WO2011147248A1 - 一种pon拉远的方法及设备 - Google Patents

一种pon拉远的方法及设备 Download PDF

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Publication number
WO2011147248A1
WO2011147248A1 PCT/CN2011/073744 CN2011073744W WO2011147248A1 WO 2011147248 A1 WO2011147248 A1 WO 2011147248A1 CN 2011073744 W CN2011073744 W CN 2011073744W WO 2011147248 A1 WO2011147248 A1 WO 2011147248A1
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WIPO (PCT)
Prior art keywords
path
distance
olt
protection
working
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PCT/CN2011/073744
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English (en)
French (fr)
Inventor
马腾
胡幸
蒋红丽
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华为技术有限公司
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Priority to EP11786020.5A priority Critical patent/EP2560302A4/en
Publication of WO2011147248A1 publication Critical patent/WO2011147248A1/zh

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J3/00—Time-division multiplex systems
    • H04J3/02—Details
    • H04J3/06—Synchronising arrangements
    • H04J3/0635—Clock or time synchronisation in a network
    • H04J3/0682—Clock or time synchronisation in a network by delay compensation, e.g. by compensation of propagation delay or variations thereof, by ranging
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/03—Arrangements for fault recovery
    • H04B10/032—Arrangements for fault recovery using working and protection systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J14/00—Optical multiplex systems
    • H04J14/02—Wavelength-division multiplex systems
    • H04J14/0287—Protection in WDM systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J3/00—Time-division multiplex systems
    • H04J3/16—Time-division multiplex systems in which the time allocation to individual channels within a transmission cycle is variable, e.g. to accommodate varying complexity of signals, to vary number of channels transmitted
    • H04J3/1694—Allocation of channels in TDM/TDMA networks, e.g. distributed multiplexers
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q11/00—Selecting arrangements for multiplex systems
    • H04Q11/0001—Selecting arrangements for multiplex systems using optical switching
    • H04Q11/0062—Network aspects
    • H04Q11/0067—Provisions for optical access or distribution networks, e.g. Gigabit Ethernet Passive Optical Network (GE-PON), ATM-based Passive Optical Network (A-PON), PON-Ring
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J2203/00—Aspects of optical multiplex systems other than those covered by H04J14/05 and H04J14/07
    • H04J2203/0001—Provisions for broadband connections in integrated services digital network using frames of the Optical Transport Network [OTN] or using synchronous transfer mode [STM], e.g. SONET, SDH
    • H04J2203/0057—Operations, administration and maintenance [OAM]
    • H04J2203/006—Fault tolerance and recovery
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q11/00—Selecting arrangements for multiplex systems
    • H04Q11/0001—Selecting arrangements for multiplex systems using optical switching
    • H04Q11/0062—Network aspects
    • H04Q2011/009—Topology aspects

Definitions

  • the invention belongs to the technical field of network communication, and relates to a method and a device for remotely extending a PON.
  • FTTH Fiber To The Home
  • PON Passive Optical Network
  • Figure 1 shows a traditional network architecture using PON access. Multiple services of users can be flexibly connected to different telecommunication service nodes through PON access and transport network transmission.
  • the basic components of the PON system include OLT (Optical Line Terminals), ONU (Optical Network Unit), and Optical Distribution Network (ODN).
  • OLT Optical Line Terminals
  • ONU Optical Network Unit
  • ODN Optical Distribution Network
  • the ODN between ONUs includes devices such as backbone fibers, passive optical splitters, and branch fibers.
  • the OLT and the passive optical splitter are connected by a trunk optical fiber, and the passive optical splitter realizes the optical power distribution of the point-to-multipoint, that is, the plurality of branching fibers are connected to the plurality of ONUs, and the direction from the OLT to the ONU In the downlink direction, the direction from the ONU to the OLT is called the uplink direction.
  • the number of ONUs connected by the OLT through the passive optical splitter is small, and the coverage radius is generally less than 20km, resulting in a large number of OLTs in the traditional network architecture, and the location area is remote and scattered, which is inconvenient to manage. And maintenance, equipment investment and maintenance costs are high.
  • next-generation optical access networks large operators have demanded to extend PONs to 100km or more.
  • the XPON over OTN method which is extended by the existing OTN (Optical Transport Network), is becoming a mainstream application scenario.
  • the OLT supports a logical distance of more than 200 km, and the distance between the working path and the protection path is greater than 170 km, which exceeds the OLT support.
  • - - 20km differential distance ie the difference between the distance between the farthest ONU and the OLT and the distance between the nearest ONU and the OLT.
  • the service coverage of the GPON (Gigabit Passive Optical Network) and the transmission distance are extended by the OTN device.
