Mitigation of Nonlinear and PMD Impairments by Bit-Synchronous Polarization Scrambling

Abstract

Abstract-Our statistical study by the importance sampling method shows that a significant performance improvement may be achieved by bit-synchronous polarization scrambling in the presence of polarization mode dispersion and fiber nonlinearity in dispersion managed, single-channel, or wavelengthdivision-multiplexed NRZ 10 Gbit/s fiber optic transmission systems.

Importance Sampling Analysis of PMD Outages in PDM-QPSK Coherent Nonlinear Transmissions

“…Therefore in non-DM QPSK systems the main effect of nonlinearity is the shift of the mean value of the PMD-induced PDF of the output Q factor. This is in contrast with the case of OOK systems in the presence of in-line DM and without PMD compensation, where it was shown that nonlinearity may strongly affect the width of the Q factor PDF as well [9]. Let us briefly discuss the dependence of the Q factor PDF in the presence of nonlinear cross-talk or XPolM from the two adjacent channels.…”

“…In practice it is not possible with simple Monte-Carlo simulations to accurately numerically evaluate the PDF of the BER, since in order to evaluate its tails one would need a prohibitively large number of simulations. On the other hand, the tails of the PDF can be computed with just a few thousands of simulations by the IS technique [8], [9].…”

“…and the index j denotes the scattering section. The PDF of the output Q factor was obtained by combining (using a simplified balance heuristic method [9]) the results of different PDFs obtained with either no bias (α = 1), or with a given bias level (e.g., α = 1/(1-C) with C = 0.1, 0.2). For each set of unbiased or biased simulations we collected 1000 runs.…”

“…We previously applied the importance-sampling (IS) technique [8] to the estimation of the PDF of the output Q factor in the presence of fiber nonlinearity, CD and PMD in nonreturnto-zero (NRZ) on-off keying (OOK) systems [9]. In this letter, we extend the use of the IS technique to the case of PDM-QPSK coherent transmissions, which enables us to directly compute the PMD-induced OP in a realistic system setup involving CD, amplified spontaneous emission (ASE) noise, and fiber nonlinearity [5].…”

Spectrally effective mitigation of polarization mode dispersion in optical fibers

“…4,13 The influence mitigation of PMD can also be done by including polarization scramblers (PSs) in certain sections of the optical path, whose role is to statistically suppress the influence of PMD or to increase the influence of polarization mode coupling (in today's modern fibers, this feature is introduced in the production of optical fibers). 13,14 Another possibility to avoid the influence of PMD (and not only PMD) is the use of system margin. If there is sufficient reserve transmission capacity, the optical signal can be rerouted along a different (backup) path.…”