Fiber Optics Illustrated Dictionary geostationary orbitA type of orbit that is timed with the movement of the body it is orbiting so the period is equal to the average rotational period of the orbited body. If, in addition, the orbit is circular, the satellite will appear to be not moving when viewed from the ground, hence the name. In simpler terms, if you place a satellite in a circular orbit at about 35,900 to 42,164 Ian from the ground, it will appear to remain in the same place because of its synchronized relationship to the EaIth's orbit. This type of orbit has some advantages for communica- tions. The satellite is always available at the same location and not many high altitude satellites are needed to provide global coverage. The main disad- vantage is that powerful sending and receiving sta- tions are needed to send and receive signals to/from such a high orbit. Geostationary orbits were described by Arthur C. Clarke in the 1940s and 1950s in con- siderable detail and with remarkable foresight. Also called geosynchronous orbit and fixed satellite orbit. Geostationary Orbit In ageostationary orbit, the movement of the satel- lite keeps pace with the movement of the Earth and is thus within the same general visual and communica- tions region at all times, as seen ji-om the Earth. geosynchronous orbit See geostationary orbit. GEOTAIL A Japanese research satellite launched in 1992 to study the structure and dynamics of the tail region of the Earth's magnetosphere. The orbit of the satellite was planned so it would cover the magnetotail over a wide range of distances. It con- tains instruments to measure the magnetic field, the electric field, plasma, energetic patticles, and plasma waves. http://www.gtl.isas.ac.jp/ German Space Operations Center GSOc. A com- plex located near Munich, Germany, that was origi- nally established to support the first German research satellite (AZUR), launched in 1969. GSOC is a fa- cility of the German Space Missions Directorate (DLR) that prepares and executes national and inter- national cooperative space flight projects through the main facility and a number of remote satellite ground stations. GSOC responsibilities include not only mis- sion preparation, acquisition, rocket operations, and payload administration, but also the development of software support systems for mission support, data handling, and ground operations. 402 One of the interesting experiments undertaken by GSOC and its associates is the GPS Small Satellite Mission Equator-S (launched in 1997). Before this mission, Global Positioning System (GPS) receivers could be used only in near-Earth regions, well below the orbiting height of the GPS satellites themselves. This experiment successfully demonstrated that GPS receivers could be used at altitudes up to 34,000 ki- lometers. http://www.gsoc.dlr.de/gsoc.htm germania A short name for germanium oxide. See germanium. germanium Germanium is a "semi-metal" substance discovered in the I 880s. It is obtained primarily as a byproduct of zinc refining. There are reports that germanium may slightly convert transverse waves to longitudinal waves and vice versa. Materials with conversion capabilities are useful for semiconductor design. The primary use for germanium is for fiber optic sys- tems, and infrared optics account for another 13±2% of the market. Germanium chloride (GeCI 4 ) is one of the chemicals that may be used in modified chemi- cal vapor disposition (MCVD) processes for creat- ing preform blanks for pulling optical fibers . In pioneer vapor deposition fiber preform fabrication at Coming, germanium tetrachloride was used to form germanium oxide. See fiber fuse effect, va- por deposition. GETS See Government Emergency Telecommuni- cations Service. GFP See global function plane. GFC See generic flow control. GGP See Gateway to Gateway Protocol. ghost I. A shadow image on a monitor with phos- phor bum-in. When a phosphor-coated display device continually displays the same image (especially if it is a bright one) an undesirable pale image that does not disappear when the screen is refreshed may be burned into the display surface, thus interfering with the display ofdesired images. This ghost image in- dicates permanent damage to the monitor (unless the coating is replaced). See screen saver. 2. In audio communications, a quieter repeat or echo of a con- versation. 