A novel active mode-locking optoelectronic oscillator employing an electro-optic phase modulator

In this manuscript, we propose and experimentally verify an active mode-locking optoelectronic oscillator (AML-OEO) based on a novel mode-locking method. In this scheme, an electro-optic Mach-Zehnder modulator (MZM) operating at carrier-suppressed double-sideband and an electro-optic phase modulator (PM) driven by a low-frequency signal are incorporated to form a parallel modulation structure. On this condition, the low-frequency phase modulation will convert to gain modulation of the OEO cavity, which enables the generation of microwave pulses occurring at the time slots corresponding to the zero points of the driving voltage. The feasibility of the proposed AML-OEO scheme is demonstrated by theoretical analysis and experiment, in which microwave pulse signals with repetition frequencies double the driving signal’s frequencies are finally obtained. Besides, since an electro-optic PM with a wideband operation range is employed as the mode-locking device, the microwave pulse signal with a large mode spacing can be generated by this scheme, which has the potential to be further used in the ultra-wideband wireless communication systems.