TW201351928A - Optical transmission system, office-side optical terminal device and communication circuit switching method - Google Patents

Abstract

An optical transmission system comprises: ONUs that are capable of shifting to a power-saving mode; OLTs; and a beam splitter that is connected by redundant trunk lines with the OLTs and that is connected by respective branch lines with the ONUs. The OLTs hold a state management table providing information relating to the power-saving modes of the ONUs, and decide whether or not to implement redundant switching of the trunk lines in accordance with this state management table.

Description

Optical transmission system, central side optical terminal device, and communication circuit switching method

The present invention relates to an optical transmission system, a central-side optical terminal device, and a communication loop switching method.

In recent years, in order to cope with the high speed and wide frequency of communication networks, it has been proposed to introduce an optical network. In the optical network, one OLT (Optical Line Terminal) and one ONU (Optical Network Unit) are transmitted through an optical transmission path (optical fiber). In addition, a PON (Passive Optical Network) system, which is one of the optical network systems, forms a PDS (Passive Double Star) type network with a plurality of ONUs because one OLT transmits a splitter. Therefore, a high speed access service can be formed at low cost. In terms of the representative specifications of the PON, there is an EPON (Ethernet (registered trademark) PON) standardized by IEEE (Institute of Electrical and Electronic Engineers) 802.3.

In the PON communication method, the upstream optical signal transmitted by the ONU toward the OLT and the downstream optical signal transmitted by the OLT toward the ONU are multiplexed by WDM (Wavelength Division Multiplexing). ONU uses TDMA (Time Division Multiple) to transmit upstream optical signals according to the timing of the transmission permitted by the OLT. Access: Time-division multiplex connection). That is, the OLT is configured to dynamically allocate the transmission timing of the connected ONUs of the connected plurality of ONUs to the uplink signals of the ONUs. The downlink optical signal transmitted by the OLT toward the ONU is TDM (Time Division Multiplexing) and is received by all ONUs connected by the optical transmission path. At this time, the ONU refers to the information of the reception station included in the preamble portion of the downlink optical signal, and discards the downlink optical signal that is not for itself.

As the communication speed increases and the number of connected electronic devices increases, the power consumption of the ONU tends to increase. The ONU is configured in the subscriber's home, and many of them are arranged on the network. In addition, the time required for the ONU to have a usable frequency band is shorter than that of the OLT and the upper switch group. Therefore, the ONU is left unattended while using the wasted power while the communication is not being performed.

Patent Document 1 discloses a PON system in which an OLT uses an ONU downlink sleep management table (table) for managing whether a downstream optical signal processing unit of an ONU is in a sleep (power saving) state, and an ONU management unit. Whether the upstream optical signal processing unit is in the sleep (power saving) state of the ONU uplink sleep management table.

Patent Document 2 listed below discloses a table that uses identification information for managing an ONU, and a management table that manages the recovery time of the ONU from a sleep (power saving) state in which a part of the uplink and downlink processing units is stopped to a recovery time. Technique (Patent Document 2).

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2012-004642

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2011-229094

There is a system in which a cumbersome configuration is switched to another communication loop if an obstacle occurs in the communication loop forming the communication network. As described above, by adopting the tedious configuration of the communication loop, the robustness to communication obstacles can be improved. In a communication network having a redundant communication circuit, when the communication device detects a communication circuit failure in the active circuit in use, the communication circuit that has been in trouble is switched to another communication circuit, and the link is established and re-established. Communication.

On the other hand, with the increase in the demand for high-speed and large-capacity communication in recent years, the power consumption of the ONU tends to increase, and the operation of the low-power operation is sought. The ONU in the sleep (power saving) state achieves a reduction in power consumption by stopping both the transmitter and the receiver used for data communication with the OLT or stopping only the transmitter. The ONU in the dormant (power saving) state does not transmit the upstream optical signal to the OLT, and does not respond to the control signal from the OLT. Therefore, when the redundant configuration is coexisted with the ONU power save, the following problems occur.

In the PON system in which the redundant configuration of the optical transmission path and the ONU are dormant, if the sleep (power saving) state of all the ONUs connected to the OLT temporarily overlaps, the ONU does not respond to the control optical signal issued by the OLT. Therefore, there will be an OLT error detecting an obstacle in the optical transmission path, and communicating The problem of switching the circuit.

Patent Document 1 discloses a method in which a OLT uses a sleep management table for managing a sleep (power saving) state of an optical signal processing unit above and below an ONU. The state management table is used to monitor the existence of the communication data and the data type, thereby reducing the power consumption of the ONU. However, the above-mentioned problem in the case where the redundant configuration of the optical transmission path is coexisting, that is, the solution to the error detection of the obstacle is Patent Document 1 does not disclose at all. In Patent Document 2, the above-described problem in the case where the redundant configuration of the optical transmission path is coexisted, that is, the solution to the error detection of the obstacle is not disclosed at all.

Patent Document 1 discloses a method in which the OLT monitors the communication state of each ONU in order to suppress the power consumption during non-communication of the ONU, and performs sleep (power saving) control on the ONU during non-communication using the sleep management table. By using this method, the ONU is controlled to be in a sleep (power saving) state within a time range in which the redundant switching condition is not satisfied, whereby power consumption can be suppressed, but a limitation occurs in the sleep (power saving) time, and the ONU system Frequently repeated state transitions, occupying a band that cannot be ignored on the optical transmission path of a multi-difference PON system, and the ONU's power consumption reduction effect is limited.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a power saving control method capable of preventing an error detection of an obstacle of an optical transmission path when a power saving control of an ONU and a redundant configuration of an optical transmission path are coexisted.

In order to achieve the above object, the present invention is an optical transmission system including: a subscriber-side optical terminal device that can be moved to a power-saving mode; a side-side optical terminal device; and a redundant trunk line. Side light a light splitter connected to the terminal side optical terminal device by a branch line, wherein the office side optical terminal device manages a power saving mode with respect to the subscriber side optical terminal device The information, that is, the power saving information, controls the lengthy switching of the aforementioned trunk lines according to the aforementioned power saving information.

In the optical transmission system, the central optical terminal device, and the communication circuit switching method of the present invention, when the power saving control of the ONU and the redundant configuration of the optical transmission path coexist, the effect of erroneous detection of the obstacle of the optical transmission path can be prevented.

1‧‧‧OLT

1-1‧‧‧wOLT

1-2‧‧‧sOLT

2-1~2-N‧‧‧ONU

3‧‧‧Light splitter

4‧‧‧Upper network

5-1, 5-2‧‧‧ User terminal

6-1~6-N‧‧‧Split fiber

7‧‧‧Trunk fiber

7-1‧‧‧Current system trunk fiber

7-2‧‧‧Prepared system trunk fiber

8‧‧‧L2SW

9‧‧‧Control Department

10, 20‧‧‧PON Control Department

11, 21‧‧‧ Physical Layer Processing Department

12, 22‧‧‧WDM coupler

13, 23‧‧‧Send buffer

14, 24‧‧‧ receiving buffer

15, 25‧‧‧ light receiving and transmitting device

16, 26‧‧‧ Optical Receiver

17, 27‧‧‧ Optical transmitter

18, 28‧‧‧Receipt Department

19, 29 ‧ ‧ Department of Communications

30, 35‧‧‧ Signal Processing Department

31, 36‧‧‧ Buffer Monitoring Department

32‧‧‧Sleep Control Signal Processing Department

33‧‧‧Status Management Table

34, 40‧‧‧ time counter

37‧‧‧Link Monitoring Department

38‧‧‧Status Table

39‧‧‧Dorm Control Department

Fig. 1 is a view showing an example of the configuration of an optical access network including the PON system of the present invention.

Fig. 2 is a diagram showing an example of the configuration of a PON system.

Fig. 3 is a view showing an example of the configuration of the OLT unit.

Fig. 4 is a view showing an example of the configuration of the ONU.

Fig. 5 is a diagram showing an example of a communication action sequence of a discovery process.

Fig. 6 is a view showing an example of a sequence in the case where an active system fiber has an obstacle.

Figure 7 is a diagram showing an example of a trunk fiber switching sequence in the event of an obstacle in the active system mains fiber.

Fig. 8 is a view showing an example of a communication operation sequence when a conventional obstacle is generated by a conventional communication path switching method.

Figure 9 is a flow chart showing an example of basic control of the OLT (flow Chart).

Fig. 10 is a flow chart showing an example of power saving control of the OLT.

Fig. 11 is a diagram showing an example of a state management table.

Fig. 12 is a flow chart showing an example of a communication path switching sequence.

Fig. 13 is a view showing an example of a sequence when the communication path switching method in the OLT of the present invention is implemented.

Fig. 14 is a view showing an example of a sequence in which power saving control in the OLT is implemented.

