Abstract

Raman amplification is a cornerstone for record transmission distances in high capacity dense wavelength division multiplexed (DWDM) systems. Transparent networking elements such as optical add-drop multiplexers and crossconnects are essential to the value proposition for these ultra-long reach systems. Rapid changes in the channel population due to fiber cuts or component failures can lead to transient power excursions on downstream channels added at these transparent network elements. The uncontrolled transient response of cascaded erbimn-doped fiber amplifiers (EDFAs) is known to exhibit an overshoot that sharpens with the number of amplifiers and places requirements on the control response time for all-EDFA long haul or mesh networks [1]. Experiments on Raman amplifiers have shown advantages because the gain saturation is much less and the response time is dictated by the intrinsic relaxation times of the amplifier [2-4], Here we examine the evolution over distance of power transient excursions in a broadband Raman amplified transmission system as a function of surviving channel wavelength. In a Raman based system, the appearance of overshoots is dependent on the relative strength of channel-channel and pumpchannel interactions at different wavelengths. We also examine the tilt behavior of uncontrolled transient propagation.

© 2007 IEEE