Microstructured optical fiber sensor with three-core Mach-Zehnder interferometer

A new type of microstructured optical fiber with a hollow channel and three cores for sensing application is designed. Fabrication method and sensing characteristics of the microstructured fiber are demonstrated. The fiber has three different kinds of cores attached on the inner wall of a capillary. One core is exposed in the capillary, another core is in an inner tube, and the last core is covered by cladding. By splicing short sections of multi-mode fiber on both ends of the microstructured fiber, these cores form a Mach-Zehnder interferometer. Light transmitted in three cores interfere with each other, as a result the spectrum consists of different interference components which can be analyzed by the Fast Fourier Transform. By extracting these components with filters, liquid refractive index and temperature sensing can be realized with sensitivities of -1319.56 nm/RIU and 0.32 nm/°C.