An experimental alternative of microwave signal generation through an optical heterodyning technique using a multimode laser diode and a tunable DFB laser

It is experimentally demonstrated as an alternative to one of the classical optical heterodyning techniques for generating microwave (MW) signals. The originality of this work resides in the use of a Multimode Laser Diode (MLD) associated with a Fiber Bragg Grating (FBG) and a tunable Distributed Feedback laser (DFB), instead of two DFBs. As an optical filter, the FBG selects a single mode among various provided by the MLD signal. The selected single-mode signal is used as a reference in the optical beating together with the signal of the tunable DFB. The tunability is achieved by varying the DFB wavelength to modify the wavelength spacing () between the two optical signals. The experimental results are corroborated with those obtained theoretically and by simulations. The system performance evaluation is achieved through the Signal-To-Noise Ratio (SNR) and the Phase Noise (PN) measurements.