Highly sensitive temperature sensor based on multimode‐interference fiber structure with gel cladding

Abstract

We present a temperature‐sensitive, single‐mode–multimode–single‐mode (SMS) fiber structure with an index‐matching gel as a cladding material in a multimode segment. A silica core with the surrounding gel is supported straight by a thin glass tube to produce a bandpass transmission response. The passband wavelength shifts by 96 nm from 1624.5 to 1528.5 nm as the temperature increased from 40 to 200°C. The maximum sensitivity obtained is 2 nm/°C in the temperature range 40–70°C, whereas the minimum sensitivity is 0.13 nm/°C in the temperature range 125–200°C. The SMS fiber structure, including the gel cladding, allows high operating temperatures and high thermal sensitivities.