Frequency stability optimization of an OEO using phase-locked-loop and self-injection-locking

Frequency stability optimization of an X-band optoelectronic oscillator (OEO) using the technique of phase-locked loop (PLL) and dual loop self-injection-locking (DSIL) is proposed and demonstrated. The relationship between the loop transfer characteristics of a PLL and the phase noise of the oscillation signal is analyzed. The close-in phase noise and frequency overlapping Allan deviation (ADEV) of the OEO are optimized by properly choosing the bandwidth of the loop filter of the PLL. The phase noise of the OEO is suppressed by 41.5 dB at 100 Hz offset and 21.3 dB at 10 kHz offset with PLL and DSIL. The frequency overlapping ADEV achieved 7.03×10-12 at average time of 100 s, which is several orders of magnitude better than that of the DSIL OEO and the free-running OEO, proves the high oscillation stability of proposed scheme.