FORWARD ERROR-CORRECTING CODES IN SYNCHRONOUS FIBER OPTIC TRANSMISSION-SYSTEMS

This paper proposes forward error correcting (FEC) codes for Synchrono us Digital Hierarchy (SDH) fiber optical transmission systems. They ar e (18 880, 18 865) and (2370, 2358) shortened Hamming codes and are en coded at the multiplex-section layer; the check bits are embedded in a uxiliary multiplex-section overhead (MSOH) bytes. The codes realize ge neral circuit configurations regardless of the transmission speed or p ath-size, perfect compatibility with SDH format, suppressed processing delay accumulation, and decrease the chance of line-switching in the case of signal degradation. To ensure that the various requirements of each network-provider such as customized usage of SOH bytes and affor dable circuit scale could be satisfied, a trial circuit board was cons tructed on the programmable hardware called PROTEUS, which enables fle xible operation in terms of code-selection and check bit area. We actu ally confirm error-correcting capability through the first STM-64 FEC- coded-optical transmission experiment. The statistics of error occurre nce in the optical transmission line are also studied. The result indi cates that the proposed codes are effective in optical transmission sy stems if the BER is limited by optical noise and dispersion.