Abstract

The ability of EDFAs to amplify over a wide bandwidth has permitted high-capacity, long-distance wavelength-division-multiplexing (WDM) systems.¹ However, there are several major challenges in incorporating WDM channels in a long-distance cascaded EDFA system. One difficulty is controlling the optical nonlinear interactions between the optical signal and the fiber, which can lead to interference and attenuation of the signals, resulting in system degradation. Among the nonlinearities, the stimulated-Raman-scattering (SRS) effect causes spectral gain to be wavelength dependent, with the longer wavelengths having higher gain. Another problem in WDM systems is that the EDFA gain is wavelength dependent, resulting in a severe signal-to-noise-ratio (SNR) differential among many channels after the signal passes through a cascade of EDFAs.

© 1995 Optical Society of America