JP2008172665A - Station-side device of pon system, receiving part, clock and data reproduction part, and method of upstream communication for pon system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a station-side device capable of establishing synchronization quickly with respect to an up signal of each transmission rate, in a multirate PON system wherein terminal devices have a plurality of kinds of upstream transmission rates. <P>SOLUTION: This station side device 1 forms the PON system together with a plurality of terminal devices 2-4 connected by one-to-many via optical fibers 5, 7-9, and manages by a time division multiplexing system, up signals of a plurality of transmission rates transmitted from the terminal devices 2-4. This station side device 1 is provided with a management part 106 for storing the plurality of transmission rates, giving grant to the terminal devices 2-4 for communication in an upstream direction and moreover specifying the time for receiving the next up signal corresponding to each grant and its transmission rate, and a reproduction part 113 for reproducing the clock of the up signal and data according to the time and transmission rate specified by the management part 106. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a PON (Passive Optical Network) system that connects a station-side device and a plurality of terminal devices through an optical fiber network, and more particularly to uplink communication from a terminal device to a station-side device.

  The PON system is an optical fiber network that branches a station side device as an aggregation station and terminal devices installed in a plurality of subscriber homes into a plurality of optical fibers from a single optical fiber via an optical coupler. They are connected (see, for example, Patent Documents 1 and 2). In this PON system, upstream burst communication from the terminal device to the station side device is managed in a time division manner by the station side device in order to prevent signal collision.

  Initially, the uplink burst communication was considered to have a constant transmission rate, but in the future, the transmission rate is expected to increase stepwise. However, even if high-speed transmission rate service provision is started, not all subscribers want it at the same time, so for upstream communication, the existing transmission rate and the high-speed transmission rate exceeding it are A multi-rate PON system coexists in one PON system (see, for example, Patent Document 3).

Japanese Patent Laying-Open No. 2004-64749 (FIG. 4) Japanese Patent Laying-Open No. 2004-289780 (FIG. 31) Japanese Patent Laid-Open No. 8-8954 (FIG. 2) Japanese Patent No. 3626365 (Claim 1)

  In the multi-rate PON system as described above, a reception function corresponding to a plurality of types of transmission rates is also required for the station side device. However, it is not technically easy to detect the transmission rate from the burst signal received from each terminal device and synchronize the reception function to the transmission rate at high speed, and it is expensive to realize this. A PON receiver is required.

  On the other hand, Patent Document 4 describes a clock and data recovery circuit that recovers a packet having a desired clock and transmission rate from a multi-rate input signal including packets having different transmission rates. In this reproduction circuit, a packet selection circuit that eliminates a packet that may disturb a desired clock reproduction operation from among packets included in the input signal is provided in front of the clock reproduction circuit and the data reproduction circuit. Instability of the operation of the clock recovery circuit due to input signals other than the transmission speed is prevented.

A clock and data recovery circuit having such a packet selection circuit is suitable for a terminal device that only needs to receive a single transmission rate.
However, when the above reproduction circuit is applied to a station apparatus of a multi-rate PON system having a plurality of uplink transmission rates, the station apparatus receives multi-rate burst packets that are time-division multiplexed and transmitted from each terminal apparatus. In this case, since the packet selection circuit excludes all packets other than the desired transmission rate, the multi-rate packet cannot be reproduced continuously with the same clock and data recovery circuit.

Therefore, even if a circuit configuration in which a packet selection circuit that excludes packets other than the desired transmission rate is provided in the clock and data recovery circuit is applied to the station side device, it can be continuously and quickly adapted to a plurality of types of transmission rates. It is difficult to synchronize, and the station-side apparatus cannot properly receive the upstream burst signal.
Further, in the case of uplink communication, effective data communication cannot be performed at other transmission rates within the time until synchronization at a certain transmission rate is established. Deteriorate.

  In the present invention, in view of the above problems, in a multi-rate PON system in which there are a plurality of types of transmission rates in the uplink direction of a terminal device, synchronization is established quickly with respect to uplink signals at each transmission rate. An object of the present invention is to provide a PON system station-side device, a receiving unit, a clock and data recovery unit, and a PON system upstream communication method that can improve upstream communication efficiency.

  A station-side device (Claim 1) of the present invention forms a PON system together with a terminal device connected one-to-many via an optical fiber, and time-division multiplexing schemes are used to transmit uplink signals of a plurality of transmission rates transmitted from the terminal device. And receiving the next uplink signal corresponding to the grant, and storing the plurality of transmission rates to give the terminal device a grant of uplink communication and A management unit that identifies the transmission rate and a reproduction unit that reproduces the clock and data of the upstream signal in accordance with the time and transmission rate identified by the management unit are provided.

  According to the station-side apparatus of the present invention, the management unit specifies the timing of receiving the next uplink signal corresponding to the grant to be given to the terminal device and the transmission rate thereof, so the uplink signal having a desired transmission rate corresponding to the grant. Can be acquired before actual reception. In addition, since the reproduction unit performs clock and data reproduction in accordance with the time and transmission rate specified by the management unit, it is possible to quickly establish synchronization with the uplink signal at each transmission rate.

In the station-side apparatus of the present invention, more specifically, the reproduction unit includes a plurality of clock and data reproduction circuits that perform clock and data reproduction from an uplink signal having one transmission rate among a plurality of transmission rates, And a controller that operates the clock and data recovery circuit corresponding to the selection signal based on the rate selection signal generated by the management unit as a signal indicating the transmission rate specified by the management unit. Can do.
In this case, since the controller operates the clock and data recovery circuit based on the rate selection signal indicating the transmission rate specified by the management unit, the transmission rate can be switched quickly. Since this rate selection signal is a signal generated by the management unit, it is not necessary to separately provide a circuit for determining the transmission rate of the uplink signal received by the station side device, and the circuit configuration becomes easy.

However, in the station side apparatus of the present invention, there is a certain time delay including a frame delay (RTT) from when a grant is transmitted to the terminal apparatus until the next uplink signal corresponding to the grant is received. Therefore, in practice, the station side apparatus receives the uplink signal after a predetermined time since the controller receives the rate selection signal. In addition, the time delay from the grant transmission to the reception of the corresponding uplink signal is not a fixed time, but differs depending on the distance to the terminal device.
Therefore, if the operation start time of the clock and data recovery circuit is determined based only on the detection of the rate selection signal, the operation of the clock and data recovery circuit may be started at a timing different from the actual reception of the upstream signal. There is.

