Design of a Vernier effect assisted optical fiber WGM microbottle for a highly sensitive temperature measurement

In this paper, a sensing scheme that produces the Vernier effect in a single microbottle cavity based on whispering gallery mode (WGM) is proposed for the first time to the best of our knowledge. The WGMs circulating in a polydimethylsiloxane microbottle are excited by a coupler composed of a single-mode fiber (SMF)-no-core fiber-SMF staggered structure. Due to the characteristics of the coupler with fewer high-order modes and the microbottle with adjustable excitation modes, few-mode resonances with similar free spectral range are excited in a single microbottle, which are superimposed to form a Vernier envelope. The experimental results show that in the range of 25°C-95°C, the Vernier envelope successfully improves the temperature sensitivity to ∼297 pm/°C, which is 6.7 times that of a WGM resonance dip. The proposed sensor has the advantages of simple fabrication and high reward and has great prospects in wide-range and highly sensitive temperature measurement applications.