Compact optical fiber temperature sensor with high sensitivity based on liquid-filled silica capillary tube

We propose a highly sensitive fiber temperature sensor based on a section of liquid-sealed silica capillary tube inserted in a single-multi-single-mode fiber structure. The liquid polymer is filled into the silica capillary tube through two micro-holes drilled by a femtosecond laser. Then the micro-holes are blocked by UV curable adhesive with ultra-small volume. Obvious Mach-Zehnder interference peaks were shown in its transmission spectrum. The proposed fiber temperature sensor can be reliably used for actual point detection owing to its high sensitivity (8.09 nm/°C), good linearity (99.93%), compact size, good mechanical property, high fabrication efficiency, and good repeatability and stability.