Ultra-stable wideband signal transfer for distributed systems

We present an ultra-stable wideband signal distribution system via a star-like fiber network. By inserting a 26 GHz probe signal and precisely measuring its round-trip delay variation with double optical mixing, the link length variation has been accurately compensated, leading to a distributed transmission network with stability on the order of femtosecond. Experimentally, a wideband signal ranging from 8 GHz to 12 GHz is distributed from a local end to 2 remote ends via 20 km fiber links. The root-mean-square delay jitters of the transmitted wideband signals are between 10 to 20 femtoseconds within an hour. The proposed wideband signal transfer scheme is highly desired for distributed systems with high stability and strict coherence requirements.