Iterated decoding of modified product codes in optical networks

Appendix I of the standard ITU-T G.975 contains several codes that have been proposed for improved performance of optical transmission. While the original application was submarine cables, the codes are now also used in terrestrial systems where wavelength-division multiplexing (WDM) is introduced. Currently codes suitable for data rates of 100 Gbits/sec in each channel are being studied. We discuss performance limits for codes with the specified block lengths of about 130,000 and rates about 15/16. The most promising codes appear to be modified product codes, and iterated decoding is used in several cases. We discuss the construction, decoding, and performance of such codes.