Digital nonlinearity compensation in high-capacity optical communication systems considering signal spectral broadening effect

Abstract

Nyquist-spaced transmission and digital signal processing have proved effective in maximising the spectral efficiency and reach of optical communication systems. In these systems, Kerr nonlinearity determines the performance limits, and leads to spectral broadening of the signals propagating in the fibre. Although digital nonlinearity compensation was validated to be promising for mitigating Kerr nonlinearities, the impact of spectral broadening on nonlinearity compensation has never been quantified. In this paper, the performance of multi-channel digital back-propagation (MC-DBP) for compensating fibre nonlinearities in Nyquist-spaced optical communication systems is investigated, when the effect of signal spectral broadening is considered. It is found that accounting for the spectral broadening effect is crucial for achieving the best performance of DBP in both single-channel and multi-channel communication systems, independent of modulation formats used. For multi-channel systems, the degradation of DBP performance due to neglecting the spectral broadening effect in the compensation is more significant for outer channels. Our work also quantified the minimum bandwidths of optical receivers and signal processing devices to ensure the optimal compensation of deterministic nonlinear distortions.

Combating Fiber Nonlinearity Using Dual-Order Raman Amplification and OPC

“…The generated nonlinear product power without OPC was up to ~-11.5dB at strongly phase matched region and oscillated with the frequency separation due to the phase mismatching accumulation (Δβ in Eq. [1]). Using the mid-link OPC, the noise floor power was increased by ~9dB because of the insertion loss of the OPC and the additional amplifier.…”

“…ibre nonlinear impairments have been a major issue to restrain the rapidly increasing data capacity demand in optical fibre communications. Several techniques including digital back propagation (DBP), phase conjugated twin-wave, and mid-link optical phase conjugation (OPC), have been investigated to combat such nonlinear impairments [1][2][3]. OPC has been proven to be a promising all-optical signal processing technique to compensate both linear (mainly dispersive) and nonlinear impairments simultaneously for multiple Wavelength Division Multiplexed (WDM) channels [4][5][6][7].…”

Impact of Equalization-Enhanced Phase Noise on Digital Nonlinearity Compensation in High-Capacity Optical Communication Systems

“…To compensate for the fiber nonlinearities in optical communication systems, multi-channel digital backpropagation (MC-DBP) has been applied at different bandwidths to mitigate intra-channel and inter-channel fiber nonlinearities, such as self-phase modulation (SPM), cross-phase modulation (XPM), and four-wave mixing (FWM) [13,[17][18][19]. The effect of the number of steps per span, the PMD, the backpropagated signal bandwidth, and the LO phase synchronization have been studied in the optimization of MC-DBP [20][21][22].…”

Influence of Spectral Broadening on Nonlinearity Compensation in Ultra-Wideband Optical Fiber Communications

“…The spectral broadening effect was studied and evaluated in optical communication systems with considerable intra-and inter-channel fiber nonlinearities [16][17][18]. The impact of the spectral broadening on the digital nonlinearity compensation in optical transmission systems was also investigated [19][20][21]. It was found in these reports that the received signal spectra were not necessarily matched to the transmitted ones any longer owing to this spectral broadening effect.…”