title: Four-core optical fiber as a calorimetric gauge.
abstract: 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.
authors.forename: Sema
authors.initials: S
authors.lastname: Güvenç
authors.forename: Belkıs
authors.initials: B
authors.lastname: Gökbulut
authors.forename: Gülşen
authors.initials: G
authors.lastname: Kösoğlu
authors.forename: Heba
authors.initials: H
authors.lastname: Yüksel
authors.forename: Mehmet Naci
authors.initials: MN
authors.lastname: Inci