A Simple Fiber-Optic Flowmeter Based on Bending Loss

The characteristics of a macrobending fiber used as an optical flowmeter are discussed. When a liquid flows through the bending area of the fiber sensor, it will result to the variation of the bending curvature and modulate the bending loss of the fiber, due to the impact or/and the drawing force of the flow which is relative to the speed of the flow. Different curvatures in initial state have different performances in the measurement. An optimum performance of the curvature radius of 8 mm in the range of flow rate from 0 to 3 m/s is found in the experiment. A block hung up the bending fiber to enhance the sensitivity and the dynamic range is demonstrated. Twenty times larger of the loss change is achieved by hanging an 11 times 11 mm² block. The experiment shows the influences of temperature and hysteresis can be ignored.