JP2008294851A - Pon system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve a TCP throughput of a downlink. <P>SOLUTION: An optical terminal (10) on a station side is connected to user side optical terminals (22-1 to 22-N) installed in houses of respective users via an optical transmission path comprised of an optical fiber (16), an optical coupler (18) and optical fibers (22-1 to 22-N). The optical terminal (10) includes a control signal and assigns all of bands of the optical transmission paths to one of the user side optical terminals (22-1 to 22-N). After terminating communication, all the bands of the optical transmission paths are assigned to other ONUs. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a passive optical network (PON) system.

  As an access technology using an optical fiber, typically, a point-to-point method in which one optical fiber is assigned to one user, a single optical fiber is shared by a plurality of users, an L2 switch, a DSLAM, An active double star system that distributes optical signals using active devices such as optical switches, and a passive optical network that shares a single optical fiber among multiple users and distributes optical signals using passive devices such as optical couplers ( Passive Optical Network) method.

  In the point-to-point method, the core cost and wiring cost of the optical fiber are high, and the device capacity of the station side device is also increased. In the active double star system, the reliability of the active device is lower than that of the passive device, and the influence of the failure of the active device is great. The PON system is superior to the above two systems in terms of cost and reliability.

  In the PON system, time division multiple access (optical division unit) is used for transmission of an upstream optical signal from an optical terminal unit (ONU: Optical Network Unit) which is a user side device to an optical terminal device (OLT: Optical Line Terminal) which is a station side device. TDMA) is used. The OLT permits upstream communication of each optical termination unit (ONU: Optical Network Unit) in a time division manner. Accordingly, frames for bandwidth management are transmitted on the optical transmission line of the PON system even when there is no communication.

  Generally, in the PON system, 32 ONUs are connected to one OLT, but technically, 64 or 128 ONUs can also be connected. As the number of ONUs increases, the number of bandwidth management frames increases accordingly.

  In the PON system, due to the distance difference from each ONU to the OLT, the optical power of the upstream optical signal received by the OLT is different for each ONU. In addition, the clock accuracy varies depending on the ONU. In order for the OLT to be able to absorb them, the upstream optical signal is specified to be equipped with a period for CDR (Clock and Data Recovery) and a period for Automatic Gain Control (AGC) in advance of the data. ing. In EPON (IEEE 802.3), CDR and AGC are each defined to be 400 ns or less. As the number of ONUs increases, the total time for CDR and AGC increases.

  FIG. 9 shows a sequence example of a situation in which only ONU 1 transmits uplink data and the remaining ONUs 2, 3, and 4 do not transmit uplink data in a PON system in which four ONUs 1, 2, 3, and 4 are connected. The ONU 1 transmits data Data_1 at the transmission timing instructed by the OLT in accordance with the bandwidth allocation by the OLT. The upstream optical signal includes AGC, CDR, and data Data_1. The other ONUs 2, 3, and 4 transmit an upstream optical signal (Report message) indicating “no communication” at the transmission timing permitted by the OLT. This Report message also includes AGC, CDR, and data part.

  The OLT sets the transmission timing and period of the upstream optical signal of each ONU so that a certain guard band period is inserted between the upstream optical signals transmitted by each ONU. Collisions on the shared optical transmission path can be avoided by the guard band period.

  Upstream optical signals from all ONUs 1, 2, 3, and 4 are allocated within one TDMA reference cycle period. Accordingly, the ONU 1 that wants to transmit data has to wait for the data that could not be transmitted within the allocated band within one reference cycle period until the next reference cycle period. This is a delay for the upstream data output from the ONU 1. That is, a delay proportional to the reference cycle period occurs in the upstream signal.

  This delay becomes a problem in downlink communication. Normally, TCP is used for HTTP and FTP. TCP throughput is represented by WS / RTT. WS is the window size (bytes) for frame reception, and RTT is the round trip time (s). Since WS is usually constant, TCP throughput is inversely proportional to transmission delay. As a result, an increase in upstream communication delay in the PON results in a decrease in HTTP / FTP download speed.

