Pulse repetition rate multiplication in fibre laser using higher-order passive modelocking

A simple technique that allows for the repetition rate multiplication of optical pulse trains generated in passively modelocked fibre lasers is experimentally demonstrated. This is achieved by initiating higher-order passive modelocking by using both a dual-channel fibre Bragg grating and a Fabry-Pérot filter inside the fibre cavity. Continuous dark pulse trains with a repetition rate of 60GHz were generated, which is a four-fold multiplication of the Fabry-Pérot free spectral range