Figure 15-1 shows an example of the power-saving control sequence in the ONU.

Figure 15-2 shows an example of the power-saving control sequence in the ONU.

Fig. 16 is a view showing an example of a configuration in which the branch line is multi-stage.

Hereinafter, embodiments of the optical transmission system, the office-side optical terminal device, and the communication circuit switching method of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited by the embodiment.

Implementation form.

Fig. 1 is a view showing an example of the configuration of an optical access network including a PON system (optical transmission system) of the present invention. The PON system of the present embodiment is composed of an OLT (office-side optical terminal device) 1 and an ONU (Attendee-side optical terminal device) 2-1 to 2-N (N is an integer of 1 or more). The OLT 1 is connected to the upper network 4. The ONU 2-1 is connected to the user terminal 5-1, and the ONU 2-1 is connected to the user terminal 5-2.

OLT1 is connected to ONU2-1~ONU2-N through optical splitter 3, and OLT1 and optical splitter 3 are connected by trunk fiber 7 The brancher 3 and the ONU2-1~ONU2-N are connected by a branch fiber 6-1~6-N, respectively. Among them, the number of ONUs connected to the OLT 1 is not limited.

OLT1 and ONU2-1~ONU2-N use the optical signals that are multiplexed by WDM to communicate. Therefore, there is no case where the optical signals in the upstream direction collide with the optical signals in the downstream direction. On the other hand, since the plurality of ONUs 2-1 to ONU2-N communicate at the same wavelength, the OLT 1 controls the light delivery timing of each of the ONUs 2-1 to ONU2-N so that the time at which the light is sent does not overlap. News moment).

Fig. 2 is a view showing an example of the configuration of a PON system of the present embodiment. As shown in FIG. 2, the OLT 1 of the present embodiment has a redundant configuration, and includes an OLT unit 1-1, an OLT unit 1-2, and a control unit 9 that controls the entire OLT 1. Each of the OLT unit 1-1 and the OLT unit 1-2 has a function as an OLT, and any of them is used for operation. Here, the OLT unit 1-1 is an active system (wOLT1-1), and the OLT unit 1-2 is a standby system (sOLT1-2). The OLT unit 1-1 and the OLT unit 1-2 are connected to the L2SW (Layer 2 Switch) 8, respectively, and are connected to the upper network 4 via the L2SW 8. In addition, the trunk fiber 7 is composed of the existing system trunk fiber 7-1 and the preparatory system trunk fiber 7-2. The current system trunk fiber 7-1 is connected to wOLT1-1, and the preparatory system trunk fiber 7-2 and sOLT1. -2 phase connection. In the second drawing, the number of ONUs is set to four, but the number of ONUs is not limited to this.

The optical splitter 3 is a passive optical component, and in the downlink communication, the downlink optical signal transmitted by the OLT 1 through the active system trunk optical fiber 7-1 and the preparatory system trunk optical fiber 7-2 is divided into itself. The number of ONU2s (for example, 4 in Figure 2), the separated optical signals are separated. Output to branch fiber 6-1~6-4. Further, in the uplink communication, the optical splitter 3 outputs the upstream optical signals transmitted by the branch optical fibers 6-1 to 6-4 to the active system trunk optical fiber 7-1 and the preparatory system trunk optical fiber 7-2.

The OLT 1 includes a function of setting and controlling a communication path with the ONUs 2-1 to 2-4. The ONUs 2-1 to 2-4 are communication devices for transmitting and receiving optical signals by control from the OLT 1, and include a power saving (sleep) mode (described later).

Fig. 3 is a view showing an example of the configuration of the OLT unit 1-1 (wOLT1-1). The OLT unit 1-2 (sOLT1-2) has the same configuration as the OLT unit 1-1. As shown in FIG. 2 and FIG. 3, the OLT unit 1-1 includes a PON control unit 10 that performs processing on the OLT side in accordance with a PON communication protocol, and a physical layer processing unit (PHY) 11; A WDM coupler (WDM) 12 for wavelength multiplexing of the signal and the downstream optical signal; a buffer for storing data of the downstream optical signal transmitted to the ONUs 2-1 to 2-4, that is, a transmission buffer The buffer area for storing the data of the upstream optical signals received by the ONUs 2-1 to 2-4 is the receiving buffer 14 and the optical transceiver 15.

The optical transceiver 15 includes: an optical receiver (Rx: Receiver) 16 that performs processing for converting the optical signals received by the ONUs 2-1 to 2-4 into electrical signals and outputting them to the PON control unit 10; The optical signal input by the PON control unit 10 is converted into an optical signal and transmitted to the optical transmitter (Tx: Transmitter) 17 of the processing of the ONUs 2-1 to 2-4. The physical layer processing unit 11 is a receiving unit (Rx) 18 that performs a physical interface function such as a NNI (Network Node Interface) with a network, and performs a communication process. The transmitting unit (Tx) 19 is configured. Wherein, in this embodiment In the PON system, WDM12 is used, and wavelength multiplexing is used, but WDM12 is not necessary when communicating at a single wavelength.

Further, the PON control unit 10 includes a signal processing unit 30, a buffer monitoring unit 31, a sleep control signal processing unit 32, a state management table 33, and a time counter 34.

Fig. 4 is a view showing an example of the configuration of the ONU2-1. ONU 2-2 to 2-4 are also the same configuration as ONU 2-1. As shown in FIG. 2 and FIG. 4, the ONU 2-1 includes a PON control unit 20 that performs processing on the ONU side according to the PON communication protocol, and a buffer for storing data of the upstream optical signal transmitted to the OLT 1. a buffer buffer 23; a buffer buffer for storing data of the downlink optical signal received by the OLT1, that is, a buffer buffer 24; a WDM coupler (WDM) 22 for wavelength multiplexing the upstream optical signal and the downstream optical signal And a physical layer processing unit (PHY) 21 that implements a physical interface function such as a UNI (User Network Interface) between the connection terminal unit 5-1.

The optical transceiver 25 is composed of an optical transmitter (Tx) 27 for transmitting optical signals and an optical receiver (Rx) 26 for receiving optical signals. Further, the physical layer processing unit (PHY) 21 is composed of a receiving unit (Rx) 28 that performs a receiving process, and a transmitting unit (Tx) 29 that performs a transmitting process. Among them, WDM 22 is not necessary when communication is performed at a single wavelength without using wavelength multiplexing.

Further, the PON control unit 20 includes a signal processing unit 35, a buffer monitoring unit 36, a connection monitoring unit 37, a status table 38, a sleep control unit 39, and a time counter 40.

In the present embodiment, the OLT 1 has a function of detecting obstacles. In the PON control unit 10, when the optical signals are not reached by the ONUs 2-1 to 2-4, the signal processing unit 30 sends out the obstacle detection signal. The obstacle detection in the PON system is reviewed by the IEEE or ITU-T (International Telecommunication Union Telecommunication Standardization Sector).

For example, in the IEEE P1904.1 ^TM with a predetermined MAC LoS (Loss of Signal, signal loss), the light barrier detecting LoS. Both the MAC LoS and the optical LoS are detected when detecting obstacles in the system trunk fiber. If the obstacle is detected, the OLT system is switched from the active system to the standby system. MACLoS is an obstacle detection when the OLT does not receive a report (report) (REPORT message) within a certain period of time. The optical LoS is in the optical receiver 16 of the OLT. It is detected when a valid optical signal cannot be received within the period.

In addition, in ITU-T G.987.3, LOBi (Loss of burst for ONUi) and LOS (Loss of Signal) are defined as obstacle detection. LOBi is detected when the OLT fails to receive a burst of four consecutive bursts of signals (sent by the ONU) after each ONU is scheduled. The LOS is detected when the OLT fails the received transmission frame in the uplink direction for four consecutive times. The LOBi is detected for each ONU, thus showing an obstacle to the ONU or branch line. If it is an obstacle of the ONU or the branch line, the switching from the active system to the standby system in the OLT 1 is not implemented, for example, the operation manager is notified of the obstacle. When the LOS is sent out, the trunk optical fiber is switched from the active system to the standby system in the same manner as the above-described optical LoS and MAC LoS.

In the configuration example shown in FIG. 2, the PON control unit 10 is based on A notification from the light receiver 15 detects the light LoS. Specifically, the optical transceiver 15 has a time counter, and when the state of the optical signal detected by the Rx 16 is equal to or less than the threshold value for a certain period or longer, the PON control unit 10 is notified by the notification. The signal processing unit 30 may send the light LoS. The optical transceiver 15 notifies the signal processing unit 30 of the reception level of the Rx16, and the PON control unit 10 uses the time counter 34. If the reception level is the threshold value. When the following state continues for a certain period of time or longer, the light LoS may be sent.

