Mach–Zehnder Interferometer Based on S-Tapered All-Solid Photonic Bandgap Fiber

We propose an S-tapered fiber Mach-Zehnder interferometer based on all-solid photonic bandgap fibers. Theoretical and experimental results reveal that the interference pattern originates from the coupling between core modes LP₀₁ and LP₁₁, LP₀₁ cladding supermode. The proposed structure exhibits quite sensitive to temperature and nearly insensitive to surrounding refractive index (RI). Moreover, the temperature-strain cross sensitivity is only 0.0092 °C/με. The strain/surrounding RI responses show little impact on the temperature sensing precision. Such a structure is easy to fabricate and can be a promising temperature sensor, eliminating the RI/strain-induced cross sensitivity.