Monitoring of cracks on offshore platforms is necessary to ensure the safe operation and prolong their service life. The crack extension width is of great significance for the calculation of stress intensity factor (SIF). This paper developed a measuring device for crack extension width based on Fiber Bragg Grating (FBG) sensing technique. The designing principle was detailed introduced upon which a sensor with measuring range of 0-5 mm and sensitivity of 0.4 nm/mm was encapsulated according to engineering requirements. The calibration results indicated that the sensor has good linearity and repeatability within the design range. Based on local model experiment with prefabricated crack, results demonstrated that the sensor has high precision and feasibility for different crack damage conditions as well as good stability towards cyclic loading tests, showing potential prospective for offshore platform crack monitoring.
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