Patent ID: 7280767

Claim:
An optical transmitter, comprising: a precoder for precoding two half-rate data streams having half-rate input symbol times into two cumulative cross parity streams, said half-rate data streams carrying data equivalent to a single full-rate data stream; and a multiplex modulator for using said parity streams for providing a return-to-zero (RZ) optical signal carrying duobinary RZ modulation having intensity corresponding to said full-rate data stream; and wherein: a current parity of a first of said parity streams is a cross parity of a current symbol of a first of said half-rate data streams with a delayed second half-rate data stream, plus a last previous parity of said first parity stream, where a second of said half-rate data streams is delayed by said input symbol time for providing said delayed second half-rate data stream; and a current parity of a second of said parity streams is a cross parity of a current symbol of said second half-rate data stream with a current symbol of said first half-rate data stream, plus a last previous parity of said second parity stream.