A novel Sagnac based fiber optic acoustic sensor using two laser diodes with ext

A novel fiber-optic acoustic sensor consisting of two laser diodes and a fiber Sagnac interferometer is presented. Two laser diodes operate under external optical injections, including self and mutual injections. The Sagnac interferometer acts as a reflectivity-variable loop mirror. When external acoustic waves perturb the Sagnac fiber loop, its reflectivity will change with the intensity of external perturbation, which alters the amount of injection lights of two laser diodes and induces the ou