Abstract
Achievable information rates of optical communication systems are inherently limited by nonlinear distortions due to the Kerr effect occurred in optical fibres. These nonlinear impairments become more significant for communication systems with larger transmission bandwidths, closer channel spacing and higher-order modulation formats. In this paper, the efficacy of nonlinearity compensation techniques, including both digital back-propagation and optical phase conjugation, for enhancing achievable information rates in lumped EDFA- and distributed Raman-amplified fully-loaded C -band systems is investigated considering practical transceiver limitations. The performance of multiple modulation formats, such as dual-polarisation quadrature phase shift keying (DP-QPSK), dual-polarisation 16 -ary quadrature amplitude modulation (DP-16QAM), DP-64QAM and DP-256QAM, has been studied in C -band systems with different transmission distances. It is found that the capabilities of both nonlinearity compensation techniques for enhancing achievable information rates strongly depend on signal modulation formats as well as target transmission distances.
Highlights
It is widely accepted that over 95% of currently estimated digital data traffic is carried over optical fibre networks forming a substantial part of the national and international communication infrastructure [1,2]
The achievable information rate (AIR) is a natural figure of merit in coded communication systems, which demonstrates the net data rates achieved assuming the ideal error corrections [3,4,5,6]. Since linear impairments, such as chromatic dispersion (CD), polarisation mode dispersion (PMD), and laser phase noise can be well compensated via digital signal processing [7,8,9], AIRs of optical transmission systems are still limited by nonlinear distortions due to the Kerr effect in optical fibres [10,11]
This paper extends the scope of the investigation to practical 1st−order distributed Raman amplification (DRA) schemes, and the achievable information rates are examined in the case of nonlinearity compensation (NLC) systems using both digital back-propagation (DBP) and optical phase conjugation (OPC) techniques
Summary
It is widely accepted that over 95% of currently estimated digital data traffic is carried over optical fibre networks forming a substantial part of the national and international communication infrastructure [1,2]. The achievable information rate (AIR) is a natural figure of merit in coded communication systems, which demonstrates the net data rates achieved assuming the ideal error corrections [3,4,5,6] Since linear impairments, such as chromatic dispersion (CD), polarisation mode dispersion (PMD), and laser phase noise can be well compensated via digital signal processing [7,8,9], AIRs of optical transmission systems are still limited by nonlinear distortions due to the Kerr effect in optical fibres [10,11]. Since numerical simulations of fully-loaded C−band systems with a range of modulation formats are computationally intractable, a theoretical model considering modulation format-dependent distortions and transceiver noise limitations was developed to investigate the performance of such systems This enabled a realistic study of the efficacy of MC-NLC to enhance AIRs for different modulation formats. The model was used to explore the transmission regimes where MC-NLC can have a significant impact on AIRs in C−band systems, and importantly to highlight the required compensation bandwidth
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