Precise frequency transfer through a fiber network by use of 1.5-μm mode-locked sources

We report the precise transfer of radio-frequency signals by use of the pulse repetition frequency of mode-locked laser sources at 1.5 mum transmitting through a fiber network. The. passive transfer instability through a 6.9-km fiber is, below 3 X 10(-14) at 1 s, which. is comparable with the optical carrier-frequency transfer of a narrow-linewidth cw laser. The instability of the measurement system is below 7 X 10(-15) at 1 s. It is noted that the pulsed mode of operation offers almost an order-of-magnitude improvement in stability at I s over that with a sinusoidal amplitude. modulation on An optical carrier. (C) 2004 Optical Society of America.