Regarding the MAC LoS, the PON control unit 10 finally measures the elapsed time after receiving the report by the ONUs 2-1 to 2-4 by the time counter 34, and does not receive a report by any ONU until a certain period of time elapses (REPORT) When the message is detected. With regard to the LOBi and LOS, the PON control unit 10 maintains the information of the uplink frequency band (uplink transmission permission time interval) allocated to the ONUs 2-1 to 2-4, and therefore the signal processing unit 30 performs detection based on the information. The PON control unit 10 sends a corresponding alarm when the obstacles are detected. The control unit 9 receives the alarm.

When the alarms of the optical LoS, MAC LoS, and LOS are sent out, the control unit 9 of the OLT 1 switches the used trunk fiber from the active system trunk fiber 7-1 to the standby system trunk fiber 7-2. As shown in Fig. 2, the current system trunk fiber 7-1 is connected to wOLT1-1, and the preparatory system trunk fiber 7-2 is connected to sOLT1-2, and the OLT for operation is switched from wOLT1-1 to sOLT1. -2, thereby switching the trunk fiber. The control unit 9 may not be included, and the wOLT 1-1 directly notifies the sOLT 1-2 of an alarm, thereby switching from the wOLT 1-1 to the sOLT 1-2.

Hereinafter, in the present embodiment, the obstacle detection signal must be included The obstacle detection (light LoS, MAC LoS, LOS, etc.) that is required to perform trunk fiber switching (that is, switching of the OLT units 1-1 and 1-2 used) is referred to as trunk obstacle detection. The trunk line detection system may be, for example, the above-described optical LoS, MAC LoS, and LOS, and may be an obstacle detection method other than the obstacle for detecting the trunk optical fiber.

When the detection method of the main line obstacle such as the light loS, the MAC LoS, and the LOS is performed based on the above, if one or more of the following conditions are satisfied, the detection is performed as a trunk line obstacle.

(1) When the optical receiver of the OLT does not receive the optical signal during X [ms] (X is a predetermined constant).

(2) When the OLT does not receive a control signal response (for example, an MPCP (Multi-Point Control Protocol) frame) from the ONU during the period of Y [ms] (Y is a preset constant).

(3) When the ONU transmits the license signal to the OLT, the ONU does not react for Z consecutive times (Z is a preset constant).

The functions of the PON control unit 10 of the OLT 1 will be described below using Figs. 2 and 3 . The PON control unit 10 includes a time counter 34. When the optical signals from the ONUs 2-1 to 2-4 do not arrive within a certain period of time (the optical signal is not received in the optical receiver 16 for a certain period of time), the light LoS is emitted. alarm.

The signal processing unit 30 performs search processing for communicating with the detected ONUs 2-1 to 2-4, and band allocation for allocating communication bands (uplink transmission time intervals) of the respective ONUs 2-1 to 2-4. Processing and so on. The signal processing unit 30 transmits the band allocation result to the ONUs 2-1 to 2-4 by the GATE message (band allocation notification). The signal processing unit 30 is based on each ONU2-1 ~2-4 The REPORT message (response signal) containing the uplink allocation request is transmitted, and the frequency band is allocated to each ONU2-1~2-4. Further, the signal processing unit 30 detects the response signal (MPCP frame) transmitted by the ONUs 2-1 to 2-4, and uses the time counter 34 to respond to the signal for each ONU 2-1 to 2-4. When the MPCP frame does not arrive at a certain time, the signal processing unit 30 issues a MAC LoS alarm. The MPCP frame is transmitted by GIF frame, REPORT frame, data or dormant permission and response at a certain time.

The sleep control signal processing unit 32 refers to the state management table 33 which is a table for managing the power saving states of the respective ONUs 2-1 to 2-4, and selects a sleep (power saving) mode for each of the ONUs 2-1 to 2-4, and transmits the shift. Control signal to sleep mode (Sleep_Allow) in sleep mode. Further, the sleep control signal processing unit 32 updates the state management table when the ONU receives the control signal of the sleep permission response (Sleep_Ack). Further, when the ONUs 2-1 to 2-4 are restored from the sleep (power saving) mode, the sleep control signal processing unit 32 transfers the ONUs 2-1 to 2-4 of the compliant sleep (power saving) mode to the normal state. The control signal for the mode recovery permission (WakeUp_Allow). The sleep control signal processing unit 32 also updates the state management table when the control signals of the recovery permission response (WakeUp_Ack) are received by the ONUs 2-1 to 2-4. In addition, when a power-off notification (R-INH or the like) is received, the state management table 33 may be updated by setting the state of the ONUs 2-1 to 2-4 of the transmission source to the sleep mode.

The processing regarding the power-off notification is, for example, implemented as follows. The power-off detection unit (not shown) of the ONUs 2-1 to 2-4 notifies the PON control unit 20 when it detects that its own power is turned off. The PON control unit 20 is connected When the detection of the power-off is known, the OLT 1 transmits a power-off notification notifying that the power-off has occurred.

In the present embodiment, when the ONUs 2-1 to 2-4 detect that their own power is turned off, the OLT 1 transmits a power-off notification, but if the ONUs 2-1 to 2-4 are in a sleep state (power-saving state), In the event of a power-off, there is a case where the transmission and non-transmission power-off notifications are available. Whether or not the power-off notification can be transmitted depends on the band update period, the start-up time of the transmission/reception function of the power-saving state of the ONUs 2-1 to 2-4, and the like.

An example of a power-off notification when hibernation is available is displayed. Each of the ONUs 2-1 to 2-4 to which the OLT 1 is connected transmits a GATE frame for each band update period even in a sleep mode. The frequency band of each of the ONUs 2-1 to 2-4 assigned to the sleep mode is a frequency band for transmitting the REPORT frame for each of the ONUs 2-1 to 2-4.

When power-off occurs in the ONUs 2-1 to 2-4 in the power-saving state (during sleep), the PON control unit 20 of the ONUs 2-1 to 2-4 releases the sleep mode, and the startup is turned off (off). The part of the state. For example, the Rx start time (reception-side start time: the time during which the portion that was originally in the sleep state of the ONU 2-1 to 2-4 is in the sleep state can be operated After the GATE frame received initially, the REPORT frame requesting the frequency band for transmitting the power-off notification is transmitted. In the meantime, the Rx start time is longer than the Tx start time (the transmission side start time: the part that is in the sleep state and the part that was originally stopped during the transmission processing of the ONUs 2-1 to 2-4 can be operated. The time) is long, so the REPORT frame can be transmitted at the point when the Rx start time has elapsed.

The PON control unit 20 of the ONUs 2-1 to 2-4 receives the GATE frame for notifying the band allocation for transmitting the power-off notification to transmit by the frequency band (transmission time interval) indicated by the GATE frame. Power off notification. During the period from the occurrence of the power-off to the time when the power-off power holding time (the time during which the power can be held by the power-off capacitor) is completed, the power supply during sleep can be performed because the power-off notification is completed. Turn off the notification.

The buffer monitoring unit 31 monitors the accumulated amount of the transmission buffer 13 and notifies the signal processing unit 32 of the monitoring result. The sleep control signal processing unit 32 determines to turn on the ONU 2-1 based on the information from the buffer monitoring unit 31 and the buffer monitoring unit 36 of the ONUs 2-1 to 2-4 received by the ONUs 2-1 to 2-4. The optical transmitter 27 of the optical transceiver 25 of ~2-4 moves to the sleep (power saving) mode, or moves both the optical transmitter 27 and the optical receiver 26 to the sleep (power saving) mode. . The signal processing unit 30 generates a sleep signal (Sleep_Allow) and a recovery permission (WakeUp_Allow) control signal based on the determination result of the sleep control signal processing unit 32, and transmits it by the optical transmitter 17.

In the sleep (power saving) mode, both the optical transmitter 27 and the optical receiver 26 are in an intermittent repeated sleep (power saving) state and a temporary starting state, and the ONUs 2-1 2-4 are in the system. In the sleep mode, signals from the OLT 1 can also be received every certain period.

When the optical receiver 16 receives the sleep permission response (Sleep_Ack) or the recovery permission response (WakeUp_Ack) from the ONUs 2-1 to 2-4, the sleep control signal processing unit 32 updates the state management table 33 via the signal processing unit 30. At the same time, the sleep control signal processing unit 32 uses the time counter 34 to monitor the sleep (power saving) time.

When the optical receiver 16 receives the data of the upstream optical signal from the ONUs 2-1 to 2-4, the signal processing unit 30 temporarily stores the received data in the receiving buffer 14. The signal processing unit 30 uses the time counter 34 to determine the processing sequence, and reads the data stored in the receiving buffer 14 at the determined timing, and transmits the data stored in the receiving buffer 14 to the L2SW 8 via the receiving unit 18 of the physical layer processing unit 11.

