通信原理论文(中英文版)

Optimized Pulse Shaping for Intra-channel Nonlinearities Mitigation in a 10 Gbaud

Dual-Polarization 16-QAM System

Benoît Châtelain1, Charles Laperle2, Kim Roberts2, Xian Xu1, Mathieu Chagnon1, Andrzej Borowiec2, François Gagnon3, John C. Cartledge4, and David V. Plant1

1McGill University, Montreal, Quebec, Canada, H3A 2A7 2Ciena Corporation, Ottawa, Ontario, Canada, K2H 8E9

3École de technologie supérieure, Montreal, Quebec, Canada, H3C 1K3 4Queen’s University, Kingston, Ontario, Canada, K7L 3N6 Email: benoit.chatelain@mail.mcgill.ca

Abstract: 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.

OCIS codes: (060.2330) Fiber optics communications; (060.4080) Modulation

1. Introduction

Intra-channel nonlinear distortion is an important source of signal degradation in optical communication systems using advanced modulation formats such as quadrature amplitude modulation (QAM). Its main impact is to reduce the maximal power that can be launched into the fiber, thereby limiting optical signal-to-noise ratio (OSNR) levels at the receiver, reducing system margins and reducing the maximum propagation distance that can be achieved. In this paper, the nonlinear tolerance of an optimized pulse and a root-raised cosine (RRC) pulse is compared in terms of bit error rate (BER) performance, for varying propagation distances and launch powers. Experimental results show that the optimized pulse considerably reduces intra-channel nonlinear effects in a long haul, 10 Gbaud

dual-polarization (DP) 16-QAM system relying on erbium-doped fiber amplifiers (EDFAs) and G.652 fiber (no optical dispersion compensation).

The improved nonlinear tolerance of the return-to-zero (RZ) pulse shape was recently highlighted in [1], for a 112 Gb/s DP-quadrature phase shift keying (QPSK) system without optical dispersion compensation. Comparing the RZ pulse to the non return-to-zero (NRZ) pulse, the authors reported an increase in single channel maximum propagation distance of 18%. However, the improved nonlinear tolerance achieved using the RZ pulse comes at the expense of increased spectral content. For instance, the bandwidth of a 50% RZ pulse is twice the bandwidth of the NRZ pulse or the RRC pulse with a roll-off factor (α) of 1. The use of a RZ pulse thus reduces spectral efficiency by a factor of two, and for a system using digital signal processing at the transmitter and receiver, at the Nyquist rate, it doubles the required bandwidth and sampling frequency of the digital-to-analog converters (DACs) and analog-to-digital converters (ADCs).

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