Optical transport network evolution: hot standardization topics in ITU-T including standards coordination aspects

The dramatic increase in capacity of telecommunication networks since the mid-1970s has been enabled by the introduction of light-wave systems for transmission. Since that time, services have evolved from voice and fax at 64 kbit/s to Ethernet and other data services at many Gbit/s, while the transmission technologies have evolved from GaAs 850 nm semiconductor lasers over multimode fiber to single mode fiber systems operating at 1300 nm, and later to multiwavelength systems operating at 1550 nm. This paper describes the evolution in services, frame formats, and optical technology along with the supporting ITU-T standardization activities that have fueled this development.