Next, the functions of the ONU 2-1 will be described using FIGS. 2 and 4 . ONU2-2~2-4 is also the same as ONU2-1. The ONU2-1 system includes a function of moving to the sleep (power saving) mode as a communication state. The so-called sleep (power saving) mode means that only the optical transmitter 27, the optical transmitter 27, and the optical receiver are attenuated if there is no data to be transmitted in the upstream or downstream direction. The power supply of both of them is stopped to achieve a mode of reducing power consumption. Here, the OLT1 requests the ONU2-1~2-4 to move to the sleep (power saving) mode, and the ONU2-1~2-4 transmits the response to the request, and then moves to the sleep mode as an example for explanation. .

The order in which the ONUs 2-1 to 2-4 are moved to the sleep mode is not limited thereto, and the migration request to be transferred from the ONU 2-1 to 2-4 to the sleep mode may be applied, and the order in which the OLT 1 transmits the permission to the request; The OLT1 requests the ONUs 2-1 to 2-4 to move to the sleep mode, and the ONUs 2-1 to 2-4 do not transmit the response to the request, but move to the sleep mode in a different order.

The buffer monitoring unit 36 monitors the accumulation amount of the transmission buffer 23, and notifies the signal processing unit 35 of the monitoring result. The signal processing unit 35 grasps the uplink transmission time interval assigned to the own device by the GATE frame received by the OLT 1 via the optical receiver 26. Further, the signal processing unit 35 accumulates in the transmission buffer 23 in accordance with the notification from the buffer monitoring unit 36. In the case of the upper transmission data, the bandwidth allocation is requested by storing the accumulation amount of the transmission buffer 23 by the REPORT message.

When the transmission unit 29 of the physical layer processing unit 21 receives the uplink transmission data, the signal processing unit 35 temporarily stores the transmission data in the transmission buffer 23. The signal processing unit 35 reads the transmission data from the transmission buffer 23 in the uplink transmission time interval allocated by the OLT 1, and transmits it as an upstream optical signal by the optical transmitter 27.

When the PON control unit 20 of the ONU 2-1 receives the sleep permission response (Sleep_Allow) transmitted by the OLT 1 by the signal processing unit 35, the sleep control unit 39 refers to the buffer monitor unit 36, and if it is non-communication In the state where the data is not stored in the transmission buffer and the reception buffer, the sleep processing response (Sleep_Ack) is sent back by the signal processing unit 35. The sleep control unit 39 recognizes and selects the sleep (power saving) mode, and moves its own state to the sleep (power saving) mode. Further, the ONU 2-1 has a state table 38 indicating the power saving state of the own device, and updates the state table 38 in response to the state transition at the time. In addition, the ONU 2-1 responds to the control signal (MPCP frame) from the OLT 1 in the sleep mode, and thus temporarily and periodically moves to the normal state. Since the temporary recovery to the normal state, the REPORT message can be sent back to the GATE message transmitted by the OLT1.

When the optical receiver 26 receives the sleep permission (Sleep_Allow) from the OLT 1, the sleep control unit 35 transmits the optical transmitter 27 and the optical receiver 26 of the optical transceiver 25 (or Only the optical transmitter 27) is moved to the control of the sleep mode of the cyclically repeated sleep state and the temporary start state. Further, the sleep control unit 39 transmits the light through the signal processing unit 35. The transmitter 27 transmits a sleep permission response (Sleep_Ack) to update the status table 38. The internal time counter 40 is also used to monitor the sleep (power saving) time.

Further, when the optical receiver 26 receives the recovery permission response (WakeUp_Ack) from the OLT 1, the transmission control unit 35 performs the optical transmitter 27 and the optical receiver for the optical transceiver 25 through the signal processing unit 35. 26 (or only the optical transmitter 27) is controlled by the sleep mode to the normal state, and the signal processing unit 35 transmits a recovery permission response (WakeUp_Ack) message from the optical transmitter 27 to update the status table 38.

Next, an example of the tedious switching of the active system trunk fiber 7-1 to the standby system trunk fiber 7-2 in the OLT 1 will be described. In this case, the trunk line detection signal that is a redundant switching condition is used, and any of the connected ONUs 2-1 to ONU2-4 is used for a certain period of time (obstacle monitoring time) using the active system wOLT1-1. An example of a light LoS alarm that is sent when an optical signal is received.

Fig. 5 is a diagram showing an example of a communication action sequence for the search process. In order to start the communication between the OLT 1 and the ONUs 2-1 to 2-4, the OLT 1 sets the logical connection by performing the search processing, and can set the required synchronization and the control function information held by the ONU 2 to perform communication in accordance with the transmission permission timing. . When the unconnected ONUs 2-1 to 2-4 are connected to the branch fiber, or when the power of the ONUs 2-1 to 2-4 in which the power is cut off is turned on, the ONUs 2-1 to 2-4 are not performed. The setting of the optical loop required for communication with OLT1. In addition, the control function information of the ONU 2 is not registered in the OLT 1, and communication cannot be performed. This state is referred to as an unregistered state. The ONUs 2-1 to 2-4 in the unregistered state are only received until they are registered (Registered) to the OLT 1, and are in a standby state from the OLT 1 until the communication is permitted.

In the fifth figure, an example in which the ONU 2-1 is reconnected is shown. The ONU 2-1 receives a newly registered GATE message (Discovery Gate) by the OLT 1 (step S1). The GATE message store stores the time of the transmission permission (the start time of the transmission permission time interval) and the amount of the transmission (when and when the number of uplink signals is better). However, if the GATE message (Discovery Gate) is being searched for, the multiple ONUs may be found at the same time. Therefore, each ONU transmits after a random standby time. When the ONU2-1 receives the GATE message (Discovery Gate), it moves to the state where the initial setting is made (exploration state). If it is moved to this state, the ONU 2-1 synchronizes the time of the self-device with the time T1 of the OLT 1 stored in the GATE message (step S2), and becomes the communication time T2 (the permission permission indicated by the GATE message) The random time is standby until the time of the random time is added (step S3). After the standby, the ONU 2-1 stores a REGISTER_REQ message storing information necessary for communication with the OLT 1 (function information held when necessary), such as identification information from the device, and transmits the message (step S4).

The OLT 1 registers the ONU 2-1 as a communication terminal based on the REGISTER_REQ message information, and calculates an RTT (Round Trip Time) with the ONU 2-1 (step S5). When the OLT 1 registers the ONU 2-1, it transmits a notification control message (REGISTER message) to the ONU 2-1 (step S6). The REGISTER message includes setting information of the communication link. When the REGISTER message has been received, the ONU 2-1 stores the setting information, and becomes a communicable state by performing necessary communication setting on the device. The ONU2-1 system moved to the REGISTER message registration state uses the stored setting information to perform data transmission and reception with the OLT1. Among them, the setting information can also Contains information about sleep mode.

When the ONU 2-1 is permitted to transmit by the GATE message (step S7), the time of the self-device is synchronized with the time T3 of the OLT 1 included in the received message (step S8), and the standby is random. After the time (step S9), a REGISTER_ACK message notifying that the communication setting has been completed is transmitted (step S10). By the above, the search processing between the OLT 1 and the ONU 2-1 is completed, and then communication between the OLT 1 and the ONU 2-1 can be performed (step S11).

Fig. 6 is a view showing an example of a sequence in the case where the active system main fiber 7-1 is in trouble. After the search processing described in FIG. 5 is completed (step S11), the OLT 1 performs band allocation on the connected ONU 2-1 for each certain GATE period Ts, and notifies the band allocation result by the GATE message (step S12, S16, S20). In Fig. 6, only ONU2-1 is connected to OLT1. The ONU 2-1 synchronizes the time of the own device with the time of the OLT 1 included in the GATE message (steps S13, S17, and S21). Next, it waits until the communication permission time notified by the GATE message (steps S14, S18), and transmits the REPORT message after the standby (steps S15, S19).

The OLT 1 uses the time counter 34 to start counting the timer (obstacle monitoring timer) for measuring the obstacle monitoring time each time the REPORT message is received as an optical signal, and if it receives the next REPORT message, it repeats A count reset is implemented and the count of the next measurement is started.

Here, as shown in FIG. 6, the ONU 2-1 receives the third GATE frame after the completion of the search processing (step S20), and after performing the time synchronization (step S21), an obstacle occurs in the active system trunk fiber 7-1. . So that is When the GATE frame is transmitted by the OLT 1 (step S23), the OLT 1 cannot receive the REPORT message from the ONU 2-1, and the obstacle monitoring timer becomes timeout to generate an optical LoS alarm (step S24).

