Signal Processing Techniques for Reducing the Impact of Fiber Nonlinearities on System Performance

Abstract

Signal processing techniques for mitigating intra-channel and inter-channel fiber nonlinearities are reviewed. More detailed descriptions of three specific examples highlight the diversity of the electronic and optical approaches that have been investigated.

Performance limits in optical communications due to fiber nonlinearity

“…Digital nonlinearity compensation techniques developed to date include direct digital back propagation, essentially solving equation 10 in each receiver [217][218][219][220][221][222][223], various simplified forms of back propagation [224][225], various coding schemes where duplicate information is transmitted (see section 5.3), Volterra series estimation [226], pilot tone estimation [227][228] and look-up tables [229]. For details of how to implement such schemes, the reader is directed to these sources, and to recent reviews of electronic nonlinearity compensation [202,230] and references therein. The numerical values of Figure 20 and the associated references are summarized in Table 2.…”

“…For OPC the widespread conception is that such non-uniformity would destroy the compensation. However, this is not strictly the case [230,[273][274]. Whilst it is likely that non-uniform spans would prevent an OPC system reaching the limit imposed by parametric noise amplification, achievement of a few dB gain over all channel simultaneously remains a reasonable option.…”

Volterra-Assisted Optical Phase Conjugation: A Hybrid Optical-Digital Scheme for Fiber Nonlinearity Compensation

“…Hybrid optical NLC schemes were previously studied, e.g. in [26], with joint operation of OPC and DBP. However, this combination was designed to relax the link placement of the OPC device, rather than a way to enhance NLC performance.…”

Link-Placement Characterization of Optical Phase Conjugation for Nonlinearity Compensation

“…A strong research effort has therefore been directed towards techniques for mitigation or at compensation of the nonlinear distortion experienced by signals during transmission. While techniques based on digital signal processing (DSP) are particularly effective in compensating for intra-channel nonlinearity, analog bandwidth limitations make them impractical for addressing inter-channel nonlinear distortion [1]. All-optical techniques, instead, may be more suited for tackling cross-channel nonlinearity due to their larger operation bandwidth.…”

“…Hence, the impact of OPC position on the nonlinearity compensation has been numerically investigated for dispersion-unmanaged links in [1,6,7]. Additionally, in [1,7], the potential to compensate for an offset in OPC position by lower complexity DBP has been proposed and numerically evaluated.…”