Characterization of intrachannel nonlinear distortion in ultra-high bit-rate transmission systems invited paper

Abstract

Signal distortion due to intrachannel cross-phase modulation and four-wavemixing limits transmission distances in ultra-high bit-rate optical communications. To gain an understanding of the effects of nonlinear pulse interactions and to quantify the effectiveness of new methods to suppress them, accurate characterization techniques are required to isolate the effects of fibre nonlinearity from the other impairments which occur in transmission. In this paper, we discuss two techniques: firstly, the direct measurements of the signal waveform distortion (pulse timing jitter, amplitude fluctuations, and FWM-induced 'ghost' pulse power) and, secondly, measurements of the BER-dependence on optical signal launch power. We describe the use of these characterization methods to investigate the suppression of nonlinear distortion through the use of optimized dispersion maps, alternate-polarization and alternate-phase return-to-zero signal formats. © 2005 Springer Science + Business Media, Inc. Boston.