WO2010031326A1

WO2010031326A1 - Method for switching data link in the optical network system, optical line terminal and system

Info

Publication number: WO2010031326A1
Application number: PCT/CN2009/073939
Authority: WO
Inventors: 隋猛; 杨素林
Original assignee: 华为技术有限公司
Priority date: 2008-09-19
Filing date: 2009-09-15
Publication date: 2010-03-25
Also published as: CN101677415B; CN101677415A

Abstract

The embodiments of the present invention disclose a method for switching data link in the optical network system, an optical line terminal and an optical network system. Wherein the method includes: while a service is switched from the first optical line terminal to the second optical line terminal, the second optical line terminal performs the following process steps: transmitting the first notification message to the optical network unit which connects to the optical splitter in the optical network system to notify the optical network unit enter an operation state; transmitting the bandwidth mapping that the uplink data transmission requires to the optical network unit; receiving the uplink data transmitted from the optical network unit responding to the bandwidth mapping, and determining the delay from the time that bandwidth mapping is transmitted to the time that the uplink data is received as the zero distance equalization delay between the second optical line terminal and the optical network unit by monitoring the processes that transmitting the bandwidth mapping and receiving the uplink data. The embodiments of the present invention can reduce the service break off time of the optical network system due to the failure of the backbone fiber or the master optical line terminal, and the service break off time can be controlled within 50ms.

Description

The present application claims priority to Chinese Patent Application No. 200810149350.9, entitled "Optical Network System Data Link Switching Method, Optical Network Unit and System", filed on September 19, 2008, the entire contents of which are incorporated by reference. In this application. Technical field

The present invention relates to the field of network communications, and in particular, to an optical network system data link switching method, an optical line terminal, and a system. Background technique

The versatile Passive Optical Network (PON) technology is a point-to-multipoint optical access technology. The PON network consists of an Optical Line Terminal (OLT), an optical splitter, an Optical Network Unit (ONU), and an optical fiber connected to each device. FIG. 1 is a schematic diagram of a PON network architecture in the prior art. The OLT is used as a central office device, and is connected to an optical splitter through a trunk optical fiber 10. The optical splitter is connected to each ONU through a separate branch optical fiber 20. In a PON network, the transmission direction of the OLT to the ONU is called downlink, and is transmitted through a 1490 nm wavelength optical fiber; the transmission direction of the ONU to the OLT is called uplink, and is transmitted through a 1310 nm wavelength optical fiber. In the downlink direction, the optical splitter implements the splitting function, and sends the downlink optical signal of the OLT to all the ONUs through the branch fiber. In the uplink direction, the optical splitter implements the optical signal convergence function, and aggregates the optical signals sent by all the ONUs. Sent to the OLT through the backbone fiber. In order to ensure that multiple ONU optical signals do not conflict when uplinking, it is necessary to transmit optical signals by one ONU at the same time under the control of the OLT.

Gigabit Passive Optical Network (GPON) standard is the International Telecommunications Union (International Telecommunications Union- Telecommunication Sector (referred to as ITU-T) The latest generation of broadband passive optical integrated access standards based on ITU-T G.984.X standard. In the GPON standard, in order to support the time when the optical signals transmitted by all ONUs arrive at the OLT, the ONU needs to delay the transmission of different time according to the difference between the ONU and the OLT when transmitting the uplink data to the OLT. This transmission delay time is called equalization delay (EqD). The OLT obtains the round trip delay (Rtd) value of the OLT to the ONU through the RANGING processing of the ONU, and calculates the EqD value of the ONU by using the Rtd value, and sets it to the ONU.

The formula for calculating the EQD of the ONU is:

EqD=Teqd-Rtd ( 1 ) where Teqd is the equalized round trip delay and is a constant value.

The ONU implements ranging processing in the RANGING state, and the following includes: The OLT opens a ranging window with no data transmission for the ONU to be measured; the OLT sends a Range Request message to the ONU to be measured; The serial number physical layer maintenance message (Serial_Number_ONU PLOAM) responds to the OLT; the OLT calculates the EQD value of the ONU and sends it to the ONU through the Ranging Time PLO AM message, which is sent 3 times.