Patent Document 1 describes a bandwidth allocation method for guaranteeing QoS (Quality of Service). Patent Document 2 describes a technique that combines fixed bandwidth allocation and variable bandwidth allocation in order to accommodate delay sensitive traffic such as telephone traffic.
JP 2007-097112 A Japanese Patent Application No. 2007-074740

  Depending on the usage situation, you may want to download or upload a large amount of data with speed priority. For example, this is a case where high-definition image data is transferred for diagnosis by telemedicine.

  In the conventional PON system that always shares the upstream bandwidth, as described above, the ONU that does not require upstream communication also transmits a bandwidth management frame, which is the maximum transfer rate of the optical transmission path. Use is hindered.

  An object of the present invention is to present a PON system in which one ONU can enjoy high throughput with low delay.

  The PON system according to the present invention connects a station-side optical termination device, a plurality of user-side optical termination devices installed in each user's home, and the station-side optical termination device and the plurality of user-side optical termination devices. A PON system including an optical transmission line, wherein the station side optical termination device allocates the entire band of the optical transmission line including a control signal to one of the plurality of user side optical termination devices. Features.

  According to the present invention, one user-side optical terminal device can temporarily dedicate an optical transmission line. This reduces delay and dramatically improves downstream TCP throughput. When sending large volumes of data, improvements can be expected in the upstream effective bandwidth.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a schematic block diagram of an embodiment of the present invention.

  An uplink port 10a of an optical termination device (OLT) 10 disposed in the center station is connected to the upper network 12, and a server 14 is connected to the upper network 12. The interface between the uplink port 10a and the upper network 12 is 1000Base-T or 1000Base-SX.

  The PON port 10 b of the OLT 10 is connected to the 1: N optical coupler 18 through the optical fiber 16. The optical coupler 18 divides the downstream optical signal from the optical fiber 16 into N and outputs the divided optical signals to the optical fibers 20-1 to 20-N. The other ends of the optical fibers 20-1 to 20-N are connected to optical terminal units (ONUs) 22-1 to 22-N arranged at the respective user houses. Computers (PC) 24-1 to 24-N are connected to the respective ONUs 22-1 to 22-N. Of course, a plurality of computers can be connected to one ONU via a router or a gateway.

  The OLT 10 controls the transmission timing and transmission period of each of the ONUs 22-1 to 22 -N and relays data transmission between the ONUs 22-1 to 22-3 and the upper network 12. In this embodiment, the OLT 10 can select a shared mode that gives each ONU 22-1 to 22 -N an opportunity for uplink transmission by TDMA and a dedicated mode that gives a communication opportunity only to a specific one ONU.

  Downlink data signals from the upper network 12 are input to the LAN interface 30 via the uplink port 10a. The LAN interface 30 stores the downlink data signal in the buffer 32. The OLT control device 34 that controls the OLT 10 monitors or snoops the downlink data signal from the LAN interface 30 to the buffer 32 in order to monitor the downlink communication status. The buffer 32 outputs the stored downlink data signals to the multiplexing device 36 in the order of priority. As will be described in detail later, in the dedicated mode, the OLT control device 34 deletes, from the buffer 32, downlink data signals other than downlink data signals destined for the ONUs that are permitted to be dedicated.

  The OLT control device 34 outputs various control signals for the ONUs 22-1 to 22 -N (for example, a Gate message indicating the transmission timing and transmission period of each ONU 22-1 to 22 -N) to the multiplexing device 36.

  The multiplexing device 36 multiplexes the control signal from the OLT control device 34 with the downlink data signal from the buffer 32 on the time axis, and applies the multiplexed signal to the electrical / optical (E / O) converter 38. The multiplexer 36 always gives priority to the control signal from the OLT controller 34 over the downlink data signal from the buffer 32. The electrical / optical converter 38 converts the multiplexed signal from the multiplexing device 36 into an optical signal (downstream optical signal) and applies it to the WDM optical coupler 40. The WDM optical coupler 40 outputs the downstream optical signal from the electrical / optical converter 38 to the optical fiber 16 via the PON port 10b. In a general PON, a 1.49 μm laser beam is used for the downstream optical signal, and a 1.31 μm laser beam is used for the upstream optical signal.

  The downstream optical signal output from the PON port 10b of the OLT 10 is input to each ONU 22-1 to 22-N via the optical fiber 16, the optical coupler 18, and the optical fibers 20-1 to 20-N.

