switch 52 is turned on to select # 2, and the second phase comparator 43 is selected. When the second phase comparator 43 is selected, a reference frequency in which a frequency difference within a preset range is recognized is input to the VCO 45, so that the frequency does not deviate greatly.
For this reason, according to the 10G-CDR 36 of this embodiment, even when a low-rate signal other than 10G or an illegal signal other than that signal is included in the downstream signal, the frequency of the VCO 45 is prevented from greatly deviating. be able to.
In the 10G-CDR 36 shown in FIG. 11, the frequency divider 47 may be omitted, and the output of the VCO 45 may be directly input to the second phase comparator 43 and the frequency comparison circuit 48. In this case, the reference clock The frequency is equivalent to a high rate (10G).

Returning to FIG. 9, a high-rate code synchronization circuit 49 is disposed after the 10G-CDR 36. The 10G code synchronization circuit 49 detects the boundary between the 64b / 66b code from the clock and data restored by the 10G-CDR 36, cuts out the 64b / 66b code, descrambles it, and restores the frame.
In this embodiment, two frame type classification circuits 50 and 51 are provided, one of which receives a signal from a code synchronization circuit (for 1G and 2G) 41 and the other has a signal from a 10G code synchronization circuit 49. Is entered.

  Among these, the first frame type classification circuit 50 that receives the signal from the code synchronization circuit 41 classifies the PON control frame transmitted at the 1G or 2G rate, and the second frame type classification that receives the signal from the 10G-code synchronization circuit 49. The circuit 51 sorts PON control frames sent at a 10G rate. These PON control frames are sent to the time stamp extraction circuit 21 and processed as follows. However, in the time stamp extraction circuit 21 of the present embodiment, the time stamp extraction target may be limited to only PON control frames transmitted at a specific rate of 1G, 2G, and 10G, or all of them. PON control frames sent at a rate of

The terminal apparatus 200 of FIG. 9 can transmit a PON uplink signal at a rate according to its own capability. Therefore, a case where the transmission rate of the uplink signal is 10 Gbps will be described. The encoding circuit 29 serializes the transmission frame after 64b / 66b encoding, and sends it to the transmitter 30 as a 10 Gbps NRZ signal string. This serialization is performed in synchronization with a 10 GHz clock output from the transmission clock generator 32 provided separately from the VCXO 25 that generates the reference rate. Accordingly, in the terminal device 200 of FIG. 9, the uplink transmission rate is independent of the basic clock output by the VCXO 25.
On the other hand, when the transmission rate of the uplink signal is set to 1.25 Gbps, the encoding circuit 29 serializes the transmission frame after 8B / 10B encoding and sends it to the transmitter 30 as a 1-bit NRZ signal.

Similar to the terminal device 100 shown in FIG. 8, the transmission clock in this case may be generated by the clock multiplier circuit 31 based on the basic clock.
The control frame processing circuit 22 interprets the received PON control frame and performs predetermined processing. Particularly for a normal gate frame, the transmission start time and transmission duration contained in the frame are extracted and sent to the transmission control circuit 27. The transmission control circuit 27 instructs the transmitter 30 to emit light when the PON counter reaches the transmission start time, and continues the light emission instruction until the transmission duration time elapses. At this time, prior to the light emission instruction, the upstream buffer 28 is instructed to extract the transmission frame.

  According to the terminal device 200 of FIG. 9 having the above-described PON interface unit, the rate determination unit 39 determines whether or not the downlink signal is a 10 Gbps high rate signal, and the 10G-CDR 36 is restored only when the downlink signal is the high rate signal. The 10G-CDR 36 does not perform the restoration operation even if the downlink signal includes a low rate signal of 1 Gbps or 2 Gbps. Therefore, it is possible to stably restore the data and clock of the high-rate 10 Gbps signal without changing a special communication procedure like the rate change notice shown in FIG.

