A method of constructing an SDH-based time transfer network and its experimental examination

Abstract

In this paper we propose a simplified SDH (Synchronous Digital Hierarchy)‐based time synchronous system that does not require the modification of existing SDH transmission equipment (STE) and clock supply equipment (CSE). The system has auxiliary time synchronizing equipment (TSE) attached to existing STE and CSE and can be expanded in a cascade and branch manner, where frequency and time are separately synchronized, and which enables us to partially time‐synchronize an SDH network or to introduce a time transfer network locally. Experimental time synchronizing devices using a 576‐kbps data communication channel (DCC) in the section overhead (SOH) showed potentially satisfactory performance, with synchronization errors of a four‐link system on the order of submicroseconds. Noise analyses of experimental TSE, DCC, CSE, and optical links showed that accuracy on the order of microseconds can be achieved. © 2000 Scripta Technica, Electr Eng Jpn, 132(2): 39–48, 2000