OPTICAL TRANSMISSION SYSTEM

摘要

A reception unit is configured to be provided with two coherent receivers which use two LO beams controlled to a predetermined optical frequency interval (ΔF) at optical frequencies (f11, f12) close to the optical frequency (f1) of a signal beam, and a digital signal processing unit which demodulates a transmission data signal sequence from an output from each of the coherent receivers. The digital signal processing unit performs processing for, when a frequency difference (Δf1) of one LO beam from a virtual reference frequency (f1') close to the optical frequency (f1) of the signal beam is set for the two LO beams, finding a frequency difference (Δf2) of the other LO beam from Δf1-ΔF, inputs respective electric signals outputted from the two coherent receivers, and compensates for phase rotations occurring in the respective electric signals due to the frequency differences (Δf1, Δf2).