Therefore, the controller preferably starts the operation of the clock and data recovery circuit based on both the rate selection signal and the data detection signal indicating that the uplink signal has actually reached. .
In this case, since the operation of the clock and data recovery circuit is started when the rate selection signal and the data detection signal are aligned under AND conditions, the time difference between the start of the operation and the actual reception timing of the upstream signal can be almost eliminated. Thus, the operation start time of the clock and data recovery circuit can be set more accurately. Note that such a data detection signal can be generated by an amplifier of an optical receiving unit provided in front of the reproducing unit (see FIG. 5). In this case, it is not necessary to provide a new detection circuit, and the circuit configuration is easy. Become.

Further, in the station apparatus of the present invention, the plurality of clock and data recovery circuits include a phase lock loop that recovers the clock and data of the upstream signal by a phase synchronization method, and a frequency lock that synchronizes its own oscillation frequency with the reference clock. And a loop.
In this case, if the controller switches the operating loop of the clock and data recovery circuit that is not selected by the rate selection signal to the frequency lock loop, the clock and data recovery circuit other than the assumed transmission rate While the signal (including noise) is input, the oscillation frequency can be stabilized by the frequency lock loop, and the oscillation frequency can be prevented from being disturbed by an unexpected signal input. .

In the station apparatus of the present invention, it is preferable that each of the plurality of clock and data recovery circuits has a deserializer that outputs the recovered data as parallel signals.
In this case, since a low-speed parallel signal is transmitted instead of a high-speed serial signal to the subsequent circuit block of the clock and data recovery unit, it is necessary to regenerate the clock and data again in the subsequent circuit block. Thus, the burden on the circuit block at the subsequent stage can be reduced. In addition, since each of a plurality of clock and data recovery circuits includes a deserializer, it is possible to avoid a disturbance at the time of switching the transmission rate, which may occur when one deserializer is shared.

  The PON receiver of the present invention (Claim 6) is a PON receiver that receives a multi-rate burst signal by a time division multiplexing method, and matches the timing and transmission rate of receiving the next burst signal corresponding to the grant. Thus, the clock and data recovery of the burst signal is performed.

  According to the PON receiver of the present invention, the clock and data are regenerated in accordance with the time when the next burst signal corresponding to the grant is received and the transmission rate thereof, so that synchronization can be quickly established for the multi-rate burst signal. can do.

  According to the communication method of the present invention (Claim 7), a station-side device connected to a plurality of terminal devices via an optical fiber transmits uplink signals of a plurality of transmission rates transmitted from the terminal device in a time division multiplexing system. A PON system uplink communication method for receiving the received data, wherein the plurality of transmission rates are stored to give an uplink communication grant to the terminal device, and a next uplink signal corresponding to the grant is transmitted. The reception time and the transmission rate are specified, and the clock and data of the upstream signal are reproduced in accordance with the specified time and the transmission rate.

  According to the communication method of the present invention, the timing for receiving the next uplink signal corresponding to the grant given to the terminal device and the transmission rate thereof are specified, so the uplink signal having the desired transmission rate corresponding to the grant is received. It is possible to acquire information on the transmission timing and transmission rate before actual reception. In addition, since the clock and data are regenerated in accordance with the time and transmission rate specified as described above, it is possible to quickly establish synchronization with the upstream signal of each transmission rate.

  Another station-side device of the present invention (Claim 8) constitutes a PON system together with a plurality of terminal devices connected one-to-many via an optical fiber, and transmits upstream signals of a plurality of transmission rates transmitted from the terminal devices. A station-side device that receives data in time division multiplexing, and a clock and data recovery circuit that recovers a clock and data from an uplink signal at one transmission rate among a plurality of transmission rates, corresponding to the plurality of transmission rates. A plurality of reproduction units, and a management unit that sets the operation timings of the plurality of clock and data reproduction circuits in accordance with the reception timing of the upstream signal of each transmission rate.

According to another station-side apparatus of the present invention, the management unit sets the operation timing of the plurality of clocks and the data recovery circuit included in the reproduction unit in accordance with the reception timing of the upstream signal at each transmission rate. When the station side apparatus receives the rate uplink signal by the time division multiplexing method, it is possible to quickly establish synchronization with the uplink signal of each transmission rate.
The operation timing setting performed by the management unit for each clock and data recovery circuit of the reproduction unit is, for example, as described above, for example, when receiving the next uplink signal corresponding to the grant given to each terminal device, and This can be done by sending the transmission rate to the playback unit.

  The clock and data recovery unit according to the present invention (claim 9) includes a clock and data recovery circuit for recovering a clock and data from a burst signal of one transmission rate among the multi-rate burst signals. A plurality of clock and data recovery units corresponding to the above, wherein the operation timings of the plurality of clock and data recovery circuits are matched with the reception timing of the burst signal at each transmission rate.

  According to the clock and data recovery unit of the present invention, the operation timing of the plurality of clock and data recovery circuits is matched with the reception timing of the burst signal at each transmission rate, so that the burst signal at each transmission rate is received by the time division multiplexing method. In this case, synchronization can be quickly established for a multi-rate burst signal.

  As described above, according to the present invention, in a multi-rate PON system in which there are a plurality of types of transmission rates in the uplink direction of the terminal device, it is possible to quickly establish synchronization with an uplink signal at each transmission rate. The communication efficiency in the direction can be improved.

FIG. 1 is a schematic configuration diagram of a PON system according to an embodiment of the present invention.
[Overall configuration of PON system]
In FIG. 1, the station side device 1 is installed as a central station for a plurality of terminal devices 2 to 4. Each of the terminal devices 2 to 4 is installed in a subscriber house of the PON system. An optical fiber network (5-5) having a configuration in which a single optical fiber 5 (main line), which is a transmission line connected to the station side device 1, is branched into a plurality of optical fibers (branches) 7-9 via an optical coupler 6. 9), and terminal devices 2 to 4 are connected to the ends of the branched optical fibers 7 to 9, respectively. Further, the station side device 1 is connected to the host network 11, and the terminal devices 2 to 4 are connected to the respective user networks 12 to 14.

