Abstract
In the past years, nonlinear frequency division multiplexing (NFDM) has been investigated as a potentially revolutionary technique for nonlinear optical fiber communication. However, while NFDM is able to exploit the Kerr nonlinearity, its performance lags behind that of conventional systems. In this work, we first highlight that current implementations of NFDM are strongly suboptimal, and, consequently, oversensitive to noise: the modulation does not ensure a large minimum distance between waveforms, while the detection is not tailored to the statistics of noise. Next, we discuss improved detections strategies and modulation techniques, proposing some effective approaches able to improve NFDM. Different flavors of NFDM are compared through simulations, showing that (i) the NFDM performance can be significantly improved by employing more effective detection strategies, with a 5.6 dB gain in Q-factor obtained with the best strategy compared to the standard strategy; (ii) an additional gain of 2.7 dB is obtained by means of a simple power-tilt modulation strategy, bringing the total gain with respect to standard NFDM to 8.3 dB; and (iii) under some parameters range (rate efficiency η≤30%), the combination of improved modulation and detection allows NFDM to outperform conventional systems using electronic dispersion compensation.
Highlights
Fiber nonlinearity can be regarded as a detrimental effect, and as an opportunity for all-optical signal processing and regeneration and for the establishment of favorable conditions for signal propagation
DF-backward NFT (BNFT) detection and nonlinear inverse synthesis (NIS) modulation with power tilt outperforms the linearly-modulated system with EDC for rate efficiency less than approximately 30%
This manuscript considers nonlinear frequency-division multiplexing (NFDM) systems in which only the continuous nonlinear spectrum is modulated: the discrete nonlinear spectrum is left empty by construction when the signal is generated at the TX, and is assumed to be still empty at the RX—if some discrete components arise during propagation because of amplified spontaneous emission (ASE) noise, they are neglected
Summary
Fiber nonlinearity can be regarded as a detrimental effect, and as an opportunity for all-optical signal processing and regeneration and for the establishment of favorable conditions for signal propagation. The analysis is performed in a simple ideal scenario, assuming ideal distributed amplification along the fiber, modulating only the continuous spectrum of a single polarization, and favoring accuracy over complexity in the implementation of the NFT algorithms, so that numerical issues with the latter are avoided. The rationale behind these choices is discussed, considering the expected impact of loss and dual-polarization modulation, the possible role of the discrete spectrum, and the extension to a network scenario.
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