Air-suspended photonic crystal fibers (PCFs) have been recently appointed as one of the most intriguing structure for sensing and detection, especially for chemical and biological applications [1], [2], [3]. The standard cross section of these fibers consist of a core surrounded by three large, non-circular, air holes creating a somewhat triangular core supported by three struts. The air holes are usually filled with solutions or inflated with the gasses to be detected which interact, differently from hollow core fibers [4], with the evanescent tails of the guided modes.