An in-line fiber optic Fabry–Perot (FP) sensor for high-temperature vibration measurement is proposed and experimentally demonstrated in this paper. We constructed an FP cavity and a mass on single-mode fibers (SMFs) by fusion, and together they were inserted into a hollow silica glass tube (HST) to form a vibration sensor. The radial dimension of the sensor was less than 500 μm. With its all-silica structure, the sensor has the prospect of measuring vibration in high-temperature environments. In our test, the sensor had a resonance frequency of 165 Hz. The voltage sensitivity of the sensor system was about 11.57 mV/g and the nonlinearity was about 2.06%. The sensor could work normally when the temperature was below 500 °C, and the drift of the phase offset point with temperature was 0.84 pm/°C.

A pressure and temperature sensor based on dual Fabry-Perot interferometers (F-PIs) using Vernier effect and fiber Bragg grating (FBG) in hollow silica microsphere-cavity (HSMC) structure is demonstrated theoretically and experimentally. The sensor consists of a F-P cavity formed by inserting the FBG into the HSMC and a reference F-P cavity. Two structures are connected by a 50% coupler to generate the Vernier effect. The change of external pressure will change the length of the microsphere F-P cavity. Utilizing the characteristics that FBG is temperature sensitive and not effected by pressure, the simultaneous detection of temperature and pressure can be realized by demodulating equation. With a pressure sensitivity of 49.5nm/MPa and a temperature sensitivity of 14.3pm/°C, the sensor is achieved pressure detection at 300°C ranging from 0 to 0.8 MPa. The sensor has the characteristics of temperature compensation, high production efficiency, low cost, strong robustness, self-encapsulation and so on. It has a broad prospect in the field of high temperature and high pressure detection.

A reflective intensity-modulated fiber-optic sensor based on microelectromechanical systems (MEMS) for pressure measurements is proposed and experimentally demonstrated. The sensor consists of two multimode optical fibers with a spherical end, a quartz tube with dual holes, a silicon sensitive diaphragm, and a high borosilicate glass substrate (HBGS). The integrated sensor has a high sensitivity due to the MEMS technique and the spherical end of the fiber. The results show that the sensor achieves a pressure sensitivity of approximately 0.139 mV/kPa. The temperature coefficient of the proposed sensor is about 0.87 mV/°C over the range of 20 °C to 150 °C. Furthermore, due to the intensity mechanism, the sensor has a relatively simple demodulation system and can respond to high-frequency pressure in real time. The dynamic response of the sensor was verified in a 1 kHz sinusoidal pressure environment at room temperature.

This paper proposes the strategy of fabricating an all fiber wide-range displacement sensor based on the macro-bend coupling effect which causes power transmission between two twisted bending plastic optical fibers (POF), where the coupling power changes with the bending radius of the fibers. For the sensor, a structure of two twisted plastic fibers is designed with the experimental platform that we constructed. The influence of external temperature and displacement speed shifts are reported. The displacement sensor performance is the sensor test at different temperatures and speeds. The sensor was found to be satisfactory at both room temperature and 70 °C when the displacement is up to 140 mm. The output power is approximately linear to a displacement of 110 mm–140 mm under room temperature and 2 mm/s speed at 19.805 nW/mm sensitivity and 0.12 mm resolution. The simple structure of the sensor makes it reliable for other applications and further utilizations, promising a bright future.