  9 is provided with a data recovery 35 that restores 1 Gbps or 2 Gbps low-rate signal data from a downlink signal and can restore not only a 10 Gbps signal but also a 1 Gbps or 2 Gbps signal data. It is a highly functional terminal device. That is, since the terminal device 200 in this case can automatically recognize the transmission rate by the data recovery 35 having the rate determination unit 39, there is no need for the rate change notice and the switching order exemplified in FIG. You can switch rates.

  As the low-rate data recovery 35 described above, the downstream signal is sampled in parallel with a multiphase clock whose product of the number of phases is equivalent to the high rate (equivalent to 10 Gbps), so that 1.25 Gbps or 2. Employs oversampling data recovery to restore 5 Gbps data, and then adopts a circuit configuration that determines the transmission rate based on the number of change points of values sampled in parallel with the multiphase clock of data recovery 35 Thus, the rate determination unit 39 is configured. Therefore, since the circuit configuration can be partially shared by the low-rate data recovery 35 and the rate determination unit 39, the manufacturing cost of the terminal device 200 can be further reduced.

  Further, according to the terminal device ONU1 of FIG. 9, the terminal device ONU1 based on the basic clock is reduced so that a time lag with respect to the time stamp at the time when the time stamp included in the control frame of the downlink signal is transmitted is reduced. Since the PON counter is adjusted and the transmission timing of the upstream signal is determined based on the PON counter based on the adjusted basic clock, communication between the station side device 1 and the terminal devices 2, 3, and 4 is performed. If used in the time-division multiplexed PON system of FIG. 1, the PON counter of the terminal device 200 can be accurately synchronized. For this reason, it is possible to efficiently transmit uplink signals from the terminal apparatuses 2, 3, and 4 without colliding.

On the other hand, the time stamp described in the PON control frame is likely to be slightly shaken depending on the implementation of the station side device 1 and is also within a predetermined range in terms of regulations (for example, in the GE-PON ONU). , 12 units of blur for a resolution of 16 ns). Therefore, even if the basic clock is adjusted based on the time stamp in which such blur is assumed, the basic clock cannot be made more accurate than the accuracy of the time stamp TS.
Therefore, in the terminal device 200 shown in FIG. 9, the transmission clock unique to the terminal device generated independently of the basic clock by the transmission clock generator 32 provided separately from the VCXO 25 that is the basic clock generator is adopted. I have to.

In this case, the transmission start timing is the same, and the transmission clock is generated by the individual transmission clock generator 32 that does not refer to the time stamp, so that the beautiful transmission clock is not affected by the jitter of the time stamp. Thus, it is possible to transmit an uplink signal that is less likely to cause a reception error.
For the same reason, it is preferable to add a function for determining a time stamp to be used as a reference based on the history of past time stamp deviations to the drift determination circuit 26.

For example, the frequency control of the VCXO 25 may be based on the history of deviation between the time stamp and the PON counter in addition to making the deviation from the time stamp respond promptly. Specifically, the influence of blur included in each time stamp is reduced by a filter that averages past deviations, and the frequency control of the VCXO 25 is performed.
Similarly, in updating the PON counter, the time stamp at that time may not be used as it is, but based on a history of deviation between the time stamp and the PON counter. Alternatively, in a PON counter update or VCXO 25 frequency control, a certain range of deviation or unique deviation may be ignored.

The drift determination circuit 26 (same as in the case of the terminal device 100 in FIG. 8) may be digital or analog. However, since the deviation between the time stamp and the PON counter is a digital quantity, it is appropriate based on the deviation quantity. The circuit for determining the voltage level is preferably a digital circuit (including those based on a processor and a program). In this case, a digital voltage level may be converted into an analog signal by a DA converter and supplied to the VCXO 25.
9 uses the VCXO 25 as an oscillator, it can be replaced with a voltage controlled oscillator (VCO).

In the terminal device 200 shown in FIG. 9, the uplink transmission rate may be fixed to only 10 Gbps, but may have 1.25 Gbps, 2.5 Gbps, or both capabilities. The reason is that the corresponding range is widened when the capability of the station-side device 1 to be connected is limited.
Further, the transmission rate may be changed according to the communication content. For example, as described above, if registration is performed at the reference rate (1G), the registration procedure is simplified. In this case, a 1G or 2G encoding circuit, or both of these encoding circuits, and a 1.25 GHz / 2.5 GHz transmission clock generator are provided in parallel with a 10 Gbps one and input to the transmitter 30 One of the outputs of both encoding circuits may be selected.

