Guidelines for optimizing system performance for 20 WDM channels propagating through a cascade of EDFAs

Erbium-doped fiber amplifiers (EDFA's) are revolutionizing both long-distance and distribution based communications. Furthermore, optically-amplified systems can have a manifold increase in the total capacity by incorporating wavelength-division-multiplexing (WDM). However, one difficulty in implementing a WDM system incorporating EDFA's is that the EDFA gain is wavelength dependent whereas the link loss between amplifiers is wavelength independent, resulting in a severe signal-to-noise (SNR) differential between channels after a cascade of EDFA's. Moreover, only single-channel systems can incorporate narrow optical filters after each amplifier to eliminate unwanted amplified spontaneous emission (ASE). In general, it remains ambiguous as to what optimal values should be chosen for the many system variables in an optically-amplified WDM system to maintain a high SNR and a low degree of SNR differential.>