It can be seen that the entire ONU ranging process requires six message interactions. In the GPON standard, a message is sent every 125 μ _δ , so the ranging process of the entire ONU takes about 1 ms. After the ONU is measured, it is switched from the RANGING state to the OPERATION state. In the OPERATION state, the ONU starts data transmission with the OLT. The ranging processing of the ONU is serial. After the OLT completes the ranging processing of the previous ONU, the ranging processing of the next ONU is started. After the ONU ranging is completed, the data transmission between the ONU and the OLT is restored. Therefore, the service interruption time due to the failure of the backbone fiber is: Service interruption time = LOS detection time + handover decision execution time + NxONU ranging time;

N is the number of ONUs accessed by the OLT.

It can be seen that the ONU re-ranging time is the longest interruption of the entire service. The distance of each ONU ranging is about lms. When accessing 128 ONUs or more under one OLT, the service interruption time is much longer than 50ms. The PON carries the Time Division Multiplex (TDM) service, which requires the service interruption time to be less than 50ms, and the prior art cannot meet this requirement. Summary of the invention

The embodiments of the present invention provide a data link switching method, an optical line terminal, and an optical network system for an optical network system, which can shorten the failure of the trunk optical fiber or the primary optical line terminal in the optical network system. The resulting business interruption time.

An embodiment of the present invention provides a data link system switching method for an optical network system, where the optical network system includes at least two optical line terminals respectively connected to the same optical splitter through optical fibers, where the optical splitter is connected to At least one optical network unit, when the service is switched from the first optical line terminal to the second optical line terminal; performing the following processing steps on the second optical line terminal:

Sending a first notification message to the optical network unit connected to the optical splitter to notify the optical network unit to enter an active state;

Transmitting, to the optical network unit, a bandwidth mapping required for uplink data transmission;

Receiving uplink data sent by the optical network unit in response to the bandwidth mapping, and

Determining, by the process of transmitting the bandwidth mapping and receiving the uplink data, a delay between transmitting the bandwidth and receiving the uplink data, between the second optical line terminal and the optical network unit Zero distance equalization delay.

The embodiment of the invention further provides an optical line terminal, including: a switching execution module, configured to switch the optical line terminal from a standby optical line terminal to a main optical line terminal;

a notification message sending module, configured to send a first notification message to the optical network unit to notify the optical network unit to enter a working state when the optical line terminal switches from the standby optical line terminal to the primary optical line terminal;

a bandwidth mapping sending module, configured to send a bandwidth mapping to the optical network unit;

An uplink data receiving module, configured to receive uplink data, where the received uplink data includes uplink data of the optical network unit;

a monitoring module, configured to monitor the bandwidth mapping sending module and the uplink data receiving module, and determine a delay for transmitting the bandwidth to receive the uplink data as the optical line terminal and the optical network unit Zero distance equalization delay between.

The embodiment of the present invention further provides an optical network system, including at least two optical line terminals, respectively connected to the same optical splitter through an optical fiber, where the optical splitter is connected to at least one optical network unit through an optical fiber, when the service When switching from the first optical line terminal to the second optical line terminal: the second optical line terminal sends a first notification message to the optical network unit to notify the optical network unit to enter a working state, The optical network unit sends the bandwidth mapping required for the uplink data transmission and receives the uplink data sent by the optical network unit in response to the bandwidth mapping, where the process of transmitting the bandwidth mapping and receiving the uplink data is sent, The delay of the bandwidth mapping to the received uplink data is determined as a zero-distance equalization delay between the second optical line terminal and the optical network unit;

The optical network unit is configured to receive a first notification message sent by the second optical line terminal, enter a working state in response to the first notification message, and receive a transmission from the second optical line terminal. After the bandwidth mapping, the uplink data is sent to the second optical line terminal according to the equalization delay assigned by the first optical line terminal recorded locally and the bandwidth mapping sent by the second optical line terminal. In the embodiment of the present invention, after the failure of the trunk optical fiber, the original primary OLT is switched to the standby OLT, and the original standby OLT is switched to the primary OLT. Then, the OLT sends a first notification message to each ONU, informing each ONU to enter the working state, and maintaining the original EqD. After the transition to the OPERATION state, each ONU can perform normal data transmission, which simplifies the service terminal process and saves the time of multiple ONU ranging, thereby meeting the time of service interruption in the optical network system. Control the requirement of 50ms.

