Towards a large-scale, optical timing distribution system with sub-femtosecond residual timing jitter

We present here key technologies for an all-optical timing distribution system with sub-femtosecond precision. Timing distribution over a 1.2-km polarization-maintaining, fiber-optic link using balanced optical cross-correlators (BOC) for link stabilization was demonstrated for 16 days with 0.6 fs RMS timing drift and during a 3-day interval only 0.13 fs drift. Jitter characterization of two identical commercial femtosecond lasers using the BOC method verified sub-100-as timing jitter for frequencies above than 1 kHz. Preliminary operation of a fiber-coupled, hybrid-integrated BOC using periodically-poled KTiOPO₄ (PPKTP) waveguides indicate great potential for improved BOC timing sensitivities and overall system efficiency and robustness.