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A fiber optic refractometer based on a novel configuration to excite localized surface plasmon resonance is demonstrated. The fiber sensor consists of a short segment of photonic crystal fiber (PCF) fusion spliced between multimode fibers. Evanescent field of cladding modes excite gold nanoparticles (AuNPs) immobilized on the PCF surface. The proposed sensor offers ease of fabrication, when normalized transmitted intensity is used to quantify external bulk refractive index (RI), sensitivity of -731%/RIU, limit of detection of 1.76×10-5 RIU can be achieved with high linearity (r2=0.9988) over RI range from 1.33 to 1.43 RIU.