Figure 7 is a diagram showing an example of a trunk fiber switching sequence in the event that an obstacle occurs in the active system mains fiber 7-1. In the example of Fig. 7, first, there is no obstacle in the active system trunk fiber 7-1, and in the OLT 1, it is assumed that wOLT1-1 is operating. First, ONU2-1 to ONU2-4 are connected to the OLT 1, and the search processing is completed for the ONU2-1 to ONU2-4 (step S11). The OLT 1 performs band allocation on the connected ONUs 2-1 to 2-4, and notifies the band allocation result by the GATE message (step S31). The ONUs 2-1 to 2-4 transmit the REPORT message by the communication permission time notified by the GATE message, respectively (step S32).

The OLT 1 is as shown in the example of Fig. 6, and the count of the obstacle monitoring timer is started every time the optical signal is received (step S34). If an obstacle occurs in the active system trunk fiber 7-1 (step S35), even if the OLT1 transmits the GATE message, all the ONUs 2-1 to 2-4 are not sent back to the REPORT message, and the obstacle monitoring timer becomes timed by wOLT1. The PON control unit 10 in -1 generates an optical LoS alarm (step S36).

The control unit 9 that has received the optical LoS alarm switches the operated OLT from wOLT1-1 to sOLT1-2, thereby changing the path of the main signal with the L2SW8. Thereby, the switching process of the standby system trunk fiber 7-2 by the active system trunk fiber 7-1 is implemented. After the switching time of the switching processing is performed (step S37), the sOLT 1-2 transmits a GATE message to the connected ONUs 2-1 to ONU 2-4 (step S38). ONU2-1~ONU2-4 are received separately The received GATE message returns a REPORT message (step S39). The sOLT 1-2 updates the RTT to any of the ONUs that are between the ONUs 2-1 and the ONUs 2-4 (step S40). In this way, the communication loop is maintained again using the preparatory system trunk fiber 7-2.

In the example of FIG. 7, when switching to a communication path through which the sOLT1-2, the preparatory system trunk fiber 7-2, the optical splitter 3, and the branch fibers 6-1~6-4 are connected, sOLT1- 2 The communication is started based on the setting information of the ONU2-1 to ONU2-4 acquired by the wOLT1-1 at the time of the search processing. The setting information is held in the common memory unit in the OLT 1, and can be referred to both the wOLT1-1 and the sOLT1-2. Alternatively, the wOLT1-1 can be transmitted to the sOLT1-2 through the control unit 9 at the time of switching. Further, since the RTT is likely to change depending on the switching of the communication path, the PON control unit 10 on the standby system sOLT1-2 side performs the ONU 2-1 to ONU 2-4 again after the switching. Calculation of RTT. The RTT with the other ONUs is updated based on the difference between the recalculated value and the value before the recalculation. As described above, wOLT1-1 reflects the acquired setting information to sOLT1-2, whereby the search processing when the communication path is switched to the standby system by the active system can be omitted.

As described above, the search processing, the trunk obstacle detection processing, and the communication path switching processing described in FIG. 5, FIG. 6, and FIG. 7 are the same as those of the normal PON system. In the example of Fig. 6 and Fig. 7, the light LoS alarm is used as an example of the main line obstacle detection signal, but the main line obstacle detection signal to be the switching condition is not limited thereto, and the MAC LoS alarm can be used. Can be LOBi alarms, LOS alarms, etc. However, if it is a LOBi alarm that sends an alarm for each ONU, if a LOBI alarm is sent for all ONUs At the time, the switching of the communication path is implemented.

Next, the problem when both the power saving control and the obstacle detection of the ONUs 2-1 to 2-4 are performed will be described. Fig. 8 is a view showing an example of a communication operation sequence when a failure occurs in a normal operation by a conventional communication path switching method. Mainly during nighttime, when the user does not use the communication service, the full ONUs 2-1 to 2-4 connected to the OLT 1 temporarily move to the sleep (power saving) mode. In the eighth drawing, an example in which the OLT 1 operates in accordance with the conventional communication path switching method is shown.

Similarly to the example of Fig. 7, after the search processing (step S11), the OLT 1 performs band allocation on the connected ONUs 2-1 to 2-4, and notifies the band allocation result by the GATE message (step S31). . The ONUs 2-1 to 2-4 respectively transmit REPORT messages at the time of the transmission permission notified by the GATE message (step S32).

When the OLT1 does not receive and send data between the ONUs 2-1 and 2-4, and decides to move the ONUs 2-1 to 2-4 to the sleep mode, the sleep (power saving state) transfer permission (Sleep_Allow) is transmitted to ONU2-1~2-4 (step S42). The ONU2-1~2-4 pairs Sleep_Allow, and send back a response signal (Sleep_Ack) indicating that they respectively move to the sleep mode (step S43), and move to the sleep mode.

At this time, when viewed from the OLT 1 side, the state in which the optical signals from all of the ONUs 2-1 to 2-4 and the control signal response are not received is formed. The obstacle monitoring timer which is counted by the last REPORT message reception (step S41) is timed out, and an optical LoS alarm is generated (step S44). Next, similarly to Fig. 7, the communication path is switched (step S45).

As described above, in the conventional communication path switching method, if all of the ONUs 2-1 to 2-4 are moved to the sleep mode, even in the case where an obstacle other than the optical transmission path occurs, it is erroneously determined to be in the active system. The trunk fiber has an obstacle, and is switched from the active system trunk fiber 7-1 to the standby system trunk fiber 7-2.

Further, when the OLT 1 is a trunk barrier, as described above, it is necessary to switch the communication path. However, if it is a branch line barrier, the communication path may not be switched. If the connected ONU2-1 to ONU2-4 are plural, it is determined whether or not the ONU2-1 to ONU2-4 are not responding, and all ONUs are not responding (the optical signal is not received). However, when there is only one ONU2-1~2-4 that is not in the normal state of the sleep mode, if the ONU or the branch line connected to the ONU has an obstacle, the OLT1 is all ONU2-1~2. -4 did not receive the optical signal. In the OLT 1, at this time, the trunk barrier and the branch line barrier are not distinguished, and in the case where the branch line barrier that does not require the switching of the communication path is originally required, the switching of the communication path is also performed, and there is also a problem that unnecessary communication interruption occurs. .

Therefore, in the present embodiment, as described below, the state management table 33 is used in the OLT 1 to manage the state of each of the ONUs 2-1 to 2-4 (whether it is the sleep mode), and the ONUs 2-1 to 2-4 When all are in the sleep mode, the communication path switching is not performed even if the LoS alarm or the like that is the communication path switching condition is not sent or the LoS alarm is issued. In addition, when the sleep mode is controlled in such a manner that the number of ONUs 2-1 to 2-4 that are not in the sleep mode is one or more, erroneous detection of the trunk obstacle can be prevented. In addition, by controlling the sleep mode by setting the number of ONUs 2-1 to 2-4 that are not in the sleep mode to two or more, the trunk obstacle and the branch line obstacle can be distinguished. Among them, the following is a description When all of the ONUs 2-1 to 2-4 are in the sleep mode, the number of ONUs 2-1 to 2-4 that are not in the sleep mode is set to two or more (or one). The above two examples of the control, but only one of them may be implemented.

In order to distinguish between the trunk line and the branch line, it is necessary to set the number of ONUs 2-1 to 2-4 that are in the sleep mode to two or more. However, in order to prevent the erroneous detection of the trunk line, the ONU 2-1 is in the sleep mode. The number of ~2-4 can also be one or more. Therefore, if it is intended to prevent erroneous detection of a trunk line, it is sufficient to set one or more ONUs 2-1 to 2-4 which are simultaneously in the sleep mode.

The operation of the OLT 1 using the state management table 33 will be described in detail below. Fig. 9 is a flow chart showing an example of the basic control of the OLT 1, and Fig. 10 is a flow chart showing an example of the power saving control of the OLT 1.

As shown in FIG. 9, in the OLT 1, the signal processing unit 30 performs the search processing as the initial setting (step S51), and if the search processing is completed, the bandwidth allocation is performed to the ONUs 2-1 to 2-4 in which the search processing has been completed. The GATE message (Gate Frame) notifies the ONUs 2-1 to 2-4 (step S52). Further, when the signal processing unit receives the signal from the ONUs 3-1 to 2-4, the data processing unit performs data processing on the received signal processing (step S53). Further, the sleep control signal processing unit 32 of the OLT 1 performs power saving control on the ONUs 2-1 to 2-4 (step S54). Furthermore, the PON control unit 10 of the OLT 1 performs obstacle monitoring such as the above-described optical LoS detection (step S55). Then, steps S52 to S55 are repeated. However, the order in steps S52 to S55 is not limited thereto, and the order of processing may be different, and two or more of the processes may be simultaneously performed.

