Optical fiber amplifiers for telecommunication systems

Optical amplification is of strategic importance for telecommunications. Optical amplifiers compensate for propagation losses in long distance links and branching losses in access networks, at the same time avoiding costly two-way conversions between optical and electrical signals. The devices available up to now are mainly represented by rare-earth-doped active fiber optical amplifiers. This article presents the state-of-the-art of optical amplifiers for telecommunications. However, erbium-doped fibre amplifiers are having a strong impact on the telecommunication market, thanks to the excellent performance of commercial devices. They are widely employed in long distance networks for the third transmission window, which is centered at λ=1550 nm, while in the second window, around λ=1310 nm, the role of semiconductor optical amplifiers is still competitive