Microwave Photonic Filtering for Interrogating FBG-Based Multicore Fiber Curvature Sensor

We propose and experimentally demonstrate an approach to perform high-resolution and temperature-insensitive interrogation of a fiber Bragg grating (FBG)-based multicore fiber (MCF) curvature sensor using a microwave photonics filtering technique. By combining two reflected sample signals from the two FBGs inscribed in MCF and a dispersion device, a two-tap notch microwave photonic filter (MPF) is formed. The notch frequency of MPF is dependent on the time delay difference between the two FBG reflected signals, which is related to wavelength spacing of the two FBGs. Due to the wavelength spacing of the two FBGs is proportional to the curvature, the curvature can be readily interrogated by monitoring the notch frequency of MPF. The proposed interrogation scheme with the sensitivity of 92 MHz/m-1is achieved, whilst the sensitivity can be easily adjusted. Moreover, the proposed interrogation scheme is temperature insensitive.