3. In optics, a light-caused image in the dispersion plane resulting from periodic ruling errors in a diffraction grating (as opposed to scattering errors). ghost, broadcast In broadcast images on a television screen, a slightly offset, pale copy of the desired im- age caused by secondary transmission of the origi- nal signal. Terrain can cause reflections of the direct signal that arrive at the receiver just slightly delayed and make the image appear slightly blurred or double. ghost port In the early days of computing, software was in its development stages and was not always written to handle processes in a secure manner. Thus, when users left a system or terminated a remote con- nection in an unexpected way, the process itself did not necessarily terminate, allowing the next user into the currently open account or process. It would some- times allow timeshare users, for example, to log in to the previous user's account through the ghost port (the unterminated session) and access the files. © 2003 by CRC Press LLC Ghost ports are less common now, with standard op- erating systems and more security-savvy program- mers developing the software, but hackers are still sometimes aware of security holes and programs and methods that create ghost port access to less robust systems. The phrase can also refer to an access port to a computer system that is visible to technical us- ers but invisible to nontechnical users, in other words, one accessible through system commands or proce- dures that are inherent to the system (as opposed to being hacked into the system) but not generally known outside of techie circles. Thus, ghost port re- fers to a port that is left behind and is mistakenly as- sumed to be a new port or one that is visible or ap- parent only to a subset of computer users. Ghostscript APostScript graphics language that is part of the Free Software Foundation's GNU project. Ghostscript is almost fully compatible with Adobe's PostScript. Ghostscript is a great tool for viewing and printing PostScript files. Adobe PDF readers, freely available on the Internet, are now beginning to su- persede the use of Ghost script for viewing and print- ing PostScript files on some systems, but enhance- ments to Ghostscript for PDF compatibility have kept it alive on others. giant magnetoresistance GMR. Aresistance effect discovered in the late 1980s by P. Gruenberg in Ger- many andA. Fert in France. Large resistance changes were observed in materials comprised of alternating, very thin layers of metallic elements when exposed to high magnetic fields at low temperatures. Other scientists were excited by this discovery and began to study many different types of materials and con- figurations of layers to better understand the effect and to see whether it could be produced without sub- jecting the materials to very low temperatures. ffiM researchers such as S. Parkin took aparticular inter- est in this area of research. It was determined that very thin combinations of nonmagnetic metals between layers of magnetic metals could induce the nonmag- netic layer to change its orientation. Oscillations in the magnetic alignment were also detected, and it was noted that resistance was low or high depending upon whether the layers were in parallel or antiparallel ar- rangement. GMR research has led to a new category of super- sensitive hard disk drives and, since this is a general reproducible effect, no doubt many other practical applications will be developed. See Kerr magneto- optic effect. .gif The conventional graphics file name extension used for CompuServe's proprietary Graphics Inter- change Format (GIF) raster-format graphics files. See Graphics Interchange Format. giga- (abbrev. - G when combined) (pron. jig-a) A prefix for 10 9 or 1,000,000,000 in the SI system. One billion. In computing, a giga is 2 30 or 1,073,741,824 (a multiple of 1024). Giga- has long been used in supercomputing, mainframe, and scientific applica- tions, but it was relatively unknown in lay language until the mid-1990s when gigabyte (Gbyte) hard drives dropped to consumer price ranges. It used to be a lot of storage space. Ten megabytes used to be a lot of storage. In fact, whole community BBS sys- tems used to run on five megabyte drives in the early 1980s. Now two gigabyte drives are considered to be average. See atto gigabit GB. (pron. jig-a-bit) 1,073,741,824 (2 30 ) bits. Gigabit Ethernet GbE. Ethernet networking capa- bilities capable of supporting half and full duplex transmissions at speeds of 1 Gbps (one billion bits per second). Fast Ethernet, the predecessor to Giga- bit Ethernet, is a widely installed international open standard. In 1997, the IEEE approved the P802.3ab study group's proposed 1 OOOBase- T standard for full duplex Gigabit Ethernet signaling over Category 5 networking systems. This approval led to the IEEE 802.3z Working Group ratifying a standard for Gi- gabit Ethernet, in June 1998, that included three physical layer specifications (one for shielded cop- per wire, two for optical fibers). Gigabit Ethernet was developed because vendors and users wanted the benefits ofa scalable high speed net- work to support existing Ethernet frame and proto- col characteristics to enhance rather than obsolete existing systems. Gigabit Ethernet uses the same frame