A comparison of optical amplifiers in optical communication systems edfa, Soa and Raman

As the optical signal travels in a fiber waveguide, it suffers attenuation (loss of power). For very long fiber spans, the optical signal may be so attenuated that it becomes too weak to excite reliably the (receiving) photo detector, however the signal may be detected at an expected low bit error rate (-10-9 to _10- 11). To reach destinations that are hundreds of kilometers away, the optical power level of the signal must be periodically conditioned. Optical amplifiers are key devices that reconstitute the attenuated optical signal, thus expanding the effective fiber span between the data source and the destination.