The main object of the bachelor´s thesis is show familiarize with optical networks and measuring when the fibres are connected to operating network. The whole thesis was separated into several parts. The first part was deals with optic fiber and properties, kinds of optic fibers, methods of propagation light inside fiber and important parameters, which has undesirable effects, such as optic loss and dispesive influences. Next part was concentrated on transfer technologies, which where used for data transmission in operating networks. We talked about differences between technologies and describe the monitoring system, which was used for measuring parameters in operating network. The last part was focused on own measuring. We was measured the...