ABSTRACT
In this chapter, applications of fibre optical devices studied in previous
chapters are described as the main components of new devices used in
communication and in sensors, amplifiers and lasers.
Direct optical amplification of signal light is of considerable
interest, especially in optical communication systems and it can be
achieved by semiconductors or in optical fibres. In the latter, as seen in
Chapter 5, it can be achieved by using non-linear phenomena such as
stimulated Raman scattering (SRS), stimulated Brillouin scattering
(SBS) or stimulated four-photon mixing (SFPM). Raman amplifiers
have wide bandwidth, low loss outside the gain bandwidth, ultralow
noise and high saturation power. Gains higher than 30 dB are
achievable. However, they require very high pump powers. They are
used in telecommunication systems as preamplifiers.
