We will discuss fabrication of twin core photonic crystal fiber (TC-PCF) using the stack-and-draw method and its application for in-line Mach-Zehnder interferometers. The small difference in the effective indexes of the two core modes leads to interference fringes and the birefringence of the twin cores results in polarization-dependent fringe spacing. The strain sensitivity was negative and wavelength-dependent. A novel intensity-based bend sensor is also demonstrated with bend-induced spatial fringe shift. High air filling fraction of fabricated TC-PCF cladding provides immunity to bend-induced intensity fluctuation.
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