The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. DRAWINGS

FIG. 1 is a schematic diagram of a PON network architecture in the prior art;

FIG. 2 is a diagram showing an embodiment of a data link switching method for an optical network system according to the present invention;

FIG. 3 is a diagram showing an embodiment of a data link switching method for an optical network system according to the present invention;

4 is a schematic structural view of an OLT embodiment of the present invention;

FIG. 5 is a schematic structural view of an ONU embodiment of the present invention;

FIG. 6 is a schematic structural diagram of an embodiment of an optical network system according to the present invention. detailed description

FIG. 2 is a flowchart of Embodiment 1 of a method for switching data link of an optical network system according to the present invention. The optical network system includes at least two OLTs, which are respectively connected to the same optical splitter through optical fibers, and the optical splitting The device is connected to the at least one ONU, and the equalization delay assigned by the second OLT to the ONU is the same as the equalization delay assigned by the first OLT to the ONU, when the service is switched from the first OLT to the second OLT. The steps performed on the second OLT include:

Step 1: Send a first notification message to the ONU connected to the optical splitter to notify the ONU to enter a working state;

Step 12: Perform an operation of sending a bandwidth mapping required for uplink data transmission to the ONU and receiving uplink data sent by the ONU, where the bandwidth mapping and receiving are sent by monitoring The process of the uplink data determines a zero distance equalization delay between the second OLT and the ONU.

Step 12 is specifically as follows: the second optical line terminal closes a window of window alarm; sends a bandwidth mapping to the ONU, and starts timing; when receiving the first uplink data after the bandwidth mapping is sent, stopping Timing, and the timing result as a zero distance equalization delay.

Optionally, the data link method for the optical network system provided by the embodiment of the present invention further includes: Step 13: Perform window drift detection by using the determined zero-distance equalization delay, and if the window drift is detected, if necessary, In the subsequent steps, the equalization delay of the ONU can also be adjusted accordingly.

Step 13 can specifically detect whether a window drift occurs by obtaining a zero-distance equalization delay (the zero-distance equalization delay refers to the time difference between the time when the OLT sends the downlink frame and the expected start of receiving the uplink frame), thereby sending a window to the OLT and the ONU. The drift alarm is used to ensure that the uplink transmission from the ONU to the optical line terminal does not conflict.

The OLT allocates the uplink bandwidth to the ONU by using the Bandwidth Map (BWMap). The delay from the BWMap sent by the OLT to the OLT receiving the uplink data of the ONU is zero distance equalization delay. If window drift occurs, the corresponding modification needs to be performed. The EqD value of the ONU.

FIG. 3 is a flowchart of Embodiment 2 of a data link switching method of an optical network system according to the present invention. The optical network system includes at least two OLTs respectively connected to the same optical splitter through optical fibers, and the optical splitting The device is connected to the at least one ONU. When the service needs to be switched from the first OLT to the second OLT, the steps executed on the ONU include:

Step 21: Receive a first notification message sent by the second OLT.

Step 22: Enter a working state in response to the received first notification message;

Step 23: Receive a bandwidth mapping required for uplink data transmission from the second OLT, and send uplink data to the second OLT according to the equalization delay of the optical network unit and the bandwidth mapping, where the ONU is balanced. The delay is assigned to the equalization delay assigned by the second OLT to the ONU. Specifically, the first notification message is a physical layer maintenance message, where the physical layer maintenance message carries information for notifying the optical network unit to enter the working state and/or notifying that the equalization delay is unchanged, where The information indicating that the optical network unit is notified to enter the working state and the notification can be kept with only one information to maintain the equalization delay. The first notification message may be a POPUP message, where the POPUP message may be a broadcast POPUP message or a unicast POPUP message, as shown in Table 1 is a POPUP message format involved in the embodiment of the present invention.

