All-Optical Wavelength Multicasting in a QD-SOA

We experimentally demonstrate multicast wavelength conversion by exploiting cross-gain modulation and cross-phase modulation in an InAs/InGaAsP/InP columnar quantum dot semiconductor optical amplifier (CQD-SOA). We report wavelength multicasting of 40 and 80 Gb/s return-to-zero signals on four 400-GHz spaced channels. We find in all cases a moderate conversion penalty which we attribute mostly to four-wave mixing (FWM) among the equally spaced converted signals. We study the effect of the FWM impairments and find that the critical number of equally spaced consecutive channels giving significant penalty is 4. Instead, two- and three-channel conversion is possible with a null or negative Q² factor penalty.