Self-Forced Opto-Electronic Oscillators Using Sagnac-Loop PM-IM Convertor

Efficient phase to intensity conversion is key in Sagnac-loop based opto-electronic oscillators (OEO). This paper features analytical modeling of phase to intensity conversion in practical Sagnac-loop interferometers, with practical coupling imbalance in 3-dB optical coupler, polarization imbalance of the non-reciprocal optical phase shifter (NRPS), and cross-talk ratio in polarization maintaining fiber (PMF). Single-sideband (SSB) phase noise of self-forced frequency stabilization technique of this OEO is also modelled using self-injection locked (SIL) and dual self-phase locked loop (DSPLL); the free-running and forced modeling results of Sagnac-loop based OEO matches with experimentally measured phase noise results. The measured phase noise of the SILDPLL based OEO at 10 GHz is -131 dBc/Hz at offset frequency of 10 kHz with approximately 11 dB phase noise reduction compared to the results of free-running OEO. Self-forced stabilization of OEO results in timing jitter of 19.5 fs, a factor of 6 times reduction in the free-running performance.