Optical generation of modulated millimeter waves based on a gain-switched laser

We propose and demonstrate two configurations for optical millimeter-wave (mm-wave) generation and transmission of 3-Gb/s downstream data based on a gain-switched laser (GSL). The first configuration generates an optical comb spectrum from a GSL that can be appropriately filtered to generate two optical sidebands with 60-GHz separation. These sidebands are modulated with baseband data by using an external intensity modulator and then transmitted via optical fiber to the remote antenna unit (RAU). The second configuration produces a modulated optical frequency comb by driving the laser with both RF local oscillator and data streams coupled together and then followed by the same optical filters to generate two modulated optical sidebands. At the RAU, these two sidebands are heterodyned using a photodetector to generate the electrical modulated mm-wave signal. We investigate the distribution of these two methods over 3-km fiber with 2-m wireless link and demonstrate the system simplicity and cost efficiency for mm-wave over fiber systems. Both configurations are simulated to verify our obtained results and show system performance at higher bit rates.