Nowadays almost network infrastructure are based on TDM ( Time Division Multiplexing ) which have been peaking soon. FUJITSU Labs has developed photonic networks which are based on WDM ( Wavelength Division Multiplexing ).
About wavelength multiplexing, I want you to imagine sunlight. Sunlight is multiplexed several light which have different wavelength each other. And a prism splits sunlight into the spectrum. WDM method is application of this. As WDM, infomation bits are coded into optical pulse. Several wavelength are multiplexed and transfered all at once. Receiver splits multiplexed signal by spectrograph which is prism-like device.
TDM method can transfer only one signal at once. But WDM method can transfer "multi" signal at once. The transfer rate depend on spectrographs. FUJITSU Labs say, "By 2000, we will grow transfer rate 40Gbps by a wavelength, and 160Gbps by a fiber. By 2015, transfer rate increase 160Gbps by a wavelength, and over Tera bytes per second by a fiber."
Nowadays, network infrastructures are so complex. Its fault-tolerance also is poor. Implementing the technology, some problems would be improved. What I wish.