JP2018182640A - Pon system and transmission method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve band efficiency and power saving if an ONU which does not communicate data for a constant period is generated in a heterogeneous network.SOLUTION: In a PON system, an ONU 18 includes a function to change over between a normal state, which supplies power to a transmitter or a receiver, and a sleep state which halts power supply to the transmitter or the receiver. On receiving a sleep start instruction from an OLT 14, or on receiving, after sending a sleep request to the OLT 14, a sleep start instruction from the OLT 14 as a response, the transmitter and the receiver are set to be the sleep state, and after the transmitter and the receiver are set to be the sleep state, the receiver is made to the normal state only during a period of receiving a common control signal which the OLT 14 transmits to all subordinate ONUs, whereas the sleep state of the transmitter is continued until data transmission becomes necessary.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a PON (Passive Optical Network) system and transmission method in which an optical line terminal (OLT) and a plurality of ONUs (Optical Network Units) are connected via an optical splitter to realize optical fiber transmission.

  Recently, the 5 G and millimeter wave band base stations have been miniaturized, and it is assumed that the configuration of the base stations will be heterogeneous networks in the future. In a C-Plane / U-Plane separation type heterogeneous network, it is known that PON (TDM-PON) is cost-effective in order to accommodate a small cell base station efficiently. However, in each small cell, it is assumed that there are often no users because the cell radius is short. Therefore, it is required to reduce unnecessary communication and power.

  In order to reduce unnecessary communication and power, Patent Document 1 discloses a technology of determining a stop time from the amount of communication data and stopping a communication device for a determined time. Further, Patent Document 2 discloses a technique for changing at least one of a sleep time for putting an ONU in a sleep state and a sleep transition threshold for putting an ONU in a sleep state. Further, according to Patent Document 3, the ONU monitors an SD (Signal Detect) signal indicating a light reception state from the OLT side optical transceiver, and detects a pulse generated along with the extinction and light emission operation of the OLT on the SD signal. At the time, a technique for releasing the sleep state is disclosed.

  In addition, according to the patent document 4, the low consumption of the conventional ONU is obtained for the low priority data by changing the queue length and the low power consumption mode threshold according to the communication volume data for each user and for each priority. A technique is disclosed that keeps the low power consumption mode for a longer period than the power mode, while making the delay time shorter for high priority data. Further, according to Patent Document 5, by notifying the upstream node located further upstream of the OLT from the OLT when the ONU is not sleeping, the data stored in the OLT until the ONU recovers from sleep is Techniques for reducing the amount are disclosed.

  Moreover, FIGS. 13-15 is a figure which shows the outline | summary of the technique described in the nonpatent literature 1. FIG. In Non-Patent Document 1, as a standardization technology, a OLT transmits a Sleep message to an ONU for a certain period of time, and the ONU is for the time shown in the Sleep message for the transmitter Tx and the receiver Rx (or only the transmitter Tx). The technology to stop) is disclosed. Thus, the ONU can save power only during the polling cycle.

JP, 2016-158220, A JP, 2016-149662, A JP, 2016-058806, A JP, 2016-015664, A JP, 2015-142300, A

  However, in the prior art, while Tx / Tx Rx (that is, the power of the ONU) is turned off while data is not transmitted / received within the PON polling cycle, bandwidth efficiency can be achieved even if power saving can be achieved. It is difficult to improve. Therefore, data is transmitted and received as to other ONUs that do not need data communication for a long time as in the other ONUs, and bandwidth efficiency and power are wasted.

  The present invention has been made in view of such circumstances, and in a heterogeneous network, even if an ONU (small cell) which does not communicate data for a fixed period is generated, it is possible to achieve band efficiency and power saving. An object of the present invention is to provide a PON system and a transmission method.

  (1) In order to achieve the above object, the present invention takes the following measures. That is, the PON system of the present invention is a PON (Passive Optical Network) system in which an OLT (Optical Line Terminal) and a plurality of ONUs (Optical Network Units) are connected via an optical splitter to realize optical fiber transmission. The ONU has a function of switching between a normal state in which power is supplied to a transmitter or receiver and a sleep state in which power supply to the transmitter or receiver is stopped, and a sleep start instruction from the OLT Or the transmitter and the receiver are put into the sleep state, and the transmitter and the receiver are After being put to sleep state, the OLT sends a synchronization maintenance and return message transmission time to all ONUs under its control. The receiver may be in a normal state only during a period of receiving a common control signal to be received, while continuing the sleep state of the transmitter until it becomes necessary to transmit data.

