As seen from the
previous post about PDH, PDH is a workable but flawed system.At the beginning it
was the best available technology and was a giant leap forward in telecom transmission,
As a result of growth in the field of silicon chips and integrated
microprocessors, customer demand soon provided the need to introduce a new and
better system.& it was expected to
solve the existing limitations of PDH.
As a next step,
Bellcore introduced SYNTRAN (Synchronous
Transmission) system. However this was only a development system. Soon it was
replaced with SONET (Synchronous
Optical Network).Initially SONET could only carry the ANSI (American National
Standards Institute) bit rates i.e. 1.5, 6, 45 Mbit/s. Aim of the project was
to provide easier international interconnection, Hence, SONET was modified to
carry the European standard bit rates of 2, 8, 34 & 140 Mbit/s.
