Towards a Smooth Integration of Quantum Key Distribution in Metro Networks

Quantum key distribution (QKD) systems have already reached a reasonable level of maturity. However, a smooth integration of commercial QKD systems in metropolitan area networks has still remained challeng ing because of technical and economical obstacles. Mainly the need for dedicated fibers and the strong dep endence of the secret key rate on both loss budget and back ground noise in the quantum channel hinder a practi cal, flexible and robust implementation of QKD in current and next-generation optical metro networks. In this paper, we discuss these obstacles and prese nt approaches to share existing fiber infrastructur es among quantum and classical channels. Particularly, a pro posal for a smooth integration of QKD in optical me tro networks, which implies removing spurious background photons caused by lasers, amplifiers and nonlinea r effects in optical fibers, is presented and discuss ed.