format, media access control, and flow con- trol characteristics as slower Ethernets. Gigabit Eth- ernet provides a practical way to set up a backbone for interconnecting Ethernet and Fast Ethernet net- works, and provides an Ethernet upgrade path as the technology becomes cheaper. The types of applica- tions that require enhanced Ethernet implementations include scientific modeling, multimedia communica- tions, data warehouse search and retrieval, and oth- ers. The most significant competitor to the faster ver- sions of Ethernet is asynchronous transfer mode (ATM). Gigabit Ethernet is implemented at the physical (PHY) and media access control (MAC) layers. It supports the same frame format and size, and carrier sense multiple access with collision detection COSMA/CD) as Ethernet, and Fast Ethernet. Quality of service (QoS) is not inherent in Gigabit Ethernet, which is primarily a high speed connectivity mecha- nism, but is incorporated through other standards. RSVP is one way ofproviding quality through an open standard that can be incorporated into a Giga- bit Ethernet system. Objectives for link distances include multimode fi- ber optic links up to 550 meters, single-mode fiber optic links up to 3 kilometers, and copper-based links up to 25 meters, and Category 5 unshielded twisted pair (UTP) links up to 100 meters. A Gigabit Media Independent Interface (GMII) is also being studied. See asynchronous transfer mode, Ethernet, Fast Eth- ernet, Gigabit Ethernet Alliance. GigabitEthernetAlliance GEA. A California-based multivendor open forum established in 1996 to pro- mote the development and acceptance ofGigabit Ethernet technology and to actively support and ac- celerate the standards process. The GEA supports IEEE activities with regard to the development and ratification ofEthernet standards, particularly the 403 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary High-Speed Study Group, the IEEE 802.3 Working Group, and the IEEE 802.3z Gigabit Ethernet task force. The group provides technical resources for implementation and product interoperability. In June 1998, it ratified a standard for Gigabit Ethernet. See Gigabit Ethernet. http://www.gigabit-ethemet.orgl Gigabit Interface Connector GBIC. An interface, commonly sold as ahub-compatible peripheral card, used in Gigabit Ethernet uplinks. A hub may have slots for more than one GBIC. The GBIC enables an optical cable to be connected to an appropriate port by converting electrical impulses into laser light sig- nals for transmission over a medium such as Fibre Channel. It is sometimes also called a Gigabit Inter- face Converter. See Gigabit Ethernet. Standardized Cabling Specifications Specification Description 1000BASE-CX Wire-based transceivers or physical layer (PRY) devices for short-haul shielded copper cable connections up to 25 meters. 1 OOOBASE- T Wire-based transceivers of physical layer (PRY) devices for four-pair twisted-pair copper cable connections up to 100 meters. 1000BASE-8X Optical transceivers or physical layer (PRY) devices for cabling through optical fibers at 770 to 860 nanometer wavelengths. Based upon Fibre Channel signaling for multimode fiber. 1 OOOBASE- LX Optical transceivers or physical layer (pRY) devices for cabling through optical fibers at 1270 to 1355 nanometers. Based upon Fibre Channel signaling for single-mode or multimode fiber. 1000BASE-LH Long-haul multivendor specification. Gigabit News Industry news on ATM/Gigabit net- works along with analysis of competing technologies and market trends, published monthly by Infonna- tion Gatekeepers, Inc. gigabyte GByte, GB. (pron.jig-a-bite) 1,073,741,824 (10 9 ) bytes. Data rates are often described in giga- bi ts per second (Gbps) or, for very fast rates, may be described as Gigabytes per seond (GBps). Gigabytes are also used to describe the storage capacities of a large number of tape and hard drive storage media. Gigabyte System Network GSN. See Hippi-6400. GIGAMOAgigabyte-class magneto-optical storage technology developed by Fujitsu Limited and Sony Corporation, announced in November 1998. It was 404 the first widely available magnetic-induced super resolution (MSR) technology, providing 1.3 GBytes of storage on a 3.5-inch disc with a 5.92 MBytes per second transfer rate. GIGAMO retains the same car- tridge size and disc diameter as ISO/IEC 15041 stan- dards but has higher linearbit densities. The data stor- age capacity is about twice that of the widely adopted 640-MByte CD-ROM discs, and the technology is backwardly compatible, using the same write heads as earlier systems. See magnetic super resolution. GIGO garbage in, garbage out. An abbreviation to describe a situation in which output cannot be better than its corresponding input, with the implication that it is the fault and responsibility of the developer or data entry person if the system