POPUP message format involved in the embodiment of the present invention

For a POPUP message with a table-one format, if the content of the byte numbered 1 in the POPUP message is ONU-ID=0xFF, the POPUP message is a broadcast POPUP message; if the content of the byte numbered 1 in the POPUP message For a specific 0NU identifier (0NU-ID), the POPUP message is a unicast POPUP message, where the 0NU identifier (0NU-ID) indicates that the unicast POPUP message is received with the message 0NU- The ID corresponding to the 0NU. The broadcast POPUP message is sent directly to all 0NUs, and the unicast POPUP message is also sent to all ONUs, but since the unicast POPUP message is for a specific ONU (single Different ONU-IDs in the POPUP message correspond to different ONUs. The corresponding ONU receives the unicast POPUP message (identified by the ONU-ID) and performs corresponding processing, while other ONUs discard the unicast POPUP message. . Therefore, for a system with multiple ONUs, the OLT needs to send a unicast POPUP message to the corresponding ONU multiple times.

The POPUP message is a type of PLOAM message that can be modified by modifying the existing physical layer.

(PLOAM) The function of the message to implement the first notification message is as shown in Table 1. The current POPUP message has the byte number from 3 to the 12th byte as a reserved bit, and has no clear meaning. The modified POPUP in the embodiment of the present invention. The message defines the byte numbered 3. It defines eight options for a, b, c, d, e, f, g, h. Definition: When a=l, it indicates that the ONU is required to switch to work (OPERATION) Status, and keep EqD, allocation identifier (Alloc-ID) and ONU identifier (ONU-ID) unchanged; when a=0, it indicates that the ONU is required to switch to the RANGING state. In a specific application, when the primary trunk fiber or the primary OLT encounters a failure, and the original primary OLT is switched from the primary to the standby and the original standby OLT is switched from the standby to the primary, the new primary OLT (ie, the original standby) OLT) may send a first notification message to all ONUs by means of broadcast, such as the modified POPUP message, wherein the content of the byte numbered 3 in the modified POPUP message is a=l, the number numbered 1 The content in the ONU-ID=0xFF indicates that the POPUP is a broadcast POPUP message, so after receiving the modified POPUP message, each ONU can switch to the OPERATION state in response to the POPUP message, and maintain the original EqD and ONU. -ID and Alloc-ID are unchanged. The OPERATION state here may be one of the states of the ONU defined in the ITU-T G984.3 standard, wherein the states of the ONU defined by the G984.3 standard include: OPERATION RANGING, POPUP, and the like.

The OLT sends a first notification message to the optical network unit connected to the optical splitter, and the ONU enters an active state according to the first notification message. Specifically, the first notification message sent by the OLT carries the information that keeps the equalization delay unchanged, and the ONU maintains the original equalization delay according to the first notification message; When a notification message enters the working state from the current suspended state, the original equalization delay is maintained by default. By maintaining the original equalization delay, ie The equalization delay after the handover is the same as before the handover. This method does not need to obtain the equalization delay from the OLT again, which simplifies the ONU process and saves time, so that the ONU can resume work quickly within 50ms.

In the first embodiment of the present invention, after the trunk optical fiber or the original primary OLT fails in the optical network system, and the switching between the original primary OLT and the standby OLT and the original standby OLT to the primary OLT is completed, it is not necessary to assign a specialization to each ONU. The ranging window allows each ONU to enter the Ranging state for ranging, and recalculates the EqD value of each ONU by ranging, but directly notifies each ONU to enter the OPERATION state, and performs uplink data transmission to the ONU. The BWMap of the required bandwidth allocation information is transmitted and the operation of receiving the uplink data sent by the ONU, and the process of transmitting the BWMap to the ONU and receiving the uplink data sent by the ONU is monitored to determine the zero-distance equalization delay. In particular, the original EqD value, the ONU-ID, and the Alloc-ID are kept unchanged on the ONU, so that the time of each ONU ranging can be omitted, and each ONU can directly enter the OPERATION state, thereby greatly shortening the backbone fiber. Or the service interruption time caused by the failure of the original primary OLT.

In the embodiment of the present invention, after the OLT sends the first notification message to each ONU, the OLT sends a BWMap to each ONU through the broadcast mode, and starts timing. After receiving the BWMap, each ONU sends the uplink data normally, and the OLT detects that the self-send is sent. After the first uplink data after the BWMap, the timing is stopped, and the timing result is used as the zero-distance equalization delay, and the obtained zero-distance equalization delay is set at the OLT for subsequent window drift detection. When the primary or secondary OLT fails, the zero-distance equalization delay is not obtained after the primary and backup OLTs are switched. Therefore, before the first notification message is sent, the window drift alarm can be turned off first, and then zero is obtained. After the equalization delay, the window drift alarm is turned on.

