Tunable multiwavelength optical short pulse generation using cascaded fiber Bragg gratings and an erbium-doped fiber amplifier in a simple self-seeding scheme

摘要

Tunable multiwavelength optical short pulse generation by the use of a self-seeded, gain-switched Fabry-Pérot laser diode is demonstrated. The laser external cavity mainly consists of cascaded fiber Bragg gratings connected with variable optical delay lines, an erbium-doped fiber amplifier, an optical coupler and two circulators. The wavelength elements from the gain-switched laser diode can be flexibly selected and intensified and their temporal feedback to the laser diode can be accurately controlled. As a result, the sidemode suppression ratio of the output pulses is better than 30 dB over the wavelength-tuning range of 27 nm for a dual-wavelength operation and more than 25 dB across 20 nm when the system is operated with three-wavelengths. The system is simple, compact and robust, and the wavelength-tuning can be carried out in a flexible manner, in a sub-mode step and at a constant repetition frequency.