  As described above, when the ONU issues a sleep start instruction from the OLT or sends a sleep request to the OLT and then receives a sleep start instruction from the OLT as a response, the ONU puts the transmitter and the receiver in the sleep state. After putting the transmitter and receiver in the sleep state, the receiver should be in the normal state only during the period when the OLT receives the common control signal to transmit to all subordinate ONUs, while the data needs to be transmitted. Since the transmitter continues to be in the sleep state, it can be in the sleep state for a longer time than in the past. In particular, the receiver sleeps in a period other than the period in which the common control signal is received, which makes it possible to achieve band efficiency. In addition, since the transmitter is in the sleep state until it becomes necessary to transmit data, it does not perform the LD light emission operation which is the largest power consumption, and power saving is remarkable. In addition, power saving can be achieved on the receiving side as well, except when receiving the common control signal.

  (2) Further, in the PON system of the present invention, the OLT transmits a Gate message including the sleep start instruction to the ONU to be put into the sleep state.

  As described above, since the OLT transmits a Gate message including a sleep start instruction to the ONU to be put to sleep, the ONU can be put to sleep whenever communication is unnecessary. As a result, it is possible to achieve bandwidth efficiency and power saving.

  (3) In the PON system of the present invention, the OLT releases the sleep state to the normal state in the sleep state when downstream traffic to the sleep state ONU is generated. Sending a Gate message including a return instruction to return to and transmitting data to an ONU as a transmission destination of the Gate message including the return instruction.

  As described above, since the OLT releases the sleep state of the ONU and transmits data when downstream traffic to the ONU in the sleep state occurs, switching between the normal state and the sleep state whenever necessary. Is possible. As a result, it is possible to achieve bandwidth efficiency and power saving.

  (4) In the PON system according to the present invention, when the ONU in the sleep state receives a Gate message including the return instruction from the OLT, the ONU transmits a return notification to the OLT and the sleep. It is characterized by switching from the state to the normal state.

  As described above, when the ONU in the sleep state receives a Gate message including a return instruction from the OLT, it sends a return notification to the OLT and switches from the sleep state to the normal state. It is possible to switch between the state and the sleep state. As a result, it is possible to achieve bandwidth efficiency and power saving.

  (5) Further, in the PON system of the present invention, the ONU transmits a Report including a return notification for releasing the sleep state and returning to the normal state when upstream traffic to the OLT is generated in the sleep state. Data is transmitted to the OLT in response to the common control signal received from the OLT.

  Thus, when upstream traffic to the OLT is generated in the sleep state, the ONU responds to the common control signal received from the OLT by transmitting a Report including a return notification for releasing the sleep state and returning to the normal state. Since data is sent to the OLT, it is possible to switch between the normal state and the sleep state whenever necessary. As a result, it is possible to achieve bandwidth efficiency and power saving.

  (6) Further, in the PON system according to the present invention, the OLT adds, to the common control signal, information instructing a timing of transmitting a report including the return notification when there are a plurality of ONUs in the sleep state. The ONU having the upstream traffic transmits the Report including the return notification to the OLT at the instructed timing.

  As described above, when there are a plurality of ONUs in the sleep state, the OLT adds, to the common control signal, information indicating a timing for transmitting a report including a return notification, and the ONU in which upstream traffic occurs is restored. Since the Report including the notification is sent to the OLT at the instructed timing, it is possible to prevent the Report including the return notification transmitted from the plurality of ONUs to the OLT from colliding at the OLT. As a result, it is possible to achieve bandwidth efficiency and power saving.