Fig. 10 shows the details of the band allocation in the above step S52 and the power saving control in step S54. After the initial setting (step S61), the OLT 1 performs band allocation, and the ONU2-1~2-4 is performed by the GATE message. Notification is made (step S62). The OLT 1 receives the REPORT message (Report Frame) from the ONUs 2-1 to 2-4 (step S63), and determines whether there is a transmission buffer amount (the transmission buffer) stored in the ONUs 2-1 to 2-4 of the REPORT message. The accumulated amount of 23) (whether or not it is a certain amount or more) (step S64). If there is a message buffer amount (YES in step S64), the process returns to step S62.

When there is no transmission buffer amount (step S64 No), the OLT 1 refers to the status table 33 (step S65). Fig. 11 is a diagram showing an example of the state management table 33. As shown in Fig. 11, the status management table 33 stores the identification numbers of the ONUs 2-1 to 2-4 for each ONU 2-1 to 2-4 (in this case, ONU2-i (i = 1, 2, 3) The identification number of 4) is set to ONU#i); the information indicating that the ONU is in the sleep mode or the normal state (active: Active) is the state (State); indicating whether the alarm of each ONU is masked (mask) The information is also the alarm (Alarm); the switching trigger signal; the starting time (the starting time of the sleep mode when in the sleep mode); and the recovery time (the recovery time by the sleep mode when in the sleep mode). The trigger trigger signal indicates that the trigger signal for switching the communication path when the alarm is not masked, and the monitoring of the example of Fig. 11 means the monitoring of the alarm. When the alarm is generated, it means that the switching process is immediately performed.

After the moment of exploration, the state of each connected ONU2-1~2-4 is all normal, and the alarm is not obscured. Next, the OLT 1 is for each ONU 2-1 to 2-4, and when the ONU 2-1 to 2-4 receives the response indicating that the transition to the sleep mode, that is, Sleep_Ack, the ONU 2-1 that has received the Sleep_Ack ~2-4, the state management table 33 is updated to the sleep mode (Sleep), and the start time and the recovery time are updated. However, regarding the start time and the recovery time, the OLT 1 grasps the Sleep_Request message for the ONUs 2-1 to 2-4, and therefore updates based on the information. Further, the OLT 1 instructs the OLTs 2-1 to 2-4 to resume the sleep mode, and when receiving the response, the state management table 33 is updated so as to be in the same state as the instant of the search processing. If the ONU2-1~2-4 in the sleep mode is transmitted and the request is restored to the normal state due to the occurrence of the transmission data, the status management table 33 is also subjected to the search processing when the recovery request is received. The same state is updated in an instant. Here, the eleventh figure shows an example of the state management table 33, and the items of the state management table 33 are not limited to these. If it contains at least the information of whether ONU2-1~2-4 is in sleep mode.

Return to the description in Figure 10. The OLT 1 determines whether or not the ONUs 2-1 to 2-4 in the active state are three or more based on the state table 33 (step S66). If not three or more (step S66 No), the process returns to step S62. When the ONUs 2-1 to 2-4 in the active state are two or less, if the ONUs 2-1 to 2-4 determined to have no transmission buffer amount in step S64 are moved to the sleep mode, the active ONU2 1~2-4 becomes one or less. Therefore, when the number of ONUs 2-1 to 2-4 in the active state is two or less, the ONUs 2-1 to 2-4 that do not have the amount of the transmission buffer are not moved to the sleep mode.

When there are three or more ONUs 2-1 to 2-4 in the active state (YES in step S66), the OLT 1 performs power saving control for shifting the ONUs 2-1 to 2-4 having no transmission buffer amount to the sleep mode. Determining the start and end times of the sleep mode of the ONU (step S67), and transmitting Sleep_Allow to the ONU Step S68). Thereafter, it is judged whether or not the Sleep_Ack has been received by the ONU (step S69), and if it has been received (YES in step S69), the state management table 33 is updated (step S70), and the process returns to step S62. If the Sleep_Ack is not received (step S69 No), the process returns directly to step S62 as it is.

If it is determined that there is no transmission buffer amount for the plurality of ONUs 2-1 to 2-4 at the same time, the ONU (the standby ONU) may not be all moved to the sleep mode, and the standby ONU may be stopped. When the ONUs 2-1 to 2-4 that have become the sleep mode are shifted to the sleep mode, two or more active controls are frequently performed.

Further, in the present embodiment, whether or not the sleep mode is managed as the ONU is controlled, and all the ONUs are not controlled to be in the sleep mode at the same time. However, the periodic power-saving state in the sleep mode may also be considered. In the temporary starting state, the power saving state or the temporary starting state is also managed, and the power saving state is controlled so that all the ONUs do not overlap.

Next, the communication path switching processing in the OLT 1 of the present embodiment will be described in detail. In the present embodiment, in order to prevent erroneous detection of the trunk obstacle, if all the ONUs are in the sleep mode, the control for not switching the communication path is performed. However, various variations are considered in the control method. For example, there is also a method in which if all the ONUs are in the sleep mode, even if the signals are not received by the ONUs 2-1 to 2-4 during the period of the obstacle monitoring time or longer, the trunk line detection signals such as the optical LoS alarms do not occur. In addition, there is also a method of replacing the main line obstacle detection signal such as the light LoS alarm, and if all the ONUs are in the sleep mode, the count of the obstacle monitoring timer is periodically reset (before expiration), and the obstacle monitoring timing is performed. The device will not expire. In addition, there is also a method even if it is issued The main line obstacle detection signal such as the raw light LoS alarm, if all the ONUs are in the sleep mode, the communication path switching process is not performed. Among these methods or methods other than these, although any method can be implemented, it is described that even if a trunk line detection signal such as an optical LoS alarm occurs, if all the ONUs are in the sleep mode, the communication path is not implemented. An example of a method of switching processing. In other words, in the present embodiment, the control unit 9 does not immediately perform communication path switching (duplicate switching) even when receiving the light LoS alarm, and performs communication path switching after receiving the Holdover signal indicating switching.

Fig. 12 is a flow chart showing an example of the communication path switching procedure in the embodiment. The PON control unit 10 of the OLT 1 performs band allocation, and notifies the ONUs 2-1 to 2-4 by the GATE message (step S71). Next, the counting of the obstacle monitoring timer is started (step S72). Next, in response to the GATE message, it is judged whether or not the REPORT message has been received (step S73), and if it has been received (YES in step S73), the process returns to step S71, and after the GATE message is transmitted, the obstacle monitoring is started again. The count of the timer.

Here, an example of starting the count of the obstacle watchdog timer when the GATE message is transmitted will be described here. The monitoring system for the obstacle time by the obstacle monitoring timer can monitor whether the response signal that should be received has been received within a certain period of time, and therefore, the signal requesting the response signal can also be obtained as shown in the example of FIG. The transmission (in this case, the GATE message) is set to the start of counting, and as shown in Fig. 6, etc., the counting is started when the response signal received in a predetermined period has been received. When the counting is started at the time when the response signal has been received, the process proceeds to step S72 when the REPORT message has been received (YES in step S73), and the process returns to step S71 via step S72.

When the REPORT message has not been received (step S73 No), the PON control unit 10 determines whether or not the count of the obstacle watchdog timer has expired (step S74), and if not, returns to step S73 (step S74 No). Here, the description of the MAC LoS is detected as an example of the detection of the trunk obstacle. However, if the optical LoS is detected, it is determined whether a valid optical signal has been received, instead of whether the REPORT message has been received.

When the count of the obstacle monitoring timer has expired (YES in step S74), the PON control unit 10 issues an alarm (Report Alarm) indicating that the trunk obstacle such as the light LoS has been detected (step S75), and updates the state management table 33 (step S76). Specifically, the field of the alarm of the status management table 33 is updated to information indicating that an alarm is occurring. Next, the PON control unit 10 refers to the state management table 33 (step S77), determines whether one or more ONUs are active (step S78), and if one or more ONUs are active (step S78 Yes), transmits the Holdover signal to Control unit 9 (step S79). However, in the case where the control unit 9 is not included, the Holdover signal is transmitted to the PON control unit 10 of the sOLT 1-2.

The control unit 9 that has received the Holdover signal transmits a redundant switching notification instructing to switch the communication path switching to the standby system to the sOLT 1-2 (step S80). Thereby, the OLT 1 performs redundant switching, and the recalculation of the RTT is performed by the sOLT 1-2 (step S81), and the process returns to step S71.

When it is determined in step S78 that all of the ONUs are not active (step S78 No), the ONUs 2-1 to 2-4 of the sleep mode are determined to mask an alarm (LOBi or the like) of each ONU (step S82). The state management table 33 is updated in such a manner that the alarms of the ONUs 2-1 to 2-4 in the sleep mode are masked (step S83), and the process returns to step S71. The so-called alerting of each ONU means, for example, even The obstacle detection is performed for each ONU, and the processing corresponding to the detection result is not performed. However, in the state management table 33, the process of masking the alarm of each ONU may be performed when the ONUs are moved to the sleep mode.