gives back bad or in- complete information. See garbage in/garbage out. Gll See global information infrastructure. gilbert A centimeter-gram-second (CGS) unit of magnetomotive force equal to 10 divided by 4p am- pere-tum. It is named after William Gilbert. Gilbert,William (1544-1603) An English physicist and physician who investigated electrostatic charges in various substances. He observed that magnetized iron lost its attractive power when heated to red heat and published De magnete (On the magnet) in 1600. He emphasized the distinctions between the magnetic effect of substances, such as lodestone, and the at- tractive properties of amber, adistinction previously promoted by 1. Cardan in 1550 but at the time still not widely considered. In his treatise, he used the word electrica to describe attractive phenomena. Gil- bert established that the Earth is a large magnet, thus explaining the general behavior of compass needles. The gilbert unit of magnetomotive force is named after him. See gilbert, versorium. GILC See Global Internet Liberty Campaign. Gilder's law Bandwidth capacity will roughly double in capacity every six or nine months or so. This law, in a sense, takes over from Moore's law, with chip processing capacities doubling about every 18 months to two years. With the emphasis away from single user systems towards network technologies, the same general idea is being applied to the growth and evolution of network transmission technologies. The term is attributed to Greg Papadopoulos at Sun Microsystems in honor of George Gilder, a business technology commentator and strong proponent of optical network technologies. See lambda switching, Moore's law. Gill, Jonathan "Jock" (ca. 1946- ) In 1992, Gill served as a Clinton/Gore campaign consultant on electronic publishing and email access and became the Director of Special Projects in the Office of Me- dia Affairs from 1993 to 1995, during the Clinton Presidential Administration. He is probably best known for developing email access to White House documents and, in 1994, being the first manager of the U.S. President's Web site, allowing users to take a virtual tour of the White House and find informa- tion on contacting government agencies. Gill is the founder of Penfield Gill, Inc., a media communica- tions and planning company. © 2003 by CRC Press LLC GILS See Government Information Locator Service. gimbal A mechanism or material that permits an at- tachment to be freely suspended or inclined in such a way that the suspended attachment remains level, or so the attachment can be inclined in any direction or several directions. Marine compasses and gyro- scopes incorporate gimbal mechanisms. gimp Extremely flexible wire or cable. Wire that can be easily threaded, woven, or spiraled. Gimp is wound up and attached to telephone handsets to al- Iowa length of wire to tighten up like a spring when not in use, so the conversant doesn't have to inter- rupt the phone conversation to reach the refrigerator. Gintl, Julius Wilhelm (1804-1883) An Austrian physicist and telegraph director who was one of the first to propose a practical means to transmit tele- graphic communications in both directions at the same time. Up to this time, telegraphs were one way, thus tieing up the lines for returning messages until the current message was finished. Using two batter- ies and a compensation method, Gintl devised two- way communications in 1853. Two-way or duplex te- legraphy was an important means of increasing line capacity that was later refined and extended by other inventors. See duplex telegraphy. Ginzton, Edward Leonard (1915-1998) A Ukrai- nian-bornArnerican inventor and professor who emi- grated to San Francisco in 1929, Ginzton headed up the Microwave Laboratory at Stanford. He developed further applications with the Klystron technology developed by the Varian brothers, the co-founders with Ginzton of Varian Associates, in 1948. In the late 1950s, he headed up the Stanford linear accelerator project. In 1959, he became the CEO of Varian As- sociates, remaining as Chairman until 1984 and serv- ing on the Board until 1992. Ginzton is remembered not only for his technical achievements with the Klystron tube and Stanford linear accelerator, but also for his pioneering man- agement policies. Ginzton was instrumental in estab- lishing employee incentives and benefits long before such practices were common or mandatory. His poli- cies aided him in attracting top talent to the firm and provided a new model for employee relations in the emerging Silicon Valley community. He also chaired the National Academy of Sciences committee that advised on the Clean Air Act of 1971 and, with David Packard, supported the development of minority- owned businesses. Ginzton has been recognized through numerous awards, including the IEEE 1969 Medal of Honor