  Each ONU 22-1 to 22-N converts a downstream optical signal input from the associated optical fiber 20-1 to 20-N into an electric signal, and a control signal (PON system) addressed to each ONU 22-1 to 22-N. The signal related to the management of the computer is captured regardless of whether it is addressed to itself, and the other data signals are captured only for the computers 24-1 to 24-N under their control. Each ONU 22-1 to 22-N internally processes the fetched control signal as will be described later, and supplies the fetched data signal addressed to PC 24-1 to 24-N to the subordinate PCs 24-1 to 24-N. To do.

  On the other hand, the computers 24-1 to 24-N output data signals directed to the upper network 12 to the ONUs 22-1 to 22-N, respectively. Each ONU 22-1 to 22-N outputs the upstream optical signal to the optical fibers 20-1 to 20-N, respectively, at the transmission timing and transmission period permitted by the OLT 10. This upstream optical signal is a data signal (including a control signal and a response signal for the server 14 and the like) addressed to a device (for example, the server 14) connected to the higher level network 12 from the subordinate computers 24-1 to 24-N. Then, each ONU 22-1 to 22-N carries a control signal output toward the OLT 10. The control signal addressed to the OLT unit 10 includes a control signal for establishing a logical link, a response signal (for example, a Report message in response to a Gate message), and the like.

  The optical coupler 18 outputs upstream optical signals from the optical fibers 20-1 to 20 -N to the optical fiber 16. The optical fiber 16 is shared by the ONUs 22-1 to 22-N. In this way, the upstream optical signal output from each of the ONUs 22-1 to 22 -N is input to the WDM optical coupler 40 via the PON port 10 b of the OLT 10.

  The WDM optical coupler 40 supplies the upstream optical signal from the PON port 10 b to the optical / electric (O / E) air converter 42. The optical / electrical converter 42 converts the upstream optical signal from the WDM optical coupler 40 into an electrical upstream signal. The separation device 44 supplies all of the electrical upstream signals output from the optical / electrical converter 42 to the OLT control device 34, and supplies the upstream signals addressed to the upper network 12 to the LAN interface 30. The OLT control device 34 can monitor the start / end of communication with the upper network 12 of each ONU by receiving all of the electrical upstream signals from the separation device 44.

  The LAN interface 30 outputs the upstream signal from the separation device 44 to the upper network 12.

  FIG. 2 shows a schematic block diagram of the ONU 22-1. The configurations of the other ONUs 22-2 to 22-N are the same as the ONU 22-1.

  The downstream optical signal from the optical fiber 20-1 enters an optical / electrical (O / E) converter 52 through the WDM optical coupler 50. The optical / electrical converter 52 converts the downstream optical signal from the WDM optical coupler 50 into an electrical downstream signal. The separation device 54 supplies all of the electrical downlink signals output from the optical / electrical converter 52 to the ONU control device 56 and supplies the downlink signal addressed to the computer 24-1 to the LAN interface 58. The ONU control device 54 can monitor the start / end of communication with the host network 12 of the subordinate computer 24-1 by receiving all of the electrical down signals from the separation device 54, and can also monitor other ONUs 22- It is possible to know the control status of the OLT 10 for 2 to 22-N. The ONU control device 54 controls the entire ONU 22-1.

  The LAN interface 58 stores the upstream data signal from the computer 24-1 in the buffer 60. The ONU controller 56 monitors or snoops the upstream data signal from the LAN interface 58 to the buffer 60 in order to monitor the upstream communication status.

  The ONU control device 56 causes the multiplexing device 62 to read the uplink data in the buffer 60 in accordance with a transmission permission signal from the OLT 10 (in EPON, a GATE frame that grants transmission permission to the logical link for the ONU 22-1). The multiplexing device 62 outputs the uplink data from the buffer 60 to the electric / optical converter 64. When there is no upstream data in the buffer 60 within the period when upstream communication is permitted by the OLT 10, the ONU control device 56 outputs an idle signal of a predetermined pattern to the multiplexing device 62, and the multiplexing device 62 receives from the ONU control device 56. An idle signal is output to the electrical / optical converter 64. Of course, the multiplexer 62 may incorporate an idle signal generator. If the signal pattern of the idle signal is EPON, it is an idle pattern conforming to IEEE802.3.

