Quasi-distributed 3-cm vibration and strain monitoring using OFDR and in-line interferometers

This study presents a new quasi-distributed vibration sensing approach with a 3-cm spatial resolution, capable of performing multiparameter measurements. In-line interferometers are employed simultaneously as strain point sensors and reflectors for vibration monitoring due to the Doppler effect. The interferometers consist of capillary fiber segments spliced between single-mode fibers, forming a sensing etalon. A study of the characteristics required for the fiber array fabrication is carried out. A 60 cm array comprising 20 sensing sections is used for the proof-of-concept of the technique for strain and vibration sensing. An analysis of the behavior for static strain and vibrations is performed, both individually and simultaneously, using a free-end cantilever experiment.