A time synchronization method and device for an optical transport network asynchronous network

Abstract

The invention discloses a time synchronization method and device for an asynchronous network of an optical transmission network. When a station in the optical transmission network receives a time message transmitted by other stations, the first line card in the station recovers one or more clocks The clock frequency of the optical channel data unit (ODUm), where m is a positive integer less than or equal to k, k is the order of the optical channel data unit, k=1, 2, 3, 4, and the service of the first line card uses the local clock Convert to the data frame format of the backplane, and send the clock ODUm to the second line card in the site through the cross-connect board; the second line card uses the local clock to receive the backplane data frame, recovers the clock frequency of the clock ODUm, and uses the optical path transmission unit (OTUn) The local clock or service recovery clock of the optical port sends the entire OTUn, where n is the order of the optical channel transmission unit. The present invention can support high-precision time synchronization under the asynchronous condition of the existing network OTN.

Description

technical field [0001] The invention relates to a time synchronization technology in the communication field, in particular to a time synchronization method and device for an asynchronous network of an optical transport network. Background technique [0002] With the development of packet services, PTN (Packet Transport Network, Packet Transport Network) is rising day by day. It is not only suitable for multi-service bearer, but also can provide clock synchronization (synchronous Ethernet) and 1588 time synchronization functions, which can be very good Supports mobile backhaul features. However, if the services converged by the PTN equipment are transmitted through the existing OTN (Optical Transport Network, Optical Transport Network), it is necessary to consider the bearer mode of the OTN for time synchronization. [0003] At present, OTN mainly supports the time transfer of PTN in the following three ways: [0004] 1. The client signal transmits the 1588 protocol on the...

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Problems solved by technology

[0007] Among them, the above-mentioned first method will cause the time synchronization performance to drop sharply due to the functions of mapping / demapping, multiplexing / demultiplexing, and switching in the OTN equipment; the second method requires the OSC-terminated 1588 The message is re-initiated on another OSC channel, which may not be supported by the existing hardware architecture, and the OSC of each manufacturer may not be compatible; the third method is that since OTN is an asynchronous system, the sending frequency of each port may be free oscillation The system clock (regeneration service) may also restore the clock for the service (transparent service), and the backplane design of the OTN equipment on the existing network may not support the synchronization of time stamps between service boards, so it may Unable to achieve time synchronization with retrofit

[0008] To sum up, if the OTN equipment system architecture of the existing network cannot be changed, the maximum clock frequency deviation of each site is 20ppm (one millionth of a second). In this case, precise time synchronization cannot be achieved

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