  The ONU controller 56 always supplies an idle signal to the multiplexer 62. When the multiplexer 62 has upstream data in the buffer 60, the upstream data is sent, and when there is no upstream data, the idle signal is sent to the electrical / optical converter. 64 may be supplied.

  The ONU control device 56 supplies a control signal or response signal to the OLT 10 described above to the multiplexing device 62. In general, the multiplexer 62 outputs the control signal, the data signal, and the idle signal preferentially to the electric / optical converter 64 in this order.

  When the ONU control device 56 determines that the upstream communication from the subordinate computer 24-1 has ended, the ONU control device 56 transmits a signal notifying the OLT 10 of the end of communication. For example, in the EPON conforming to IEEE 802.3, the ONU 22-1 transmits a report frame “request band = 0” to the OLT 10. Thereafter, the ONU controller 56 causes the multiplexer 62 to stop outputting the signal to the electrical / optical converter 64.

  As described above, the OLT 10 can avoid burst reception by inserting an idle signal between uplink data signals within a period in which uplink communication is permitted.

  In general, the ONU control device 56 outputs various control signals to the OLT 10 to the multiplexing device 62 in addition to the signal indicating the end of communication. Such a control signal generally includes a response signal for establishing a logical link, a bandwidth request for an uplink signal, and the like, for example, a Report message in response to a Gate message.

  The multiplexer 62 multiplexes the control signal and idle signal from the OLT controller 56 on the upstream data signal from the buffer 60 on the time axis, and applies the multiplexed signal to the electrical / optical (E / O) converter 64. The multiplexer 62 gives priority to the control signal from the ONU controller 56 over the uplink data signal from the buffer 60, and sets the idle signal to the lowest priority.

  The electrical / optical converter 64 converts the multiplexed signal from the multiplexer 62 into an optical signal (upstream optical signal) and applies it to the WDM optical coupler 50. The WDM optical coupler 50 outputs the upstream optical signal from the electrical / optical converter 64 to the optical fiber 20-1.

  As described above, the upstream optical signal output from the ONU 22-1 to the optical fiber 20-1 enters the OLT 10 via the optical fiber 20-1, the optical coupler 18, and the optical fiber 16, as described above.

  Although this embodiment operates in the conventional shared mode, it also operates in a dedicated mode in which a specific ONU is dedicated to the optical fiber 16. The operation in the dedicated mode, which is a characteristic operation of this embodiment, will be described.

  FIG. 3 is a timing chart of upstream optical signals in the shared mode (conventional PON system) and the dedicated mode. 3A shows a timing chart of the upstream optical signal in the shared mode (conventional PON system), and FIG. 3B shows a timing chart of the upstream optical signal in the dedicated mode. In the shared mode, CDR and AGC periods are required for each frame. On the other hand, in the dedicated mode, an idle signal is arranged between frames, so that only one CDR and AGC period is required at the beginning.

  FIG. 4 shows a flowchart of the bandwidth allocation operation in the dedicated mode in this embodiment. The OLT control device 34 first determines an ONU that permits exclusive use (S1). For example, it is determined in ascending order of the logical link identifier (LLID) or in order of priority of communication.

  A communication permission signal (or a signal for assigning an upstream signal band) is transmitted from the OLT 10 to the determined ONU (S2). The ONU that has received this communication permission signal starts communication with the desired server (S3), and the OLT 10 monitors the end of communication of the ONU that has been permitted to be dedicated (S4). In the dedicated mode, the OLT 10 deletes, from the buffer 32, data that is downlink data from the upper network 12 and is not intended for the ONU that is permitted to be dedicated.

  In TCP communication, “00000110” (hexadecimal 0x06, decimal 6) is set in the “Protocol” portion of the IP header defined by RFC 791 of IETF. Further, when establishing a TCP connection, the transmission apparatus (for example, the server 14), the TCP frame in which “1” is set in the “SYN” bit in the “Control Bits” portion of the TCP header defined in RFC793. Is transmitted to a receiving device (for example, any one of the computers 24-1 to 24-N). When disconnecting the TCP connection, the transmission apparatus transmits a TCP frame in which “1” is set in the “FIN” bit of the “Control Bits” portion of the TCP header to the reception apparatus. Therefore, the TCP communication can be determined by the “Protocol” portion of the IP header of the downstream signal, the start of the TCP communication can be determined by the “SYN” bit in the “Control Bits” portion of the TCP header, and the “Control Bits” of the TCP header. The end of TCP communication can be determined by the 'FIN' bit of the part.

