Ultra-low noise microwave extraction from fiber-based optical frequency comb

In conclusion, we have used two FOFC based optical to microwave division frequency synthesizers referenced to a common optically source to create 11.55 GHz microwave signals with a relative frequency stability of 1.6×10
⁻¹⁶
at 1 s. The relative phase noise spectral density at a 1 Hz offset from the 11.55 GHz carrier is measured at 111 dBrad
²
/Hz, limited by the readout system noise floor. Long term stability and accuracy down to 3×10
⁻¹⁹
at 65536 s was also demonstrated from a set of 3 days continuous measurement. These results are obtained with classical double balanced mixers measurement scheme. By using a noise measurement system based on the carrier suppression method and advanced noise reduction techniques we are able to improve the results down to a phase noise spectral density at a 1 Hz of 117 dBrad
²
/Hz and a FFS is of 1.5×10
⁻¹⁹
at 1000s (for a single system).