  (7) Further, in the PON system according to the present invention, when only downstream traffic to an ONU in a sleep state occurs, the OLT generates a Gate message including the return instruction to the ONU in a sleep state. , And transmits data to the ONU that transmitted the Gate message including the return instruction, and thereafter, when no downstream traffic to the ONU occurs for a predetermined period, the Gate message including the sleep start instruction is transmitted to the ONU On the other hand, when the ONU receives a Gate message including the return instruction from the OLT, the ONU switches only the receiver to a normal state.

  As described above, when only downstream traffic to an ONU in sleep state occurs, the OLT transmits a Gate message including a return instruction to the ONU in sleep state, and a Gate message including the return instruction. When data is transmitted to the transmitted ONU, and then downstream traffic to the ONU does not occur for a certain period, a Gate message including the sleep start instruction is transmitted to the ONU, so power saving can be achieved. In addition, when the ONU receives a Gate message including a return instruction from the OLT, it switches only the receiver to the normal state, so that only downstream traffic can be received while the transmitter is in the sleep state, and bandwidth efficiency is improved. And, it becomes possible to save power.

  (8) In the PON system of the present invention, when upstream traffic to the OLT occurs in the sleep state, the ONU cancels the sleep state by transmitting data with the Report to the OLT. The OLT is notified to return to the state.

  As described above, when upstream traffic to the OLT is generated in the sleep state, the ONU notifies the OLT that the sleep state is released and the normal state is restored by transmitting data with the Report to the OLT. It is possible to transmit data earlier than receiving and responding to the common control signal.

  (9) Further, according to the transmission method of the present invention, an optical line terminal (OLT) and a plurality of ONUs (Optical Network Units) are connected via an optical splitter to realize optical fiber transmission. A transmission method of a system, comprising, in the ONU, switching between a normal state of supplying power to a transmitter or a receiver and a sleep state of stopping supply of power to a transmitter or a receiver; Placing the transmitter and the receiver in a sleep state when there is a sleep start instruction from an OLT, or when a sleep start instruction is sent from the OLT as a response after sending a sleep request to the OLT; After putting the transmitter and the receiver in the sleep state, the OLT receives a common control signal to be transmitted to all subordinate ONUs. Maintaining the receiver in a normal state only during a communication period, and continuing the sleep state of the transmitter until it becomes necessary to transmit data.

  As described above, when the ONU issues a sleep start instruction from the OLT or sends a sleep request to the OLT and then receives a sleep start instruction from the OLT as a response, the ONU puts the transmitter and the receiver in the sleep state. After putting the transmitter and receiver in the sleep state, the receiver should be in the normal state only during the period when the OLT receives the common control signal to transmit to all subordinate ONUs, while the data needs to be transmitted. Since the transmitter continues to be in the sleep state, it can be in the sleep state for a longer time than in the past. In particular, since the receiver sleeps during a period other than the period for receiving the common control signal, and the transmitter sleeps until it becomes necessary to transmit data, the improvement of the band efficiency and the power saving are remarkable. is there.

  According to the present invention, in a heterogeneous network, even if an ONU (small cell) that does not communicate data for a fixed period occurs, it is possible to achieve band efficiency and power saving.

It is a figure which shows schematic structure of the PON system which concerns on this embodiment. It is a figure which shows the example which comprised the PON system which concerns on this embodiment as "very many branch operation | use." It is a figure which shows the operation | movement before entering a sleep state, the case where sleep is instruct | indicated from OLT, and the case where sleep is performed from ONU. It is a figure which shows operation | movement when ONU of the PON system which concerns on 1st Embodiment is a sleep state. It is a figure which shows the power saving effect when each ONU is sleeping. It is a figure which shows the operation | movement which ONU switches from a sleep state to a normal state. It is a figure which shows the other aspect of the operation | movement which ONU switches from a sleep state to a normal state. It is a figure which shows the other aspect of the operation | movement which ONU switches from a sleep state to a normal state. It is a figure which shows the other aspect of the operation | movement from which two ONU switches from a sleep state to a normal state. It is a figure which shows schematic structure of the PON system which concerns on 2nd Embodiment. FIG. 13 is a diagram showing an operation of switching from the sleep state to the normal state in the second embodiment. FIG. 14 is a diagram showing another form of the operation of switching from the sleep state to the normal state in the second embodiment.

