Intel recently announced their implementation of a 100 GB optical network to connect their computers: http://goparallel.sourceforge.net/fa...tel-photonics/
100 GB through a fiber means a bit change every 10e-12 seconds, or every 10 picoseconds. Given the speed of light at 3e8 m/s it means that light trains of approximately 3 mm are traveling through that fiber. That is really short.
Thinking about this, a pattern of 0101010... has a frequency of 50 GHz. Green light has a frequency of 550 THz, which is only 10,000 times as high. What happens if the bit frequency approaches the light frequency? In radio technology, the modulating frequency had to be well below the carrier frequency. I just cannot scale up my thoughts to light/bitrate