Assessment of gain saturation in cascaded semiconductor optical amplifier for high-bit-rate wavelength-division-multiplexing signals over long transmission distance

Abstract

In this paper, the investigation of 10 channels at 80-Gb/s wavelength-division-multiplexing (WDM) transmission over 910-km single-mode fiber and dispersion compensating fiber using cascaded in-line semiconductor optical amplifiers at a span of 70 km for soliton return zero differential phase-shift keying (RZ-DPSK) modulation format is achieved. With the narrow channel spacing (i.e., 200 GHz), the results of quality is more than 15 dB the received signals after covering 910-km transmission distance without any power drop. The semiconductor optical amplifier (SOA) structure parameters for in-line amplifier is optimized to obtain low cross talk in multichannel WDM systems at nil power penalty with sufficient gain. For the differential gain 200 atto cm 2 and length 750 mm of SOA has minimum SOA-induced cross talk is observed. The impact of optical power received and the Q factor at different differential gain, carrier lifetime, and length has been illustrated. It is found that for a transmission distance of 700 km, with decrease the channel spacing, there is an increase in cross talk among channels, hence the signal quality continues to decrease. A clear eye diagram and a good optical spectrum are observed at a transmission distance of 910 km in a soliton RZ-DPSK system.