Abstract
In this paper, we propose two modifications to reduce the complexity of the subcarrier-multiplexing (SCM) based digital backpropagation (DBP) for high symbol rate SCM systems. The first one is to reduce the number of interfering subcarriers (RS-SCM-DBP) when evaluating the cross-subcarrier nonlinearity (CSN). The second one is to replace the original frequency domain CSN filters with the infinite impulse response (IIR) filters (IIR-RS-SCM-DBP) in the CSN compensation. The performance of the proposed schemes are numerically evaluated in three-channel dual-polarization (DP) 16QAM wavelength-division multiplexing (WDM) transmissions. The aggregate symbol rate for each channel is 120 GBaud and the transmission distance is 1600 km. For the SCM system with 16 subcarriers, the IIR-RS-SCM-DBP with only 4 interfering subcarriers and 2 steps can achieve a 0.3 dB Q-factor improvement in the WDM transmission. Compared to the original SCM-DBP, the proposed IIR-RS-SCM-DBP reduces the complexity by 48% at a performance loss of only 0.07 dB.
Highlights
Coherent optical transmission systems have been commercialized and deployed in regional, long-haul and submarine backbone networks [1]
In a 3 × 120 GBaud wavelength-division multiplexing (WDM) simulation of DP-16QAM 16-subcarrier SCM signals at a transmission distance of 20 × 80 km, we show that infinite impulse response (IIR)-RS-SCM-digital backpropagation (DBP) with only 4 interfering subcarriers in cross-subcarrier nonlinearity (CSN) compensation only reduces the Q factor by 0.07 dB compared to SCM-DBP at 2 steps, while the complexity of the former is reduced by 48% compared to the latter
We propose to use the IIR filter to replace the CSN LPF in the CSN compensation step, which is denoted as IIR-RS-SCM-DBP, in order to further reduce the computational complexity
Summary
Coherent optical transmission systems have been commercialized and deployed in regional, long-haul and submarine backbone networks [1]. In this context we anticipate a heightened role for digital nonlinear compensation in generation 400 Gb/s and 1 Tb/s systems It was numerically [6,7], experimentally [8], and theoretically [9] demonstrated that subcarriermultiplexing systems can achieve a higher nonlinear tolerance by optimizing the symbol rate of each subcarrier compared to single carrier (SC) systems. The selfsubcarrier nonlinearity (SSN) of each subcarrier and the cross-subcarrier nonlinearity (CSN) between subcarriers are compensated separately It was demonstrated in a 34.94 GBaud single channel SCM experiment with transmission distances of 6400 km for QPSK and 2560 km for 16QAM that SCM-DBP only required two steps to achieve sizable improvements. The overall performance improvement compared to SC systems with linear compensation only is ~0.8 dB
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