1. A method of forward error correction (FEC) decoding, said method comprising: receiving a modulated FEC encoded signal containing a FEC encoded data stream; demodulating the modulated FEC encoded signal to produce a constructive signal and a destructive signal, said constructive signal being the result of splitting and constructively recombining said modulated FEC encoded signal and said destructive signal being the result of splitting and destructively recombining said modulated FEC encoded signal; differentially detecting said constructive signal and said destructive signal to produce a hard decision differential detection signal corresponding to said FEC encoded data stream; producing an error locating signal indicating possible errors in said differential detection signal using a hard-decision detection of said constructive signal to produce a first binary signal and a hard decision detection of said destructive signal to produces a second binary signal and comparing said first binary signal and said second binary signal using a logic circuit; converting said hard decision differential detection signal into a soft decision signal using said error locating signal, said soft decision signal including multi-level soft values; and decoding said soft decision signal to produce an output data stream.