A stable nano-displacement sensor based on large mode area photonic crystal fiber (PCF) modal interferometer is presented. The compact setup requires simple splicing of a small piece of PCF with a single mode fiber (SMF). The excitation and recombination of modes is carried out in a single splice. The use of a reflecting target creates an extra cavity that discretizes the interference pattern of the mode interferometer, boosting the displacement resolution to nanometer level. The proposed modal interferometric based displacement sensor is highly stable and shows sensitivity of 32  pm/nm.

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We propose and demonstrate a simple and highly sensitive optical microphone based on S-shaped tapered fibre (STF). The short pigtailed end of the STF is attached to the centre of a thin circular nitrile diaphragm. The applied acoustic signal deforms the nitrile diaphragm and due to the affixation, the STF structure gets modified leading to change in the bending angles of the two STF bends. As a consequence, the photodetector output, detecting the reflected light intensity of the STF, varies in accordance with the applied acoustic signal. Various properties of the proposed sensing setup can be easily tailored by changing the diaphragm diameter and thickness, and the shapes and size of the STF. For an optimized configuration, the proposed sensor achieves a sensitivity of 3.07 mV Pa −1 and a minimum detectable pressure of 36.48 mPa Hz −1 . The sensor shows a linear behaviour up to 1300 Hz and the experimental value of its first order natural frequency is

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We propose a highly sensitive curvature sensor based on cascaded single mode fiber (SMF) tapers with a microcavity. The microcavity is created by splicing a small piece of hollow core photonic crystal fiber (HCPCF) at the end of an SMF to obtain a sharp interference pattern. Experimental results show that two SMF tapers enhance the curvature sensitivity of the system and by changing the tapering parameters of the second taper, the curvature sensitivity of the system can be tailored, together with the fringe contrast of the interference pattern. A maximum curvature sensitivity of 10.4 dB/m−1 is observed in the curvature range 0 to 1 m−1 for a second taper diameter of 18 μm. The sensing setup is highly stable and shows very low temperature sensitivity. As the interrogation is intensity based, a low cost optical power meter can be utilized to determine the curvature.