Abstract:A four-core optical fiber is employed to investigate a novel temperature-sensing mechanism, which is based on the strain-induced optical path-length difference between the fiber core pairs. A short segment of a four-core fiber is wound around a solid stainless steel cylinder to form a tight circular loop, which is exposed to temperatures of up to 100 • C. Temperature-induced radial expansion of the stainless steel cylinder causes a shear strain in the fiber and introduces an optical path-length difference between the fiber core pairs. This results in a total phase shift of about 20.40 ± 0.29 rad in the interference pattern of the four-core fiber, which is monitored by a CMOS camera. The temperature-induced phase and strain sensitivities are measured to be 3.74 rad/m• C and 0.18 µε / • C, respectively.

A four-core optical fiber is demonstrated as a calorimetric gauge for investigation of one-dimensional heat transfer measurements. Transient heat pulses from a Nd:YAG laser of 600 ms duration with a repetition rate of the order of 10 s are delivered onto the cleaved distal end face of the four-core fiber, aiming at one of the single cores only, which cause an optical path length difference between four guiding cores due to the temperature-induced change in the index of refraction and physical length of the targeted fiber core of concern. This results in a shift in the fringe pattern, which is operated in the reflection scheme. A phase shift of 0.43±0.015  rad is measured with a CMOS camera for 40 mW pulses. The thermal heat diffusion length in the selected fiber core is determined to be 2.8 mm, which contains 10.9±0.38  kJ/m²s heat, causing a temperature rise of 1.43±0.05  K.

No abstract

No abstract

No abstract