  • the GPON downlink data is encapsulated into the OTN network on the OLT node access device, and the OTN network access path is used to decapsulate the GPON downlink data from the OTN network through the OTN network access device. Broadcasting to the following ONUs; In the uplink direction, the OTN access nodes encapsulate the uplink data of each ONU into the OTN network, reach the access node of the OLT via the working path of the OTN network, and decapsulate the OLT node access device. The GPON uplink data is sent to the OLT.
  • Embodiments of the present invention provide a method and a device for remotely extending a PON, which have better flexibility in adjusting a working path and a protection path within a PON system, and a differential distance between an ONU and an OLT in a process of zooming out an XPON.
  • the XPON network can be used normally when it is more than 20km.
  • a method for remotely extending a PON including:
  • the data on the path of the shorter distance is delayed by T, so that the time of passing the data through the shorter distance path is the same as the time of the longer distance path.
  • a PON remote device including:
  • a distance measuring unit configured to obtain a distance between the working path and the protection path of the remote device and the OLT; and a comparing unit, configured to compare the distance between the working path and the protection path to obtain a shorter distance path and a longer distance path; - a delay unit, configured to delay the data on the path of the shorter distance on the remote device, and make the data pass the shorter distance path and the longer The distance from the path is the same.
  • the distance between the working path and the protection path of the remote device and the OLT is obtained, and the data on the path of the shorter distance is delayed, thereby realizing the PON system.
  • the distance between the working path and the protection path is flexibly adjusted, and the XPON network can be normally used when the differential distance between the ONU and the OLT exceeds 20 km in the process of XPON zooming out.
  • FIG. 1 is a schematic diagram of the basic composition of a prior art PON system
  • FIG. 2 is a schematic diagram of a GPON over OTN remote scene in the prior art
  • FIG. 3 is a schematic flowchart of a method for remotely extending a PON according to an embodiment of the present invention
  • FIG. 4 is a schematic flowchart of a method for obtaining a distance between a working path and a protection path by responding to an OLT according to an embodiment of the present invention
  • FIG. 5 is a schematic diagram of a request for an OTN node access device to respond to an OLT sequence code request according to an embodiment of the present invention
  • FIG. 6 is a schematic diagram of an ONU sending data by using a remote device and an OTN according to an embodiment of the present invention
  • FIG. 7 is a schematic structural diagram of a device for remotely extending a PON according to an embodiment of the present invention. detailed description
  • An embodiment of the present invention provides a method for remotely extending a PON. As shown in FIG. 3, the method may specifically include:
  • Step 31 Obtain a distance between the working device and the protection path of the remote device and the OLT.
  • the logical distance of the OLT can be set to a large value, for example, 10 to 20% larger than the working path or the protection path or directly set the maximum distance that the OLT can support.
  • the method for obtaining the distance between the working path and the protection path between the remote device and the OLT may include: manually measuring the distance between the working path and the protection path in establishing an engineering wiring process of the PON system network; accessing the device or the OTN node by the OLT node The access device simultaneously sends a flag to the working path and the protection path, and then obtains the distance between the working path and the protection path by calculating the time difference between the two flags on the OLT node access device or the OTN node access device; On the device, the ONU responds to the OLT's sequence code request, and after receiving the response message from the OLT, obtains the distance between the working path and the protection path through the ranging request of the responding OLT.
  • the method may specifically include The following steps
  • Step 311 Respond to the serial code request of the OLT, and send a predetermined number of sequence code response messages. Specifically, the OTN node access device first responds to the OLT sequence code request, and sends a sequence code response message. In order to fall within the window opening range of the OLT as much as possible, the predetermined number may be set to be sent 3 to 5 times each time. The sequence code responds to the message.
  • Step 312 After each predetermined number of sequence code response messages are sent, a fixed delay t is added to the time T1 of the normal response OLT, and after the N times fixed delay t is added, the response message of the OLT is received; An integer greater than or equal to 0.
  • the OTN node access device does not receive the sequence code configuration message of the OLT after transmitting the predetermined number of sequence code response messages, it is considered that the sequence code response message sent by the OTN node access device does not fall in the window of the OLT.
  • a fixed delay t is added to the time T1 required for the normal response to the OLT sequence code request as the new sequence code response delay time ( This time is defined as Tl+t. Because of the delay, T1 cannot fall within the window of the OLT every time. Therefore, a t is added after each response to save the ranging time.
  • the OTN node access device After adding N ts, the OTN node access device receives the serial code configuration message of the OLT, When the sequence code response message sent by the OTN node access device falls within the window opening range of the OLT, the finally obtained sequence code response delay time is Tl+N xt, where N is an integer greater than or equal to 0.
  • Step 313 Using Tl+N X t as the OLT delay, responding to the ranging request of the OLT, to obtain the distance between the working path and the protection path of the remote device and the optical line terminal.
