In-fiber interferometers for temperature corrected refractive index sensing with guided and leaky modes

Refractometry based on a tapered bend-insensitive fiber Mach-Zehnder interferometer operating in both guided and leaky mode domains is investigated for the first time to our knowledge. We propose a novel approach that offers refractive index measurement by monitoring power change in leaky outer-cladding modes and simultaneous phase-based detection for guided inner-cladding modes as temperature reference in the nonlinear refractive index sensing regime where guided-leaky mode transition occurs. The experimental results agree well with theoretical predictions that demonstrate the potential of fabricating in-fiber refractometers with large measuring range and high sensitivity.