FIBER OPTICS Introduction

Written by Colby C. Young    Sunday, 08 March 2009

The development of optical fiber technology has been a critical milestone in the global telecommunications and information technology revolution. The ability to communicate worldwide on demand would not have been possible without the development of low-loss silica fiber as a broadband medium for transporting voice, video, and data traffic. At the time the laser was invented in 1958, it was already recognized that communication using lightwaves offered immense potential, but it took some twenty years before a practical medium capable of transporting light pulses around the world was developed. The manufacture of optical fiber began in the 1970s and has been accelerating at an incredible pace since that time. Today, optical fiber is being installed worldwide at a rate of about 3,000 miles per hour--a distance of three times around the world every day. At the same time, the data-carrying capacity of each strand of optical fiber is doubling every year as technological advances in photonics and electronics permit more and more wavelengths of light to be transmitted at ever-increasing data rates. Commercial systems that transmit 400 Gb/s over a single optical fiber (equivalent to 12,000 encyclopedic volumes per second) are now available. Several laboratory experiments conducted during 1999 demonstrated that capacity increase will continue for the foreseeable future. These experiments included: - 1.60-Tb/s transmission over 400 km using 40 individual wavelengths of light, each moduated at 40 Gb/s( n1); - Transmission of a single wavelength channel at 160 Gb/s over 300 km using practical semiconductor technology( n2); and - Transmission of 1,022 wavelength channels using a single laser source.( n3) It is often asked how long this rate of progress can continue. The region of optical transparency of silica fiber where the attenuation is sufficiently low for long-haul transmission is approximately 50 THz. If the explosion in bandwidth continues on its current course of doubling each year, this capacity will be reached in only eight to ten years. Research is still required to understand how to effectively use this bandwidth in practical systems--how many wavelengths for wavelength division multiplexing (WDM) and how high a modulation rate of each channel for time division multiplexing (TDM). Since progress in photonics transmission capacity has been faster than progress in electronics speed, we can expect the functionality of photonic devices to increase. However, such progress will be contingent on the development of a host of optical devices, including optical filters for efficient multiplexing and demultiplexing of channels, refined optical fiber designs capable of meeting challenging system requirements, optical amplifiers covering the entire wavelength region, and a multitude of sources, modulators, signal regenerators, wavelength converters, and optical switches. These optical devices and the technologies on which they rely are discussed elsewhere in this paper.

Last Updated ( Sunday, 08 March 2009 )