Distributed fiber optic sensing (DFOS) is a disruptive technology set to change the way infrastructures are managed. DFOS is unique in the sense that it uses standard optical fiber, typically identical to the one used for communications, for sensing. It turns the fiber into a spatially continuous transducer that provides a distribution of the measurand (temperature, strain, vibration,...) along its length. In this talk, the fundamentals of DFOS will be introduced together with a discussion of its use in practical infrastructure monitoring applications. Besides, the possibilities of this technology will be illustrated with the help of several real-world deployment examples in which the presenter has been directly involved.