  In the PON system for realizing the heterogeneous network, if power is supplied to the transmitter and the receiver even when there is no communication from the BBU / RRH / UE under the ONU, the bandwidth utilization efficiency Focusing on reduction and waste of power, if communication is not occurring, power saving can be achieved by putting the transmitter and receiver of the ONU to sleep mode, and the polling scheme between OLT and ONU It has been found that it is possible to reduce wasteful use of bandwidth and to achieve the present invention.

  That is, the PON system according to the present invention is a PON system in which an OLT and a plurality of ONUs are connected via an optical splitter to realize optical fiber transmission, and the ONU supplies power to the transmitter or the receiver. And a sleep state in which the supply of power to the transmitter or receiver is stopped, and when an instruction to start sleep is given from the OLT, or after sending a sleep request to the OLT When a response to start sleep is given from the OLT as a response, the transmitter and the receiver are put in the sleep state, and after the transmitter and the receiver are put in the sleep state, the OLT sends to all subordinate ONUs. On the other hand, the receiver is put in a normal state only during a period of receiving a common control signal giving synchronization maintenance and return message transmission time Write, characterized by continuing the sleep state of the transmitter to need to transmit data is generated.

  As a result, the present inventors have been able to put the ONU to sleep for a longer time than before. In particular, since the receiver sleeps during a period other than the period for receiving the common control signal, and the transmitter sleeps until it becomes necessary to transmit data, the improvement of the band efficiency and the power saving are remarkable. is there. Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings.

  FIG. 1 is a view showing a schematic configuration of a PON system according to the present embodiment. Containment station 10 includes BBU 12 and OLT 14. The BBU 12 controls the RRH 16 functioning as a macro station and the OLT 14 constituting the PON. Although the RRH of the macro station is directly controlled in FIG. 1, it may be controlled via the ONU. Under the OLT 14, a plurality of ONUs 18 are connected via an optical fiber 15. Each ONU 18 is provided with an RRH 20 functioning as a small cell station. In the present embodiment, the present invention is applied to a heterogeneous configuration. Since the communication area in the small cell is narrow and the number of users to be accommodated is small, the frequency of occurrence of communication is low. Therefore, power saving can be achieved by taking a long time for the ONU 18 to be in the sleep state.

  FIG. 2 is a diagram showing an example in which the PON system according to the present embodiment is configured as “super multi-branch operation”. That is, it is assumed that the configuration of the heterogeneous network shown in FIG. 1 is used in a dense area. The feature is that the number of ONUs 18 accommodated in the OLT 14 is very large. When communicating with all of these ONUs 18 at the same time, it will deteriorate from the viewpoint of bandwidth utilization efficiency, but in fact, most of the ONUs 18 can be switched to the sleep state. In this way, bandwidth utilization efficiency and power saving can be achieved.

The features of the PON system according to the present embodiment are as follows.
-Of the OLT / ONU, the sleep state (target of operation stop) is only ONU.
-When not communicating from subordinates of ONU, long-term sleep (not sent) becomes possible.
-If there are multiple ONUs in sleep state, the OLT can use "LLID for Broadcast" to make the bandwidth efficient.
The ONU is activated only at the timing of receiving the downstream common control signal. This makes it possible to receive OLT messages with minimal power and maintain synchronization.
-It is also possible to notify sleep from the ONU side. That is, by intentionally sending data at the time of switching (restoring) from the sleep state to the normal state, distinction from a failure can be made.
It is possible to quickly recover from sleep when downstream or upstream traffic occurs.
-When there is only traffic in the downlink, the power required for transmission can be reduced by continuing the uplink sleep state.

First Embodiment
FIG. 3 is a diagram showing an operation before entering the sleep state, a case where the OLT instructs sleep, and a case where the ONU sleeps. In normal operation, the OLT periodically transmits a Gate message to the ONU, to which the ONU transmits a Report. Next, when the OLT side instructs the ONU to sleep, the OLT adds “Sleep start”, which is an instruction to switch to the sleep state, to the Gate message, and transmits it to the ONU. When the ONU receives the Gate message with “Sleep start”, the ONU adds “Sleep ACK” to Report and transmits it to the OLT. Thereafter, the ONU goes to sleep, and the OLT periodically transmits to the ONU "B-GATE" which is a Gate message for the sleeping ONU. The "B-GATE" corresponds to the common control signal.

