XPM Model-Based Digital Backpropagation for Subcarrier-Multiplexing Systems

Abstract

Abstract-An advanced digital backpropagation (ADBP) algorithm is proposed to compensate fiber nonlinearities in subcarrier-multiplexing (SCM) systems. We derive the analytical expression and describe the implementation of the ADBP. In addition, the computational complexity of the ADBP as well as the conventional low-pass filter assisted DBP (LDBP) is analyzed and compared. In a 34.94 Gbaud/s single channel SCM transmission experiment, we demonstrate that the proposed ADBP with only two steps (40 spans/step for QPSK at 6400 km and 16 spans/step for 16QAM at 2560 km) has a comparable performance to the LDBP algorithm with 40 steps (2 spans/step) for QPSK and 8 steps (4 spans/step) for 16QAM, respectively. Moreover, compared to single carrier (SC) systems using only linear compensation (LC), the ADBP algorithm with 40 spans/step for QPSK and 16 spans/step for 16QAM can extend the maximum reach by 49.7% and 27.3% for the two formats, respectively. The contribution to the reach extension consists of 19.7% and 23.6% which are attributable to the nonlinear compensation algorithm when compared to SCM systems using LC for QPSK and 16QAM, respectively. The remainder of the improvements are attributable to the use of the SCM scheme. Finally, simulations of 60 Gbaud/s systems show additional improvements using the ADBP schemes compared to the LDBP schemes, indicating the benefits of ADBP in future high capacity optical transmission systems. IndexTerms-Subcarrier-multiplexing system, digital backpropagation, fiber nonlinearity, coherent transmission.

Experimental demonstration of low complexity nonlinear compensation algorithm based on logistic regression

“…The compensation effect becomes better when the gamma values increase. Figure 3C experimentally shows the curves of BER versus launch power for three different cases including CDE, traditional DBP, ADBP, and LR‐DBP 20 . The parameters chosen for the algorithm is shown in Table 1.…”

Distributed Nonlinear Compensation Using Optoelectronic Circuits

“…The physical effect of the filter is to transform the waveform of the interfering channel at the start of the span into the average waveform that causes the XPM distortion. Using the XPM transfer functions for several WDM channels has been explored as a way to simplify full-field DBP [12], [68], [74], [75], and we briefly looked at implementing this in optoelectronics [56]. An additional consideration is that the contributions of each spectral component from different spans add coherently [76], which creates nulls in the magnitude response of the XPM transfer function of multi-span links.…”