Abstract
This paper studies different signaling techniques on the continuous spectrum (CS) of nonlinear optical fiber defined by nonlinear Fourier transform. Three different signaling techniques are proposed and analyzed based on the statistics of the noise added to CS after propagation along the nonlinear optical fiber. The proposed methods are compared in terms of error performance, distance reach, and complexity. Furthermore, the effect of chromatic dispersion on the data rate and noise in nonlinear spectral domain is investigated. It is demonstrated that, for a given sequence of CS symbols, an optimal bandwidth (or symbol rate) can be determined so that the temporal duration of the propagated signal at the end of the fiber is minimized. In effect, the required guard interval between the subsequently transmitted data packets in time is minimized and the effective data rate is significantly enhanced. Moreover, by selecting the proper signaling method and design criteria a distance reach of 7100 km is reported by only singling on CS at a rate of 9.6 Gbps.
Highlights
Extensive efforts have been made to develop new techniques for higher achievable data rates in optical fiber communication over long-haul systems, where nonlinear effects are significant [1,2,3]
The real and imaginary parts of the noise in continuous spectrum (CS) may not be assumed independent after propagation over the nonlinear optical fiber unlike the conventional linear channels, and they can be modeled [26] as E{ [ηL(λ)]2} = E{ [ηL(λ)]2} = f [| ρ0(λ)|]/2
When the outer ring is π/4 shifted in phase all the methods results in better bit error rate (BER) except the nonuniform signaling based on variance normalizing transform (VNT)
Summary
Extensive efforts have been made to develop new techniques for higher achievable data rates in optical fiber communication over long-haul systems, where nonlinear effects are significant [1,2,3]. Nonlinear frequency division multiplexing (NFDM) was proposed [4,5,6], where, rather than on the time domain, the data is mapped on either of the two available nonlinear spectra defined by NFT, namely, continuous spectrum (CS) [8,9,10] and discrete spectrum (DS) [11,12,13,14,15,16,17,18] Simultaneous signaling on both CS and DS has been recently investigated [10, 19]. It is demonstrated that 9.6 Gbps can be transmitted over 7100 km using 26 GHz bandwidth
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