  The presence / absence of downstream TCP communication can also be determined based on the presence / absence of data. That is, when the “Protocol” portion in the IP header is “00000110” (0x06 in hexadecimal and 6 in decimal) representing TCP, and the “ACK” bit in the “Control Bits” portion in the TCP header is “0” This indicates the presence of downlink data by downlink TCP communication. Since the ACK bit is used to indicate that a predetermined packet has been received, when the 'ACK' bit is '0', the downlink TCP frame is a frame carrying downlink data.

  When the OLT 10 detects the end of communication of the ONU permitted to be dedicated (S4), it next determines the ONU permitted to be dedicated (S5). As described above, the ONU that is allowed to be dedicated next is determined, for example, in ascending order of the logical link identifier (LLID) or in order of communication priority. In step S2, a communication permission signal is transmitted to the newly determined ONU.

  In this way, the optical transmission line is temporarily dedicated to each of the ONUs 22-1 to 22-N. Of course, when the ONU that has permitted communication does not actually require communication, there is no uplink communication data from the ONU. When detecting this state, the OLT 10 immediately permits communication to the next ONU.

  In the PON system only in the dedicated mode, the burst receiver is unnecessary. Instead, the CDR / AGC period becomes relatively long, and the band use efficiency decreases. However, the cost reduction effect that an expensive burst receiver is not required is great, and the system cost can be dramatically reduced.

  FIG. 5 shows a flowchart of the control operation of the OLT control device 34 in the dedicated mode. The OLT control device 34 initializes a variable i for designating an ONU that permits the exclusive use of the optical transmission path to 1 (S11). In FIG. 5, an ONU that is permitted to use an optical transmission line is denoted as ONU (i). The OLT control device 34 starts the timer T1 (S12) and starts the timer T0 (S13). The timer T0 is a timer for forcibly switching ONU (i) when communication is interrupted. The timer T1 is a timer that defines a period during which the ONU (i) can dedicate an optical transmission line (dedicated period). The set values of the timers T0 and T1 depend on the operating policy. For example, it is preferable to set the timer T0 to a short time such as several tens of ms to several seconds and set the timer T1 to a long time such as several minutes. That is, T0 <T1 is preferable.

  The OLT control device 34 periodically transmits a communication permission signal to the ONU (i) (S14), and receives a communication request signal from the ONU (i) (S17). This communication permission signal corresponds to a Gate signal that gives transmission permission to LLID (i) in the EPON of IEEE802.3. When receiving the communication request signal from the ONU (i) (S17), the OLT control device 34 starts the timer T0 again (S13), and periodically transmits a communication permission signal to the ONU (i) (S14). .

  If the timer T1 times out while permitting communication to the ONU (i) (S15), the variable i is incremented and the ONU dedicated to the optical transmission line is switched (S20). Also, when the end of TCP communication by the TCP FIN bit is detected (S16), the variable i is incremented and the ONU dedicated to the optical transmission path is switched (S20). Even when a communication end signal is received from the ONU (i) (S18), the variable i is incremented and the ONU dedicated to the optical transmission line is switched (S20).

  The end of TCP communication by the TCP FIN bit is not detected (S16), the communication request signal from ONU (i) is not received (S17), and the communication end signal is not received from ONU (i) ( S18) Even when the timer T0 times out (S19), the variable i is incremented and the ONU dedicated to the optical transmission line is switched (S19). This is typically a state in which communication with the ONU (i) is interrupted. If the timer T0 does not time out (S19), S14 and subsequent steps are repeated.

  When the variable i does not exceed the number N of ONUs (S21), the process returns to step S12, the timers T0 and T1 are started again (S12 and S13), and the steps after step S14 are repeated. If the variable i exceeds the number N of ONUs (S21), the process returns to step S11, the variable i is initialized with 1 (S11), and the timers T0 and T1 are started again (S12, S13). Steps S14 and after are repeated.