  • the OTN node access device obtains the equalization delay E allocated by the OLT according to the finally obtained sequence code response delay time T1+N xt, and responds to the OLT's ranging request, and then sends the buffer time Td to the OLT to calculate.
  • Td Tl+(Nl) x t+E.
  • Step 32 Compare the distance between the working path and the protection path to obtain a shorter distance path and a longer distance path.
  • the distance between the working device and the protection path of the remote device and the OLT is first compared, and the path with a shorter distance is used as the target of the delay.
  • Step 33 On the remote device, delay the data on the path of the shorter distance, so that the time of the data passing through the shorter distance path is the same as the time of the longer distance path.
  • the data on the path shorter than the shorter distance is delayed by T, which is the time when the data passes through the shorter distance path and the time of the longer distance path.
  • T the time when the data passes through the shorter distance path and the time of the longer distance path.
  • the uplink data needs to be adjusted or the distance between the working path or the protection path is re-measured. Specifically, the following steps may be included:
  • Step 34 When protection switching occurs, the remote device performs buffering or de-buffering of the uplink data to complete the protection switching of the uplink data.
  • the working path or the protection path changes greatly, protection switching occurs.
  • the working path or the protection path between the remote device and the OLT changes, so the cache configured during the data transfer also changes. For example, if the working path of the uplink data after the delay T is reduced by 1 km, the working path of the uplink data needs to be cached. If the working path of the uplink data is increased by 1 km, the working of the uplink data is required. The path increases the cache.
  • Steps 35 When the distance of the working path or the protection path changes less than the predetermined value, the remote device adjusts the positioning frame of the uplink data on the remote device by detecting the position change of the frame header of the uplink data, and adjusts The distance between the working path and the protection path is such that the distance between the working path and the protection path is the same after the delay T.
  • the working path or the protection path may be changed less than a predetermined value (the predetermined value may be set to 1 km), and the length of the working path or the protection path needs to be re-measured.
  • the remote device can detect the position change of the frame header of the uplink data to adjust the framing window of the uplink data on the remote device, and adjust the distance between the working path and the protection path to make the distance between the working path and the protection path The same after the delay T.
  • Step 36 When the distance of the working path or the protection path changes more than a predetermined value, the remote device re-measures the distance length of the working path or the protection path.
  • the length of the protection path can be re-measured by the method described in step S31. If the working path is greater than the predetermined value (the predetermined value can be set to 1 km) due to the addition, deletion, or replacement of the device, the protection switching occurs at this time, and the length of the working path can be re-measured by the method in step 31. .
  • the uplink data and the downlink data transmitted by the remote device between the OTN and the ONU are as shown in FIG. 6, and may include a signal that the OLT sends a signal to the ONU through the OTN and a signal that the ONU sends to the OLT through the OTN.
  • the signal that the OLT sends to the ONU through the OTN includes: continuously receiving 0/E, performing photoelectric conversion, and receiving downlink data; ODU (Optical Distribution Unit) demapping: Gigabit PON Transmission Convergence (Gigabit PON Transmission Convergence)
  • ODU Optical Distribution Unit
  • the data is demapped from the ODU; the sequence code request and the ranging request are extracted: the sequence code request and the ranging request are extracted from the downlink GTC data; the E/0 is continuously transmitted, and the downlink GTC data is sent to the ONU through the electro-optical conversion.
  • the process in which the ONU sends a signal to the OLT through the OTN includes: burst receiving light 0/E, performing optical power adjustment, photoelectric conversion, and performing amplification and shaping; buffer: buffering the uplink GTC data by using the Td obtained in step 313; Request, ranging request response: response to the OLT's sequence code request and ranging request by delay compensation; uplink data selection: selecting the uplink data or response of the transmitting ONU according to the ranging state of the remote device Data; ODU mapping: Mapping uplink GTC data into ODU; Continuously transmitting E/O: Sending ODU data to OLT through electro-optical conversion.
  • the embodiment of the present invention realizes the flexible adjustment of the working path and the length of the protection path in the PON system by obtaining the distance between the working path and the protection path of the remote device and the OLT, and delaying the data on the path of the shorter distance.
  • the XPON network can be used normally; and the length of the working path and the protection path are re-detected during the protection switching process, thereby realizing that the OLT is not changed.
  • the ONU can register successfully, which improves the flexibility of the XPON system adjustment and reduces the time consumed by the protection switching process.
  • this embodiment only improves the remote device of the XPON system, and does not change the current
  • the embodiment of the present invention further provides a device for remotely extending a PON.
  • the distance measuring unit 71, the comparing unit 72, and the delay unit 73 may be included.
  • the ranging unit 71 is configured to obtain a distance between the working path and the protection path of the remote device and the OLT;
  • the comparing unit 72 is configured to compare the distance between the working path and the protection path to obtain a shorter distance path and a longer distance path; It is used to delay the data on the path of the shorter distance on the remote device, so that the time of the data passing through the shorter distance path is the same as the time of the longer distance path. .
