Transmission and reception of duobinary multilevel pulse-amplitude-modulated optical signals using subtraction-based encoder

摘要

Methods and apparatus to transmit and receive information bits encoded in duobinary, multilevel pulse-amplitude-modulated (PAM) optical signals. The transmitted optical signal has a narrow optical spectrum and a low symbol rate. Information bits are encoded in a M-ary PAM symbol sequence, where M≳2. A subtraction-based encoder precodes and duobinary filters the M-ary PAM symbol sequence, yielding an encoded sequence. The encoded sequence is lowpass filtered and modulated onto an optical electric field. The receiver processes a received optical electric field to obtain an electrical signal proportional to the received optical intensity, and performs M-ary symbol-by-symbol decisions to recover the transmitted information bits, without potential error propagation.