 a power ratio named in honor of Alexander Graham Bell. The bel equals 10 log (PO/P ) where P1 is power output while PI is the input or transmitted power. broadband WDM a small section of a fiber modified to create changes in the index of refraction that reflects certain wavelengths. Bragg gratings a small section of fiber modified to create changes in the index of refraction that reflects certain wavelengths. carrier an oscillating wave which is modulated to convey information. centralized cabling cabling from a work area routed to a central location. chromatic dispersion a change in the speed of optical pulses as their wavelength changes, resulting in a broadening of pulses. cladding the area between the core and outer area of a fiber that coats the fiber. Class I repeater a Fast Ethernet repeater that is capable of connect- ing segments using different coding. Class II repeater a Fast Ethernet repeater that is only capable of con- necting segments that use the same signaling method. coherent light light in which emitted photons travel in the same wave pattern. collimation the process of converting divergent light into a beam of parallel light. connector a mechanical device physically connected to the end of a fiber-optic cable. Copyright 2001 The McGraw-Hill Companies, Inc. Click Here for Terms of Use. Glossary critical angle the angle at which light is totally refracted back into the core of a fiber. cross-phase modulation the broadening of light pulses in a dense wavelength division multiplexing environment. coupling method the method by which connectors mate. The cou- pling method includes threaded, bayonet, and push-pull. dark fiber fiber strands not yet used or illuminated. decibel a more precise power measurement than bel. A decibel equals one-tenth of a bell. demarcation the point where a circuit enters a building. dibit coding the process of encoding two bits in one signal change. direct ray the flow of light through a fiber on a direct route from end to end. dispersion the smearing or broadening of an