Although three terminal devices 2 to 4 are shown in FIG. 1, it is possible to connect 32 terminal devices by branching, for example, 32 from one optical coupler 6. In FIG. 1, only one optical coupler 6 is used. However, more terminal devices can be connected to the station-side device 1 by providing a plurality of optical couplers in a column.
In FIG. 1, data is transmitted at a wavelength λ <b> 1 in the upstream direction from each terminal device 2 to 4 to the station side device 1. Conversely, data is transmitted at the wavelength λ2 in the downstream direction from the station-side device 1 to the terminal devices 2 to 4. These wavelengths λ1 and λ2 can be set to values in the following range based on Clause 60 of IEEE standard 802.3ah-2004.
1260nm ≦ λ1 ≦ 1360nm
1480 nm ≦ λ2 ≦ 1500 nm

In addition, the transmission rates of uplink communication in the terminal devices 2, 3, and 4 are L [Gbps], M [Gbps], and H [Gbps], respectively. Here, the values of L, M, and H have a relationship of L <M <H, and for example, L = 1, M = 2, and H = 10.
On the other hand, the transmission rate of the downlink communication in the station side device 1 is one type of D [Gbps], and the value of D is 1, for example. In the present embodiment, three terminal devices are used and three different transmission rates are used. However, the number of terminal devices and the number of different transmission rates may have various patterns.

[Configuration of station side equipment]
FIG. 2 is a block diagram showing an outline of the internal configuration of the station-side device 1 constituting the PON system. Each unit (101 to 115) in the station-side device 1 is connected as shown.
In FIG. 2, a frame from the upper network 11 is received by the upper network side receiving unit 101 and sent to the data relay processing unit 103. The data relay processing unit 104 passes the frame to the PON side transmission unit 105, which converts the frame into a downstream optical signal (downlink signal: wavelength λ 2 and transmission rate D [Gbps]) in the optical transmission unit 108. It is sent to the terminal devices 2 to 4 via the unit 110.

On the other hand, an optical signal (upstream signal: wavelength λ1 and transmission rate L / M / H [Gbps]) transmitted in the upstream direction from the terminal devices 2 to 4 (FIG. 1) passes through the multiplexing / demultiplexing unit 110 and is optically transmitted. Received by the receiving unit 109.
The optical receiving unit 109 includes a photoelectric conversion element 111 and an amplifier 112 inside. The photoelectric conversion element 111 is a semiconductor light receiving element such as a photodiode or an avalanche photodiode, and outputs an electrical signal corresponding to the amount of received light. The amplifier 112 amplifies and outputs the electric signal, and the output signal is input to the PON side receiving unit 107.

The PON side receiving unit 107 includes a clock / data reproducing unit 113, a physical layer encoding / decoding unit 114, and a frame reproducing unit 115. The clock / data recovery unit 113 recovers a timing component (clock) and data in synchronization with the electrical signal received from the amplifier 112. Details of the reproducing unit 113 will be described later.
The physical layer encoding / decoding unit 114 decodes a code applied to the reproduced data. The frame reproducing unit 115 detects a frame boundary from the decoded data and restores, for example, an Ethernet (registered trademark) frame.

Also, the frame playback unit 115 determines whether the received frame is a data frame or a frame of control information for media access control such as a report frame by reading the header portion of the frame.
An example of control information is MPCP (Multi-point Control Protocol) PDU (Protocol Data Unit) described in Clause 64 of IEEE Standard 802.3ah-2004. The station side device 1 instructs the terminal devices 2 to 4 for the transmission start time and the transmission permission amount of the uplink data, and the terminal device 2 to 4 transmits the uplink direction to the station side device 1. A report, which is control information for notifying a value related to the amount of accumulated data, is a kind of MPCP PDU.

As a result of the determination, if it is a data frame, the frame reproduction unit 115 sends this to the data relay processing unit 103. The data relay processing unit 103 performs predetermined relay processing such as change of header information of the data frame and transmission control for the upper network side transmission unit 102, and the processed frame is transmitted from the upper network side transmission unit 102 to the upper network 11. Is done.
If the result of the determination is that the frame is a report frame, the frame playback unit 115 sends it to the control signal processing unit 104. Based on this report, the control signal processing unit 104 generates a grant frame as control information, which is transmitted from the PON side transmission unit 105 and the optical transmission unit 108 via the multiplexing / demultiplexing unit 110 to the wavelength λ2, the transmission rate D. [Gbps] Transmitted in the downlink direction.

The grant is also sent to the next received burst determination unit (management unit) 106. The next reception burst determination unit 106 stores the transmission rate used by the terminal devices 2 to 4, and specifies the next reception timing of the burst signal and the transmission rate based on the grant.
The identified transmission rate is notified to the optical receiving unit 109 and the PON side receiving unit 107. The optical reception unit 109 and the PON side reception unit 107 can correspond to the reception function for the specified transmission rate in accordance with the time.

Specifically, the multiplication factor of the photoelectric conversion element 111 in the optical reception unit 109, the gain of the amplifier 112, the quantization determination threshold value in the PON side reception unit 107, the allowable lock range in the clock / data recovery unit 113, and the reference clock By switching circuit parameters related to burst reception such as frequency, it is possible to correspond to a predetermined transmission rate.
For example, in a case where the terminal devices 2 to 4 are connected under the same line condition (the same optical power budget is required) and the transmission quality of the same bit error rate must be satisfied, the terminal device When receiving from the terminal device 4 having a higher transmission rate compared to 2 and 3, the gain of the optical receiving unit 109 is lowered to widen the band.

For example, when the terminal devices 2 and 4 perform burst communication in the upstream direction at 1.25 Gbps and 10.3125 Gbps, respectively, the transmission rate of the next burst is 1 Gbps and 10 Gbps, respectively, in advance with respect to the clock / data recovery unit 113. If it is notified that there is, then it is only necessary to add the fractions, so that the synchronization of the clock / data recovery unit 113 can be established reliably in a short time.
Furthermore, when it is assumed that physical layer encoding / decoding is performed with 8B / 10B code and 64B / 66B code for 1.25 Gbps and 10.3125 Gbps, respectively, for the next burst The decoding circuit to be used can be selected easily and reliably.

