Accurate Control of Active Recirculating Structures for Microwave Photonics Signal Filtering

We experimentally and theoretically demonstrate the critical dependence of erbium-doped fiber (EDF) gain characterization and control on the performance of active recirculating microwave photonic reconfigurable filters. Several factors found in the EDF cavity formed by the recirculating structure are analyzed such as splice losses, laser emission, and gain saturation. The control of the effective gain in the EDF cavity permits one to modify the bandwidth of the filter from 1 to 30 MHz with a shape factor from 0.26 to 0.33.