Single-Mode-Multimode Silica Rod-Single-Mode High Refractive Index Fiber Sensor
Siti Mahfuza Saimon, Muhammad Yusof Mohd Noor, Asrul Izam Azmi, Ahmad Sharmi Abdullah, Mohd Haniff Ibrahim, Mohd Rashidi Salim, Mohd Hafizi Ahmad, Ahmad Fauzi Othman
Abstract
This paper reports a robust high refractive index (RI) sensor based on a multimode silica rod structure. The sensor was fabricated by splicing a segment of multimode silica rod between two single-mode fiber (SMF) leads. The measurement of high-RI is realized by monitoring the change of power spectrum caused by the reaction of leaky modes to different surrounding high-RI. The 0.5-cm long multimode silica rod sensing element exhibits a sensitivity of up to 115.12 dBm/RIU for high-RI ranging between 1.450 and 1.531. The sensor also demonstrated its potential in power transformer application by distinguishing various ageing levels of transformer oil. The leaky modes mechanism in all-silica based structure is essentially temperature insensitive, and therefore very practical to be deployed in extreme temperature conditions.