The next reception burst determination unit 31 generates a rate determination signal S1 as a signal indicating the transmission rate of the next uplink signal corresponding to the grant, and receives a report that is the next uplink signal corresponding to the grant (FIG. 5). The report determination signal S1 is transmitted to the clock / data reproduction unit 113 of the PON side reception unit 107 at time Ta2 and time Ta4) shown in FIG. This rate selection signal S1 corresponds to each of the three transmission rates L, M, and H, for example, when there are three types of transmission rates L, M, and H used in the plurality of terminal devices 2 to 4. It consists of an identification code.
The amplifier 112 of the light receiving unit 109 generates a data detection signal S2 indicating that an upstream signal has been input to the amplifier 112. Simultaneously with the generation, the detection signal S2 is transmitted to the clock data of the PON side receiving unit 107. Transmit to the playback unit 113.

[Configuration of terminal device]
FIG. 3 is a block diagram illustrating an outline of the internal configuration of the terminal device 2 (transmission rate L [Gbps]), and each unit (201 to 209) in the terminal device 2 is connected as illustrated. .
In FIG. 3, an optical signal transmitted in the downstream direction from the station side device 1 (FIG. 1) passes through the multiplexing / demultiplexing unit 201 and is converted into an electrical signal by the optical receiving unit 202. Furthermore, this electrical signal Is received by the PON side receiving unit 204.

The PON side receiving unit 204 reads the header part (including the preamble part) of the received frame, and means that the frame is addressed to itself (here, addressed to itself or a device in the user network 12 under its control). ).
As a result of the determination, if it is addressed to itself, the frame is taken in. If not, the frame is discarded. For example, a logical link identifier (LLID) described in IEEE standard 802.3ah-2004 can be given as an example of header information for performing the above destination determination.

Furthermore, the PON side receiving unit 204 determines whether the received frame is a data frame or a grant frame by reading the header portion of the frame.
As a result of the determination, if it is a data frame, the PON side receiving unit 204 sends this to the data relay processing unit 207. The data relay processing unit 207 performs predetermined relay processing such as transmission control for the user network side transmission unit 208, and the processed frame is transmitted from the user network side transmission unit 208 to the user network 12.
As a result of the determination, if the frame is a grant frame, the PON side receiving unit 204 transfers it to the control signal processing unit 206. The control signal processing unit 206 instructs the data relay processing unit 207 to perform uplink transmission based on the grant frame.

On the other hand, the frame from the user network 12 is received by the user network side receiving unit 209 and transferred to the data relay processing unit 207. The transferred frame is temporarily stored in the buffer memory in the data relay processing unit 207, and the data amount is notified to the control signal processing unit 206.
The control signal processing unit 206 performs transmission control on the PON side transmission unit 205 and outputs the frame stored in the buffer memory to the PON side transmission unit 205 at a predetermined timing, and in the notified buffer memory. A report frame is created based on the amount of data stored and is output to the PON side transmission unit 205. The output of the PON side transmission unit 203 is converted into an optical signal by the optical transmission unit 203, and is transmitted in the upstream direction through the multiplexing / demultiplexing unit 201 as a signal of wavelength λ1 and transmission rate L [Gbps].

FIG. 4 is a block diagram illustrating an outline of the internal configuration of the terminal device 4 (transmission rate H [Gbps]), and each unit (401 to 411) in the terminal device 4 is connected as illustrated. . Among these, 401 to 409 are circuit elements corresponding to 201 to 209 in FIG. 3 and have the same function.
3 is different from the terminal device 2 (transmission rate L [Gbps]) in FIG. 3 in that a registration request transmission unit 411 is provided between the control signal processing unit 406 and the optical reception unit 403, and the PON side transmission unit 405 The registration request transmission unit 411 can be switched by the transmission unit switching determination unit 410, and the transmission unit switching determination unit 410 is configured to perform transmission unit switching in response to a command from the control signal processing unit 406. This is the point.

  Normally, as the transmission unit, the PON side transmission unit 405 operates. Note that the terminal device 4 (transmission rate H [Gbps]) when the PON-side transmission unit 405 operates is substantially the same as the terminal device 2 (transmission rate L [Gbps]). Further, the apparent configuration of the terminal device 3 is the same as that in FIG. However, as described above, the transmission rate of the terminal device 3 is M [Gbps], which is different from the transmission rate H [Gbps] of the terminal device 4.

[Clock and data recovery unit of station side device]
FIG. 5 is a block diagram showing an example of a circuit configuration of the clock / data recovery unit 113 of the station-side device 1.
As shown in FIG. 5, the reproduction unit 113 corresponds to a plurality of types of uplink transmission rates, and a plurality of clock and data reproduction circuits 51L, which respectively reproduce clocks and data from uplink signals at the respective transmission rates. In the example shown in FIG. 5, a clock and data recovery circuit 51L for a low transmission rate L [Gbps] and a clock and data recovery circuit 51H for a high transmission rate H [Gbps] are provided. It has been.
In order to cope with the medium-speed transmission rate M [Gbps], a clock for the transmission rate M and a data recovery circuit may be added in parallel.

Each of the clock and data recovery circuits 51L and 51H recovers the clock and data by the phase synchronization method, and the frequency increases from the front side (left side in FIG. 5) to the rear side (right side in FIG. 5). A comparator 52, a phase comparator 53, a switch 54, a charge pump and loop filter 55, an oscillator (VCO or VCXO) 56, a frequency divider 57 and a deserializer 58 are provided.
The upstream signal from the amplifier 112 of the optical receiver 109 is input to the phase comparator 53 of each clock and data recovery circuit 51L, 51H. The phase comparator 53, together with the switch 54, the loop filter 55, and the oscillator 56, constitutes a phase locked loop 59 that performs clock and data recovery of the upstream signal.

On the other hand, a reference clock which is a local clock in the station side apparatus 1 is input to the frequency comparator 52. The frequency comparator 52, together with the switch 54, the loop filter 55, the oscillator 56, and the frequency divider 57, constitutes a frequency lock loop 60 that synchronizes its own oscillation frequency with the reference clock.
The switch 54 of each clock and data recovery circuit 51L, 51H is composed of a switching element for switching to either the phase lock loop 59 or the frequency lock loop 60, and is switched by a controller 61 composed of a logic circuit such as an AND circuit. Is done. The controller 61 switches the switch 54 so that the operating loop of the clock and data recovery circuits 51L and 51H becomes the phase lock loop 59 when the rate selection signal S1 and the data detection signal S2 are aligned under the AND condition. .

