A simple, compact, and highly sensitive gas pressure sensor based on a Fabry–Perot interferometer (FPI) with a silicone rubber (SR) diaphragm is demonstrated. The SR diaphragm is fabricated on the tip of a silica tube using capillary action followed by spin coating. This process ensures uniformity of its inner surface along with reproducibility. A segment of single mode fiber (SMF) inserted into this tube forms the FPI which produces an interference pattern with good contrast. The sensor exhibits a high gas pressure sensitivity of −0.68 nm/kPa along with a low temperature cross-sensitivity of ≈ 1.1 kPa/°C.

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In this paper, we present a novel accelerometer based on the Sagnac interferometer configuration using a polarization-maintaining photonic crystal fiber (PM-PCF), which has a sensitivity of ~8 pm/G, and a resonant frequency exceeding 2.5 kHz. The proposed accelerometer is capable of functioning with a constant sensitivity in a large frequency range from 0 to 1 kHz which is much wider than many FBG-based accelerometers. Experimental results obtained from a field test in railway monitoring, demonstrate a broader frequency range for the proposed accelerometer compared to that of the FBG based accelerometer and is comparable to the conventional piezoelectric sensor. The abrupt change in the acceleration measured by the sensor aids in locating any defect or crack present on the railway track. To the best of our knowledge, this is the first demonstration of an accelerometer based on a fiber interferometer aimed for the railway industry. The proposed accelerometer operating at high accelerations (>40 G) and capable of functioning at a broad frequency range, shows significant potential in being used in applications which require detection of strong and fast vibrations, especially in structural health monitoring of trains and railway tracks in real time.

This paper presents a sensitive and large dynamic range pressure sensor based on a novel birefringence microstructured optical fiber (MOF) deployed in a Sagnac interferometer configuration. The MOF has two large semicircle holes in the cladding and a rectangular strut with germanium-doped core in the center. The fiber structure permits surrounding pressure to induce large effective index difference between the two polarized modes. The calculated and measured group birefringence of the fiber are 1.49 × 10−4, 1.23 × 10−4, respectively, at the wavelength of 1550 nm. Experimental results shown that the pressure sensitivity of the sensor varied from 45,000 pm/MPa to 50,000 pm/MPa, and minimum detectable pressure of 80 Pa and dynamic range of better than 116 dB could be achieved with the novel fiber sensor. The proposed sensor could be used in harsh environment and is an ideal candidate for downhole applications where high pressure measurement at elevated temperature up to 250 °C is needed.

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