Technologies towards Terabit Transmission Systems

Recently the first commercial 100 Gb/s system has been introduced. This system takes benefit from different basic technologies: QPSK modulation scheme, polarization multiplex and coherent reception technology in conjunction with digital signal processing. This system exploits the available channel bandwidth at 50 GHz channel spacing ideally. The most simple approach towards 1 Tb/s rate may take benefit from the superior characteristics of 100 Gb/s systems by applying 10 parallel 100 Gb/s channels in a reverse multiplexing scheme. Alternatively both, the symbol rate as well as the number of transmitted bit per symbol may be increased. Both are limited by either the speed of the electrical subsystems in the transmitter and in the receiver or by the available OSNR in a multi fiber span transmission system. Finally the available optical bandwidth may be used more efficient. Today up to 35 GHz bandwidth are applied for the transmission channel, the unused guard bands can be omitted by shifting the channels closer together with or without overlapping of spectra. Each technology itself enables an increase of bitrate, towards 1 Tb/s a combination of them will be advantageous. FRED BUCHALI received the diploma degree in electrical engineering in 1988 and the PhD degree in 1991 from Humboldt-University Berlin. During his PhD he worked on InGaAs/InP p-i-n photodiodes for fibre-optic communication. 1992 Fred Buchali joined Alcatel-Lucent Germany. He was involved in development of high speed pin photodiodes including packaging.