A coupled optoelectronic oscillator based on enhanced spatial hole burning effect

We propose and demonstrate a coupled optoelectronic oscillator (COEO) based on enhanced spatial hole burning (SHB) effect in an unpumped erbium-doped fiber (EDF). A novel structure is designed to form strong standing waves in the unpumped EDF, which enables large SHB effect to improve the side-mode suppression and ensure stable operation. A proof-of-concept experiment is carried out. A 10-GHz stable optical pulse train is successfully generated. The side-mode suppression ratio (SMSR) of the 10-GHz RF output is more than 72.5 dB and the phase noise is -123.6 dBc/Hz at 10-kHz offset, which is achieved without introducing any long fiber in the optoelectronic oscillator (OEO) loop, showing that the standing-wave forming structure significantly improves the performance of the COEO. The system is operated in the lab environment for 4 hours and no significant variation is observed.