Abstract

As recent experiments have shown, it is feasible to communicate at multi-Gbit/s rates through large amplifier cascades compensating for several thousand dB of loss.^1–2 However, if each gain module requires an optical bandpass filter, an isolator, and a means of active gain-control, the system’s cost and complexity rise rapidly. Here we explore the performance consequences of removing in-line isolators and bandpass filters, while still relying on saturation properties to provide automatic power control. We employ a simple description of saturated amplifier cascades, obtained by modifying the recent approach of Giles and Desurvire.³ Emphasis is placed on degradations due to saturation and ASE-induced noise; it is important to note, however, that we do not include limitations resulting from fiber nonlinearities, dispersion, multiple reflections, or Rayleigh scattering.

© 1992 Optical Society of America