Repetition rate multiplication in figure-eight fibre laser with 3 dB couplers

The operation of a passively modelocked figure-eight laser with all fibre repetition rate multiplier is reported. Thirty two times the fundamental repetition rate is achieved with six conventional 3 dB couplers at a repetition rate of 182 MHz. The repetition rate 2^N times multiplication only requires (N + 1) passive fibre couplers and N fibre delay-lines. This method makes it possible to achieve high multiplication and is inexpensive when compared with conventional methods employing sub-ring cavity or special fibre Bragg grating to control repetition rate.