  • the ranging unit may specifically include a response sending unit, a delay adjusting unit, and a remote configuration unit.
  • the response sending unit is configured to respond to the sequence code request of the OLT, and send a predetermined number of sequence code response messages;
  • the delay adjustment unit is configured to increase the time T1 of the normal response OLT after each predetermined number of sequence code response messages are sent. a fixed delay t, until the N fixed delay t is received, the response message of the OLT is received; N is an integer greater than or equal to 0; the remote configuration unit is used to
  • Tl+Nt responds to the ranging request of the OLT to obtain the distance between the working path and the protection path of the remote device and the optical line terminal.
  • the delay unit 73 may specifically include a switching protection unit, when the protection switching occurs, the remote device buffers or debuffers the uplink data to complete the protection switching of the uplink data.
  • the PON remote device may further include a first path retest unit and a second path retest unit.
  • the first path re-measurement unit is configured to: when the distance of the working path or the protection path changes less than a predetermined value, the remote device adjusts the position on the remote device by detecting a change in the position of the frame header of the uplink data.
  • the second path retest unit is used as the working path or the protection path
  • the remote device re-measures the distance of the working path or the protection path.
  • the storage medium may be a magnetic disk, an optical disk, a read-only memory (ROM), or a random access memory (RAM).

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  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
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Abstract

一种PON拉远的方法及设备，包括获得拉远设备与光线路终端OLT的工作路径和保护路径的距离；比较所述工作路径和保护路径的距离，获得较短距离路径和较长距离路径；在所述拉远设备上，对所述较短距离的路径上的数据进行延时T，使所述数据经过所述较短距离路径的时间和所述较长距离路径的时间相同。本发明具有在PON系统内部对工作路径和保护路径调整的灵活性较好以及在XPON拉远的过程中，当ONU与OLT的差分距离超过20km时XPON网络能够正常使用。

Description

一 一
一种 PON拉远的方法及设备
本申请要求于 2010 年 5 月 27 日提交中国专利局、 申请号为 201010187511.0、发明名称为 "一种 P0N拉远的方法及设备"的中国专利申请的 优先权， 其全部内容通过引用结合在本申请中。 技术领域
