Improved Phase Stabilization of a Radio-Over-Fiber Link Under Large and Fine Delay Tuning

In this paper, we propose and demonstrate a phase-stabilized radio-frequency (RF) reference transmission scheme by actively stabilizing the optical path delay of the fiber link. The reference RF tone is round-trip transferred between the central station and the remote end to obtain the delay variation. The fast and small part of the delay fluctuation is cancelled by a piezoelectric fiber stretcher, benefitting from its short response time and fine adjusting granularity. The slow and large part of the delay variation is used to alter a wavelength tunable laser, which results in a dispersion-induced tunable optical delay line with very large compensation range. Experimentally, a 2.48-GHz RF signal has been transferred through a 60-km optical fiber link with suppressed noise. The fractional frequency stability achieved is 6.5 × 10^-14 at 1 sand 2.1 × 10^-17 at 10⁴ s averaging time, respectively.