A simple fiber optic vibration sensor is designed and demonstrated using fiber optic fused 2 × 2 coupler that utilized the principle of reflected light intensity modulation. In order to avoid source signal power fluctuations and fiber bending losses, the rational output (RO) technique is adopted. A calibrated 1-mm linear and high sensitivity of 0.36 a:u:∕mm (2.1 mV∕μm) region of the displacement characteristic curve is considered for vibration measurement. The experimental results show that the sensor is capable of measuring the frequency up to 3500 Hz with ∼0.03 − μm resolution of vibration amplitude over a dynamic range of 0 to 1 mm. The signal-to-noise ratio of the RO is also improved with respect to the sensing signal. In comparison with dual-fiber and bifurcated-bundle fiber, the designed sensor consists only of a single slope that makes the sensor alignment simple by eliminating the dark region and front slope. Simplicity in design, noncontact measurement, high degree of sensitivity, and economical, along with advantages of fiber optic sensors, are the attractive attributes of the designed sensor that lend support to real-time monitoring and embedded applications.

No abstract

No abstract

A non-contact vibration sensor is demonstrated using bifurcated bundle fiber based on the principle of extrinsic reflective intensity modulation for monitoring the health condition of the diesel engine. An IR-source is used along with glass fibers to avoid the effect of stray light in sensing. The encapsulation of the sensor enables easy alignment, flexible handling and usage in harsh environments. The sensor is capable of measuring the frequencies up to 650Hz with vibration amplitude resolution of 10µm, enough to monitor the vibrations generated in heavy machines like diesel engine.

No abstract