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In this report, we carry out simulation and experimental investigations of directional coupler structures with different separations between the glycerin selectively infiltrated channel and silica core of a large mode area Photonic Crystal Fiber (PCF). We assess their coupling characteristics and the corresponding temperature sensing capabilities. The temperature sensitivities of the glycerin selectively infiltrated channel adjacent to the silica core and two periods away from the silica core are −3.115 nm/°C and −2.332 nm/°C respectively. The glycerin selectively infiltrated channel three periods away from the silica core displays −107.8 pm/°C, an order of magnitude less temperature sensitive. The simulation results agree with the experimental results that there is a strong correlation between the coupling strength of the glycerin selectively infiltrated channel and the silica core, affecting its temperature response. [ABSTRACT FROM AUTHOR]

Abstract: A high sensitive fiber-optic refractive index tip sensor based on a simple inline hollow glass micro-sphere is presented. The inline hollow glass micro-sphere can be automatically constructed at the splicing joint break time when splicing a hollow core photonic crystal fiber to an SMF. Simultaneously, the micro-sphere is tipped on the SMF end. It is temperature insensitive in the air due to its micro size and hollow cavity sphere structure. The ambient refractive index can be measured by detecting the extinction ratio variation of the sensor, with a high sensitivity. [Copyright &y& Elsevier]