If the first notification message is a unicast POPUP message, the OLT sends a unicast POPUP message to each ONU that needs to transmit data to notify each ONU to enter a working state. The OLT sends a BWMap to each ONU to start timing. After receiving the first uplink data after sending the BWMap, the OLT stops timing and obtains a zero-distance equalization delay. BWMap is sent every 125μ _δ At a time, the BWMap delivered each time includes the bandwidth allocation of the ONU that is currently in the working state. The zero-distance equalization delay can be obtained after the first BWMap is sent after the first unicast POPUP message is sent. After the subsequent BWMap is sent, the zero-distance equalization delay can be obtained. Of course, multiple zero-distance equalization delays can be obtained through multiple BWMap transmission and uplink data reception processes, and multiple zero-distance equalization delays are processed correspondingly (such as mean processing) to obtain a more accurate zero-distance equalization delay. .

The beneficial effects of the method provided by the embodiment of the present invention are briefly described below in conjunction with specific application scenarios. An application scenario of the embodiment of the present invention is a PON network architecture: two OLT devices that are mutually backup are connected to an optical splitter through independent trunk fibers, and three ONUs are taken as an example in the network, namely 0NU1, ONU2, and ONU3. The lengths of the branches of the optical fibers between the three and the optical splitter are respectively, 1 ₂ and 1 ₃ , the length of the original primary trunk fiber is Li, and the length of the primary trunk fiber switched to the original standby trunk fiber is L _{2 .} . The data transmission rate of the ONU to the OLT is the speed of light c. According to the formula (1) for calculating EqD, the EqD values of the ONUs before the failure can be obtained, respectively: EqD _u = A-2 ( lj + Li ) / c; EqD ₁₂ =A-2 ( 1 ₂ +Li ) /c; EqD ₁₃ =A-2 ( 1 ₃ +Li ) /c; The difference between each EqD is:

AEqDj

(2) AEqD ₁₂ =EqD ₁₃ -EqD ₁₂ =[A-2 ( + ) /c]-[A-2 (\ ₂ + ) /c]=2(l ₃ -l ₂ )/c (3) After the fault, the EqD values of the respective ONUs are: EqD ₂₁ = A-2 ( + L ₂ ) /c _; EqD ₂₂ = A-2 (1 ₂ + L ₂ ) / c _; EqD ₂₃ = A-2 (1 ₃ +L ₂ ) /c _{; the} difference between each EqD is: AEqD ₂₁ =EqD ₂₂ -EqD ₂₁ = [A-2 (1 ₂ +L ₂ ) /c]-[A-2 (l!+L ₂ ) /c]=2(l ₂ -l!)/c (4) AEqD ₂₂ =EqD ₂₃ -EqD ₂₂ = [A-2 (1 ₃ +L ₂ ) /c]-[A-2 (1 ₂ +L ₂ ) /c]=2(l ₃ -l ₂ )/c (5) In the above equations, A is a constant and represents the equalization round trip delay Teqd.

In a PON network, only one ONU can send uplink data to the OLT at the same time. In order to make the round-trip delays of the OLT to each ONU equal, the ONUs do not conflict when sending uplink data according to the bandwidth mapping (BWMap). Need to set the EqD value. From the above formulas (2) - (5), it can be seen that the difference AEqD between each EqD before the failure occurs, AEqD ₁₂ is equal to the difference between each EqD after the failure, AEqD ₂₁ and AEqD ₂₂ , that is, after the failure and the completion of the switching between the primary and backup OLTs and the switching of the primary and backup trunk fibers, even if the calculations are recalculated The EQD value of the ONU, and the difference between each EqD is equal to the effect that the round-trip delay of the OLT to each ONU is equal before the failure occurs. According to the method provided by the embodiment of the present invention, after the failure of the primary standby OLT after the failure occurs, the EqD values before the failure are still used, and the difference between the EqD values can be ensured, and the OLT to each ONU The round trip delay is equal. Therefore, in the case where the trunk fiber fails, after completing the switching of the primary standby OLT and the switching of the primary standby trunk fiber, the EqD value may not be recalculated, and each EqD value before the failure occurs.

