Generation of a chirp-free optical pulse train with tunable pulse width based on a polarization modulator and an intensity modulator

摘要

A simple method for the generation of a chirp-free optical pulse train with tunable pulse width using a po-nlarization modulator (PolM) and a zero-chirp intensity modulator (IM) is proposed and demonstrated. In thenproposed system, a light wave with its polarization direction oriented at an angle of 45° with respect to thenprincipal axis of the PolM is polarization modulated by a sinusoidal drive signal. An optical polarizer is con-nnected after the PolM to convert the polarization-modulated signals to a pulse train with the main peaksnhaving a narrow pulse width. Then, the main peaks are selected by the IM, leading to the generation of anshort optical pulse train with a repetition rate that is identical to or twice the frequency of the sinusoidalndrive signal, depending on the dc bias of the IM. The pulse width of the generated pulse is easily tuned bynadjusting the phase modulation index of the PolM. An experiment is carried out, and a pulse train with anduty cycle as small as 8.16% is generated. © 2009 Optical Society of America