Temperature measurement using a microfiber knot ring encapsulated in PDMS

A microfiber knot ring (MKR) with a temperature sensitivity of 183 pm/℃ has been proposed and experimentally demonstrated. To further improve its stability and sensitivity, the polydimethylsiloxane (PDMS) film was used to encapsulate it to be a slice probe. The temperature sensitivity was increased for more than 9 folds with a good stability and repeatability. The contribution ratios of thermal-optic coefficient and thermal-expansion coefficient of silica and PDMS were analyzed and discussed. The high sensitivity of 1.67 nm/℃ and miniature slice structure enables its application for precisely monitoring the temperature fluctuation in some special occasions.