  In FIG. 3, when the ONU notifies the OLT of the sleep, the ONU transmits a Report with “Sleep Request” in response to the Gate message received from the OLT. The OLT receives the Report with "Sleep Request" from the ONU, and acknowledges this, adds "Sleep start" to the Gate message and transmits it to the ONU. When the ONU receives the Gate message with “Sleep start”, the ONU adds “Sleep ACK” to Report and transmits it to the OLT. Thereafter, the ONU goes to sleep, and the OLT periodically sends "B-GATE" to the ONU.

  FIG. 4 is a diagram showing an operation when the ONU of the PON system according to the first embodiment is in the sleep state. FIG. 4 exemplifies a state in which the OLT and two ONUs communicate. In normal operation, a gate message is periodically transmitted from the OLT to two ONUs, and each ONU transmits a report to the OLT. Next, a gate message with “Sleep start” is transmitted from the OLT to each ONU, and each ONU transmits a report with “Sleep ACK” to the OLT, and the state is switched to the sleep state. In addition, since the Gate message with “Sleep start” transmitted from the OLT to each ONU is individually transmitted as Unicast for each ONU, the ONUs do not simultaneously switch to the sleep state.

  In FIG. 4, when each ONU is in the sleep state, the OLT periodically transmits “B-GATE” which is a common control signal to all the ONUs in the sleep state. As a result, regardless of how many ONUs are sleeping, it suffices to transmit "B-GATE" having the same content once each. Each ONU does not need to do anything for this "B-GATE" unless there is data to be sent to the OLT. That is, the transmitter of each ONU can continue the sleep state. Also, the receiver of each ONU may be restored, that is, switched to the normal state, only for a period necessary to receive "B-GATE" transmitted periodically. This makes it possible to save power.

FIG. 5 is a diagram showing a power saving effect when each ONU is sleeping. FIG. 5 shows a state in which the transmitter _{T X} where one ONU comprises a receiver _{R X} is ON / OFF. Within a period of normal operation, the receiver _{R X} is always ON, the transmitter _{T X} becomes ON at a timing of transmitting the Report. Next, the operation entering sleep, ONU receiver _{R X} until it receives a "Sleep start" with a Gate message from the OLT becomes then a ON OFF. The transmitter _{T X} is next ON timing of transmitting the Report with "Sleep ACK", then it turned OFF. During sleep operation, the transmitter T _X is always off and does not operate at all. The receiver R _X starts only while receiving the "B-GATE", but switched to the normal state, otherwise the sleep state.

  FIG. 6 is a diagram showing an operation of the ONU switching from the sleep state to the normal state. When the ONU is sleeping, "B-GATE" is periodically transmitted from the OLT. Next, when downstream traffic addressed to the ONU is generated in the OLT, the OLT instructs the ONU in sleep mode to switch from the sleep state to the normal state (Sleep release message in FIG. 6). Add "Wakeup message" to "B-GATE" and send it. The ONU that has received the "B-GATE" with the "Wakeup message" switches from the sleep state to the normal state. Next, the OLT waits for the time required for the ONU to switch from the sleep state to the normal state, and then transmits data to the ONU. Thereafter, the ONU continues communication with the OLT in the normal state.

  FIG. 7 is a diagram showing another aspect of the operation of the ONU switching from the sleep state to the normal state. When the ONU is sleeping, "B-GATE" is periodically transmitted from the OLT. Next, when downstream traffic addressed to the ONU is generated in the OLT, the OLT instructs the ONU in sleep mode to switch from the sleep state to the normal state (Sleep release message in FIG. 7). Add "Wakeup message" to "B-GATE" and send it. The ONU that has received the “B-GATE” with the “Wakeup message” switches from the sleep state to the normal state, transmits a Report with “Wakeup ACK” to the OLT, and notifies the release of Sleep. The OLT then sends data to the ONU. Thereafter, the ONU continues communication with the OLT in the normal state.