That is, as shown in FIG. 6A, in the case of the low speed clock and data recovery circuit 51L, when the identification code of the rate selection signal S1 becomes L (low speed) and the data detection signal S2 rises, The operating loop of the clock and data recovery circuit 51L is switched to the phase lock loop 59. At other times, the operating loop of the clock and data recovery circuit 51L is a frequency lock loop 60.
Further, as shown in FIG. 6B, in the case of the high-speed clock and data recovery circuit 51H, when the identification code of the rate selection signal S1 becomes H (high speed) and the data detection signal S2 rises, The operation loop of the data recovery circuit 51H is switched to the phase lock loop 59, and at other times, the operation loop of the clock and data recovery circuit 51H is a frequency lock loop 60.

Therefore, when the transmission rate of the upstream signal input from the amplifier 112 is low L, the phase lock loop 59 of the low-speed clock and data recovery circuit 51L operates, and the clock and data at the low transmission rate L are operated. At this time, the high-speed clock and data recovery circuit 51H is a frequency lock loop 60 and synchronizes its own oscillation frequency with the reference clock.
When the transmission rate of the upstream signal input from the amplifier 112 is high-speed H, the phase lock loop 59 of the high-speed clock and data recovery circuit 51H operates to recover the clock and data at the high transmission rate H. At this time, the low-speed clock and data recovery circuit 51L is a frequency lock loop 60, and synchronizes its own oscillation frequency with the reference clock.

  As described above, in the clock / data recovery unit 113 of the present embodiment, the controller 61 operates the clock and data recovery circuits 51L and 51H based on the rate selection signal S1 generated by the transmission / reception burst determination unit 106. Can be switched quickly. Since this rate selection signal S1 is a signal generated by the transmission / reception burst determination unit 106 using a grant, there is no need to separately provide a circuit for determining the transmission rate of the uplink signal received by the station side device 1, The circuit configuration becomes easy.

  Further, in the clock / data recovery unit 113 of this embodiment, the controller 61 starts the operation of the clock and data recovery circuits 51L and 51H when the rate selection signal S1 and the data detection signal S2 are aligned under the AND condition. Compared with the case where the operation start time of the clock and data recovery circuits 51L and 51H is determined based only on the detection of the selection signal S1, the time difference between the operation start time and the actual reception timing of the upstream signal can be almost eliminated. The operation start time of the clock and data recovery circuits 51L and 51H can be set more accurately.

  Furthermore, in the clock / data recovery unit 113 of the present embodiment, the controller 61 that controls the switching of the switch 54 switches the operating loops of the clock and data recovery circuits 51L and 51H that are not selected by the rate selection signal S1 to a frequency lock loop. Therefore, the frequency lock loop 60 can stabilize the oscillation frequency while a signal (including noise) other than the transmission rate assumed by the clock and the data recovery circuits 51L and 51H is input. Thus, it is possible to prevent the oscillation frequency from being disturbed by an unexpected signal input.

The deserializer 58 converts the data reproduced by the clock and data recovery circuits 51L and 51H into parallel signals and outputs the parallel signals. The deserializer 58 includes a data signal (serial) output from the phase comparator 53 and an oscillator. 56 full-rate clocks and a divided clock obtained by dividing the clock by a frequency divider 57 are input.
FIG. 7 shows an example of the circuit configuration of the deserializer 58. As shown in FIG. 7, the deserializer 58 of this embodiment includes a shift register 64 composed of a plurality of D flip-flops 63 and a latch circuit 65 arranged at the subsequent stage of the shift register 64.

The shift register 64 shifts the serial signal input from the phase comparator 53 with the full rate clock of the oscillator 56 and outputs it, and this output signal is input to the latch circuit 65 at the subsequent stage. The latch circuit 65 includes a flip-flop circuit for parallel signals, latches a signal input from the shift register 64 with the divided clock obtained from the frequency divider 57, and outputs a parallel signal corresponding to the signal.
As described above, since the clock / data recovery unit 113 of the present embodiment has the built-in deserializer 58 that converts the recovered data into a parallel signal and outputs the parallel signal, A low-speed parallel signal is transmitted instead of a high-speed serial signal. Therefore, it is not necessary to regenerate the clock and data again in the subsequent circuit block, and the burden on the subsequent circuit block can be reduced.
Further, in the clock / data recovery unit 113 of the present embodiment, each of the plurality of clock and data recovery circuits 51L and 51H includes the deserializer 58, so that a transmission rate that may occur when one deserializer 58 is shared is used. There is also an advantage that disturbance at the time of switching can be avoided.

[Operation procedure of PON system (uplink communication method)]
Next, the operation procedure in the PON system configured as described above will be described with reference to the sequence diagram of FIG. This sequence diagram is for the operation between the station side device 1 and the terminal device 2 (transmission rate L [Gbps]), but the same applies to the other terminal devices 3 and 4.
In FIG. 8, the station-side device 1 has already calculated an RTT (Round Trip Time) related to the terminal device 2 at the operation time start time T0. At time Ta1, the station apparatus 1 transmits a grant (grant frame) G1 including a report transmission start time Tb2 to the terminal apparatus 2 in order to notify the transmission request amount. This report transmission start time Tb2 is calculated so as not to collide with reports transmitted from other terminal apparatuses 3 and 4.

When the terminal device 2 receives the grant G1 for itself, the terminal device 2 calculates the transmission request amount with reference to the data amount stored in the buffer memory of the data relay processing unit 207, and at the report transmission start time Tb2 included in the grant G1, A report (report frame) R1 including a transmission request amount is transmitted to the station apparatus 1.
Upon receiving the report R1, the station side device 1 calculates a value that is less than the fixed or variable maximum transmission allowable amount and can send as much data as possible in the buffer memory included in the report R1, and calculates the calculation result. It is inserted into the grant G2 as a transmission permission amount.

