Analysis of the Lowest Order Cladding Mode of Long Period Fiber Gratings Near Turn Around Point

A long period fiber grating (LPFG) sensor has been fabricated, after theoretical analysis, obtaining the maximum enhancement of the evanescent field working with the lowest order cladding mode (LP0,2 cladding mode) near turn around point. Both the wavelengths of the dual peak resonance and the coupling conditions of the mode have been analyzed in detail. A flow cell has been fabricated to characterize the sensor in term of surrounding refractive index (SRI) sensitivity. The sensitivity of the sensor resulted to be similar to 8751 nm/SRIU, with a resolution in the order of 10(-5), within the SRI range of 1.333 to 1.3335.

Automated summary

A long period fiber grating sensor with maximum enhancement of the evanescent field working with the lowest order cladding mode has been fabricated and analyzed in terms of dual peak resonance wavelengths and coupling conditions. The sensitivity of the sensor to surrounding refractive index was measured to be 8751 nm/SRIU with a resolution of 10(-5) within a specific SRI range.