Noise Characterization of an Injection-Locked COEO With Long-Term Stabilization

Extensive noise analysis is presented of a semiconductor-based coupled opto-electronic oscillator using continuous-wave optical injection for the generation of an optical frequency comb with 10.24 GHz spacing. The suppression of unwanted optical axial mode groups arising from the harmonic nature of mode locking is achieved via gain competition. Amplitude noise measurements show a marked reduction in noise due to optical injection for multiple injection powers. Supermode noise spur suppression is shown to be greater than 15 dB in absolute phase noise measurements, taken using the frequency discriminator technique. Allan deviation measurements are also shown for both the free-running and injection-locked states.