After the ONUs are switched to the OPERATION state by transmitting the first notification message, normal communication can be performed between each ONU and the OLT. In order to better implement the embodiments of the present invention, it is also possible to detect whether a window drift occurs by acquiring a zero-distance equalization delay, thereby transmitting a drift of window alarm to the OLT and the ONU.

For the method provided by the embodiment of the present invention, the service interruption time is:

Service interruption time = LOS detection time + handover decision execution time + time when N ONUs switch back to the working state; POPUP message is sent by broadcast to notify each ONU to switch to the OPERATION state, and keep the original EqD, ONU-ID And Alloc-ID is unchanged. In this way, the time for the N ONUs to switch back to the working state is the time required to send a message, which is about 125μ8, which causes the service interruption time to be about 2ms+125 s =2.125ms.

It can be seen from the above description that the fault recovery method provided by the embodiment of the present invention can meet the requirement of limiting the time of the middle segment of the service to 50 ms, and adopting the prior art method, when the number of ONUs is large, this The requirements are difficult to meet.

FIG. 4 is a schematic structural diagram of an OLT embodiment of the present invention. The optical line terminal (OLT) 1 may include: a handover execution module 101, a notification message sending module 102, a bandwidth mapping sending module 103, an uplink data receiving module 104, and a monitoring module. The switching execution module 101 is connected to the notification message sending module 102, and the uplink data receiving module 104 and the notification message sending module 102 respectively The monitoring module 105 is connected, and the bandwidth mapping sending module 103 is connected to the notification message sending module 102 and the monitoring module 105, respectively. The handover execution module 101 controls the optical line terminal (OLT) 1 to switch to the primary OLT. Specifically, the handover execution module 101 may be connected to a fault monitoring module (not shown) on the OLT. When the fault monitoring module detects that the primary trunk fiber connected to the primary OLT or the primary OLT fails, the notification is notified. The handover execution module 101 performs the handover; the handover execution module 101 may also perform the handover according to the alarm indication or the handover indication of the primary OLT; the handover execution module 101 may also perform the handover according to the alarm indication or the handover indication of the upper layer network device, where the upper layer network device has Equipment Management System (EMS) and Access Node Control Protocol (ANCP) servers for fault maintenance. Specifically, the handover execution module 101 notifies the message sending module 102 to send a first notification message to each ONU, for notifying each ONU to enter an OPERATION state and/or keeping the original EqD unchanged.

After the notification message sending module 102 sends the first notification message to each ONU, the bandwidth mapping transmitting module 103 sends a bandwidth mapping to each ONU. The uplink data receiving module 104 waits to receive the uplink data. The monitoring module 105 is configured to monitor the bandwidth mapping sending module 103 and the uplink data receiving module 104, and the bandwidth mapping sending module 103 sends the bandwidth mapping and the uplink data receiving module 104 receives the delay of the uplink data sent by the optical network unit in response to the bandwidth mapping. As a zero distance equalization delay between the optical line termination and the optical network unit. For example, monitoring the zero equalization delay of the first ONU as an example, the monitoring module 105 monitors the bandwidth mapping sent by the bandwidth mapping sending module 103 to the first ONU, and starts timing; when the first ONU is detected, the first one is sent. When the uplink data is ended, the timing is used as the zero distance equalization delay of the first ONU. If the bandwidth mapping is periodically sent, the monitoring module 105 starts timing by transmitting a bandwidth mapping of a certain period, and ends the timing when receiving the first uplink data of the period, and uses the timing result as a zero-distance equalization delay.

The OLT 1 further includes a first storage module 106 coupled to the monitoring module 105. The monitoring module 105 stores the timing result to the first storage module 106 for use by the window drift detection module 107 for window drift detection. The window drift detection module 107 detects and processes the alarm process as described above. The content mentioned in the law. The above monitoring module 105 can also monitor the zero equalization delay of any other ONUs of the plurality of ONUs. Since multiple ONUs share the backbone fiber, the branch fiber corresponding to each ONU does not change before and after the switch. Therefore, in order to simplify the system to save the switching time, only one ONU can be selected for zero-equalization delay measurement, according to the selected ONU zero. The distance equalization delay determines the zero distance equalization delay of other ONUs.