本发明属于网络通信技术领域， 涉及一种 PON拉远的方法及设备。
背景技术
现随着视频点播、 高清晰度电视、 网络游戏等新兴业务的兴起， 用户对带 宽的需求日益增长， FTTH(Fiber To The Home, 发展光纤到户）可有效保证 "最 后一公里" 的接入网带宽。 其中， PON(Passive Optical Network, 无源光网络) 技术是目前应用最广泛的 FTTH技术之一。 图 1是传统的使用 PON接入的网 络架构， 用户的多种业务通过 PON的接入和传送网传输， 能灵活地接到不同 的电信业务节点。 如图 1 所示， PON 系统的基本组成包括 OLT(Optical Line Terminals , 光线路终端）、 ONU(Optical Network Unit , 光网络单元）和 ODN(Optical Distribution Network, 光分配网）等部分， 其中 OLT与 ONU之间 的 ODN包括了主干光纤、 无源光分路器和分支光纤等设备。 OLT和无源光分 路器之间通过主干光纤连接， 无源光分路器实现一点对多点的光功率分配， 即 通过多个分支光纤连接到多个 ONU, 从 OLT到 ONU的方向称为下行方向， 从 ONU到 OLT的方向称为上行方向。
在传统的 PON系统中， OLT通过无源光分路器对接的 ONU数量较少， 覆盖半径一般不超过 20km, 导致传统的网络架构中 OLT数量较多， 且位置区 域偏远、 分散， 不方便管理和维护， 设备投资和维护成本较高。 随着下一代光 接入网络的兴起，大型运营商提出将 PON拉远至 100km甚至 200km以上的需 求。 而借用目前的现有的 OTN(Optical Transport Network, 光传送网络)进行拉 远的 XPON over OTN方式日益成为一种主流的应用场景。
在如图 2所示的 GPON over OTN拉远场景中， OLT支持 200km以上的逻 辑距离， 其工作路径和保护路径的距离差大于 170km, 已经超过了 OLT支持 - - 的 20km的差分距离（即最远 ONU和 OLT之间的距离与最近 ONU和 OLT之 间的距离之差）。并且在该场景中，通过 OTN设备来扩大 GPON(Gigabit Passive Optical Network, 吉比特无源光网络)的服务覆盖范围、 延长传输距离。 在下行 方向， 在 OLT节点接入设备上将 GPON的下行数据封装进 OTN网络， 通过 OTN网络的工作路径到达 OTN的接入节点 , 通过 OTN节点接入设备从 OTN 网络里解封装出 GPON下行数据广播给下面的 ONU; 在上行方向， 在 OTN 的接入节点将各 ONU的上行数据封装进 OTN网络， 经由 OTN网络的工作路 径到达 OLT的接入节点，并在 OLT节点接入设备上解封装出 GPON上行数据， 发送给 OLT。 但是在上述场景中， 当 OTN上发生保护倒换的时候， 由于工作 路径和保护路径的距离差超过 GPON支持的最大差分距离 20km, 在不改变配 置的情况下 ONU不能重新注册成功， 需要手动配置 OLT的覆盖范围或增加 OLT的差分距离。
在实现本发明过程中， 发明人发现现有技术中至少存在如下问题： 在现有的将 PON拉远的系统中，存在 PON系统内部对于工作路径和保护 路径的调整灵活性较差以及在 XPON拉远的过程中， 当 ONU与 OLT的差分 距离超过 20km时导致 XPON网络无法使用的问题。
发明内容
本发明的实施例提供了一种 PON拉远的方法及设备，具有在 PON系统内 部对工作路径和保护路径调整的灵活性较好以及在 XPON拉远的过程中， 当 ONU与 OLT的差分距离超过 20km时 XPON网络能够正常使用。
一种 PON拉远的方法， 包括：
获得拉远设备与光线路终端 OLT的工作路径和保护路径的距离； 比较所述工作路径和保护路径的距离， 获得较短距离路径和较长距离路 径；
在所述拉远设备上， 对所述较短距离的路径上的数据进行延时 T, 使所述 数据经过所述较短距离路径的时间和所述较长距离路径的时间相同。
一种 PON拉远的设备， 包括：
测距单元， 用于获得拉远设备与 OLT的工作路径和保护路径的距离； 比较单元， 用于比较所述工作路径和保护路径的距离， 获得较短距离路径 和较长距离路径； - - 延时单元， 用于在所述拉远设备上，对所述较短距离的路径上的数据进行 延时 T,使所述数据经过所述较短距离路径的时间和所述较长距离路径的时间 相同。
由上述本发明的实施例提供的技术方案可以看出， 通过获得拉远设备与 OLT的工作路径和保护路径的距离， 并对较短距离的路径上的数据进行延时， 实现了在 PON系统内灵活调整工作路径和保护路径的距离， 并且在 XPON拉 远的过程中，当 ONU与 OLT的差分距离超过 20km时 XPON网络能够正常使 用。 附图说明
为了更清楚地说明本发明实施例的技术方案，下面将对实施例描述中所需 要使用的附图作简单地介绍，显而易见地， 下面描述中的附图仅仅是本发明的 一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动性的前提下， 还可以根据这些附图获得其他的附图。
