Optical injection locking assisted all-optical microwave oscillator

This paper reports an optical injection locking (OIL) assisted all-optical microwave oscillator (AOMO) scheme for the photonic generation of a microwave (MW) signal and demonstrates a 40th harmonic single-mode signal generation with an external low-frequency radio-frequency (RF) signal. In this all-optical single-loop oscillator that only depends on optical devices, the stimulated Brillouin scattering (SBS) effect of a coil of single-mode fiber (SMF) and a semiconductor optical amplifier (SOA) are used to select the oscillation frequency and modulate the optical feedback signal, respectively. The OIL effect in a distributed feedback (DFB) laser multiplies the frequency of the external RF signal. Thanks to the OIL module, it only requires an optical loop to acquire a single-mode oscillation and the oscillation signal is phase-related to the low-frequency RF source. The experiment demonstrates the generation of a single-mode MW signal of 10.71 GHz with an external RF signal of 267.8 MHz, with a frequency multiplication factor of 40. Mode-hopping is not evident in the output signal, and a moderately low-quality OIL signal is acceptable since unwanted harmonics and the phase noise floor of the OIL signal have little impact on the generated MW signal.