PCF Modal Interferometer Based on Macrobending for Refractive Index Sensing

We experimentally demonstrated a photonic crystal fiber (PCF)-based modal interferometer with macrobending for the detection of analyte refractive index (RI). The interferometer consists of a section of large mode area PCF spliced between single mode fibers (SMFs), i.e., SMF-PCF-SMF structure. The PCF is subjected to macrobending of the order of cm^-1 and its modal properties for different values of macrobending radii have been analyzed using finite-element method. Experimental results show that this simple and compact interferometer has low temperature and power dependence but its RI sensitivity is found to be as high as 258 nm/RIU for a curvature of 0.36 cm^-1 (which is 165% higher than zero curvature) with a resolution 3.9 × 10^-5 RIU.