图 1为现有技术的 PON系统的基本组成示意图；
图 2为现有技术的 GPON over OTN拉远场景示意图；
图 3为本发明的实施例提供的 PON拉远的方法流程示意图；
图 4为本发明的实施例提供的通过响应 OLT获得工作路径和保护路径的 距离的方法流程示意图； 图 5为本发明的实施例提供的 OTN节点接入设备响应 OLT的序列码请求 的示意图；
图 6为本发明的实施例提供的 ONU通过拉远设备与 OTN发送数据的示 意图；
图 7为本发明的实施例提供的 PON拉远的设备结构示意图。 具体实施方式
下面将结合本发明实施例中的附图，对本发明实施例中的技术方案进行清 楚、 完整地描述， 显然， 所描述的实施例仅仅是本发明一部分实施例， 而不是 一 一 全部的实施例。基于本发明中的实施例， 本领域普通技术人员在没有作出创造 性劳动前提下所获得的所有其他实施例， 都属于本发明保护的范围。
本发明的实施例提供了一种 PON拉远的方法， 如图 3所示， 具体可以包 括：
步骤 31 , 获得拉远设备与 OLT的工作路径和保护路径的距离。
具体地， 在建立 PON系统网络的过程中， 可以将 OLT的逻辑距离设置到 一个较大的值，例如大于工作路径或保护路径的 10~20%或直接设置 OLT能够 支持的最远距离。 获得拉远设备与 OLT之间的工作路径和保护路径的距离的 方法可以包括： 在建立 PON系统网络的工程布线过程中手工测量工作路径和 保护路径的距离；由 OLT节点接入设备或 OTN节点接入设备向工作路径和保 护路径同时发送一个标志，然后在 OLT节点接入设备或 OTN节点接入设备上 通过计算收到两个标志的时间差获得工作路径和保护路径的距离； 在 OTN节 点接入设备上由 ONU响应 OLT的序列码请求， 在收到 OLT的响应消息后， 再通过响应的 OLT的测距请求获得工作路径和保护路径的距离，如图 4所示， 该方法具体可以包括如下的步骤： 。
步骤 311 , 响应 OLT的序列码请求， 并发送预定数量的序列码响应消息。 具体地， 首先由 OTN节点接入设备响应 OLT的序列码请求， 并发送序列 码响应消息， 为了能够尽量落在 OLT的开窗范围内， 可以将预定数量设定为 每次发送 3至 5个序列码响应消息。
步骤 312, 在每发送一次预定数量的序列码响应消息后， 在正常响应 OLT 的时间 T1上增加一个固定延时 t, 直到增加 N次固定延时 t后， 收到 OLT的 响应消息； N为大于等于 0的整数。
具体地， 若 OTN节点接入设备发送了预定数量个序列码响应消息后还没 有收到 OLT的序列码配置消息，则认为 OTN节点接入设备发出的序列码响应 消息没有落在 OLT的开窗范围内。 如图 5所示， 当序列码响应消息没有落在 OLT的开窗范围内时， 在正常响应 OLT序列码请求需要的时间 T1上增加一 个固定延时 t作为新的序列码响应延时时间（该时间定义为 Tl+t, 由于有延时 的存在，使 T1不能每次都落在 OLT的开窗范围内， 因此在每次响应之后都要 加上一个 t,为节省测距时间， t可设为 OLT支持的最大差分距离对应的时间）。 直到增加了 N个 t后， OTN节点接入设备收到了 OLT的序列码配置消息， 此 时 OTN节点接入设备发出的序列码响应消息落在 OLT的开窗范围内，则最终 获得的序列码响应延时时间为 Tl+N x t, 其中 N为大于等于 0的整数。
步骤 313 , 将 Tl+N X t作为 OLT延时， 响应 OLT的测距请求， 以获得拉 远设备与光线路终端的工作路径和保护路径的距离。
具体地，由 OTN节点接入设备根据最终获得的序列码响应延时时间 T1+N x t, 响应 OLT的测距请求， 获得 OLT分配的均衡时延 E, 再将緩存时间 Td 发送给 OLT 以计算获得拉远设备与光线路终端的工作路径和保护路径的距 离， 其中 Td=Tl+(N-l) x t+E。
步骤 32, 比较工作路径和保护路径的距离， 获得较短距离路径和较长距 离路径。
具体地， 在获得拉远设备与 OLT的工作路径和保护路径的距离后， 会首 先比较工作路径和保护路径的距离， 将距离较短的路径作为延时的目标。
步骤 33 , 在拉远设备上，对较短距离的路径上的数据进行延时 T,使数据 经过较短距离路径的时间和较长距离路径的时间相同。
具体地，在获得较短距离的路径后，对较短对较短距离的路径上的数据进 行延时 T ,是数据经过较短距离路径的时间和较长距离路径的时间相同。例如 , 保护路径的距离比工作路径的距离短 1km,则对在保护路径上传送的数据进行 延时，使传送的数据在保护路径上传递的时间与该数据在较长的工作路径上传 递的时间相同， 以达到将工作路径和保护路径在 PON系统拉远的过程中保持 为一致的目的。
进一步地， 当工作路径或保护路径的距离发生变化时，还需要对上行数据 进行调整或者重新测量工作路径或保护路径的距离，具体还可以包括以下的步 骤：
步骤 34, 当发生保护倒换时， 拉远设备对上行的数据进行延时 T的緩存 或去緩存， 以完成对上行的数据的保护倒换。