When the transmission request amount included in the report R1 is zero, the calculation result by the station side device 1 is zero, so no band is allocated, but the terminal device 2 needs to send the report R2, so the station side The device 1 always sends a grant G2 to the terminal device 2.
The transmission start time Tb4 included in the grant G2 includes the previously calculated scheduled reception time of the previous terminal device data, the previous transmission permitted amount of the terminal device 2, the RTT related to the current terminal device 2, and the guard time which is a fixed time. Used so that data and reports do not collide with data or reports from other terminal devices 3 and 4.

The station-side device 1 calculates a time Ta3 for sending the grant G2 including the sending permission amount and the sending start time Tb4 so that the grant G2 arrives at the terminal device 2 by the sending start time Tb4.
When the terminal device 2 receives the grant G2 for itself, the terminal device 2 sends the data D corresponding to the transmission permission amount to the station side device 1 together with the report R2 including the next transmission request amount at the transmission start time Tb4 included in the grant G2. To do.

The report R2 is sent immediately before or after the data D. When the report R2 is sent immediately before the data D, the value to be reported to the station side device 1 as the send request amount is the data stored in the buffer memory. This is the difference between the amount and the data amount of data D.
When receiving the data D and the report R2, the station-side device 1 sends the data D to the upper network 11, and the report R2 performs the same processing as the processing for the report R1. The sequence processing described above is performed independently for all the terminal devices 2 to 4, and the processing from time Ta3 to time Ta4 is repeated until the operation time ends.

FIG. 9 is a sequence diagram illustrating bandwidth allocation for the terminal devices 2 to 4 and transmission / reception regarding uplink communication performed between the station-side device 1 and the plurality of terminal devices 2 to 4.
FIG. 9 shows an example of the distributed allocation method. The operation of the system when the station side apparatus 1 is viewed as a subject will be described assuming that time advances from the left side to the right side of the figure.
First, the station-side device 1 sequentially sends grants G41, G31, and G21 to the terminal devices 4, 3, and 2, respectively. When receiving the reports R41, R31, and R21 from the terminal devices 4, 3, and 2, the station-side device 1 first sends a grant G42 to the terminal device 4 that is permitted to send data.

  The station side device 1 receives the data D41 sent from the terminal device 4 and the next report R42, and sends a grant G32 to the terminal device 3 in parallel therewith. The station side device 1 receives the data D31 sent from the terminal device 3 and the next report R32, and sends a grant G22 to the terminal device 2 in parallel therewith. Subsequently, the grant G43 for the terminal device 4 is also transmitted.

The station side apparatus 1 receives the data D21 and the next report R22 transmitted from the terminal apparatus 2. Further, the station-side device 1 receives the data D42 sent from the terminal device 4 and the next report R43, and at the same time, sends the grant G33 to the terminal device 3.
Furthermore, the station side apparatus 1 receives the data D32 and the next report R33 transmitted from the terminal apparatus 3, and simultaneously transmits the grant G23 for the terminal apparatus 2. Here, if there is no data transmitted from the terminal device 2, the station side device 1 receives only the next report R23. Thereafter, the same processing is repeated, and the station apparatus 1 sequentially allocates bands to the terminal apparatuses 2 to 4 and repeats reception of data.

  According to the sequence shown in FIG. 9, the waiting time until the data transmitted from the user networks 12 to 14 (FIG. 1) arrives at the corresponding terminal devices 2 to 4 and is transmitted from there is the terminal device 2. -4 depends on the time from when the report is sent until the data corresponding to the report is sent. That is, it varies depending on the amount of data transmitted from all the terminal devices 2-4.

For example, if all the transmission request amounts by the reports from the terminal devices 2 to 4 are permitted, the waiting time from the transmission of the report to the transmission of data is greatly increased, which not only affects the service for which real-time processing is required. Also, TCP (Transmission Control Protocol) throughput is greatly affected.
Therefore, the station apparatus 1 needs to control the amount of data transmitted from the terminal apparatuses 2 to 4 so that the waiting time in the buffer in the terminal apparatus can be suppressed within an allowable time.

  In the sequence (FIG. 9), for example, when the grant G42 is transmitted to the terminal device 4, the same information on the grant G42 is also transmitted from the control signal processing unit 104 of FIG. Based on this grant G42, the next reception burst determination unit 106 optically receives the transmission rate H (10 Gbps) of the next received burst (report R42 + data D41) in the interburst gap period before receiving the report R42. Unit 109 and the PON side receiving unit 107.

The optical receiving unit 109 and the PON side receiving unit 107 that have received this notification associate the receiving function with 10 Gbps and wait for the burst. Then, the clock / data recovery unit 113 of the PON side receiving unit 107 generates a clock for the transmission rate H (10 Gbps) based on the rate determination signal S1 (S1 = H) generated by the next reception burst determination unit 106 from the grant G42. And the data reproduction circuit 52H is switched.
Therefore, when the burst arrives, the reception system corresponding to the high-speed transmission rate H is prepared, and synchronization can be established very quickly.

  Similarly, for example, when the grant G22 is transmitted to the terminal device 2, the same grant G22 information is also transmitted from the control signal processing unit 104 to the next reception burst determination unit 106. Based on the grant G22, the next reception burst determination unit 106 determines the transmission rate L (1 Gbps) of the next received burst (report R22 + data D21) during the interburst gap between the data D21 and the report R22. The optical receiver 109 and the PON side receiver 107 are notified.

Upon receiving this notification, the optical receiver 109 and the PON side receiver 107 make the reception function compatible with 1 Gbps and wait for the burst. Then, the clock / data recovery unit 113 of the PON side receiving unit 107 generates a clock for the transmission rate L (1 Gbps) based on the rate determination signal S1 (S1 = L) generated by the next reception burst determination unit 106 from the grant G22. And switch to the data reproduction circuit 51L.
Therefore, when the burst arrives, the reception system corresponding to the low transmission rate L is prepared, and synchronization can be established very quickly.

