Study On The Time Transfer Method Based SDH Network

Unified time is need when improving the quality of telecommunication network operation, developing new telecommunication business, and doing net accounts between operators. In order to satisfy the need of telecommunications networks to synchronize time while searching for a new time service method with the accuracy equal to the one of GPS to meet the requirement for time unification of other industries at the same time, this article develops a research on time delivery research based on the SDH network.To build nationwide synchronized time net using SDH network, we must study the time delay in SDH network transmission path. In a way of combing theory analysis, engineering measurement, and simulated research, this article offers a method for time transmission suitable for the characteristics of SDH network structure—loop-back and sampling method, which effectively solves the problem of the asymmetric two-way signal transmission path of the SDH ring-network and, to a great extent, enhances the accuracy of time transmission. This method also has a wide scope of application and can be used in SDH network as well as network element with any structure.This article simulates the time-delay in the single-node SDH network element processing, and gains the same result with the one of engineer measurement after comparison.With the stated loop-back and sampling method, this article makes theory analysis and simulated measurement on the asymmetric processing time-delay in the transmitting and receiving part of the single-node SDH network element. Based on this, the time accuracy transmitted through 81 SDH network elements at the length of 8000 kilometers is calculated; the accuracy within one nanosecond is gained In this article, a specific plan to realize loop-back and sampling time transmission with hardware circuit and software process needing to be added is designed. The time synchronizing network designed in this article and the existing SDH frequency synchronizing network are unified, which effectively solves the problem of time synchronization in all kinds of telecommunication network, and is capable of providing time synchronizing signals for other industries.