具体地， 当工作路径或保护路径发生较大变化时， 就会发生保护倒换。 此 时拉远设备与 OLT之间的工作路径或保护路径发生了变化， 因此在传送数据 过程中配置的緩存也要发生变化。例如，若经过拉远设备进行延时 T后的上行 数据的工作路径减少了 1km, 则需要对上行数据的工作路径去緩存； 若上行数 据的工作路径增加了 1km, 则需要对上行数据的工作路径增加緩存。 一 一 步骤 35, 当工作路径或保护路径的距离发生小于预定值的变化时， 拉远 设备通过检测上行数据的帧头的位置变化，调整拉远设备上的上行数据的定帧 窗口，调整的工作路径和保护路径的距离，使工作路径和保护路径的距离经过 延时 T后相同。
具体地， 由于光纤老化等原因，会导致工作路径或保护路径发生小于预定 值 (预定值可以设定为 1km)的变化，需要重新测量工作路径或保护路径的长度。 可以由拉远设备通过检测上行数据的帧头的位置变化，以调整拉远设备上的上 行数据的定帧窗口， 并调整的工作路径和保护路径的距离， 以使工作路径和保 护路径的距离经过延时 T后相同。
步骤 36, 当工作路径或保护路径的距离发生大于预定值的变化时， 拉远 设备重新测量获得工作路径或保护路径的距离长度。
具体地， 若由于添加、删除节点或更换设备等原因导致保护路径发生大于 预定值 (预定值可以设定为 1km)的变化， 可以通过步骤 31叙述的方法重新测 量保护路径的长度。若由于添加、删除节点或更换设备等原因导致工作路径发 生大于预定值 (预定值可以设定为 1km)的变化， 则此时发生保护倒换， 也可以 通过步骤 31的方法重新测量工作路径的长度。
在已有技术中比较常用的 TDM-PON(Time Division Multiplex PON, 时分 复用无源光网络)系统中， 为了尽量兼容已有的 GPON设备， 避免拉远成本过 高， 本实施例只提供对拉远设备改进的技术方案。 在 OTN与 ONU之间通过 拉远设备传送的上行数据和下行数据如图 6所示，可以包括 OLT通过 OTN向 ONU发送信号和 ONU通过 OTN向 OLT发送的信号。其中 OLT通过 OTN向 ONU发送的信号包括： 连续接收 0/E, 进行光电转换， 并接收下行数据； ODU(Optical Distribution Unit, 光分配单元)解映射： 将下行 GTC(Gigabit PON Transmission Convergence, 传输汇聚层)数据从 ODU中解映射出来； 序列码请 求、 测距请求提取： 从下行 GTC数据中提取序列码请求和测距请求； 连续发 送 E/0, 将下行 GTC数据通过电光转换发给 ONU。 ONU通过 OTN向 OLT 发送信号的过程包括： 突发接收光 0/E, 进行光功率调整、 光电转换， 并进行 放大和整形； 緩存： 利用步骤 313获得的 Td对上行 GTC数据进行緩存； 序列 码请求、 测距请求响应： 通过延时补偿响应 OLT的序列码请求和测距请求； 上行数据选择： 根据拉远设备的测距状态选择发送 ONU的上行数据或者响应 数据； ODU映射： 将上行 GTC数据映射进 ODU; 连续发送 E/O: 将 ODU数 据通过电光转换发送给 OLT。
本发明的实施例通过获得拉远设备与 OLT 的工作路径和保护路径的距 离， 并对较短距离的路径上的数据进行延时， 实现了在 PON系统内灵活调整 工作路径和保护路径的长度， 并且在 XPON拉远的过程中， 当 ONU与 OLT 的差分距离超过 20km时 XPON网络能够正常使用；还通过在保护倒换过程中 重新检测获得工作路径和保护路径的长度， 实现了在不改变 OLT配置的情况 下 ONU就能注册成功， 提高了 XPON系统调整的灵活性， 减少了保护倒换过 程消耗的时间； 另夕卜， 本实施例只对 XPON 系统的拉远设备进行改进， 不改 变目前已有的 OLT和 ONU的配置即可支持 XPON over OTN网络中 OTN上 的保护倒换， 具有实现简单和成本低廉的特点。
本发明的实施例还提供了一种 PON拉远的设备， 如图 7所示， 具体可以 包括测距单元 71、 比较单元 72和延时单元 73。 测距单元 71用于获得拉远设 备与 OLT的工作路径和保护路径的距离；比较单元 72用于比较工作路径和保 护路径的距离， 获得较短距离路径和较长距离路径； 延时单元 73用于在拉远 设备上， 对较短距离的路径上的数据进行延时 T, 使数据经过较短距离路径的 时间和较长距离路径的时间相同。 。
进一步地， 测距单元具体可以包括响应发送单元、延时调整单元和拉远配 置单元。 响应发送单元用于响应 OLT的序列码请求， 并发送预定数量的序列 码响应消息； 延时调整单元用于在每发送一次预定数量的序列码响应消息后， 在正常响应 OLT的时间 T1上增加一个固定延时 t, 直到增加 N次固定延时 t 后， 收到 OLT的响应消息； N为大于等于 0的整数； 拉远配置单元， 用于将
Tl+Nt作为 OLT延时， 响应 OLT的测距请求， 以获得拉远设备与光线路终端 的工作路径和保护路径的距离。
以及，延时单元 73具体可以包括倒换保护单元， 用于当发生保护倒换时， 拉远设备对上行的数据进行延时 T的緩存或去緩存，以完成对上行的数据的保 护倒换。
