Abstract
We report a comprehensive set of experimental, simulation and analytical results on the benefit of nonlinear mitigation strategies for multi-subcarrier (MSC) PM-16QAM transmission systems. First, we demonstrate ~9% maximum reach gain enabled by symbol-rate optimization (SRO) of MSC-PM-16QAM in a 31 channels WDM transmission experiment. Then, we demonstrate that, in the considered experimental scenario, the gain provided by digital backpropagation (DBP) over single-carrier (SC) transmission is similar to that achieved by SRO over MSC transmission. Furthermore, we show that the SRO phenomenon can be weakened after self-channel interference (SCI) removal through DBP. As a result, and due to DBP performance limitations in the experiment, the combined effect of SRO and DBP was found to enable only an additional 4% gain in maximum reach. Finally, we address the impact and symbol-rate dependence of nonlinear phase noise (NLPN) in MSC-PM-16QAM transmission, discussing on the NLPN mitigation capability of standard carrier phase estimation (CPE) and on respective gains that could be achieved through its enhanced mitigation.
Highlights
The use of multi-subcarrier (MSC) signals has been recently emerging as an alternative optical transmission technique for the widely deployed single-carrier (SC) systems
After self-channel interference (SCI) mitigation through digital backpropagation (DBP), we report on the combined benefit of symbol-rate optimization (SRO) + DBP, and we discuss on the maximum performance limits of such a strategy
Through an experimental campaign on PM-16QAM MSC transmission we have demonstrated ∼9% maximum reach gain through symbol-rate optimization, a similar gain to that obtained by DBP in SC transmission
Summary
The use of multi-subcarrier (MSC) signals has been recently emerging as an alternative optical transmission technique for the widely deployed single-carrier (SC) systems. 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. In order to assess the impact of NLI format dependence on the SRO benefit achievable with PM-16QAM subcarriers, several experiments have been recently performed [2, 7, 8]. It has been shown that the NLI format dependence mostly manifests itself in the form of long-correlated nonlinear phase noise (NLPN) [17,18,19], which increases the phase variance of the received constellation symbols This NLPN phenomenon is characterized by long-term time correlations, opening up the possibility of its mitigation through CPE. In this paper, extending the work of [24], we report a 31-channel WDM experimental campaign
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