and induction into the 1995 Silicon Valley Engineering Council's Hall of Fame. When the Microwave Labo- ratory at Stanford University broadened in focus, around 1970, it began to be called the E.L. Ginzton Laboratory. It is an independent lab for engineering and physics research. See Klystron, magnetron, Sili- con Valley, Varian Associates. Giorgi System A system of measurement in which the units are meter, kilogram, second, and ampere (MKSA). GIP See Global Intemet Project. GIS See geographic information system. Gisborne, Frederic Newton (1824-1892) An En- glish-born Canadian inventor who devised new ways of insulating communications cables against harsh en- vironments. With the financial backing of Americans, most notably Cyrus Field, Gisborne was a strong motivational and administrative force in linking Eu- rope and North America, in 1858, with the first suc- cessful transatlantic telegraph cable and the first suc- cessful permanent cable a few years later. Leading up to this important historical achievement, Gisbome studied telegraphy in Quebec in the 1840s, excelling in his courses and subsequently accepting &~~:~:;~;:;~!~~~~J~:~~;£~t~J~~ •• (BNAETA) and, on its behalf, negotiated unsuccess- fully with eastern Canadian governments to set up a Halifax-to-Quebec telegraph line. Thereafter, Gisbome took the position of superintendent of the N ova Scotian telegraph lines. He sought backing from the government for an underwater line from Halifax to Newfoundland, expressing an interest in solving the problems associated with undersea installation and maintenance. In 1851, the Nova Scotia Electric Telegraph Company was established to oversee ex- isting lines and create new ones. In 1852, Gisbome left his position with the Nova Scotia Electric Telegraph Company to establish the Newfoundland Electric Telegraph Company. His as- sociation with financier Cyrus Field began in 1854 when Gisborne contacted Cyrus' brother, Matthew D. Field, on behalfof the financially stressed Newfound- land telegraph project. The American collaborators purchased the assets of the Newfoundland Electric Telegraph Company and settled its debts, traveling the difficult wilderness journey to St. Johns, New- foundland in spring 1854, to present the charter for a proposed New York, Newfoundland, and London Telegraph Company. The first undertaking of the ex- panded venture was to link Newfoundland with neighboring regions and with the U.S. Thus, subma- rine cables were installed between Cape Breton, New- foundland, and Prince Edward Island, and telegraph lines were installed across the perilous Gulf of St. Lawrence (though not on the first try). With the involvement of the U.S. collaborators, who envisioned oceanic telegraphy, Gisbome's ambitions increased. He became determined to establish a cable between Canada and Ireland. Despite months of harrowing travel and political arrangements further aggravated by financial difficulties, Gisbome contin- ued to pursue his goal ofestablishing a transatlantic cable. Gisbome's contribution is sometimes over- looked, as he pulled out of the partnership near its successful completion, due to distrust and disagree- ments with his collaborators, but he was an impor- tant contributor, both to the inception and progress of the project. See Field, Cyrus West; Gooch, Daniel; gutta-percha; transatlantic cable. GITS Government Information Technology Ser- vices. 405 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary Gladstone-Dale law The refractive index ofa sub- stance varies with a change in temperature or volume according to a formula in which the index of refrac- tion (n) plus one, over the density (r), equals a con- stant (k). glassA strong, brittle substance primarily composed of silica, that ranges from transparent to opaque, de- pending upon the quantity and composition ofother materials contained within the material. Impurities can affect the color, opacity, polarizing and transmit- tance characteristics, index ofrefraction, strength, flexibility and other properties of glass. The glass in jars and windows typically contains about 75% silica combined with a number of oxides to enhance the fabrication properties of the glass. Pure glass is generally preferred for fiber optics com- munications components (e.g., the conducting core), but impurities may be "doped" into the fiber to alter its refractive index or selective transmittance of cer- tain wavelengths. There are special challenges asso- ciated with pulling out long filaments ofpure glass. F or example, the process itself may introduce bubbles or a crystalline structure within the glass, which would interfere with light transmission. The addition of oxides to enhance the fluidity of the glass is not practical because it introduces undesired impurities. It has been discovered that pulling fibers or fiber pre- forms