Often it might be as simple as routing right wavelength through right path, as in WDM systems. Optical amplifiers, such as EDFA [0] are interesting thing, too.

Often it might be as simple as routing right wavelength through right path, as in WDM systems. Optical amplifiers, such as EDFA [0] are interesting thing, too. [0]: http://www.fiber-optical-networking.com/the-application-of-edfa.html http://www.fiber-optical-networking.com/the-application-of-e...