Hitless path switching ring network, hitless path switching transmission system, node device for a hitless path switching ring network, and failure occurrence-time hitless path switching transmission method in a ring network

Abstract

A hitless path switching ring network capable of switching from a work transmission line to a protection transmission line without instantaneous hitting of a signal when a failure occurs in the work transmission line. In the hitless path switching ring network, a node device includes a first memory section storing a signal being transmitted onto the work transmission line during normal operation, and a first read control section, at the time of failure occurrence, reading out the transmitted signal, held before failure occurrence, from the first memory section and sending out the transmitted signal through the protection transmission line in the opposite direction from the transmission direction employed before failure occurrence. Another node device includes a second memory section for storing the signal received through the work transmission line during normal operation, a third memory section for storing the signal received through the protection transmission line during failure occurrence, and a phase adjusting section for matching the time phase of the received signal in the second memory section with the time phase of the received signal in the third memory section and outputting the received signal held before failure occurrence.