Generation of UWB Doublet Pulse Based on Directly Modulated Laser and Chromatic Dispersion

An ultra-wideband (UWB) doublet pulse generation technique in the optical domain for UWB-over-fiber systems is presented. Our solution is based on the direct modulation of a semiconductor laser, optical filtering, and chromatic dispersion in a transmission fiber. When the integration of the transmitter in optical access network infrastructure is considered, the transmission length difference, or the difference in accumulated dispersion, is an issue to exactly obtain the desired pulse shape. To solve this problem, we propose to adjust the transmitter operation point, specifically the laser chirp, with respect to the targeted transmission fiber length. Bit error rate measurements prove that doublet pulses can be achieved with fiber length variation from 15 to 40 km of single-mode fiber.