Abstract
In linear communication channels, spectral components (modes) defined by the Fourier transform of the signal propagate without interactions with each other. In certain nonlinear channels, such as the one modelled by the classical nonlinear Schrödinger equation, there are nonlinear modes (nonlinear signal spectrum) that also propagate without interacting with each other and without corresponding nonlinear cross talk, effectively, in a linear manner. Here, we describe in a constructive way how to introduce such nonlinear modes for a given input signal. We investigate the performance of the nonlinear inverse synthesis (NIS) method, in which the information is encoded directly onto the continuous part of the nonlinear signal spectrum. This transmission technique, combined with the appropriate distributed Raman amplification, can provide an effective eigenvalue division multiplexing with high spectral efficiency, thanks to highly suppressed channel cross talk. The proposed NIS approach can be integrated with any modulation formats. Here, we demonstrate numerically the feasibility of merging the NIS technique in a burst mode with high spectral efficiency methods, such as orthogonal frequency division multiplexing and Nyquist pulse shaping with advanced modulation formats (e.g., QPSK, 16QAM, and 64QAM), showing a performance improvement up to 4.5 dB, which is comparable to results achievable with multi-step per span digital back propagation.
Highlights
The rapidly increasing demand on communication speed is exerting great pressure on the networks’ infrastructure at every scale, which explains the real motivation behind all optical communications research
We have shown that the nonlinear inverse synthesis (NIS) method can be successfully combined with high-SE transmission techniques (e.g., orthogonal frequency division multiplexing (OFDM), Nyquist-shaped) and advanced modulation formats, such as QPSK, 16QAM, and 64QAM
This novel transmission scheme suggests the encoding of the information onto the continuous part of the nonlinear spectrum and requires only single-tap equalization at the receiver to compensate for all the deterministic fiber nonlinearity impairments accumulated along the fiber link
Summary
The rapidly increasing demand on communication speed is exerting great pressure on the networks’ infrastructure at every scale, which explains the real motivation behind all optical communications research. We utilize the transmission based on the nonlinear inverse synthesis (NIS) [30], a method which allows one to avoid the problems associated with the solitary degrees of freedom in the anomalous dispersion NLSE Within this approach, the encoded input signal (or, to be more specific, its linear spectrum) is first mapped onto a complex field in the time domain via the GLME (i.e., via the BNFT) before transmission (see the detailed flowchart presented in Fig. 1 of [30]). We discuss the challenges and current limitations of the NIS approach for high-capacity optical communications
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