Spectrum online-tunable Mach-Zehnder interferometer based on step-like tapers and its refractive index sensing characteristics

A novel refractive index (RI) sensor based on an asymmetrical Mach-Zehnder interferometer (MZI) with two different step-like tapers is proposed. The step-like taper is fabricated by fusion splicing two half tapers with an appropriate offset. By further applying offset and discharging to the last fabricated step-like taper of MZI, influence of taper parameters on interference spectrum is investigated using only one device. This simple technique provides an on-line method to sweep parameters of step-like tapers and speeds up the optimization process of interference spectrum, meanwhile. In RI sensing experiment, the sensor has a high sensitivity of −185.79 nm/RIU (refractive index unit) in the RI range of 1.3333-1.3673.