Similarly, the clock / data recovery unit 112 receives the rate determination signal S1 generated from the grant by the transmission / reception burst determination unit (management unit) 106 for the upstream signals of all transmission rates (L, M, H). The transmission rate clock and data recovery circuit corresponding to the determination signal S1 are switched.
Therefore, the transmission / reception burst determination unit (management unit) 106 of the present embodiment has the same time series as the time division multiplexing set by the station side device 1 for each of the terminal devices 2 to 4, and each transmission rate (L, M, H) functions as a management unit that sets the operation timings of the clock and data recovery circuits 51L and 51H provided in the clock / data recovery unit 112 in accordance with the reception timing of the upstream signal.

As described above, the station-side device 1 according to the present embodiment acquires information about the next time of receiving the uplink signal and the transmission rate information before actual reception based on the grant given to the terminal devices 2 to 4. Since the signal is received by making the reception function correspond to the acquired transmission rate, synchronization can be quickly established with respect to the time-division multiplexed multi-rate uplink signal.
Accordingly, it is possible to improve the communication efficiency of uplink communication in which the uplink transmission rate is multirate.

As described above, in the station side device 1 of the present embodiment, the “management means” composed of the control signal processing unit 104 and the next received burst determination unit 106 is used for a plurality of types of uplink directions used by the terminal devices 2 to 4. A function for storing a transmission rate, giving a grant of uplink communication to the terminal devices 2 to 4, and specifying a timing for transmitting an uplink signal next time and a transmission rate based on the grant Have.
In addition, the “reception unit” including the optical reception unit 109 and the PON side reception unit 107 has a function of making the reception state correspond to the specified transmission rate in accordance with the time.

In addition to the transmission rate, the management means may further specify the type of upstream signal encoding. In addition, the receiving unit may make the receiving function correspond to the specified type of encoding in accordance with the above time.
In this case, based on the grant given to the terminal device, it is possible to know the type of encoding of the uplink signal to be received next before actual reception. Further, if a signal is received in a state where the reception function corresponds to the type of encoding, decoding can be performed quickly. Furthermore, if the encoded code is an error correction code, the distance that can be transmitted with the same transmission power can be extended with respect to the optical transmission power of the terminal device.

In addition to the transmission rate, the management unit may further specify the type of uplink signal encryption, and the reception unit determines the reception function according to the above-mentioned period. It is also possible to make it correspond to the type.
In this case, based on the grant given to the terminal device, it is possible to know the type of encryption of the uplink signal to be received next before actual reception. Further, if a signal is received in a state where the reception function corresponds to the type of encryption, the decryption can be performed quickly. Therefore, the confidentiality of communication with a specific terminal device can be improved.

[Discovery process]
In the embodiment described above, it is assumed that a plurality of terminal devices 2 to 4 have already joined the PON system. However, in practice, there is a procedure for recognizing the station-side apparatus 1 when the power is turned on and joining the PON system from a power-off state that is not recognized by the station-side apparatus 1.
This procedure is called a discovery process and is defined in Clause 64 of IEEE standard 802.3ah-2004. Hereinafter, this discovery process will be described.

In the first place, the terminal device before being recognized by the station side device 1 has no opportunity to be granted a grant. On the other hand, all terminal devices cannot perform uplink communication unless a grant is explicitly given from the station-side device 1.
Therefore, the station-side device 1 is turned on from power-off (including unconnected), and a discovery process for detecting a terminal device (hereinafter referred to as an unregistered terminal device) that intends to join the PON system is performed. Run periodically and give the unregistered terminal device an opportunity to respond.

FIG. 10 is a diagram illustrating a discovery process performed between a station-side device and an unregistered terminal device.
In FIG. 10, the station side apparatus starts the discovery process at time T1, and broadcasts a discovery gate message in the downlink direction.
This discovery gate message includes information on the start time and the length of the discovery period during which a response to the discovery gate message is allowed. This discovery period is called a discovery window and is, for example, a time ΔTd from time T2 to T4.

The unregistered terminal device that has received the discovery gate message waits for a random waiting time ΔTw having a random length from time T2 (synchronized with the station side device), and sends a registration request message to the station side device at time T3. Send to. This random waiting time ΔTw is a random value within a range in which the registration request message fits in the discovery window.
Therefore, even if there are a plurality of unregistered terminal devices that are going to join the PON system, the probability that registration request messages from a plurality of unregistered terminal devices collide with each other can be reduced.

The registration request message includes the MAC address as the individual identification number of the unregistered terminal device. The station-side device that has successfully received the registration request message assigns a logical link number (LLID) on the PON system to the unregistered terminal device, associates the MAC address with the LLID, and registers them in the PON system. .
Next, the station-side device transmits a registration message to the newly registered terminal device at time T5. The registration message includes the LLID of the terminal device and information on the synchronization time necessary for the station side device to receive the uplink burst communication.

Thereafter, at time T6, the station side device transmits a grant (grant gate message) that permits uplink communication to the terminal device.
The unregistered terminal device that has received the grant transmits a registration acknowledgment to the station side device at time T7 using the grant, and the station side device receives this, and the discovery process ends. Thereafter, normal PON system communication is started.

Here, in the PON system shown in FIG. 1, for example, if the above discovery process is performed for all the terminal devices 2 to 4, the station side device 1 must receive the registration request message from each of the terminal devices 2 to 4. Don't be.
In normal PON communication after the terminal devices 2 to 4 have joined the PON system, as described above, the reception status of the station side device 1 can be adjusted based on the grant (the reception function is made to correspond to the transmission rate). However, this is not possible at the unregistered stage.
Therefore, the station side device 1 receives the uplink communication (registration request message) from the unregistered terminal device, for example, as follows.

In other words, even if the terminal apparatuses 2 to 4 have different transmission rates in normal PON communication, if one type of transmission rate (typically L) is used for the registration request message, the terminal apparatus 2 to 4 receive the registration request message. From this, the transmission rate is known. Specifically, the terminal device 2 having the transmission rate L transmits a registration request message at the transmission rate L in the same manner as normal PON communication.
On the other hand, when receiving the discovery gate message, the terminal device 4 having the transmission rate H shown in FIG. 4 sends this message from the control signal processing unit 406 to the transmission unit switching determination unit 410. As a result, the transmission unit switching determination unit 410 switches the transmission function from the PON side transmission unit 405 to the registration request transmission unit 411. Then, the control signal processing unit 406 causes the registration request transmission unit 411 to transmit a registration request message at the transmission rate L.

