Laser amplifiers in optical communications

The use of single mode fibers makes it possible to obtain a considerable reduction in chromatic and polarization dispersion. In such a case, the range of a communication system is only limited by attenuation. Direct light amplifiers appear to be very attractive as 'on-line' amplifiers for attenuation compensation. The present investigation is concerned with the feasibility of an employment of laser amplifiers and, in particular, semiconductor laser amplifiers, in a single mode fiber communication system. Questions regarding the signal-to-noise ratio of an optical communication system with a laser amplifier are explored. Attention is given to the direct detection scheme, the 'on-line' amplifier, and the coherent detection scheme. It is concluded that, in the near future, semiconductor laser amplifiers could show much promise for different applications in single mode, high bit-rate optical communication systems.