Tunable Broadband Optoelectronic Oscillator Based on Integrated Mutually Coupled Distributed Feedback Lasers

A photonic approach to generating an optoelectronic oscillator (OEO) based on an integrated mutually coupled (IMC) distributed feedback (DFB) laser is reported. Compared with the traditional construction of an OEO, the IMC-DFB has functions of the laser source, intensity modulator, and microwave photonic filters (MPFs), which could simplify the OEO scheme. An optical feedback loop (O-Loop) and an optoelectronic feedback loop (OE-Loop) are used simultaneously in the proposed scheme. The optical loop was used to reduce the optical linewidth of the IMC-DFB to improve the quality of the laser source in the OE loop. The IMC laser consisted of two distributed feedback (DFB) laser sections with a semiconductor optical amplifier (SOA) section in between. The optical linewidth of the IMC-DFB is reduced from 5.86 MHz to 3.94 kHz due to the feedback of the optical loop. By tuning the current of the SOA and DFB sections, tunable microwaves ranging from 24.9 to 46.5 GHz with single-sideband (SSB) phase noise below -110 dBc/Hz at a 10 kHz offset from the carrier were realized.