Patent ID: 7474858

Claim:
A duobinary optical transmission device using at least one semiconductor optical amplifier (SOA), comprising: a light source for outputting a carrier wave as an optical signal to at least one SOA; a precoder for encoding an input non-return-to-zero (NRZ) electrical signal; wherein an interferorneter type semiconductor optical amplification unit comprising said at least one SOA further including; a bias input for modulating a phase of the carrier wave according to a change of an applied bias current coupled to the encoded electrical signal output from the precoder; an interferometer having a plurality of arms for branching input light, combining the branched input light, and outputting a combined signal, said at least one semiconductor optical amplifier (SOA) provided on at least one arm of the interferometer; and an optical isolator for preventing light reflection at an output terminal of the SOA; and an optical band pass filter (OBPF) for: receiving the phase-modulated optical signal from the semiconductor optical amplification unit, filtering the received phase-modulated optical signal to adjust the transmission characteristics of an optical signal according to a designated bandwidth, wherein said bandwidth is adapted to adjust transmission characteristics of the optical duobinary signal based on a data transmission bit rate; and outputting an optical duobinary signal, wherein the phase-modulated signal has a substantially same power level for “0” and “1” bits of the NRZ electrical signal and has phases of “π” and “0” for “0” and “1” bits of the NRZ electrical signal, respectively.