When the 1G and 2G capabilities are provided, the common encoding circuit performs 8B / 10B conversion and serialization at respective rates. The transmission clock generator 32 is set to 2.5 GHz, and when a 1.25 GHz signal is transmitted, the same value may be transmitted as a 2.5 Gbps signal having 2 bits.
Note that the PON receiving unit of the station side device 1 corresponding to the uplink multirate can have the same configuration as the PON receiving unit of the terminal device 200 of FIG. 10, as shown in FIG. However, when the rate is switched in units of bursts and the rate is determined in advance, the rate determination in the data recovery 35 is not necessary, and the station apparatus 1 instructs the rate type.

In the terminal device 200 shown in FIG. 9, the data recovery 35 may be limited to only a portion for determining a rate. Whether the number of phases of the multi-phase clock is limited for the rate determination, sampling with a 2-phase clock of 10 GHz, and whether the value frequently changes three times in any phase. It may be something like checking.
There are many variations regarding which rate is used in PON control communication and multicast communication for registration and PON access control in relation to the assumptions regarding the capabilities of the terminal devices 2, 3, and 4.

  Assuming that all the terminal devices 2, 3, and 4 have transmission / reception capability of a reference rate (for example, 1 Gbps), as already described in the description of the communication method shown in FIG. 3 and FIG. It is convenient to perform communication at a reference rate. After the registration, by negotiating the capabilities of the station side device 1 and the terminal devices 2, 3, and 4, the subsequent one-to-one communication can be shifted to use a higher rate.

  On the other hand, if it is assumed that the transmission / reception capability of the terminal devices 2, 3, and 4 may be limited to a specific rate, the registration procedure is performed for each rate as described in the description of the communication method shown in FIGS. It can also be performed independently. In this case, registration request polling is performed for each rate. When the frame is a multicast frame and the receiver has a plurality of rates, the multicast frame may be repeatedly transmitted for each rate of the receiver.

1 is a schematic configuration diagram of a multi-rate PON system assumed by the present invention. FIG. It is a circuit diagram of the station side apparatus which concerns on embodiment of this invention. It is a figure which shows the communication procedure from automatic registration to main signal communication of the multi-rate PON system which concerns on 1st embodiment of this invention. It is a figure which shows the communication procedure when each terminal device operate | moves of the multi-rate PON system which concerns on 1st embodiment of this invention. It is a figure which shows the communication procedure from automatic registration to main signal communication of the multi-rate PON system which concerns on 2nd embodiment. It is a figure which shows the communication procedure when each terminal device operate | moves of the multi-rate PON system which concerns on 2nd embodiment. It is a figure which shows an example of the downstream signal frame of a multi-rate PON system. It is a circuit diagram which shows the PON interface part of the terminal device which can be employ | adopted by this invention. It is a circuit diagram which shows the PON interface part of the other terminal device which can be employ | adopted by this invention. It is a circuit diagram which shows the specific example of the data recovery of the terminal device shown in FIG. It is a circuit diagram which shows the specific example of 10G-CDR of the terminal device shown in FIG.

Explanation of symbols

1 Station side device 2 Terminal device (for 1G)
3 Terminal device (for 2G)
4 Terminal device (for 10G)
DESCRIPTION OF SYMBOLS 5 Optical fiber 6 Optical coupler 7 Optical fiber 8 Optical fiber 9 Optical fiber 10 Optical fiber network 100 Terminal device 200 Terminal device

Claims (8)

