Andrzej Borowiec

Reducing the complexity of perturbation based nonlinearity pre-compensation using symmetric EDC and pulse shaping

Perturbation based nonlinearity pre-compensation has been performed for a 128 Gbit/s single-carrier dual-polarization 16-ary quadrature-amplitude-modulation (DP 16-QAM) signal. Without any performance degradation, a complexity reduction factor of 6.8 has been demonstrated for a transmission distance of 3600 km by combining symmetric electronic dispersion compensation and root-raised-cosine pulse shaping with a roll-off factor of 0.1. Transmission over 4200 km of standard single-mode fiber with EDFA amplification was achieved for the 128 Gbit/s DP 16-QAM signals with a forward error correction (FEC) threshold of 2 × 10(-2).

Demonstration of an 8-dimensional modulation format with reduced inter-channel nonlinearities in a polarization multiplexed coherent system.

We demonstrate a polarization-managed 8-dimensional modulation format that is time domain coded to reduce inter-channel nonlinearity. Simulation results show a 2.3 dB improvement in maximum net system margin (NSM) relative to polarization multiplexed (PM)-BPSK, and a 1.0 dB improvement relative to time interleaved return-to-zero (RZ)-PM-BPSK, for five WDM channels propagating over 1600 km ELEAF with 90% inline optical dispersion compensation. In contrast to the other modulations considered, the new 8-dimensional format has negligible sensitivity to the polarization states of the neighboring WDM channels. High-density WDM (HD-WDM) measurements on a 5000 km dispersion-managed link show a 1.0 dB improvement in net system margin relative to PM-BPSK.

A family of Nyquist pulses for coherent optical communications

A new family of Nyquist pulses for coherent optical single carrier systems is introduced and is shown to increase the nonlinearity tolerance of dual-polarization (DP)-QPSK and DP-16-QAM systems. Numerical investigations for a single-channel 28 Gbaud DP-16-QAM long-haul system without optical dispersion compensation indicate that the proposed pulse can increase the reach distance by 26% and 19%, for roll-off factors of 1 and 2, respectively. In multi-channel transmissions and for a roll-off factor of 1, a reach distance increase of 20% is reported. Experimental results for DP-QPSK and DP-16-QAM systems at 10 Gbaud confirm the superior nonlinearity tolerance of the proposed pulse.

SPM-Tolerant Pulse Shaping for 40- and 100-Gb/s Dual-Polarization QPSK Systems

An intersymbol-interference-free pulse shape is specifically designed for self-phase-modulation (SPM) mitigation. It is experimentally shown to increase the SPM tolerance of a 40-Gb/s single-channel postcompensated dual-polarization quadrature phase-shift keying system by 1.5 dB. Numerical analyses at 40 and 100 Gb/s indicate that the specialized pulse shape can increase the maximum reach for G.652 fiber and G.655 fiber up to 1190 and 820 km, respectively.

Frequency-Domain Volterra-Based Equalization Structures for Efficient Mitigation of Intrachannel Kerr Nonlinearities

Toward reduced-complexity digital implementation, frequency domain Volterra-based nonlinear equalization (VNLE) structures for multistep fiber nonlinearity compensation are proposed. In the cascade structures, nonlinear equalization is performed before (cascade-1) or after (cascade-2) the dispersion compensation in each step. Superior performance with the shorter discrete Fourier transform (DFT) lengths and fewer equalization steps compared to the conventional VNLE with parallel structure is demonstrated in a transmission experiment. The experimental results are obtained for 256 Gb/s single-carrier dual-polarization 16-ary quadrature-amplitude-modulation with root-raised-cosine pulse shaping and a roll-off factor of 0.1. The new cascade structures demonstrate superior robustness to insufficient DFT lengths and/or a limited complexity budget. Compared to the conventional parallel arrangement of linear and nonlinear compensation filters, the cascade-1 structure provides more than 90% complexity reduction without any notable performance penalty. The structure enables the extension of the transmission reach by 1570 km, a 48% increase compared to the linear solution that uses only electronic dispersion compensation.

Optimized pulse shaping for intra-channel nonlinearities mitigation in a 10 Gbaud dual-polarization 16-QAM system

An optimized pulse shape is shown to reduce intra-channel nonlinear effects in a 10 Gbaud dual-polarization 16-QAM EDFA-amplified system without optical dispersion compensation.

High Resolution Characterization of the Spectral Broadening Due to Fiber Nonlinearities

Balanced heterodyne detection and a gated microwave spectrum analyzer are used to precisely measure the spectral broadening due to intra-channel fiber nonlinearities. Polarization resolved spectra for a 224 Gb/s dual polarization 16-ary quadrature amplitude modulation signal are quantified in terms of the spectral edge power, which serves as a useful metric for capturing the effects of both fiber nonlinearities and amplified spontaneous emission noise. It is shown that without and with perturbation-based pre-compensation for the signal distortion due to the Kerr effect, the launch powers that minimize the bit error ratio and spectral edge power coincide.

Information rates for the SP 128-QAM and DP 16-QAM modulation formats

Information rates for the set-partitioning (SP) 128-QAM and dual-polarization (DP) 16-QAM modulation formats are compared for the same bit rate (256 Gbit/s) and baud rate (32 Gbaud). For 256 Gbit/s transmission over 3600 km, SP 128-QAM offers an increase of 8.2%.

Volterra-based nonlinearity compensation structures with improved performance-complexity trade-offs

Cascade Volterra-based nonlinear equalization structures are shown to provide robust performances with shorter discrete Fourier transforms (DFT) by a factor of 4 compared to the parallel structure, enabling successful data recovery in a 4500 km single-channel 256 Gbit/s experiment.

Complexity reduction of frequency-domain Volterra-based nonlinearity post-compensation using symmetric electronic dispersion compensation

Using symmetric electronic dispersion compensation, root-raised-cosine pulse shaping, and DFT block length optimization, the complexity of single-step frequency domain Volterra-based fiber nonlinearity compensation is reduced by a factor of 2.4, for a 3600 km 128 Gbit/s DP 16-QAM link.