OPTICAL COMMUNICATIONS
from Bell Labs Technical Journal, "Advances in Fiber Optics," Jan.-Mar. 2000 p. 168-
 

 
Fiber "Gee Whiz" Facts
     Manufacture of optical fiber began in the 1970's
     Currently being installed worldwide at a rate of about 3000 miles per hour (a distance of 3 times around the world every day!)
     Data-carrying capacity (bandwidth) of each strand of optical fiber is doubling every year
     400 Gb/s over a single optical fiber is now possible (equivalent to transmitting 12,000 encyclopedic volumes per second)
     Lab experiments in 1999 showed that increases are still possible:


1.60-Tb/s transmission over 400 km using 40 individual wavelengths of light, each modulated at 40 Gb/s

Transmission of a single wavelength channel at 160 Gb/s over 300 km using practical semiconductor technology

Transmission of 1022 wavelength channels using a single laser source

     How long can this bandwidth explosion continue?  The region of optical transparency of silica fiber (sufficiently low attenuation for long-haul transmission) is about 50 THz.  With bandwidth doubling every year, this number will be reached by about 2008-2010.  Still to be researched and developed:

How many wavelengths are optimum for wavelength division multiplexing (WDM), and how high a modulation rate of each channel for time division multiplexing (TDM).

Associated optical devices need to be developed:  optical filters for WDM, better optical fiber designs, optical amplifiers, sources, modulators, signal regenerators, and optical switches.