Digital and Optical Compensation of Signal Impairments for Optical Communication Receivers

Abstract

Three new receiver designs, incorporating novel digital and optical signal processing solutions, are presented for fiber-optic communication in long-haul transmissions and access networks. Firstly, a complex-weighted decision-aided maximum-likelihood joint phase noise and frequency offset estimator is derived for coherent receivers in long-haul transmissions. Additionally, the resilience of several 4-, 8-, and 16-point constellations to phase rotation and cycle slips are investigated. Secondly, an adaptive complex-weighted decision-aided carrier estimator for coherent receivers is introduced, whose effective filter length automatically adapts according to the signal-to-noise ratio, laser-linewidth-per-symbol-rate, nonlinear phase noise, and modulation format, without any preset parameters. Thirdly, a direct-detection receiver incorporating a passive optical delay interferometer is proposed for radio-over-fiber optical backhaul employing reflective semiconductor optical amplifier (RSOA) in broadband wireless access networks. Effectiveness of the receiver in alleviating the constrained modulation bandwidth, limited transmission distance, and radio frequency signal fading, is assessed through an upstream transmission of a 2-Gb/s 6-GHz radio signal in loopback-configured network using a directly modulated RSOA.