Reconfigurable Multiband Microwave Filters using Programmable Photonic Integrated Circuit

A programmable square mesh architecture of photonic integrated circuit comprised of 14 tunable balanced Mach-Zehnder interferometers has been investigated using silicon photonics technology platform for the demonstration of reconfigurable multiband microwave photonic filters. The photonic chip was electrically packaged for its reconfigurable operations using external16-channel programmable power supply for tuning the thermo-optic phase-shifters integrated in both the arms of Mach-Zehnder interferometers. The operating temperature of the packaged chip is stabilized within ±0.002º???? using a PID controller, to avoid any interference of ambiance temperature fluctuations. The mesh architecture is programmable into three different microring resonators in all-pass configurations operating independently for three different free-spectral ranges (23.25 GHz, 11.75 GHz, 8.75 GHz), respectively. The multiband microwave photonic filter characteristics have been experimentally obtained using fiber-coupled off-chip laser source (operating at ???? ∼ 1550 nm), modulator (bandwidth ∼ 40 GHz) and photodetector (bandwidth ∼50 GHz). Thus we have demonstrated microwave filters with two, three and four bands within the bandwidth of the modulator used in the experiments. Among these, the two-band filter realized for X and Ka-band was thoroughly investigated in the experiments to understand the effect of the MRR coupling condition (Q-factor) on the realized filter bandwidth and its tuning range, link gain and rejection. The bandwidth of both the filter bands was tuned over the extensive range of 1.6 GHz to 12.7 GHz by controlling the MRR Q-factor and the resonance spacing from the28 carrier. At the same time, the bandwidth tuning range of the three-band filter realized for C, Ku, and Ka-band (2 GHz to 6 GHz) and four-band filter realized for C, Ku, K and Ka-band (3 GHz to 5 GHz) in our experiments were limited by the MRR’s resonance bandwidth and free spectral range.