Fiber Optic Wiki

Figure 3-2 Total Internal Reflection

August 22, 2011

The critical angle is fixed by the indices of refraction of the core and cladding and is computed using the following formula: qc = cos–1 (n2/n1)The critical angle can be measured from the normal or cylindrical axis of the core. If n1 = 1.557 and n2 = 1.343, for example, the critical angle is 30.39 degrees.

Figure 3-3 Acceptance Cone

August 22, 2011

The amount of light that can be coupled into the core through the external acceptance angle is directly proportional to the efficiency of the fiber-optic cable. The greater the amount of light that can be coupled into the core, the lower the bit error rate (BER), because more light reaches the receiver.

Practical Systems Take Shape

August 20, 2011

Still, it would take more than good fiber to build commercial-grade communication systems. Lasers--which would require lifetimes of up to 1,000,000 hours--were still coming up short in reliability, failing after no more than a few hours of operation. Moreover, there was as yet no economical method of producing reliable lasers in the quantities that would be needed.

Fiber OpticsTo The Fore

August 20, 2011

The prospect of widespread installation of fiber-optics systems was exhilarating. In the United States, railroad rights-of-way offered convenient paths for long-distance fiber cables, which were so robust that even the strong vibrations of heavy trains did not disturb them.

Basic Research Remains Vital

August 20, 2011

In early fiber-optic systems, the amplifiers for regenerating a weak signal constituted a bottleneck. Although optical devices could be used to detect an incoming laser signal, some sort of electronic circuitry was needed to convert it to electric current, amplify the current, and then drive a new laser to recreate the optical signal. This limited the system to the capacity of the electronic amplifiers, which was considerably less than the potential capacity of the lasers and optical fibers.

The Path from Research to Human Benefit

August 20, 2011

This article was adapted by science writers Roberta Conlan and T. A. Heppenheimer largely from an article written by Robert Laudise, Malcolm Lines, and Morton Panish of Bell Laboratories, Lucent Technologies, and R. H. Stolen of AT&T Laboratories. Beyond DiscoveryTM: The Path from Research to Human Benefit is a project of the National Academy of Sciences. The Academy, located in Washington, D.C., is a society of distinguished scholars engaged in scientific and engineering research and dedicated to the use of science and technology for the public welfare. For more than a century, it has provided independent, objective scientific advice to the nation.

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