All-Digital Radio-Frequency Signal Distribution Via Optical Fibers

We present a radio-frequency (RF) signal distribution system via optical fibers. We utilize an all-digital platform that encompasses a phase-locked loop, numerically-controlled oscillator, and fiber phase noise cancellation system. Our system achieves a fractional frequency transfer stability of 4 × 10
^-13
at 1 s and 6 × 10
^-17
at one day for the distribution of RF signals over 70 km of optical fiber. We demonstrate that this performance can be achieved with standard crystal oscillators. Our system is scalable, configurable, and flexible, allowing distribution of signals at different frequencies while maintaining over two orders of magnitude of the fiber phase noise suppression.