Ultra-Stable Microwave Signal Generation with Er: Fiber-Based Optical Frequency Comb

We demonstrate 9.192 GHz microwave signals from photonic microwave generation based on Er:fiber-based optical frequency combs and $1.55 \mu \mathrm {m}$ ultra-stable lasers, which used for local oscillators of cesium fountain clock. The frequency instability of the 9.63 GHz/9.54 GHz microwave signals is $3 \times 10^{-15} \text{@}$ 1s, with phase noise is of -94 dB rad
²
/Hz @ 1 Hz, and the synthesized tunable 9.192 GHz signal exhibits an instability of $6.7 \times 10^{-15}$ @1s. Further improvement of the photonic oscillators is undergoing.