Compact Mach–Zehnder Interferometer Based on Tapered Hollow Optical Fiber

A compact fiber Mach-Zehnder interferometer based on tapered hollow optical fiber (THOF) has been demonstrated. The THOF is sandwiched between two single mode fibers (SMFs), forming a SMF-THOF-SMF (STS) structure. The discharging during the splicing and tapering processes induces the collapsed regions in the hollow fiber, which form the modal coupling/re-coupling areas of the interferometer. The THOF has a length of about 2 mm and the taper waist diameter is about 66.5 μm. The refractive index (RI), stress, and temperature response properties of the STS interferometer have been investigated, which show a high RI sensitivity and low temperature cross-sensitivity. The STS interferometer holds the merits of compact structure, low cost and easy fabrication, making it a suitable candidate in the biochemical and physical sensing fields.