  FIG. 6 shows a flowchart of the control operation of the ONU control device 56 in the dedicated mode. The ONU (i) waits for a communication permission signal from the OLT 10 (S31). When the communication permission signal is received (S31), first, it is confirmed whether or not the uplink data signal to be transmitted is in the buffer 60 (S32).

  When the uplink data signal to be transmitted is in the buffer 60 (S32), the timer T2 is started (S33), and a communication request signal is transmitted to the OLT 10 (S35). For example, in the case of EPON, the communication request signal is a Report frame in which the bandwidth request is non-zero. The ONU (i) transmits the upstream data signal in the buffer 60 to the OLT 10 with a dedicated band (S36). When there is no upstream data signal in the buffer 60, the ONU (i) transmits an idle signal to the OLT 10 as described above (S36). When a communication permission signal addressed to the own ONU is received (S37), the process returns to step S32. By transmitting an idle signal to the OLT 10 when there is no uplink data, the OLT 10 can avoid burst reception.

  When there is no uplink data signal to be transmitted in the buffer 60 (S32), it is checked whether the timer T2 has timed out (S34). The timer T2 is a timer that defines a period during which dedicated data is maintained when there is no uplink data to be transmitted. For example, when downloading is a file download, the uplink signal has a very small transmission capacity like an ACK packet for confirming reception, and the buffer 60 is often emptied. By setting the timer T2, it is possible to prevent erroneous recognition of the end of communication when there is no upstream signal in the buffer 60 temporarily.

  If the timer T2 has not timed out (S34), the ONU (i) transmits a communication request signal to the OLT 10 (S35), and continues to transmit an upstream data signal or an idle signal with a dedicated band (S36). .

  If the timer T2 has timed out (S34), the ONU (i) transmits a communication end signal to the OLT 10 (S40), and stops transmission of the upstream data signal and the idle signal to the optical transmission line (S41). It returns to step S31 and waits for a communication permission signal.

  When a communication permission signal addressed to another ONU is received when the band is dedicated (S38), the transmission of the upstream data signal or idle signal to the optical transmission line is immediately stopped (S41), and the communication permission signal is Wait (S31).

  When the end of TCP communication by the TCP FIN bit is detected in the upstream data signal (S39), the ONU (i) transmits a communication end signal to the OLT 10 (S40), and the optical transmission path of the upstream data signal and the idle signal The transmission to is stopped (S41). It returns to step S31 and waits for a communication permission signal.

  When a communication permission signal addressed to the own ONU is not received (S37), a communication permission signal addressed to another ONU is not received (S38), and the end of TCP communication by the TCP FIN bit is not detected (S39) (S36).

  In the first embodiment, since the band occupation permission is given to all the ONUs 22-1 to 22 -N in order, for example, in the order of LLID, a band is also temporarily allocated to an ONU that does not require communication. This deteriorates the bandwidth usage efficiency.

  In the second embodiment, bandwidth requests are collected from all the ONUs 22-1 to 22-N, and bandwidth occupancy is permitted to the ONU having the largest required bandwidth. FIG. 7 shows an operation flowchart of the OLT 10 in the second embodiment. FIG. 8 shows an operation flowchart of the ONUs 22-1 to 22-N corresponding to FIG.

  The OLT 10 inquires the bandwidth request to all the ONUs 2-1 to 22-N (S51). For example, in the EPON of IEEE 802.3ah, a Gate frame that specifies the transmission time and transmission timing is transmitted to each ONU. Each ONU 22-1 to 22-N checks whether there is upstream data in the buffer 60 in response to the bandwidth request inquiry from the OLT 10, and transmits the upstream data amount in the buffer 60 to the OLT 10 at the designated transmission time and transmission timing. Reply as a request. In EPON of IEEE 802.3ah, requested bandwidth information can be transmitted by using a Report frame. When the requested bandwidth is 0, the OLT 10 is notified as “requested bandwidth = 0”.

