Mitigation of nonlinear transmission effects for OFDM 16-QAM optical signal using adaptive modulation

Abstract

The impact of the fiber Kerr effect on error statistics in the nonlinear (high power) transmission of the OFDM 16-QAM signal over a 2000 km EDFA-based link is examined. We observed and quantified the difference in the error statistics for constellation points located at three power-defined rings. Theoretical analysis of a trade-off between redundancy and error rate reduction using probabilistic coding of three constellation power rings decreasing the symbol-error rate of OFDM 16-QAM signal is presented. Based on this analysis, we propose to mitigate the nonlinear impairments using the adaptive modulation technique applied to the OFDM 16-QAM signal. We demonstrate through numerical modelling the system performance improvement by the adaptive modulation for the large number of OFDM subcarriers (more than 100). We also show that a similar technique can be applied to single carrier transmission.

Natural Brain-Inspired Intelligence for Non-Gaussian and Nonlinear Environments with Finite Memory

“…Typically, in the analysis of long-haul fiber optic systems, the fiber optic channel is assumed to be nonlinear and the noise is assumed to be Gaussian to simplify the problem [34]. Under the Gaussian noise assumption, it follows that the variance of nonlinear noise should be proportional to the total distance L. However, in [34], it was shown that the variance of nonlinear noise scales as L x where x ∈ (1, 2) depending on the dispersion map. Therefore, the Gaussian noise assumption is not accurate for OFDM systems in the presence of nonlinearity.…”

“…However, the estimatedX k n after FEC can be used instead of the database shown in Figure 7 in fiber optic link for model extraction. The bit error rate after forward error correction (FEC) is between 10 −15 and 10 −12 [34] when the BER before FEC is less than the FEC-threshold. In addition, the decision-making error can be calculated as the BER.…”

“…We illustrate the modeling process by performing a numerical simulation of an OFDM system (see Figure 8). Signal propagation in an optical fiber is described by the nonlinear Schrödinger equation (NLSE), which is solved using the standard split-step Fourier scheme [34]. The output of the linear equalizer is passed to the perceptor (see Figures 4 and 8).…”

Loss of phase and universality of stochastic interactions between laser beams

“…PACS numbers: 42.65.Tg, 42.65. Sf,42.65.Jx Nonlinear interactions between two or more laser beams, pulses, and filaments [1] are related to applications ranging from modulation methods in optical communication [2], to coherent combination of beams [3][4][5][6][7], interactions between filaments in atmospheric propagation [8] and ignition of nuclear fusion using up to 192 beams [9]. In the integrable one-dimensional cubic case, such interactions can only lead to phase and lateral shifts, which can be computed analytically using the Inverse Scattering Transform [10][11][12].…”

“…In such cases, the notion of a "typical experiment" or a "typical solution" may be misleading, and one should adopt a stochastic approach. The loss of phase can explain some of the difficulties in phasedependent methods in optical communications such as Quadrature Amplitude Modulation (QAM) [2], and in coherent combining of hundreds of laser beams in a small space for ignition of nuclear fusion [14], and for creating a more powerful laser beam [6]. In these applications, controlling the phases of the input beams or pulses might not provide a good control over their interaction or combination, due to the loss of phase.…”