Noise analysis for optical fiber communication systems

The optical fiber transmission links form the backbone of the communications infrastructure. Almost all of voice and data (internet) traffic is routed through terrestrial and submarine optical fiber links, connecting the world together. Invention of the optical amplifiers (OAs) and wavelength-division multiplexing (WDM) technology enabled very high capacity optical fiber communication links that run for thousands of kilometers without any electronic repeaters, but at the same time brought many design challenges. As electronic amplifiers do, OAs add noise to the signal they amplify. In the design of an optical fiber communication link, the prediction of the deterioration the information signals experience due to the nonlinearity of the optical fiber and the optical noise generated by the OAs is essential. In this paper, we first present a short overview of optical fiber communication systems and the challenges that faces one from a modeling, analysis and design perspective. Then, we describe novel formulations and computational techniques for the analysis of the interplay between the information signals and the optical noise due to the fiber nonlinearity as they propagate together along the fiber link. Our formulations are similar, in spirit, to the linear(ized), time-varying formulations for noise analysis in analog/RF electronic circuits. We then investigate signal-noise mixing due to optical fiber nonlinearities using the techniques developed. Finally, we discuss the use of the generated results in the performance evaluation of communication links, and comment on system design implications.