Photonic crystal fiber based optical studies of oil deterioration by near field imaging

Mode pattern changes of LMA-20 solid core photonic crystal fiber, caused by change in refractive index of fluid infiltrated into its micro structured cladding has been theoretically modeled and experimentally verified through simple low cost near field CCD imaging of distal tip of infiltrated samples. This technique tracks degradation induced fractional changes in the oil index, over a large range from +30% to â¿¿30% through the mode pattern changes associated with shifts from index guidance to multi-waveguide and band gap guidance. Simple estimation of fluid index by visual tracking of transmission band edges and quantification within transmission region through MFD changes extracted from recorded mode patterns are reported.