Harmonic millimeter-wave generation and frequency up-conversion using a passively mode-locked multisection DFB laser under external optical injection

We demonstrate that a passively mode-locked multi-section distributed-feedback (PML-MS DFB) laser can perform both harmonic millimeter-wave generation and harmonic frequency up-conversion under the external optical injection. Optical multiple modes generated by a PML-MS DFB laser produce harmonic millimeter-waves by mode-beating in a photodiode (PD), and the phase quality and stability are enhanced by the injection of external optical signal modulated at f(LO). In addition, if the external optical signal is modulated simultaneously by f(LO) and f(IF), the PML-MS DFB laser performs all-optical frequency up-conversion producing sidebands at f(LO) +/- f(IF) when detected by a PD. Using this method, we demonstrate generation of stable harmonic millimeter-waves at 30.42 and 60.84 GHz with f(LO) of 15.21 GHz, and up-conversion of 10-Mb/s quadrature-phase-shift keying data at 150 MHz f(IF) into the 60-GHz band. These functions of a PML-MS DFB laser can be useful for radio-over-fiber applications in which a compact optical source is needed for processing high-frequency radio signals in optical domain.