Efficient signalling on the continuous spectrum of nonlinear optical fibre

Due to the so-called capacity crunch, an increasing number of research have been focused on the subject of efficient signalling on nonlinear optical fibres and particularly methods based on nonlinear Fourier transform (NFT) [1-6]. This field of research includes the design of optical transmission using discrete spectrum, continuous spectrum (CS) [1], and combination of all degrees of freedom [2]. Recently in [4, 5], the capacity of the continuous spectrum is estimated and it is demonstrated that CS can be a suitable alternative for application in long-haul optical fibre links. A very important and unique property of the CS channel is the dependence of noise variance in nonlinear frequency domain on the signal amplitude [4, 5]. In this abstract, based on the statistical behaviour of noise in nonlinear frequency domain, we propose a simple but efficient method for signalling and performance improvement. Using this method, the channel is converted into an additive white Gaussian noise (AWGN) channel.