A Fiber Optic Sensing Network (FOSN) consists of FO-sensors connected to and multiplexed/distributed along one or several lines carrying the signals modulated by the measurand. The optical signals are processed by opto-electronic units. Each set of sensors interconnected in the same fiber optic web and connected to one opto-electronic unit builds up a fiber optic sensing sub-network (or sub-FOSN). The opto-electronic units also provide interfacing to the communicating network, exchanging data and information between sensing sub-networks and a central monitoring station. Different FO-sensing sub-networks, connected by one communicating network to a central data analyzing and processing station build up an overall fiber optic sensing network.