Study on the optimum Reed-Solomon-based FEC codes for 40-Gb/s-based ultralong-distance WDM transmission

The optimum redundancy for various Reed-Solomon (RS)-based forward-error correcting codes in 40-Gb/s-based ultralong-distance wavelength-division multiplexing (WDM) transmission based on erbium-doped fiber amplifier repeater and dispersion-flattened fiber span using A_eff-enlarged single-mode fiber and slope-compensating disperion compensation fiber is numerically studied. In the case of single RS codes, a redundancy of approximately 7% was found to be the best choice and useful for the systems that are less than transoceanic distances. For transoceanic applications, the concatenated codes with a redundancy between 10% and 14% with four iterative decoding were found a better choice for transatlantic applications, and the product RS codes with a redundancy between 10% and 14% with four iterative decoding seem necessary for further distance expansion.