A wide range fiber optic sensor system for displacement and crack monitoring is developed. In the proposed fiber optic sensor system, a number of fiber loops are formed from a single fiber and each fiber loop is used as a crack or displacement sensor. The feasibility and the dynamic range of the fiber sensor developed in this manner are investigated experimentally. Both glass fibers and plastic fibers are used in the experiments. Experimental results show that the new fiber optic sensor has a

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... de range (maximum range is 88 mm) and this sensor also has a high sensitivity for displacement and crack monitoring when an appropriate diameter of the fiber loop is selected as the sensor. Moreover, the proposed method is very simple and has low cost, so in situ application potential of the proposed sensor is high.