Electrooptic phase tracking of microwave signals beyond 18.5 GHz using an integrated electrooptic modulator as an optoelectronic harmonic mixer in a phase lock loop

We demonstrate electrooptic phase tracking of microwave signals beyond 18.5 GHz using a gain-switched laser diode as the optical clock. The key element of this system is a fiber-pigtailed integrated-optic Mach-Zehnder modulator (IOM). The IOM functions as an optoelectronic harmonic mixer in a phase lock loop. The conversion loss of the OEHM is 66 dB. The phase error and the single sideband phase noise density of the phase-locked 18.5 GHz signal is 5.6/spl times/10/sup /spl minus/5/ rad//spl radic/(Hz) and -54 dBc/Hz, respectively.<>