An optical fiber amplifier is a key component for enabling efficient transmission of
wavelength-divisionmultiplexed(WDM)signalsoverlongdistances.Eventhough
many alternative technologies were available, erbium-doped fiber amplifiers won
theraceduringtheearly1990sandbecameastandardcomponentforlong-haulopti-
caltelecommunicationssystems.However,owingtotherecentsuccessinproducing
low-cost, high-power, semiconductor lasers operating near 1450 nm, the Raman
amplifiertechnologyhasalsogainedprominenceinthedeploymentofmodernlight-
wavesystems.Moreover,becauseofthepushforintegratedoptoelectroniccircuits,
semiconductor optical amplifiers, rare-earth-doped planar waveguide amplifiers,
and silicon optical amplifiers are also gaining much interest these days.
