Optical amplifiers-a telecommunications revolution

Advances in the field of optical amplifiers are briefly reviewed, with emphasis on the Er-doped fiber amplifier (EDFA). It is noted that the development of the EDFA worldwide has been astonishingly rapid. The noise performance is found to be virtually quantum-limited and this permits hundreds of amplifiers to be cascaded without significant degradation. The fiber transmission medium can thus be made effectively lossless and laboratory experiments to date have indicated that transoceanic distances can readily be traversed. Only four years after the invention of the EDFA, commercial EDFAs are now offered by more than 30 companies. The impact of the EDFA is being felt within a number of allied technologies, such as nonlinear optical fiber switching and routing, where the amplifier provides the ability to generate high-power pulses sufficient to access the nonlinear regime.<>