A simple macro-bending loss optical fiber crack sensor for the use over a large displacement range

Abstract

Abstract An optical fiber crack sensor based on macro-bending loss for detecting the crack opening displacement (COD) is developed in this paper. The sensor incorporates an extremely simple design, light source and detector. The decrease of the light intensity with displacement variation was reported. The verification experiments to the sensing principle were conducted. The sensor shows a response over a wide range of 212.1 and 87.9 mm in shrinkage and elongation, respectively. The response has two distinct nonlinear regions. A slab cracking model was established and random COD conditions were simulated. It is found that the predicted displacements of the sensor are nearly identical to the measured COD, and both relative errors are basically within 10%. Additionally, the sensor can be connected in series on one optical link to realized quasi-distributed monitoring; if crack shrinkage or elongation can be known in advance, the sensor by designed properly has a larger range of 300 mm. This optical fiber crack sensor is characterized by large measurement range, simple design, high flexibility and low economic cost, which shows a promising application in the field of displacement monitoring.