Depressed index clad fiber as a highly sensitive low-cost refractive index sensor

We present a simple, compact, low cost and ultra high sensitive refractive index sensor based on depressed index clad fiber. The leakage loss of the fiber is highly sensitive to the variations in the refractive index of the outermost leaky layer. We utilize different portions of leakage loss curve to design sensors in different ranges, with different resolutions and for specific applications. One of such designed sensor work in the range 1.4573250-1.4573500, which corresponds to the refractive index of jojoba oil. The resolution within this range is of the order of 4 × 10−7 which is the maximum resolution of the sensor. The fabrication of the sensor only requires etching of some portion of the cladding of the fiber and does not require costly methods of wavelength or polarization interrogation.