Wherein, if the number of times that the predicted frame of the LOBi or the LOS is not received is counted to perform the obstacle detection, if the number of times the predicted frame is unreceived is a constant In place of the above-described obstacle monitoring timer to determine whether or not the obstacle monitoring time has elapsed, the same communication path switching process can be performed.

In addition, as shown in the description of Fig. 11, in the present embodiment, two or more ONUs 2-1 to 2-4 are controlled to be active, and thus the branch line (or ONU) is mistaken as a trunk obstacle. The possibility of testing can be greatly reduced.

Fig. 13 is a view showing an example of a sequence when the communication path switching method in the OLT 1 of the present invention is implemented. In the example of Fig. 13, it is shown that the ONUs 2-1 to 2-4 which are simultaneously active are not controlled to be two or more, and the same control as the conventional control is performed for the power saving control. The wOLT1-1 and ONU2-1~2-4 of the OLT1 are the same as the example of FIG. 8, and perform GATE message transmission (step S31), REPORT message transmission (step S32), Sleep_Allow transmission (step S42), and Sleep_Ack. The message is sent (step S43). Next, when receiving the Sleep_Ack, the PON control unit 10 of the wOLT 1-1 updates the state management table 33 as described above (step S85).

When the PON control unit 10 of the wOLT 1-1 receives the REPORT frame, the count of the obstacle monitoring timer is started (step S41), and all of the ONUs 2-1 to 2-4 are moved to the sleep mode, so that the obstacle monitoring timer expires. Generated The alarm for the line obstacle detection (step S44). In the present embodiment, as shown in the description of Fig. 12, even if an alarm for the detection of the trunk obstacle is generated, the PON control unit 10 of the wOLT1-1 refers to the state management table 33, and it is understood that all the ONUs 2-1 to 2-4 are in the sleep state. Mode, so lengthy switching is not implemented. As a result, in the ONUs 2-1 to 2-4 that have been restored by the sleep mode, the GATE frame is transmitted by the wOLT 1-1 as in the case of the alarm occurrence (step S31a). As described above, in the present embodiment, it is possible to prevent unnecessary redundant switching due to erroneous detection of the trunk obstacle.

Fig. 14 is a view showing an example of a sequence in the case where power saving control is performed in the OLT 1 of the present embodiment. Fig. 14 shows an example in which all of the ONUs 2-1 to 2-4 have no transmission buffer amount, and all of the ONUs 2-1 to 2-4 can be moved to the sleep mode. In the above-described example, the ONUs 2-1 to 2-4 are moved to the sleep mode almost at the same time. Therefore, all of the ONUs 2-1 to 2-4 are in the sleep mode. However, in the present embodiment, In the transmission, the ONUs 2-1 to 2-4 which are simultaneously active are set to two or more Sleep_Allow transmissions (step S42). Next, when the OLT 1 receives the Sleep_Ack (step S43), the OLT 1 updates the state management table 33 (step S85). Specifically, in the example of FIG. 14, considering the fairness of the power saving effect, the ONU2-1~2-4 is used to shift the time to move to the sleep mode by the round-robin method. Control is performed by setting the number of active ONUs 2-1 to 2-4 to two or more. In addition, the method of determining the start time of the sleep mode of each of the ONUs 2-1 to 2-4 in which the active ONUs 2-1 to 2-4 are simultaneously set to two or more is not limited to the example of FIG.

In addition, in the example of Fig. 12, if the number of active ONUs 2-1 to 2-4 is three or less, the new ONUs 2-1 to 2-4 may not be moved to the sleep mode, but if the new ONU 2-1 is made When ~2-4 is moved to sleep mode, it is moved to sleep mode. The ONU2-1~2-4 is temporarily restored to the normal state or the end time of the sleep mode is shifted to perform the control as shown in FIG. In other words, the ONUs 2-1 to 2-4 that have been formed into the sleep mode and the ONUs 2-1 to 2-4 that have been re-shifted to the sleep mode can be made to have two or more staggered sleep times as shown in FIG. For the control of the event.

Next, the power saving control in the ONUs 2-1 to 2-4 will be described. Fig. 15-1 and Fig. 15-2 show an example of the power saving control sequence in the ONUs 2-1 to 2-4. The PON control unit 20 of the ONUs 2-1 to 2-4 first performs initial setting (exploration) processing (step S91). If the frame is received by the OLT 1 (step S92), it is determined whether the received frame is a GATE message (step S93), if it is not a GATE message (that is, a data frame) (Step S93 No), the data frame is received (step S94), and the type of the data is discriminated (step S95).

Next, it is determined whether the received frame is Sleep_Allow (step S96), and if it is Sleep_Allow (step S96 is Yes), the PON control unit 20 refers to the amount of the transmission buffer (the accumulation amount of the transmission buffer 23) (step S97), it is judged whether there is a transmission buffer amount (step S98). If there is no transmission buffer amount (step S98 No), Sleep_Ack is returned (step S99). Next, the PON control unit 20 starts a timer (Sleep_Timer) for measuring the sleep time of the primary power saving state in the sleep mode (step S100), and causes the optical transmitter 27 (or optical transmitter). 27 and the optical receiver 26) shift to the power saving state (Sleep_Duration) (step S101). The PON control unit 20 determines whether the count of the Sleep_Timer has expired (step S102), and if it has expired (YES in step S102), the optical transmitter 27 (or the optical transmitter 27 and the optical receiver 26) is enabled. Temporarily moved to the startup state (step S103).

Next, the PON control unit 20 receives the GATE message (step S104), and refers to the amount of the transmission buffer (step S105), and determines whether or not there is a transmission buffer amount (step S106). If there is no transmission buffer amount (step S106 No), the amount of the transmission buffer (in this case, the value indicating that there is no transmission buffer amount) is input to the REPORT message (step S107), and the REPORT message is transmitted (step S108). And it returns to step S101.

If it is determined in step S96 that it is not Sleep_Allow (step S96 No), predetermined data processing is performed on the received data (step S109), and the process returns to step S92. When it is determined in step S98 that there is a transmission buffer amount (YES in step S98), Sleep_Ack (Wakeup) is returned (step S110). Sleep_Ack (Wakeup) is different from the above-mentioned Sleep_Ack that promises to move to the sleep mode, and is a frame that is required to return to the normal state. Next, the REPORT message and the data frame are transmitted (step S111), and the process returns to step S92.

If it is a GATE message in step S93 (YES in step S93), the GATE message is received (step S112), and the amount of the transmission buffer is referred to (REFERENT S113), and the amount of the transmission buffer is input to the REPORT message (step S114). Next, after the standby to the transmission permission time (step S115), the REPORT message is transmitted (step S116), and the process returns to step S92.

Further, if there is a transmission buffer amount in step S106 (YES in step S106), the PON control unit 20 returns the Sleep_Ack (Wakeup) (step S117), and transmits the REPORT message and the data frame (step S118). The process returns to step S92.

In addition, in the above description, the optical splitter is one, and the branch line is In one stage, but also considering that the optical splitter is set to multiple stages, the branch line becomes a multi-stage configuration. Fig. 16 is a view showing an example of a configuration in which the branch line is multi-stage. The OLT1 and the active system trunk fiber 7-1 and the preparatory system trunk fiber 7-2 are the same as the example of Fig. 2, but in the example of Fig. 16, the optical splitter 3-1 and the second segment are formed as the first segment. The two-stage configuration of the optical splitters 3-2 and 3-3 of the segment. The optical splitter 3-1 is connected to the active system trunk fiber 7-1 and the preparatory system trunk fiber 7-2, and the optical splitters 3-2 and 3-3 are respectively connected to the branch fibers 6-1 and 6-2. connection. The optical splitter 3-2 is connected to the optical splitter 3-1 by the branch fiber 6-1, and is connected to the ONUs 2-1 to 2-4 by the respective branches, and the optical splitter 3-3 is borrowed. It is connected to the optical splitter 3-1 by the branch fiber 6-2, and is connected to the ONUs 2-5 to 2-8 by the respective branches. Here, the branch lines of the first stage, that is, the branch fibers 6-1 and 6-2, are set to the branch line #1, and the branch lines connecting the optical splitters 3-2, 3-3 and the ONUs 2-1 to 2-8 are set. Branch line #2.

In the case of a multi-stage configuration as shown in Fig. 16, when two or more ONUs that are active at the same time are ONUs connected to the same branch line #1 (for example, when ONU2-1 and ONU2-2 are active) ), it is impossible to distinguish between the obstacle of the branch line #1 or the trunk line obstacle. Therefore, in the case of the above, the OLT 1 first becomes an active ONU to become an ONU connected to a different branch line #1 by first holding information on whether or not each ONU is an ONU connected to any branch line #1. The way to control is appropriate. For example, as shown in Fig. 16, the ONU 2-1 connected to the branch fiber 6-1 and the ONU 2-6 connected to the branch fiber 6-2 are made active.

