PHOTONIC GENERATION OF 60 GHz MILLIMETER-WAVE BY FREQUENCY QUADRUPLING BASED ON A MODE-LOCKING SOA FIBER RING LASER WITH A LOW MODULATION DEPTH MZM

Generation and processing of millimeter-wave (MMW) signal based on photonic technologies is a new trend. A simple and effective optical technique to generate 60 GHz millimeter-wave signal by frequency quadrupling is proposed and demonstrated. In this approach, the frequency quadrupling efficiency is greatly improved by a semiconductor optical amplifier (SOA) fiber ring laser with 2nd-order rational harmonic mode-locking and a Mach-Zehnder modulator (MZM) which is biased at odd-order optical modulation side-bands suppressing state. A center-wavelength tunable comb filter outside the ring laser is tuned to select the optical sidebands separated by 60GHz. The result shows that the power ratio between quadruple-frequency signal and double-frequency signal is improved at least 30 dB with the mode-locking ring laser when the modulation depth is less than 0.4 and the phase noise of the 60GHz signal generated is better than -75dBc/Hz at 1-kHz offset. The key advantage of the technique is that a high-frequency MMW signal can be generated with high efficiency by a low power microwave signal.