另外， 该 PON拉远的设备还可以包括第一路径重测单元和第二路径重测 单元。第一路径重测单元用于当工作路径或保护路径的距离发生小于预定值的 变化时，拉远设备通过检测上行数据的帧头的位置变化， 调整拉远设备上的上 一 一 行数据的定帧窗口，调整的工作路径和保护路径的距离，使的工作路径和保护 路径的距离经过延时 T后相同； 第二路径重测单元，用于当工作路径或保护路 径的距离发生大于预定值的变化时，拉远设备重新测量获得工作路径或保护路 径的距离。
上述设备中包含的各单元的处理功能的具体实施方式在之前的方法实施 方式中已经描述， 在此不再重复描述。
本领域普通技术人员可以理解实现上述实施例方法中的全部或部分流程 , 是可以通过计算机程序来指令相关的硬件来完成，所述的程序可存储于一计算 机可读取存储介质中，该程序在执行时，可包括如上述各方法的实施例的流程。 其中，所述的存储介质可为磁碟、光盘、只读存储记忆体（Read-Only Memory, ROM )或随机存储记忆体（ Random Access Memory, RAM )等。
以上所述，仅为本发明较佳的具体实施方式，但本发明的保护范围并不局 限于此，任何熟悉本技术领域的技术人员在本发明揭露的技术范围内， 可轻易 想到的变化或替换， 都应涵盖在本发明的保护范围之内。 因此， 本发明的保护 范围应该以权利要求的保护范围为准。

Claims

权 利 要 求
1、 一种 PON拉远的方法， 其特征在于， 包括：
获得拉远设备与光线路终端 OLT的工作路径和保护路径的距离； 比较所述工作路径和保护路径的距离， 获得较短距离路径和较长距离路 径；
在所述拉远设备上， 对所述较短距离的路径上的数据进行延时 T, 使所述 数据经过所述较短距离路径的时间和所述较长距离路径的时间相同。
2、 根据权利要求 1所述的方法， 其特征在于， 所述获得拉远设备与光线 路终端的工作路径和保护路径的距离的过程具体包括：
响应所述 OLT的序列码请求， 并发送预定数量的序列码响应消息； 在每发送一次所述预定数量的序列码响应消息后， 在正常响应 OLT的时 间 T1上增加一个固定延时 t, 直到增加 N次固定延时 t后， 收到 OLT的响应 消息； N为大于等于 0的整数；
将 Tl+N X t作为 OLT延时， 响应 OLT的测距请求， 以获得拉远设备与光 线路终端的工作路径和保护路径的距离。
3、 根据权利要求 1所述的方法， 其特征在于， 所述对所述较短距离的路 径上的数据进行延时 T的步骤具体为，
当发生保护倒换时，所述拉远设备对上行的数据进行延时 T的緩存或去緩 存， 以完成对所述上行的数据的保护倒换。
4、 根据权利要求 3所述的方法， 其特征在于， 该方法还包括：
当所述工作路径或保护路径的距离发生小于预定值的变化时，所述拉远设 备通过检测所述上行的数据的帧头的位置变化，调整所述上行的数据的定帧窗 口，调整所述的工作路径和保护路径的距离，使所述的工作路径和保护路径的 距离经过延时 T后相同。
5、 根据权利要求 1至 3任意一项所述的方法， 其特征在于， 该方法还包 括：
当所述工作路径或保护路径的距离发生大于预定值的变化时，所述拉远设 备重新测量获得工作路径或保护路径的距离。
6、 一种 PON拉远设备， 其特征在于， 包括：
测距单元， 用于获得拉远设备与 OLT的工作路径和保护路径的距离； 比较单元， 用于比较所述工作路径和保护路径的距离， 获得较短距离路径 和较长距离路径；
延时单元， 用于在所述拉远设备上，对所述较短距离的路径上的数据进行 延时 T,使所述数据经过所述较短距离路径的时间和所述较长距离路径的时间 相同。
7、 根据权利要求 6所述的设备， 其特征在于， 所述测距单元具体包括： 响应发送单元， 用于响应所述 OLT的序列码请求， 并发送预定数量的序 列码响应消息；
延时调整单元， 用于在每发送一次所述预定数量的序列码响应消息后， 在 正常响应 OLT的时间 T1上增加一个固定延时 t,直到增加 N次固定延时 t后， 收到 OLT的响应消息； N为大于等于 0的整数；
拉远配置单元 , 用于将 Tl+N X t作为 OLT延时 , 响应 OLT的测距请求 , 以获得拉远设备与光线路终端的工作路径和保护路径的距离。
8、 根据权利要求 6所述的设备， 其特征在于， 所述延时单元具体包括： 倒换保护单元，用于当发生保护倒换时，对上行的数据进行延时 T的緩存 或去緩存， 以完成对所述上行的数据的保护倒换。
9、 根据权利要求 8所述的设备， 其特征在于， 该设备还包括：
第一路径重测单元，用于当所述工作路径或保护路径的距离发生小于预定 值的变化时，通过检测所述上行的数据的帧头的位置变化，调整所述拉远设备 上的上行的数据的定帧窗口，调整所述的工作路径和保护路径的距离，使所述 的工作路径和保护路径的距离经过延时 T后相同。
10、 根据权利要求 6至 8任意一项所述的设备， 其特征在于， 该设备还包 括：
第二路径重测单元，用于当所述工作路径或保护路径的距离发生大于预定 值的变化时， 所述拉远设备重新测量获得工作路径或保护路径的距离。
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