Spurious level and phase noise improved Fourier domain mode-locked optoelectronic oscillator based on a self-injection-locking technique.

We propose and experimentally demonstrate a spurious level and phase noise improved Fourier domain mode-locked optoelectronic oscillator (FDML-OEO) based on a self-injection-locking (SIL) technique. The scheme applies a dual-loop FDML-OEO structure, in which a long optical fiber delay loop is used to injection-lock the OEO with a short oscillating optical fiber delay loop. SIL is achieved so long as the delay of the long loop is tuned at the integral multiple of the oscillation loop. The spur suppression ratio of the wideband linear frequency modulated (LFM) signal generated by the FDML-OEO can be improved by 14 dB under SIL. Furthermore, the modification of the spur suppression ratio depending on the injection power is also demonstrated. The phase noise of the proposed OEO is -127.5 dBc/Hz at 10 kHz offset, which is much improved comparing with a free-running OEO.