Use of optical amplifiers in long haul transmission systems

Optical amplifiers have recently come to the fore in optical research work because of their potential to significantly enhance the capacity and transmission span of optical fibre systems. They offer the attraction of performing signal amplification without the need to perform opto-electric and electro-optic conversion, but because they are linear amplifiers they lose the ability to effect full 3R regeneration. A system using optical amplifiers is transparent to the bit rate of the data and the system capacity can be further increased by using WDM or FDM multichannel techniques. The optical amplifier can be deployed as a transmitter postamplifier, a receiver preamplifier or a system line amplifier. This paper focuses upon the long haul system potential using optical line amplifiers.