Self-Oscillating Optical Frequency Comb: Application to Low Phase Noise Millimeter Wave Generation and Radio-Over-Fiber Link

Abstract

A self-oscillating optical frequency comb generator (SOFCG) is demonstrated by applying the optoelectronic loop feedback to an optical frequency comb generator (OFCG) based on a dual-drive Mach-Zehnder modulator. The resulting SOFCG provides 23 comb lines with a frequency spacing of 11.84 GHz, corresponding to the oscillation frequency defined by the optoelectronic loop. The corresponding OFCG is also implemented by replacing the optoelectronic feedback loop with a microwave synthesizer at 11.84 GHz. A 94.8-GHz millimeter (mm)-wave signal is then generated by selecting two tones and heterodyning in a high-speed photodetector for both the SOFCG and the OFCG. The SOFCG system offers superior single sideband phase noise performance compared to the OFCG approach. Using the SOFCG developed here, it is possible to generate mm-wave signals up to 260 GHz, and this method is applicable to multiband radio-over-fiber (RoF) links. An RoF link is implemented with the SOFCG at 94.8 GHz. An LTE Advanced OFDM FDD 64-QAM signal of 20-MHz bandwidth is transmitted over a 1.3-m wireless distance.