Intra-channel Nonlinear Distortions Research Articles

Digital compensation of cross-phase modulation distortions using perturbation technique for dispersion-managed fiber-optic systems

A digital compensation scheme based on a perturbation theory for mitigation of cross-phase modulation (XPM) distortions is developed for dispersion-managed fiber-optic communication systems. It is a receiver-side scheme that uses a hard-decision unit to estimate data for the calculation of XPM fields using the perturbation technique. The intra-channel nonlinear distortions are removed by intra-channel digital backward propagation (DBP) based on split-step Fourier scheme before the hard-decision unit. The perturbation technique is shown to be effective in mitigating XPM distortions. However, wrong estimations in the hard-decision unit result in performance degradation. A hard-decision correction method is proposed to correct the wrong estimations. Numerical simulations show that the hybrid compensation scheme with DBP for dispersion and intra-channel nonlinear impairments compensation and the perturbation technique for XPM compensation brings up to 3.7 dBQ and 1.7 dBQ improvements as compared with the schemes of linear compensation only and intra-channel DBP, respectively. The perturbation technique for XPM compensation requires only one-stage (or two-stage when hard-decision correction is applied) compensation and symbol-rate signal processing.

Optical Equalization of Nonlinear Signal Distortion in 42.7-Gb/s RZ Transmission

We describe an experimental demonstration of the reduction of intrachannel nonlinear distortion in 42.7-Gb/s return-to-zero transmission with 107.5-km amplifier spans without Raman amplification using an optical equalizer (OEQ). This allowed an increase in the transmission distance from 2043 to 3010 km. The mechanism of nonlinear penalty mitigation by the OEQ-generated satellite pulses is described.

Investigation of the Optimum Alternate-Phase RZ Modulation Format and Its Effectiveness in the Suppression of Intrachannel Nonlinear Distortion in 40-Gbit/s Transmission Over Standard Single-Mode Fiber

The results of a detailed study of the performance of 40-Gbit/s optical transmission over standard single-mode fiber with alternate-phase return-to-zero (AP-RZ) modulation formats are presented. While in the highly dispersed propagation regime, the use of RZ format signals with alternate phase between adjacent pulses can lead to a significant reduction in nonlinear interaction between pulses, allowing increased launch powers and, hence, increased transmission distances, this has not been systematically investigated. In this paper, we investigate the use of AP-RZ formats, both numerically and experimentally, to explain and quantify the effects of varying the peak-to-peak phase modulation, the amount of precompensation at the transmitter and the presence of multiplexer prefiltering for the case of wavelength-division multiplexing systems with high spectral efficiency. It is shown that, while the use of pulses with alternate /spl pi//2 rad phase shifts minimizes the build-up of shadow pulses in the zero bit slots due to intrachannel four-wave mixing, the best overall performance is obtained with /spl pi/ rad peak-to-peak phase modulation. We show experimentally, for the first time, that the optimum value of precompensation to minimize intrachannel nonlinear distortion is dependent on the signal format used.

Effective suppression of intra-channel nonlinear distortion in 40 Gbit∕s transmission over standard singlemode fibre using alternate-phase RZ and alternate polarisation

For the first time suppression of intra-channel nonlinear distortion in 40 Gbit/s transmission is shown, by combining alternate polarisation with the alternate-phase-RZ signal format in an optical-time-division-multiplexed system, doubling the maximum transmission distance compared to standard RZ.

Investigation of Intrachannel Nonlinear Distortion in 40 Gbit/s Transmission over Standard Fiber

We describe new distance-dependent experiments investigating intrachannel nonlinear distortion in 40 Gbit/s optical time division mulitplexed transmission over standard fiber. Simulation results predicting significant reduction in the distortion due to intrachannel four-wave mixing by using alternating pulse polarization were experimentally confirmed.

Investigation of Intrachannel Nonlinear Distortion in 40 Gbit/s Transmission over Standard Fiber

Investigation of Intrachannel Nonlinear Distortion in 40 Gbit/s Transmission over Standard Fiber

Reduction of intrachannel nonlinear distortion in 40-Gb/s-based WDM transmission over standard fiber

Intrachannel cross-phase modulation and four-wave mixing in high-bit-rate WDM transmission systems employing standard single-mode fiber are investigated. The effects of imperfect third-order dispersion compensation are included in the study and analytical expressions giving optimum values of dispersion precompensation minimizing the distortion due to the intrachannel nonlinear effects are derived.