  FIG. 8 is a diagram showing another aspect of the operation of the ONU switching from the sleep state to the normal state. When the ONU is sleeping, "B-GATE" is periodically transmitted from the OLT. Next, when upstream traffic from a subordinate of the ONU occurs, the ONU adds “Wakeup message” to switch to the normal state from the sleep state to the OLT and transmits it to the Report. Here, if it collides with a report with “Wakeup message” from another ONU, it can wait at random and then transmit the report with “Wakeup message” to the OLT again. Next, the OLT transmits a Gate message to the ONU, and the ONU receiving this transmits a Report with data. Thereafter, the ONU continues communication with the OLT in the normal state.

  FIG. 9 is a diagram showing another aspect of an operation in which two ONUs switch from the sleep state to the normal state. When each ONU is sleeping, “B-GATE” is periodically transmitted from the OLT to each ONU. This “B-GATE” may include the timing (transmission frame) at which each ONU transmits a report with “Wakeup message” multiple times. FIG. 9 shows the case where three transmission frames are designated by one “B-GATE”. Next, when traffic from subordinates of each ONU is generated, each ONU adds “Wakeup message” to switch to the normal state from the sleep state to the OLT and transmits it to Report. The timing for transmitting the “Wakeup message” Report is randomly selected from the timing (transmission frame) indicated by “B-GATE”. This makes it possible to reduce the collision of reports with “wakeup messages” transmitted from a plurality of ONUs at the OLT.

Second Embodiment
FIG. 10 is a diagram showing a schematic configuration of a PON system according to the second embodiment. Here, use in the configuration of the heterogeneous network shown in FIG. 1 is assumed. In other words, C-Plane (control information) is transmitted via the macro station (RRH 16) via the small cell station's 20 subordinate user terminals, and only U-Plane (user data) is received via the small cell. . This is suitable for IoT dedicated networks such as spot cells and sensors.

  FIG. 11 is a diagram showing an operation of switching from the sleep state to the normal state in the second embodiment. When the ONU is sleeping, "B-GATE" is periodically transmitted from the OLT. Next, when downstream traffic addressed to the ONU is generated in the OLT, the OLT instructs the ONU in sleep mode to switch from the sleep state to the normal state (Sleep release message in FIG. 11). Add "Wakeup message" to "B-GATE" and send it. The ONU that has received the "B-GATE" with the "Wakeup message" switches only the receiver from the sleep state to the normal state. The OLT waits for the time required for the ONU receiver to switch from the sleep state to the normal state, and then transmits data to the ONU. During this time, the transmitter of the ONU continues the sleep state.

  The OLT transmits all data addressed to the ONU, and if there is no traffic addressed to the ONU for a certain period of time, the OLT transmits a Gate message with "Sleep start" to the ONU, and the ONU switches to the sleep state.

  FIG. 12 is a diagram showing another form of the operation of switching from the sleep state to the normal state in the second embodiment. FIG. 12 illustrates a state in which the OLT and two ONUs communicate. When each ONU is sleeping, "B-GATE" is periodically transmitted from the OLT. Next, when downstream traffic addressed to the ONU 1 occurs in the OLT, the OLT instructs the ONU 1 in sleep mode to switch from the sleep state to the normal state (Sleep release message in FIG. 12). Add "Wakeup message" to "B-GATE" and send it. The ONU 1 that has received the "B-GATE" with the "Wakeup message" switches only the receiver from the sleep state to the normal state. The OLT waits for the time required for the receiver of ONU 1 to switch from the sleep state to the normal state, and then transmits data to ONU 1. During this time, the transmitter of the ONU 1 continues the sleep state.

  After the OLT transmits all the data addressed to ONU1, ONU1 switches to the sleep state. When each ONU is sleeping, "B-GATE" is periodically transmitted from the OLT. Next, when upstream traffic is generated from subordinates of the ONU 2, the ONU 2 transmits a Report to the OLT, receives a Gate message for this from the OLT, and transmits a Report with data. When the Report from ONU 2 becomes 0, that is, there is no transmission data, the OLT does not transmit a Gate message any more. When the ONU 2 switches to the sleep state, the OLT periodically transmits "B-GATE" to each ONU.