A station-side device, an optical fiber network configured to branch from an optical fiber connected to the station-side device to a plurality of optical fibers via an optical coupler, and a plurality of devices connected to the ends of the branched optical fibers, respectively A multi-rate PON system in which downlink or uplink or bidirectional communication between the station-side device and each terminal device is performed at a plurality of transmission rates including a reference rate.
For the terminal device having communication capability at another transmission rate different from the reference rate, the station side device registers the terminal device and performs management communication for recognizing the capability of the terminal device at the reference rate. A multi-rate PON system comprising: a first step to perform; and a second step to perform downlink, uplink, or bidirectional main signal communication with the terminal device at another transmission rate different from a reference rate .   The station side device and the terminal device communicate the transmission permission and the transmission request for controlling the main signal communication in the second step at the reference rate, and the station side device transmits the transmission request from all the terminal devices. The multi-rate PON system according to claim 1, wherein centralized dynamic bandwidth allocation is performed in which centralized collection is performed, bandwidth allocation is dynamically performed, and transmission permission is centrally transmitted to each terminal device. A multi-rate PON that is connected to a plurality of terminal devices via an optical fiber in a P2MP form and performs communication in the downlink direction or the uplink direction or in both directions at a plurality of transmission rates including a reference rate with the plurality of terminal devices. In the system side equipment,
For the terminal device having communication capability at another transmission rate different from the reference rate, the terminal device is registered and the management communication for recognizing the capability of the terminal device is performed at the reference rate, and the terminal device A station apparatus for a multi-rate PON system that performs downlink, uplink, or bidirectional main signal communication with a transmission rate different from the reference rate. A station-side device, an optical fiber network configured to branch from an optical fiber connected to the station-side device to a plurality of optical fibers via an optical coupler, and a plurality of devices connected to the ends of the branched optical fibers, respectively And the terminal device is configured to perform a downlink communication from the station device to each terminal device at a plurality of transmission rates, and an uplink communication from each terminal device to the station device is a single transmission rate. In the multi-rate PON system performed in
The station side device transmits a transmission permission of a registration request for each terminal device for each transmission rate, and performs a downlink communication of a management system for registering a terminal device that has responded at the transmission rate. And a second step of performing all downlink communications including the management communication including the transmission permission to the terminal apparatus after registration and the transmission request from the terminal apparatus and the main signal communication at the transmission rate. A featured multi-rate PON system. A station-side device, an optical fiber network configured to branch from an optical fiber connected to the station-side device to a plurality of optical fibers via an optical coupler, and a plurality of devices connected to the ends of the branched optical fibers, respectively In a multi-rate PON system in which bidirectional communication between the station-side device and each terminal device is performed at a plurality of transmission rates,
A first step in which the station side device transmits a registration request transmission permission for each terminal device for each transmission rate, and performs management communication for registering the terminal device that has responded at the transmission rate; A multi-rate characterized by having a second step of performing all communication including management communication and main signal communication including transmission permission to the terminal device after registration and a transmission request from the terminal device at the transmission rate. PON system.   The station side device and the terminal device communicate the transmission permission and the transmission request for controlling the main signal communication in the second step at individual transmission rates, and the station side device receives each of the terminal devices from the terminal device. 6. The multi-rate PON system according to claim 5, wherein band allocation is performed individually when a transmission request arrives, and distributed dynamic band allocation is performed in which transmission permission is transmitted to the terminal device at each transmission rate. Connected to multiple terminal devices via optical fiber in P2MP form, downlink communication toward the multiple terminal devices is performed at multiple transmission rates, and uplink communication from the multiple terminal devices is a single transmission In the station apparatus of the multi-rate PON system performed at a rate,
The transmission permission of the registration request to each terminal device is transmitted for each transmission rate, and the management system downlink communication for registering the terminal device that has responded is started, and all the downlink communication is performed at the transmission rate. The station apparatus of the multi-rate PON system characterized by this. In a station apparatus of a multi-rate PON system that is connected to a plurality of terminal devices in a P2MP form via optical fibers and performs bidirectional communication with the plurality of terminal devices at a plurality of transmission rates including a reference rate,
A registration request transmission permission for each terminal device is transmitted for each transmission rate, and management communication for registering a terminal device that has responded is started, and all communications are performed at the transmission rate. Station device of the rate PON system.

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