THE WHATIS.COM WORD-OF-THE-DAY June 5, 2001 erbium amplifier ______________ TODAY'S SPONSOR: The whatis.com Learning Zone Bookstore Teach Yourself TCP/IP in 24 Hours! In just 24 easy sessions of one hour or less, you will master theinner workings of TCP/IP. Each lesson builds upon previous lessons for a technical, yet refreshingly accessible, tour of the elegant protocol suite that forms the foundation of the Internet. http://www.digitalguru.com/dgstore/product.asp?isbn=0672320851&ac_id=76 _____________ QUIZ #6: Servers Nothing makes us tremble in our boots more than those dreaded words "the server is down". Think you know a little about servers? Take this week's quiz and find out! http://whatis.techtarget.com/definition/0,289893,sid9_gci556836,00.html _____________ TODAY'S WORD: erbium amplifier See our definition with hyperlinks at http://whatis.techtarget.com/definition/0,289893,sid9_gci213764,00.html An erbium amplifier, also called an optical amplifier or an erbium-doped fiber amplifier or an EDFA, is an optical or IR repeater that amplifies a modulated laser beam directly, without opto-electronic and electro-optical conversion. The device uses a short length of optical fiber doped with the rare-earth element erbium. When the signal-carrying laser beams pass through this fiber, external energy is applied, usually at IR wavelengths. This so-called pumping excites the atoms in the erbium-doped section of optical fiber, increasing the intensity of the laser beams passing through. The beams emerging from the EDFA retain all of their original modulation characteristics, but are brighter than the input beams. In fiber optic communications systems, problems arise from the fact that no fiber material is perfectly transparent. The visible-light or infrared (IR) beams carried by a fiber are attenuated as they travel through the material. This necessitates the use of repeaters in spans of optical fiber longer than about 100 kilometers. A conventional repeater puts a modulated optical signal through three stages: (1) optical-to-electronic conversion, (2) electronic signal amplification, and (3) electronic-to-optical conversion. (The term optical encompasses IR as well as visible-light energy in this context.) Repeaters of this type limit the bandwidth of the signals that can be transmitted in long spans of fiber optic cable. This is because, even if a laser beam can transmit several gigabits per second (Gbps) of data, the electronic circuits of a conventional repeater cannot. Besides eliminating complex and inefficient conversion and electronic amplification stages, the EDFA allows the transmission of signals that employ wavelength-division multiplexing (WDM). This increases the realizable bandwidth relative to conventional repeaters still further. RELATED TERMS: repeater http://whatis.techtarget.com/definition/0,289893,sid9_gci212890,00.html fiber optic http://whatis.techtarget.com/definition/0,289893,sid9_gci212113,00.html dense wavelength division multiplexing http://whatis.techtarget.com/definition/0,289893,sid9_gci213892,00.html ____________________ SELECTED LINKS [1] At Paderborn University, there is a paper on Erbium-Doped Devices. http://fb6www.uni-paderborn.de/ag/ag-sol/fres.htm [2] SearchNetworking.com has more information on erbium amplifiers. http://searchnetworking.techtarget.com/bestWebLinks/0,,sid7_tax1635,00.html __________________________ SUPPORT OUR SPONSOR! What do you like? Networks? Computer Games? Shareware? Get FREE info on the topics that interest you most. Postmaster Direct will find related news, information and special offers and deliver them directly to your e-mailbox, all at no charge! http://whatis.techtarget.com/postmasterDirect/1,289639,sid9,00.html _________________________ RECENT ADDITIONS [1] pixie dust http://whatis.techtarget.com/definition/0,289893,sid9_gci556046_top1,00.html [2] BREW http://whatis.techtarget.com/definition/0,289893,sid9_gci557319,00.html [3] hot site and cold site http://whatis.techtarget.com/definition/0,289893,sid9_gci557324,00.html [4] PPGA http://whatis.techtarget.com/definition/0,289893,sid9_gci557328,00.html [5] Electrohippies Collective http://whatis.techtarget.com/definition/0,289893,sid9_gci557340,00.html ======================================================== If you would like to sponsor this or any techtarget newsletter, please contact Gabrielle DeRussy at [EMAIL PROTECTED] ======================================================== If you no longer wish to receive this newsletter simply reply to this message with "REMOVE" in the subject line. Or, visit http://WhatIs.techtarget.com/register and adjust your subscriptions accordingly. If you choose to unsubscribe using our automated processing, you must send the "REMOVE" request from the email account to which this newsletter was delivered. Please allow 24 hours for your "REMOVE" request to be processed.