  As described above, according to the present embodiment, even if the PON system is operated in a large number of connections, the operation is performed without loss of efficiency, assuming that the simultaneous use rate is low. Is possible. For example, if only 32 units communicate at the same time, the bandwidth and delay efficiency will not change even if 256 units or 512 units are connected. In addition, there is more power saving than other methods (including standardization). That is, since the LD light emission operation which is the maximum power consumption is not performed without communication, power saving is remarkable, and power saving can be achieved except for timing when the common control signal is received on the receiving side as well. Become.

10 Containing Station 12 BBU
14 OLT
15 optical fiber 16, 20 RRH
18 ONU

Claims (9)

This is a PON (Passive Optical Network) system that realizes optical fiber transmission by connecting an OLT (Optical Line Terminal) and a plurality of ONUs (Optical Network Units) via an optical splitter.
The ONU is
It has a function to switch between a normal state in which power is supplied to the transmitter or receiver and a sleep state in which power supply to the transmitter or receiver is stopped.
When the sleep start instruction is issued from the OLT or when the sleep start instruction is sent from the OLT as a response after the sleep request is transmitted to the OLT, the transmitter and the receiver are put in the sleep state.
After putting the transmitter and the receiver in the sleep state, the receiver is in the normal state only during a period in which the OLT receives a common control signal giving synchronization maintenance and return message transmission time to all ONUs under the control. While maintaining the sleep state of the transmitter until it becomes necessary to transmit data.   The PON system according to claim 1, wherein the OLT transmits a Gate message including the sleep start instruction to an ONU to be put into a sleep state.   The OLT transmits a Gate message including an instruction to return from the sleep state to the normal state to the ONU in the sleep state when downlink traffic to the ONU in the sleep state occurs. The PON system according to claim 1 or 2, wherein data is transmitted to an ONU to which a Gate message including the return instruction is sent.   When the ONU in the sleep state receives a Gate message including the return instruction from the OLT, the ONU transmits a return notification to the OLT and switches from the sleep state to the normal state. The PON system according to claim 3.   The ONU responds to the common control signal received from the OLT by transmitting a Report including a return notification for releasing the sleep state and returning to the normal state when upstream traffic to the OLT is generated in the sleep state. The PON system according to claim 1 or 2, wherein data is transmitted to the OLT. When there are a plurality of ONUs in the sleep state, the OLT adds, to the common control signal, information instructing a timing of transmitting a Report including the return notification,
The PON system according to claim 5, wherein the ONU having the upstream traffic transmits a Report including the return notification to the OLT at a timing selected from the plurality of timings.   The OLT transmits a Gate message including the recovery instruction to the ONU in the sleep state when only downstream traffic to the ONU in the sleep state occurs, and transmits a Gate message including the recovery instruction. After transmitting data to the transmitting ONU, and thereafter, when downstream traffic to the ONU does not occur for a fixed period, a Gate message including the sleep start instruction is transmitted to the ONU, while the ONU issues the return instruction from the OLT. 4. A PON system according to claim 3, wherein only the receiver is switched to the normal state when receiving a Gate message including.   When upstream traffic to the OLT is generated in the sleep state, the ONU notifies the OLT of releasing the sleep state and returning to the normal state by transmitting data together with Report to the OLT. The PON system according to claim 1 or 2, characterized in that A transmission method of a PON (Passive Optical Network) system in which an Optical Line Terminal (OLT) and a plurality of ONUs (Optical Network Units) are connected via an optical splitter to realize an optical fiber transmission.
Switching between a normal state in which power is supplied to a transmitter or a receiver and a sleep state in which power supply to the transmitter or receiver is stopped in the ONU;
Placing the transmitter and the receiver in the sleep state when there is a sleep start instruction from the OLT or when a sleep start instruction is sent from the OLT as a response after transmitting the sleep request to the OLT; ,
After putting the transmitter and the receiver in the sleep state, it is necessary to transmit the data while making the receiver in the normal state only during a period in which the OLT receives a common control signal transmitted to all subordinate ONUs. Continuing the sleep state of the transmitter until a failure occurs.

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