Abstract
We present a low-complexity fully pilot-based digital signal processing (DSP) chain designed for high spectral efficiency optical transmission systems. We study the performance of the individual pilot algorithms in simulations before demonstrating transmission of a 51×24 Gbaud PM-64QAM superchannel over distances reaching 1000 km. We present an overhead optimization technique using the system achievable information rate to find the optimal balance between increased performance and throughput reduction from adding additional DSP pilots. Using the optimal overhead of 2.4%, we report 9.3 (8.3) bits/s/Hz spectral efficiency, or equivalently 11.9 (10.6) Tb/s superchannel throughput, after 480 (960) km of transmission over 80 km spans with EDFA-only amplification. Moreover, we show that the optimum overhead depends only weakly on transmission distance, concluding that back-to-back optimization is sufficient for all studied distances. Our results show that pilot-based DSP combined with overhead optimization can increase the robustness and performance of systems using advanced modulation formats while still maintaining state-of-the-art spectral efficiency and multi-Tb/s throughput.
Highlights
Today, optical networks use high symbol rate transceivers with advanced modulation formats to maximize the channel spectral efficiency (SE) [1]
We have described and investigated fully pilot-based digital signal processing (DSP) focusing on advanced modulation formats and powerful forward error correction
We have evaluated the performance of individual algorithms building up the DSP chain and compared to powerful blind algorithms
Summary
Optical networks use high symbol rate transceivers with advanced modulation formats to maximize the channel spectral efficiency (SE) [1]. These transceivers use all four available dimensions in single-mode fibers (SMFs) to transmit independent information, i.e. both I and Q on two orthogonal polarizations. System impairments limiting the performance consist of both transceiver imperfections and distortions induced by the fiber channel. Transceiver imperfections include limited effective number of bits (ENOBs) [4, 5], limited bandwidth of both digital-to-analog converters (DACs) and analog-to-digital converters (ADCs) as well as nonlinear distortions [6, 7]. Distortions from transmission include amplified spontaneous emission noise from erbium-doped fiber amplifiers (EDFAs) and non-linear signal degradation from the fiber itself [8, 9]
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