A simple 1x2 plastic optical fiber coupler based vibration sensor

A simple noncontact fiber optic vibration sensor is designed using multimode fiber optic coupler. The sensor works on principle of reflection intensity modulation. A single fiber port of the coupler is used as sensing head. A linear change in light intensity during its displacement from the reflecting surface within 1 mm of linear region shows a high sensitivity of 2.45 mV/mu m which is used for the vibration measurement. Experimental results show that the sensor has the capability of measuring vibrations of frequencies up to 1300 Hz with similar to 1 mu m resolution of vibration amplitude over a range of 0-1mm. In comparison with dual-fiber and bifurcated-bundle fiber, this sensor eliminates the dark region and front slope which facilitates the easy alignment. The high degrees of sensitivity, economical along with advantages of fiber optic sensors are attractive attributes of the designed sensor that lend support to real time monitoring and embedded applications.