Single-mode Optoelectronic Oscillator Based on ASE Source and Cascaded Zero-dispersion Recirculating Loops

A single-mode optoelectronic oscillator with low phase noise and high sidemode suppression ratio (SMSR) is demonstrated by using an amplified spontaneous emission (ASE) source in combination with three cascaded zero-dispersion recirculating loops (ZD-RL). The longest ZD-RL enhances the Q-factor of the microwave photonic (MWP) filter by a factor of 4100 while the two shorter ZD-RLs enlarge the free spectrum range (FSR) of the MWP filter, enabling stable single-mode oscillation. As a result, we experimentally generate a high-purity microwave signal, achieving an SMSR of 72.7 dB. The phase noise of the 10 GHz carrier is measured to be -122 dBc/Hz at a 10 kHz offset-comparable to the performance of a commercial signal generator. The frequency drift is 0.72 kHz within 5 minutes at 6.5 GHz. The whole system is simple, robust, and cost-effective compared to single-wavelength-laser-based OEOs, thereby holds significant promise for applications in high-precision microwave photonic radar and next-generation wireless communication systems.