An Optical Domain Combined Dual-Loop Optoelectronic Oscillator

A dual loop optoelectronic oscillator (OEO) is able to effectively suppress the sidemodes in each single loop. In this paper, a dual-loop OEO scheme is reported. By utilizing a polarization-beam splitter and a polarization-beam combiner, the two loops are directly joined in the optical domain without adding any active electrical device. The laser's phase-to-intensity noise is discussed. We present free-running experimental results, which show a phase noise of -109 dBc/Hz at 10kHz away from the carrier (12 GHz) and a Q value of 10 ¹⁰ with a sidemode suppression ratio of 60 dB, which is improved by 30-50dB in the experimental comparison. Meanwhile, the experimental comparison indicates that no significant noise is introduced by this configuration