Forward error correction for the synchronous optical network (SONET) signal standard

The design, feasibility, performance, and implementation of a single-error correcting code, applicable to the STS-1 format of the SONET standard, are considered. It is shown that if two of the presently unallocated bytes in the path overhead field of STS-1 are assigned for FEC (forward error correction), an optional {6208,6195} shortened Hamming code can be implemented in as few as 16500 gates, achieving single-error correction over the STS-1 payload. The shortened code is derived from {8191,8178} perfect Hamming code having 13 check bits. The suggested implementation is such that all path, line, and section overhead functions can be performed at intermediate sites without requiring FEC decoding. The motivation for STS-1 level FEC in SONET is to improve end-to-end performance to virtually error-free levels, to obtain relaxations in laser specifications, and improved dispersion tolerance in gigabit-rate OC-n transmission systems, and to obtain an advanced performance monitoring function