FIG. 5 is a schematic structural diagram of an ONU embodiment of the present invention. The ONU 2 includes: a notification message receiving module 201, a state switching module 202, a data sending module 204, and a second storage module 205, and a notification message receiving module 201 and a state switching module 202. The connection, data sending module 204 is connected to the state switching module 202, the bandwidth mapping receiving module 203, and the second storage module 205, respectively. When a handover is required, such as after a failure of the backbone fiber or the primary OLT, the ONU receives a first notification message sent from the OLT, and the first notification message is used to notify the ONU to transition to an OPERATION state, for example, Is a notification message in the format described in Table 1. After the notification message receiving module 201 receives the first notification message, the state switching module 202 controls the ONU to enter an OPERATION state, such as sending an indication to the data sending module 204, instructing the data sending module 204 to enter an operating state to send uplink data; The bandwidth mapping receiving module 203 is configured to receive the bandwidth mapping from the optical line terminal, and send the received bandwidth mapping to the data sending module 204. The second storage module 205 is configured to store the equalization delay assigned by the first OLT. The sending module 204 is configured to receive a bandwidth mapping sent by the OLT, and send uplink data to the OLT according to the bandwidth mapping and the equalization delay stored locally by the second storage module 205. The data sending module 204 performs delay waiting by using the locally stored equalization delay to ensure that the uplink data transmission of the ONU does not conflict with the uplink data transmission of other ONUs.

FIG. 6 is a schematic structural diagram of an embodiment of an optical network system according to the present invention. The optical network system includes at least two optical line terminals OLT11 and OLT12, which are respectively connected to the same optical splitter 3 through optical fibers, and the optical splitter 3 Connected to the optical network unit ONU21, ONU22, ONU23 through optical fiber, optical line terminal 0LT11, OLT12 and OLT shown in Figure 4, optical network unit The ONUs 21, the ONUs 22, and the ONUs 23 are the same as the ONUs shown in FIG. 5. The foregoing is only an example. The optical network unit is not limited to three, and may be one or more ONUs.

In an optical network system, an equalization delay assigned by the second optical line terminal (such as OLT 12) to the optical network unit and the first optical line terminal (such as OLT11) are assigned to the optical network unit (such as ONU23) The equalization delay is the same, when the service is switched from the first optical line terminal to the second optical line terminal:

The second optical line terminal (OLT12) sends a first notification message to the optical network unit (such as the ONU 23) to notify the optical network unit (such as the ONU 23) to enter a working state, and performs uplink data transmission to the optical network unit. The required bandwidth mapping and receiving the uplink data sent by the optical network unit, wherein the second optical line terminal and the optical network unit are determined by monitoring a process of transmitting the bandwidth mapping and receiving the uplink data Zero distance delay between.

The optical network unit is configured to receive a first notification message sent by the second optical line terminal (OLT12), enter a working state in response to the first notification message, and receive the second optical line terminal from the second optical line terminal ( After the bandwidth mapping of the OLT 12), the equalization delay assigned by the first optical line terminal (OLT11) recorded locally and the bandwidth mapping sent by the second optical line terminal (OLT12) are sent to the second optical line terminal. (OLT12) Sends upstream data.

The data link switching method of the GPON system provided by the embodiment of the present invention is particularly applicable to a fault recovery scenario. After the trunk optical fiber or the primary OLT fails, the original primary OLT switches to the standby OLT, and the original standby OLT switches to the primary OLT, and then The OLT sends a first notification message to each ONU to notify each ONU to enter the working state, and keeps the original EqD, ONU-ID, and Alloc-ID unchanged, without opening a special ranging window pair after completing the switching of the primary standby OLT. Each ONU performs ranging, eliminating the need for multiple ONU ranging times. After each ONU transitions to the working state, normal data transmission can be performed, thereby satisfying the requirement of controlling the time of service interruption to 50 ms. In addition, in all embodiments of the present invention, the ONU has no limitation on the state before the handover, and may be any state allowed by the ONU, such as a suspended state. It should be noted that the method and apparatus provided by the embodiments of the present invention are applicable not only to an active optical network but also to a passive optical network, and are applicable not only to a GPON system but also to an isochronous transmission mode passive optical network (Asynchronous Transfer Mode Passive). Optical Network, Apollo (APON), Broadband Passive Optical Network (BPON) and other optical network systems that use GPON-like similar ranging technology.

