Refractive index and strain sensing using inline Mach-Zehnder interferometer comprising perfluorinated graded-index plastic optical fiber

This paper details the fabrication and performance evaluation of an inline Mach-Zehnder interferometer (MZI) consisting of a perfluorinated graded-index plastic optical fiber fabricated via a heat-and-pull tapering technique. This MZI exhibits interference fringes that are sufficiently sharp for usage as refractive-index (RI) and strain sensors. These interference fringes shift linearly with the RI of the surrounding medium, with a proportionality constant of 3.44 nm/RI unit. The measured strain sensitivity of 0.2 pm/μɛ suggests that the MZI may be viable for strain-sensing applications.