Improved configuration and reduction of phase noise in a narrow linewidth ultrawideband optical RF source

In this Letter, we report on the improved configuration of a widely tunable optical RF generation system, particularly for the generation of low-frequency RF, as well as the reduction of phase noise in that same system. Using an amplitude modulator, a simplified system design was demonstrated with fewer components and improved phase noise performance, especially at RF frequencies below ∼36 GHz. Excess phase noise due to acoustic vibrations of the optical fibers was also successfully eliminated by mechanical isolation. A minimum phase noise of -124 dBc/Hz at 10 kHz offset was demonstrated at 4 GHz.