Pipeline monitoring using an integrated MFC/FBG system

This study proposes a new hybrid macro fiber composite/fiber Bragg grating (MFC/FBG) system that can excite and measure guided waves for pipeline monitoring using a single laser source and optical cables removing the need for conventional wire cables. Among various ultrasonic transducers, piezoelectric transducers and FBG sensors have been widely used because of their light weight, non-intrusive nature and compactness. Particularly for pipeline monitoring, a MFC transducer among other piezoelectric transducers is used because of its flexibility and conformability to a curved surface. In addition, conventional electric cables needed for power and data transmission are all replaced by optical cables, alleviating problems such as electromagnetic interference, signal attenuation and vulnerability to noise. A tunable laser is used as a common power source for guided wave generation and sensing. One of two laser beams split from the tunable laser, is used to actuate MFC transducers, and the other beam is used with FBG sensors to measure generated guided waves. The measured signals are processed to identify the existence of defects in pipeline structures such as wall thinning and longitudinal cracks. The feasibility of the proposed hybrid measurement system has been experimentally verified in a laboratory setup.