Nonlinear interference noise in 100-Gbit s^-1communication lines with the DP-QPSK modulation format

New method to obtain optimum performance for 100Gb/s multi-span fiber optic lines

“…Let's find the minimum of the expression in the left part of the inequality (22) considering it as a function of P n , n N 1, ... , = . The optimization is performed independently for each span, so we can find an optimal power for each span using the new method: …”

“…Simple analytical expressions were obtained in a theoretical model based on perturbation theory that proved to be very usable for analysis of fiber optic transmission systems without periodical dispersion compensation [17][18][19][20][21][22][23][24]. In this model nonlinear distortions are regarded as a nonlinear interference noise.…”

Accumulation of nonlinear noise in coherent communication lines without dispersion compensation

“…Recent experimental and theoretical researches have shown that the nonlinear noise power in a long multi-span line increases with the number of spans a bit faster than linearly [7,11]. Two mechanisms were suggested in [11] to explain the superlinear dependence of accumulated nonlinear noise power on communication line length: a) correlation of noises that are generated in different spans, and b) increase of nonlinear noise power generated in a span with increasing of accumulated dispersion.…”

“…The Gaussian noise (GN) model of NLI noise is attractive for practical use because it allows elementary system optimization rules based on the signal to noise ratio [17,18]. Several analytical models for performance evaluation and design of such systems have been proposed [5][6][7][8][9]19]. An alternative timedomain theory predicts that a large fraction of nonlinear noise can be characterized as phase noise [20].…”

“…This nonlinear noise can be described as a Gaussian noise [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19], at least in dispersion uncompensated (DU) coherent systems. Gaussian nature of the nonlinear interference (NLI) noise fields is conditioned by Gaussian distribution of the information sampled signal [4][5][6][14][15][16].…”