Application of fiber optic communication in telecommunication domain can be broadly grouped into two categories, long-haul and short-haul. This classification is done based on whether the optical signal is transmitted over relatively long or short distances compared with typical intercity distances that is in the ranges of 100 km.
Fiber optics makes its best use in Long-haul telecommunication systems. Such long-haul systems require high-capacity trunk lines. In the initial stages of development, the technology behind optical fiber communication was driven mainly by long-haul applications. Currently the focus of development in lightwave systems has been shifted more towards to the capacity of transmission. In fact, recent developments combine the transmission capacity with distance. The longer and high capacity lightwave systems have been reported from each successive generation of lightwave experiments.
Periodic regeneration of the optical signal by using repeaters is still required for most long-haul optical systems. Advantage of terrestrial guided lightwave systems is that the transmission distances of a few thousands kilometers is possible by using optical amplifiers. Researches are progressing to reduce the number of amplifiers and regenerators in transoceanic lightwave systems, where installation and maintenance of such devices are practically difficult and expensive.
Short-haul lightwave systems cover intra-city and local ring telecommunication traffic. Short-haul systems typically operate at low bit rates over distances of less than 10 km. Generally single-channel lightwave systems are employed in Short-haul transmission networks. Single-channel lightwave systems is not very cost-effective for such systems. Multi-channel transmission systems are introduced in Short-haul lightwave systems, for example, the broadband digital network. Broadband digital networks need to support high bit rate transmission of multiple services.