Progress on Development of Photonic Microwave Generation at NTSC

We demonstrate the ultra-stable microwave frequency sources aiming to improve the short time instability of primary frequency standards. These sources are realized by using photonic generation approach, and composed of ultra-stable lasers, optical frequency combs, and optical signal detecting parts. This paper reported a 48th harmonic (9.6 GHz) of optical frequency comb is photodetected by a balanced optical-microwave phase detector with frequency instability of 2.8×10
^-15
@ 1s. Further improvement is undergoing.