Micro In-Fiber Mach-Zehnder interferometers fabricated in single mode fibers and fiber tapers for visible (VIS) and near infrared (NIR) operation

In this paper, we analyze the performance of single-mode fiber (SMF) microcavity in-line Mach–Zehnder interferometers (μIMZI) in the visible (VIS) and near-infrared (NIR) spectral ranges. Furthermore, we study the causes leading to a seeming paradox that NIR SMFs for the VIS range perform better in the NIR range and vice versa. We propose the use of short double tapers to improve the spectral range and visibility of the micro-interferometers. The sensitivities to surrounding refractive index obtained were as high as 11,400 nm/RIU.