Fiber optical transmission systems and tract, their design, optical transmission networks, optical networks with SDH, SDH architecture, synchronic transmission frame STM 1, multiplex transmission principle in SDH, CROSSCONNECT function, CROSSCONNECT systems CC, CROSSCONNECT multiplexer CCM, ADD/DROP multiplexer ADM, networks architecture, signaling for maintenance in the SDH networks, prevention and restoration in the optical SDH networks, mixed ATM and TDM traffic, contributory signal mapping and ATM cells into SDH frames, networks with optical frequency multiplexer, wavelength multiplexer principle, optical networks elements, optical amplifier, optical terminal multiplexer, optical Add/Drop multiplexer OADM, WDM Crossconnect, passive router, optical regenerator, WDM networks, optical mesh level creation, routing in optical networks, protection in WDM networks, WDM circular networks with optical protection, separation of logical and physical structure in optical networks, optical networks layers.