It should be noted that the above embodiments are only intended to illustrate the technical solutions of the present invention and are not to be construed as limiting the embodiments of the present invention. The technical solutions of the present invention may be modified or equivalently substituted, and the modified technical solutions may not deviate from the spirit and scope of the technical solutions of the present invention.

Claims

Claim

An optical network system data link switching method, the optical network system comprising at least two optical line terminals respectively connected to the same optical splitter through an optical fiber, the optical splitter being connected to at least one optical network a unit, wherein when a service is switched from the first optical line terminal to the second optical line terminal; performing the following processing steps on the second optical line terminal:

The optical network system data link switching method according to claim 1, wherein the first notification message is a physical layer maintenance message, and the one physical layer maintenance message carries a notification light. The network element maintains information with equalization delay.

The optical network system data link switching method according to claim 2, wherein the physical layer maintenance message is a broadcast suspension message; and the first is sent to the optical network unit connected to the optical splitter The notification message specifically includes: transmitting a broadcast suspend message to all optical network units connected to the optical splitter or transmitting a unicast suspend message to each optical network unit.

The data link system switching method of the optical network system according to claim 1, wherein the method further comprises:

Window drift detection is performed using the determined zero-distance equalization delay.

The method for switching data link of an optical network system according to claim 4, wherein the method further comprises:

Therefore, before the first notification message is sent, the window drift alarm is turned off; After obtaining the zero-distance equalization delay, the window drift alarm is turned on, if the window drift is detected

The method for switching data link of an optical network system according to claim 4 or 5, wherein the method further comprises:

The equalization delay of the optical network unit is adjusted using the determined zero-distance equalization delay.

7. An optical line terminal, comprising:

a switching execution module, configured to switch the optical line terminal from a standby optical line terminal to a main optical line terminal;

The optical line terminal according to claim ,, wherein the monitoring module is configured to start timing when the bandwidth mapping sending module sends a bandwidth mapping to the optical network unit, and in the uplink data. The receiving module ends the timing when receiving the first uplink data sent by the optical network unit in response to the bandwidth mapping, and determines the timing result as a zero-distance equalization delay between the optical line terminal and the optical network unit.

The optical line terminal according to claim ,, further comprising: a first storage module and a window drift detecting module;

The first storage module is connected to the monitoring module, and configured to store the zero distance equalization delay of the monitoring module; The window drift detection module is connected to the first storage module, and configured to perform window drift detection according to the zero distance equalization delay stored by the first storage module.

10 . An optical network system comprising at least two optical line terminals respectively connected to the same optical splitter by optical fibers, wherein the optical splitter is connected to at least one optical network unit through an optical fiber, wherein when the service is from When the first optical line terminal switches to the second optical line terminal:

Transmitting, by the second optical line terminal, a first notification message to the optical network unit to notify the optical network unit to enter a working state, sending a bandwidth mapping required for uplink data transmission to the optical network unit, and receiving the optical network unit response The uplink data sent by the bandwidth mapping, wherein, by monitoring the process of sending the bandwidth mapping and receiving the uplink data, determining a delay for transmitting the bandwidth to receive the uplink data is determined as the second light a zero distance equalization delay between the line terminal and the optical network unit;

The optical network unit is configured to receive a first notification message sent by the second optical line terminal, enter a working state in response to the first notification message, and receive a transmission from the second optical line terminal. After the bandwidth mapping, the uplink data is sent to the second optical line terminal according to the equalization delay assigned by the first optical line terminal recorded locally and the bandwidth mapping sent by the second optical line terminal.

11. The optical network system according to claim 10, wherein

The second optical line terminal performs window drift detection using the determined zero distance equalization delay.

The optical network system according to claim 11, wherein the second optical line terminal turns off the window drift alarm before transmitting the first notification message, and starts window drift after obtaining the zero distance equalization delay. Alarm, if a window drift is detected for alarm.

The optical network system according to claim 11 or 12, wherein the method further comprises:

The second optical line terminal adjusts the equalization delay of the optical network unit using the determined zero-distance equalization delay.