Dynamic effects of EDFA Spectral Hole Burning in optical burst switching systems

The benefits of adopting optical burst switching (OBS) in optical networks as well as the technological issues of the optical layer have been extensively studied. One of the challenges in developing commercial OBS systems is the use of the Erbium-Doped Fiber Amplifier (EDFA) technology to amplify bursty optical signals. A significant impairment in EDFA-based OBS systems is caused by the Spectral Hole Burning (SHB) of the EDFA. Due to this effect, the presence of a channel at a given wavelength induces a localised reduction in the EDFA gain spectrum that is a few nm wide (“a spectral hole”). An optical burst crossing an EDFA will require a certain amount of time to induce a hole in the gain spectrum; during this time the burst itself will therefore experience a variable gain. Under particular traffic conditions, this effect accumulates over a cascade of EDFAs resulting in large power excursions of the burst. In this paper the authors characterize the dynamics of SHB in OBS systems and describe its effect on the optical performance.