Stable and Widely Tunable Optoelectronic Oscillator Using a Cascade Microwave Photonic Filter

A widely tunable optoelectronic oscillator (OEO) with stable output based on a cascade microwave photonic filter (MPF) is proposed and demonstrated. The cascade MPF is implemented by a combination of a finite impulse response (FIR) filter based on shifted dispersion-induced power fading and an infinite impulse response (IIR) filter based on a double-parallel recirculating delay lines (DP-RDLs). Through adjusting the time delay difference between the upper and lower connecting arms of the dual-input Mach-Zehnder modulator within FIR filter, the center frequency of cascade MPF is changed and the oscillation frequency of the OEO can be tuned. The theoretical analysis and verified experiment of the proposed OEO is performed. Tunable oscillation signals from 6.1 to 11.98 GHz with an average step size of 490 MHz are generated. Due to the introduce of the IIR filter, the stable performance of the OEO is obtained, where the maximum frequency drift at 7.48 GHz is observed to be 1.817 kHz over 1 hour. The phase noise of the structure is also investigated