Effect of Confined Heating on Down-tapered Fiber In-line Mach-Zehnder Interferometer

A systematic study on the characteristics of a Mach-Zehnder interferometer based on down-tapered fiber under confined heating is presented. The effect of confined heating to this structure is also compared to distributed heating over the entire structure. The study unveils, for the first time, that only change in peak power of the transmission spectrum is observed during confined heating at the taper waist, with a sensitivity of 0.0216 dB/°C at peak wavelength of 1558.28 nm, whereas the distributed heating over the entire structure causes wavelength shift with a sensitivity of 0.053 nm/°C for the observed peak at initial wavelength of 1557.476 nm. These distinct responses can be exploited as a new approach for spectrum shaping and multi-parameter sensing.