As described above, in the present embodiment, the OLT 1 manages the power saving states of the ONUs 2-1 to 2-4 using the state management table 33, and uses the state management table 33. To determine whether to implement a lengthy switch. Therefore, unnecessary lengthy switching due to erroneous detection of the trunk obstacle can be prevented. In addition, power saving control is performed so that the number of ONUs 2-1 to 2-4 that are simultaneously active is two or more, whereby the determination of the branch line obstacle and the trunk line obstacle can be performed.

[Industrial Availability]

As described above, the optical transmission system, the office side optical terminal apparatus, and the communication loop switching method of the present invention are PON systems for making the OLT redundant, and are particularly suitable for the PON system for performing power saving control.

1-1‧‧‧wOLT

10‧‧‧PON Control Department

11‧‧‧ Physical Layer Processing Department

12‧‧‧WDM coupler

13‧‧‧Send buffer

14‧‧‧ Receiving buffer

15‧‧‧Light Receiver

16‧‧‧Light Receiver

17‧‧‧Optical Transmitter

18‧‧‧Receipt Department

19‧‧‧Delivery Department

30‧‧‧Signal Processing Department

31‧‧‧Buffer Monitoring Department

32‧‧‧Sleep Control Signal Processing Department

33‧‧‧Status Management Table

34‧‧‧Time counter

Claims (18)

An optical transmission system comprising: a subscriber-side optical terminal device that can be moved to a power-saving mode; a central-side optical terminal device; and is connected to the central-side optical terminal device by a redundant trunk, and by a light splitter connected to the aforementioned subscriber-side optical terminal device, wherein the office-side optical terminal device manages information about a power-saving mode of the subscriber-side optical terminal device, that is, power-saving information, according to The aforementioned power saving information controls the lengthy switching of the aforementioned trunk lines. The optical transmission system of claim 1, wherein the office-side optical terminal device includes state information indicating whether the subscriber-side optical terminal device is in a power-saving mode for each of the subscriber-side optical terminal devices. The power saving information is used to determine whether the subscriber side optical terminal device is in the power saving mode based on the status information, and determine whether to implement the trunk according to the response signal from the subscriber side optical terminal device that is not in the power saving mode. The redundant switching determines that the response signal of the subscriber-side optical terminal device from the power saving mode is not used in the implementation of the redundant switching of the trunk. The optical transmission system of claim 2, wherein the office-side optical terminal device receives, by the participant-side optical terminal device, a notification indicating that the subscriber-side optical terminal device moves to a power-saving mode, according to The notification updates the status information, and when the subscriber-side optical terminal device receives the notification that the subscriber-side optical terminal device is restored to the normal mode by the power-saving mode, the status information is updated based on the notification. The optical transmission system of claim 2, wherein the office-side optical terminal device transmits a power-off notification to the power-off notification device when the power-on notification is received by the subscriber-side optical terminal device The state information corresponding to the subscriber side optical terminal device is updated to a value indicated as a power saving mode. The optical transmission system of claim 3, wherein the office-side optical terminal device transmits a power-off notification to the power-off notification when the subscriber-side optical terminal device receives the power-off notification The state information corresponding to the subscriber side optical terminal device is updated to a value indicated as a power saving mode. The optical transmission system according to any one of claims 1 to 5, wherein the office-side optical terminal device performs the foregoing if the aforementioned subscriber-side optical terminal device does not receive the predetermined obstacle detection time In the obstacle detection processing for detecting the signal in response to the signal, the subscriber-side optical terminal device in the power saving mode does not detect the response signal when the response signal is not received within the predetermined obstacle detection time. The optical transmission system according to any one of claims 1 to 5, wherein the office-side optical terminal device is configured to be received by any of the aforementioned subscriber-side optical terminal devices within a predetermined obstacle detection time. In the trunk line detection processing for detecting the trunk signal as the trunk obstacle, when all of the subscriber side optical terminal devices are originally in the power saving mode, if the response signal is not received within the predetermined obstacle detection time, the response signal is not The above-mentioned trunk obstacles are detected. The optical transmission system of claim 6, wherein the side light is The terminal device is configured to perform a trunk obstacle detection process that is detected as a trunk obstacle when any of the subscriber-side optical terminal devices does not receive the response signal within a predetermined obstacle detection time, and all of the subscriber-side optical terminal devices In the original power saving mode, if the response signal is not received within the predetermined obstacle detection time, the detection is not performed as the trunk obstacle. The optical transmission system according to any one of claims 1 to 5, wherein the office-side optical terminal device is configured to be received by any of the aforementioned subscriber-side optical terminal devices within a predetermined obstacle detection time. In the trunk line detecting process for detecting the trunk signal as the trunk line error, when all of the subscriber side optical terminal devices are originally in the power saving mode, even if the trunk line obstacle is detected, the redundant switching of the trunk line is not performed. The optical transmission system of claim 6, wherein the office-side optical terminal device is configured to perform, when any of the aforementioned subscriber-side optical terminal devices does not receive the response signal within a predetermined obstacle detection time, as a trunk In the trunk line detection processing for detecting the obstacle, when all of the subscriber-side optical terminal devices are originally in the power saving mode, even if the trunk barrier is detected, the redundant switching of the trunk is not performed. The optical transmission system according to any one of claims 1 to 5, wherein the office-side optical terminal device controls power saving in the subscriber-side optical terminal device for each of the aforementioned subscriber-side optical terminal devices In the start and end time of the mode, the start and end time are managed as the power saving information, and one or more of the subscriber side optical terminal devices that are not in the power saving mode are determined, and each of the subscriber side is determined. The aforementioned opening of the optical terminal device The start and end times determine whether or not to perform the redundant switching of the trunk line based on the response signal from the subscriber-side optical terminal device that is not in the power saving mode. The optical transmission system of claim 6, wherein the office-side optical terminal device controls the start and end times of the power saving mode in the subscriber-side optical terminal device for each of the subscriber-side optical terminal devices The start and end times are managed as the power saving information, and the number of the subscriber-side optical terminal devices that are not in the power saving mode is one or more, and the start of each of the subscriber-side optical terminal devices is determined. And the end time, based on the response signal from the subscriber-side optical terminal device that is not in the power saving mode, whether or not to perform the redundant switching of the trunk line is determined. The optical transmission system of claim 8, wherein the office-side optical terminal device controls the start and end times of the power saving mode in the subscriber-side optical terminal device for each of the subscriber-side optical terminal devices The start and end times are managed as the power saving information, and the number of the subscriber-side optical terminal devices that are not in the power saving mode is one or more, and the start of each of the subscriber-side optical terminal devices is determined. And the end time, based on the response signal from the subscriber-side optical terminal device that is not in the power saving mode, whether or not to perform the redundant switching of the trunk line is determined. The optical transmission system of claim 10, wherein the office-side optical terminal device controls the start and end times of the power saving mode in the subscriber-side optical terminal device for each of the subscriber-side optical terminal devices The start and end times are managed as the power saving information, and one or more of the subscriber side optical terminal devices that are not in the power saving mode exist. The method determines the start and end time of each of the subscriber-side optical terminal devices, and determines whether or not to perform the redundant switching of the trunk line based on the response signal from the subscriber-side optical terminal device that is not in the power-saving mode. The optical transmission system of claim 11, wherein two or more of the subscriber-side optical terminal devices that are not in the power saving mode are used, and the start and end of each of the subscriber-side optical terminal devices are determined. time. The optical transmission system according to any one of claims 2 to 5, wherein the response signal is set as a response signal to the frequency band allocation notification. A central-side optical terminal device is connected to a subscriber-side optical terminal device that can be moved to a power-saving mode via an optical splitter, wherein a trunk line between the optical splitter and the optical splitter is redundant, respectively, by a branch line And connecting to the optical splitter, and comprising: managing information about a power saving mode of the subscriber side optical terminal device, that is, power saving information, and controlling the redundant switching PON control unit according to the power saving information. . A communication loop switching method includes: a subscriber-side optical terminal device that can be moved to a power-saving mode; a central-side optical terminal device; and is connected to the central-side optical terminal device by a redundant trunk, and respectively borrows A communication loop switching method in an optical transmission system of an optical splitter connected to the aforementioned subscriber-side optical terminal device by a branch line, characterized by comprising: a management step of managing the side-side optical terminal device with respect to the subscriber side Power saving information of the power saving mode of the optical terminal device; and The switching step is to control the lengthy switching of the trunk line according to the foregoing power saving information.