Accordingly, in the normal PON communication, the terminal device 4 that uses the high transmission rate H transmits the registration request message at the low transmission rate L. After transmitting the registration request message, the transmission unit switching determination unit 410 returns the transmission function from the registration request transmission unit 411 to the PON side transmission unit 405.
Similarly, in normal PON communication, the terminal device 3 having a transmission rate M transmits a registration request message or the like at the transmission rate L.

As a result, registration request messages received from the unregistered terminal devices 2 to 4 within the period of the discovery window to the station side device 1 (if two or three units are powered on at the same time, they will arrive randomly before and after the same period. Are sent at the transmission rate L.
On the other hand, the next reception burst determination unit 106 of the station side device 1 notifies the optical reception unit 109 and the PON side reception unit 107 of the transmission rate L of the next burst (registration request message) in response to the discovery gate message. To do. The optical receiving unit 109 and the PON side receiving unit 107 that have received the notification associate the reception function with the transmission rate L and wait for a registration request message.

Therefore, when the registration request message arrives, the station side device 1 is ready to receive the transmission rate L, and can quickly and reliably receive registration request messages from the unregistered terminal devices 2 to 4. it can.
As for the registration acknowledgement, as in the case of normal PON communication, the reception function of the station side device 1 can be made to correspond to the transmission rate based on the grant given to the terminal devices 2 to 4 before that. it can.

  In FIG. 10, the discovery window ΔTd is set using one type of transmission rate L. However, the station apparatus 1 sets a discovery window corresponding to each transmission rate L, M, N, Discovery may be performed between the terminal apparatuses 2, 3, and 4 communicating at the transmission rates L, M, and N in the discovery window for the transmission rates L, M, and N. In this case, it is not necessary for each of the terminal devices 2, 3, and 4 to have a function of communicating at the low rate L that is the reference rate.

1 is a schematic configuration diagram of a PON system according to an embodiment of the present invention. It is a block diagram which shows the internal structure of the station side apparatus which comprises the said PON system. It is a block diagram which shows the internal structure of one terminal device which comprises the said PON system. It is a block diagram which shows the internal structure of the other terminal device which comprises the said PON system. It is a block diagram which shows the internal structure of the clock data reproduction | regeneration part of a station side apparatus. It is a time chart which shows the operating state of a clock and a data reproduction circuit. It is a block diagram which shows the internal structure of a deserializer. It is a sequence diagram which shows the operation | movement between a station side apparatus and a terminal device. It is a sequence diagram which shows transmission / reception regarding the bandwidth allocation with respect to a terminal device, and the uplink communication between a station side apparatus and a terminal device. It is a sequence diagram which shows the discovery process performed between a station side apparatus and an unregistered terminal device.

1 Station side device 2-4 Terminal device 5, 7-9 Optical fiber 106 Next received burst judgment unit (management unit)
107 Clock / data recovery unit (reproduction unit)
51L Clock and Data Recovery Circuit 51H Clock and Data Recovery Circuit 58 Deserializer 59 Phase Lock Loop 60 Frequency Lock Loop 61 Controller

Claims (9)

A station-side device that configures a PON system together with a plurality of terminal devices connected one-to-many via an optical fiber and receives uplink signals of a plurality of transmission rates transmitted from the terminal devices in a time-division multiplexing method,
A management unit that stores the plurality of transmission rates and gives the terminal device a grant of uplink communication, and specifies a timing for receiving a next uplink signal corresponding to the grant and the transmission rate;
A reproduction unit for reproducing the clock and data of the upstream signal in accordance with the time and transmission rate specified by the management unit;
A station side device characterized by comprising: The reproduction unit includes a plurality of clock and data reproduction circuits that perform clock and data reproduction from an upstream signal of one transmission rate among a plurality of transmission rates;
And a controller for operating the clock and data recovery circuit corresponding to the selection signal based on a rate selection signal generated by the management unit as a signal indicating the transmission rate specified by the management unit. The station side apparatus of description.   3. The station side according to claim 2, wherein the controller starts the operation of the clock and data recovery circuit based on both the rate selection signal and a data detection signal indicating that the uplink signal has actually arrived. apparatus. The plurality of clock and data recovery circuits include a phase lock loop that performs clock recovery and data recovery of an upstream signal by a phase synchronization method, and a frequency lock loop that synchronizes its own oscillation frequency with a reference clock,
The station-side device according to claim 2 or 3, wherein the controller switches an operation loop of the clock and data recovery circuit that is not selected by the rate selection signal to the frequency lock loop.   5. The station-side device according to claim 2, wherein each of the plurality of clock and data recovery circuits includes a deserializer that converts the recovered data into a parallel signal and outputs the parallel signal. A PON receiver that receives a multi-rate burst signal in a time-division multiplexing manner,
A PON receiver that performs clock and data recovery of the burst signal in accordance with the timing and transmission rate of receiving the next burst signal corresponding to the grant. This is an upstream communication method of a PON system in which a station side device connected to a plurality of terminal devices via an optical fiber receives uplink signals of a plurality of transmission rates transmitted from the terminal device by a time division multiplexing method. And
Storing the plurality of transmission rates and giving an uplink communication grant to the terminal device, specifying a timing and a transmission rate for receiving the next uplink signal corresponding to the grant,
An upstream communication method of a PON system, wherein an upstream signal clock and data recovery are performed in accordance with the specified time and transmission rate. A station-side device that configures a PON system together with a plurality of terminal devices connected one-to-many via an optical fiber, and receives uplink signals of a plurality of transmission rates transmitted from the terminal devices in a time division multiplexing method,
A reproduction unit comprising a plurality of clock and data reproduction circuits for performing clock and data reproduction from an upstream signal of one transmission rate among a plurality of transmission rates corresponding to the plurality of transmission rates;
A management unit configured to set the operation timing of the plurality of clock and data recovery circuits in accordance with the reception timing of the upstream signal of each transmission rate;
A station side device characterized by comprising: A clock and data recovery unit provided with a plurality of clock and data recovery circuits for performing clock and data recovery from a burst signal of one transmission rate among multi-rate burst signals, corresponding to the plurality of transmission rates,
A clock and data recovery unit, wherein operation timings of the plurality of clock and data recovery circuits are matched with reception timings of burst signals of respective transmission rates.

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