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.

Investigation of a novel temperature-sensing mechanism based on strain-induced optical path-length difference in a multicore optical fiber

“…Four-core optical fibers were used previously in twoaxis bend measurement [3] and three-dimensional optical profilometry [9]. Recently, Guvenc et al successfully used the same type of fiber to demonstrate that a four-core optical fiber can be used as a calorimetric gauge in heat transfer measurements [10]. The sensitivity of the device was given to be 7.37 × 10 −6 K −1 .…”