Reflective Microring Sensing Probe based on Narrowband Microwave Photonic Notch Filter

A novel, reflective, high performance microring sensing probe based on narrowband microwave photonic notch filtering is proposed and experimentally demonstrated. The system employs an integrated silicon-on-insulator microring resonator with a reflective loop as a sensing probe, which allows the sensed light to be reflected back and measured from a point source, thus enabling the capability to perform remote measurements at locations with limited accessibility. To enhance the beating cancellation of the optically filtered sideband, a programmable wideband optical equalization filter is used to create an amplitude equalization profile of the sidebands, thus achieving a desirable narrowband microwave photonic notch filter, which is a key feature for implementing sensor interrogation systems with high resolution. As an application example, a highly sensitive temperature sensor which monitors the temperature dependent notch locations of the narrowband microwave photonic notch filters has been experimentally verified. It achieves a high sensitivity of 11.57 GHz/oC, which provides the capability to detect and convert a small temperature change into a large variation in the radio frequency domain with clear notch frequency shifts in the order of several hundred MHz.