Digital subcarrier multiplexing for fiber nonlinearity mitigation in coherent optical communication systems

Abstract

In this work we experimentally investigate the improved intra-channel fiber nonlinearity tolerance of digital subcarrier multiplexed (SCM) signals in a single-channel coherent optical transmission system. The digital signal processing (DSP) for the generation and reception of the SCM signals is described. We show experimentally that the SCM signal with a nearly-optimum number of subcarriers can extend the maximum reach by 23% in a 24 GBaud DP-QPSK transmission with a BER threshold of 3.8 × 10(-3) and by 8% in a 24 GBaud DP-16-QAM transmission with a BER threshold of 2 × 10(-2). Moreover, we show by simulations that the improved performance of SCM signals is observed over a wide range of baud rates, further indicating the merits of SCM signals in baud-rate flexible agile transmissions and future high-speed optical transport systems.

XPM Model-Based Digital Backpropagation for Subcarrier-Multiplexing Systems

“…4 shows the experimental setup. The transmitter-side DSP for the generation of the SCM signal is the same as that in [11]. 34.94 Gbaud/s dual polarization (DP)-QPSK and DP-16QAM SCM signals were transmitted with root raised cosine (RRC) pulse shapes (roll-off factor = 0.1).…”

“…In offline DSP processing, the signals were first re-sampled into 2 samples/symbol, and then the frequency offset was estimated based on training symbols [20]. After subcarrier de-multiplexing [11], the proposed ADBP compensator was employed with the optimized compensation factor ξ. The remaining DSP blocks included the timing recovery, the adaptive equalization to compensate residual linear impairments and de-multiplex polarizations, and carrier phase recovery [21].…”

“…Recently, an experimental demonstration of the increased nonlinear tolerance of subcarrier-multiplexing (SCM) signals compared with the conventional single carrier (SC) signals was reported [11], [12]. By splitting a high symbol rate SC signal into multiple low symbol rate subcarriers, the nonlinearity tolerance can be improved.…”

Experimental investigation on nonlinear tolerance of subcarrier multiplexed signals with spectrum optimization

“…Although several techniques such as forward error correction (FEC) and digital nonlinear compensation (NLC) have been proposed to overcome this limitation, the trade-off between computational complexity and performance improvement still needs improvement 1 . Recently, in order to improve the nonlinear tolerance, a symbol rate optimization method has been proposed in a multi-subcarrier modulation scheme such as orthogonal frequency division multiplexing (OFDM) and Nyquist-FDM (NFDM) systems and experimentally demonstrated [2][3][4] . With enjoying the improvement, the multisubcarrier modulation scheme can reduce the complexity of digital signal processing (DSP) because a lower symbol rate signal suffers less impairments due to chromatic dispersion and polarization mode dispersion 5 .…”

Impact of intra- and inter-subcarrier nonlinearities on the information rate of a 1.206 Tbit/s DP 16-QAM superchannel

“…The dependence of multi-carrier performance and maximum system reach on percarrier symbol rate has been considered based on numerical simulations [5][6][7] and experiments 8 . In this paper, the impact of the number of superchannel subcarriers on the relative strength of the intra-and inter-subcarrier nonlinearities and on the information rate is investigated using numerical simulation.…”