SONET requirements for jitter interworking with existing networks

Existing asynchronous transport networks have been engineered to maintain jitter at levels low enough that it causes essentially no errors. SONET will interwork with existing networks by transporting signals originating in those networks (e.g. DS1- and DS3-rate signals) as part of its payload. As SONET is introduced, it is important to ensure that jitter on these signals remains within acceptable levels. Both high-frequency jitter that affects clock recovery circuits, and broad-band jitter that affects circuits in multiplexers and demultiplexers present interworking issues. The paper addresses broad-band jitter. There are two major mechanisms by which SONET generates broad-band jitter on a payload: pulse-stuffing used to map a signal into SONET, and the pointer mechanism employed by SONET to maintain phase alignment of tributaries. The effect of pointer adjustments depends on equipment characteristics, network architecture, and characteristics of the signals that provide timing to SONET devices. The paper discusses the requirements for controlling jitter from both mapping and pointer adjustments