Noise Evolution and Analysis of long Repeated/Regenerated IMDD Links

Long haul optical links provides the backbone for most of today's communication and the Internet in general. The throughput of an optical link witnessed a major breakthrough with the advent of optical amplifiers in the early 1990s. These optical amplifiers with their large bandwidth facilitated the introduction of Wavelength Division Multiplexing (WDM) and a bandwidth explosion followed. Though they provide good gain and large bandwidth, all while keeping the information in optical domain; optical amplifiers do add noise of its own to the data, which when cascaded over long distances starts to limit the link length. Optical-Electrical-Optical (OEO) regenerators are used to clean and regenerate the signal but are expensive and adds potential delays in the link. In this paper we investigates their theoretical performance differences and highlights the advantages of all regenerators link over all repeaters ones. We undertake this analytical study to investigate the absolute theoretical gains of implementing an all regenerator link which is to serve as a baseline, or a precursor, for further investigations on the advantages of all optical regenerative link. Here we derive the performance limits of an all regenerator systems and compare it with its amplifier/repeater counterparts. Noise evolution in all repeater links and BER accumulation for both are illustrated. We illustrate general optical link BER curves and compare all repeater/regenerator link performances against input power for single and multiple hops. We also translate the BER advantage of all regenerator link to longer link reaches or lower power requirements. The later is repeated for different target BER too.