Effect of optical filtering on pulses generated with a gain-switched DFB laser

Gain-switched laser diodes are widely used to generate short optical pulses, which find several applications in optical fiber measurements and high-speed optical communication systems. Temporal and spectral properties of the gain-switched pulses can be tailored by filtering their optical spectrum. Optical filtering leads to suppression of frequency chirp and generation of transform-limited pulses, We show that tuning of the center frequency of an optical bandpass filter can result in not only pulse compression, but also in the generation of a series of secondary oscillations after the primary pulse. The origin of these secondary oscillations is investigated both experimentally and analytically. (C) 2001 Elsevier Science B.V. All rights reserved.