  The OLT 10 receives the bandwidth request from each of the ONUs 22-1 to 22 -N (S 52), and determines the ONU having the largest requested bandwidth as the ONU dedicated to the bandwidth (S 53). Steps S54 to S61 subsequent to step S53 are the same as steps S13 to S19 in FIG. Since the ONUs dedicated to the band are not forwarded, steps S20 and S21 in FIG. That is, when the timer T1 times out (S57), the process returns to step S51, and the ONU (i) dedicated to the bandwidth is determined again from all the ONUs. Even when the end of TCP communication by the TCP FIN bit is detected (S58), the process returns to step S51, and the ONU (i) dedicated to the band is determined again from all ONUs. When a communication end signal is received from the ONU (i) (S60), the process returns to step S51, and the ONU (i) dedicated to the band is determined again from all the ONUs. When the timer T0 has timed out (S61), the process returns to step S51, and the ONU (i) dedicated to the bandwidth is determined again from all the ONUs.

  The operation of each ONU 22-1 to 22-N is different from FIG. 6 in that an answer process corresponding to the bandwidth request inquiry in step S51 is added. The processing after the ONU dedicated to the bandwidth is designated is as follows. This is the same as FIG.

  When a bandwidth request inquiry is received from the OLT 10 (S71), a bandwidth request signal is transmitted to the OLT 10 (S72). When a communication permission signal is received from the OLT 10 (S73), it is checked whether the communication permission signal is addressed to itself or another ONU (S74). If it is addressed to another ONU (S74), it again waits for a bandwidth request inquiry from the OLT (S71). If it is addressed to itself, the optical transmission is dedicated (S75) as in step S32 and subsequent steps of the flow shown in FIG.

  In each of the above embodiments, for the sake of simplicity, IEEE 802.3ah has been described as an example. However, in the present invention, the bit rate of the optical transmission line portion is not limited. In particular, the first embodiment is effective in a high-speed PON in which it is difficult to create a burst receiver such as 10GE-PON.

  Although the invention has been described with reference to specific illustrative embodiments, various modifications and alterations may be made to the above-described embodiments without departing from the scope of the invention as defined in the claims. This is obvious to an engineer in the field to which the present invention belongs, and such changes and modifications are also included in the technical scope of the present invention.

It is a schematic block diagram of one Example of this invention. It is a schematic block diagram of ONU22-1. The timing chart of the upstream optical signal in shared mode and exclusive mode is shown. It is a basic operation | movement flowchart in the exclusive mode of a present Example. It is an operation | movement flowchart of OLT10. It is an operation | movement flowchart of ONU22-1 to 22-N. It is another operation | movement flowchart of OLT10. 8 is an operation flowchart of the ONU corresponding to FIG. In the PON system to which four ONUs 1, 2, 3, and 4 are connected, only the ONU 1 transmits upstream data, and the remaining ONUs 2, 3, and 4 show a sequence example in which upstream data is not transmitted.

Explanation of symbols

10: Optical termination device (OLT)
10a: Uplink port 10b: PON port 12: Host network 14: Server 16: Optical fiber 18: Optical couplers 20-1 to 20-N: Optical fibers 22-1 to 22-N: Optical terminator (ONU)
24-1 to 24-N: Computer 30: LAN interface 32: Buffer 34: OLT controller 36: Multiplexer 38: Electrical / optical converter 40: WDM optical coupler 42: Optical / electrical converter 44: Separating device 50: WDM optical coupler 52: optical / electrical converter 54: separation device 58: LAN interface 60: buffer 62: multiplexing device 64: electric / optical converter

Claims (4)

A PON system comprising a station-side optical termination device, a plurality of user-side optical termination devices installed in each user's home, and an optical transmission line that connects the station-side optical termination device and the plurality of user-side optical termination devices Because
A PON system, wherein the station side optical termination device allocates the entire band of the optical transmission line including a control signal to one of the plurality of user side optical termination devices.   2. The PON system according to claim 1, wherein the user-side optical termination device to which all of the bandwidth of the optical transmission path is assigned sends an idle signal to the optical transmission path during the uplink signal.   3. The PON system according to claim 1, wherein the station-side optical termination device cyclically switches the user-side optical termination device to which the entire band of the optical transmission path is allocated.   The station side optical terminator allocates all of the bandwidth of the optical transmission line to the user side optical terminator that requests the most bandwidth among the plurality of user side optical terminators. The PON system according to 1 or 2.

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