Integrated Tunable Sideband Suppressor for Optical Carrier Reuse in Millimeter-Wave Radio-Over-Fiber Transmission

An integrated Si photonic tunable sideband suppressor is presented for application of remote optical carrier reuse. This tunable sideband suppressor is constructed by a two-rings-coupled Mach Zehnder interferometer with a tuning function to synthesize a box-like, narrow band-pass filter through dual Fano resonance interference. By varying the resonant wavelengths of the ring resonators, we can tune the suppression band adapted to the working millimeter wave (mmWave) frequency. We demonstrate a suppression ratio more than 25 dB on both 28 and 39 GHz downlink mmWave radio-over-fiber (RoF) signals. By applying this component in a bi-directional mmWave RoF system, we observe the quality of the uplink signal modulated on the recycled optical carrier is almost the same as that modulated on a clean laser source without extra power penalty. Since the sideband suppressor is made by Si photonic circuits, it potentially can be integrated with other high-speed Si photonic components to implement an on-chip mmWave radio-over-fiber transceiver.