Pulse repetition rate doubling in FM actively mode-locked fiber-optic parametric oscillator

A photonic method to generate pulse trains with double repetition rate in FM actively mode-locked fiber-optic parametric oscillator (FOPO) has been proposed and experimentally demonstrated. Pulse trains can exist at either of the two extremums of phase modulation, which can be controlled by tuning an intra-cavity polarization controller (PC) before a phase modulator. Moreover, the pulse formation and spectral characteristics of the proposed FOPO are investigated. By continually rotating the intra-cavity PC, two optical pulse trains corresponding to two different mode-locked states are generated simultaneously. In the experiment, 8, 10, 12 and 14GHz pulse trains are generated using RF drive frequencies of around 4, 5, 6 and 7GHz, respectively.