Physical layer impairments in WDM core networks: a comparison between a North-American backbone and a Pan-European backbone

In the absence of all-optical 3R regenerators, the quality of transmission has a strong impact of the feasibility of all-optical long-haul transmission. Four main physical layer impairments degrade the quality of an optical analog signal, namely chromatic dispersion (CD), polarization mode dispersion (PMD), optical signal to noise ratio (OSNR), and nonlinear phase shift (Phi_NL). In most previous studies, a Q factor evaluates the quality of transmission in considering the aforementioned parameters individually (Q_i with i isin {1,2,3,4}). In this paper, we propose a tool implementing a global Q factor that takes into account the interaction between the four impairments and from which we derive the bit error rate (BER). This new factor referenced as Q₈ enables to study the suitability of optical transparency in transport networks. By means of numerical applications, we compare two backbone networks: the North-American NSF network (NSFNET) and the Pan-European backbone (EBN)