A Temperature-Insensitive Refractive Index Sensor Based on No-Core Fiber Embedded Long Period Grating

A novel long-period fiber grating via periodically embedding no-core fiber (NCF) has been achieved. The 11-period SMF-NCF-SMF-long period fiber grating (SNS-LPG) can exhibit an extremely high loss resonant dip (>20 dB). Theoretical analysis shows good agreement with the measured transmission spectrum. We investigated both refractive index and temperature sensitivity of SNS-LPG. The fabricated sensor achieve an average wavelength sensitivity of 141.837 nm/RIU in the range of 1.333-1.400 RIU, and exhibit lower temperature sensitivity (-6.43 pm/ °C and 0.005 dB/ °C).