Effect of second order signal-noise interactions in nonlinearity compensated optical transmission systems.

Mohammad A Z Al-Khateeb,Andrew Ellis,Christian Sánchez,Mary Mccarthy

doi:10.1364/ol.41.001849

Abstract

In this Letter, we theoretically and numerically analyze the performance of coherent optical transmission systems that deploy inline or transceiver based nonlinearity compensation techniques. For systems where signal-signal nonlinear interactions are fully compensated, we find that beyond the performance peak the signal-to-noise ratio degradation has a slope of 3 dBSNR/dBPower suggesting a quartic rather than quadratic dependence on signal power. This is directly related to the fact that signals in a given span will interact not only with linear amplified spontaneous emission noise, but also with the nonlinear four-wave mixing products generated from signal-noise interaction in previous (hitherto) uncompensated spans. The performance of optical systems employing different nonlinearity compensation schemes were numerically simulated and compared against analytical predictions, showing a good agreement within a 0.4 dB margin of error.

Highlights

Such links are limited by amplified spontaneous emission (ASE) noise and the nonlinear Kerr effect [2] in which the highest signal-to-noise ratio (SNR) is achieved by optimizing the optical signal launched power
They can mitigate the impact of deterministic Kerr effects namely the inter and intra channel nonlinear interference [5] leaving the system limited by the nondeterministic Kerr effects due to the influence of polarization mode dispersion (PMD) and signal-noise interactions
High levels of PMD can severely degrade the performance of the compensated system, such that the uncompensated signal-signal nonlinearity dominates over the effects of the signal–noise nonlinear Kerr effects [8], but the influence of PMD can be avoided by using either low PMD or polarization maintaining (PM) fibers

Summary

Introduction

In this Letter, we propose and validate an accurate closed form SNR expression covering both lumped and ideal Raman amplified optical transmission systems that compensate deterministic nonlinearities using DBP or OPC.

Results

Conclusion