This paper will at first explain the requirement of high speed optical transport network
on forward error correction (FEC) codes in terms of code length, code rate, coding gain, burst
error correction capability, error floor, latency, coding/decoding complexity. Then, a few code
schemes used in current optical transport systems such as Reed-Solomon codes recommended by
ITU-T G.709 and enhanced FECs listed in ITU-T, G.975.1 are introduced. Advanced codes
recently developed by vendors used for 100Gbps systems and their performances are summarized.
Features and special requirements on soft decoding FEC (SDFEC) especially inter-working
between SDFEC and equalizer, with and without deferential coding etc. are analyzed. Some
perspectives of future FEC for optical transport are also given.