Experimental demonstration of fiber nonlinearity mitigation in a WDM multi-subcarrier coherent optical system

Nonlinear mitigation on subcarrier-multiplexed PM-16QAM optical systems

“…Its performance limits in terms of maximum reach gain in fully-loaded WDM transmission have been estimated to be in the range of 10-25% [21,22]. SRO and DBP can also be combined together to maximize nonlinear mitigation, as already demonstrated in [23], expanding the MSC-PM-QPSK results of [5] to show an additional 8% reach increase provided by DBP, on top of the baseline 12% enabled by SRO, totalling 20% extended reach over SC transmission.…”

“…Other PM-QPSK-based experiments have followed, proving the existence of SRO also in WDM transmission. A 19 × 128 Gb/s PM-QPSK experiment has been reported in [5], where 12% extended reach was found with an 8-subcarrier channel configuration. In [4], enhanced SRO benefits were found by increasing the inter-subcarrier spacing in a 8channel PM-QPSK experiment, yielding 0.7 dB gain in required OSNR after propagation, even suffering from a 0.3 dB back-to-back (B2B) MSC implementation penalty.…”

“…It exploits the flexibility on signal design provided by fast digital-to-analog converters (DACs), enabling to create multiple electrically-generated subcarrier signals composed of an adjustable number of low symbol-rate tributaries. The main competitive advantage of MSC over standard SC transmission lies on the additional nonlinear robustness provided by the recently identified symbol-rate optimization (SRO) phenomenon [1][2][3][4][5][6][7][8]. Exploring the additional degree of freedom (number of subcarriers) provided by MSC transmission, several analytical, simulation and experimental works have identified that the total nonlinear interference (NLI) impinging on a given channel under test (CUT) turns out to depend on the per-subcarrier symbol-rate [1][2][3][4][5][6][7][8].…”

Advanced Techniques for Digital Nonlinear Compensation in Multi-carrier Optical Transmission Systems

“…A different flavour of multi-carrier transmission based on subcarrier multiplexing (SCM) has recently started to attract significant attention [20][21][22][23], mostly due to the inherent nonlinear mitigation phenomenon that is enabled by symbol-rate optimization (SRO) [22,23]. In SCM systems, each optical channel is subdivided into low symbolrate subcarriers (typically 2-4 Gbaud), which are electronically generated by the same transceiver.…”

Carrier Phase Estimation in Multi-Subcarrier Coherent Optical Systems

“…Although linear impairments like polarization mode dispersion (PMD) and chromatic dispersion (CD) can be effectively compensated by DSP, performance of the optical communication system is still limited by the fiber nonlinearities. In [1]- [3] it has been shown that the non-linear performance of coherent optical systems is significantly affected by the symbol rate: dividing the available bandwidth of a high baud-rate single-subcarrier (SC) into several low baudrate subcarriers (SCs) can significantly improve the tolerance towards fiber non-linearities [4], [5]. For current 32 Gbaud systems, the optimum symbol rate for the SCs lies in the range of 2 − 4 Gbaud and can result in 10% − 20% increase in the maximum reach for polarization-multiplexed quadrature phase shift keying (PM-QPSK) systems [4], [5].…”