at 0 gravity results in a fine, pure glass with- out the problems of crystallization associated with Earth-based fabrication. See pulling fiber, vapor deposition. glass house colloq. A term to describe the large, glassed-in, controlled environments used to house and protect (and in some cases air-condition) large computer installations. These environments still ex- ist, to some extent, in supercomputing systems, but technological advances have decreased the size and fragility of many computers, and glass houses are no longer needed for small- or medium-sized comput- ing systems. Glass houses or clean houses are still used in chip manufacturing environments to provide a carefully regulated environment where temperature, humidity, and even tiny particles can affect the struc- ture and functioning ofcertain delicate or micromin- iature components. glass insulatorA historic utility pole insulating safety device ranging in size from about 6 inches to about 18 inches that was very commonly used to support live wires on utility poles. See insulator, utility pole for a chart and more detailed information. glitch 1. Unexpected, small, but annoying problem, usually causing a delay or minor informational error. This term is usually applied in instances where rep- etition of the problem is unlikely or infrequent. 2. Un- desirable brief surge or interruption of electrical power. GlobalArea Coverage GAC. One of the sample data set archives of the National Oceanic and Atmospheric Administration (NOAA) derived from the Advanced Very High Resolution Radiometer (AVHRR) sensors onboard TIROS and NOAA-x satellites. As the sat- ellites orbit, they collect Local Area Coverage data, 406 which is stored, combined, and compressed into GAC, available for download. In order to compress the data from LAC to GAC lev- els, four pixels in a scanline are sampled and aver- aged and the fifth pixel is skipped, with the process repeating to the end of the scanline. The following two scanlines are then skipped, thus creating a pat- tern for each three scanlines on through the data file. GAC resolution is approximately 7.6 km. Various agencies distribute data products based on GAC downloads. For example, the SeaWiFS GAC Level 1 consists of radiance data from combined north-to-south scan swaths with file sizes of about 19 MBytes. Sea WiFS GAC Level 2 is taken from Level 1A data that has been further processed, calibrated, and corrected. Unusual conditions may also be marked within the data. The National Science Foun- dation, the Office of Naval Research, and other or- ganizations have provided support to a number of research and educational associations for GAC data. See Advanced Very High Resolution Radiometer. global area network GAN. A network that is acces- sible to most or all nations in the world. The Internet is the closest thing we have to a GAN, although it is not yet ubiquitous or accessible by all nations or people. Global Atmospheric Research Program GARP. A program in the 1970s to study atmospheric trends and patterns and to extend the range of daily weather fore- casts over a longer period than was previously pos- sible. The GARP Atlantic Tropical Experiment (GATE) was the first major experiment in the GARP, carried out in 1974. GATE is ofinterest, not only be- cause it was international in scope, but because it in- volved intercommunication among a host of research ships, aircraft, and communications buoys. In the late 1970s and early 1980s, NOAA meteorological satel- Iites were designed and launched to support the GARP. NOAA-7, for example, launched in 1981, had sensors for measuring the Earth's atmosphere, sur- face, and cloud patterns. The GOES system of sens- ing satellites also form part of the GARP. See GOES. GlobalAtmosphereWatch GAW. A United.Nations Commission for Atmospheric Sciences monitoring and assessment program that uses technology to track pollution, ozone, and other aspects of atmosphere composition around the world. Global Business Communications Systems GBCS. An AT&T business, which was rolled in with the AT &T Laboratory restructuring of Bell Laboratories in 1995-1996, along with the Network Systems Group, AT&T Paradyne, Microelectronics, and Con- sumer Products. GBCS is moving into the area of multimedia and secure telecommunications selVices. Products include a Unix-based selVer that works on a private branch exchange (PBX) to provide video- conferencing capabilities over data networks such as Ethernet and mM Token-Ring. The selVer software is called Multimedia Communication Etchange (MMCX) and was implemented first on Unix sta- tions, with the intention ofporting it to PC operating systems. © 2003 by CRC Press LLC Global ChangeMasterDirectory GCMD. ANASA multidisciplinary database project originating from the Goddard Space Flight Center (GSFC) Global Change Data Center. The GCMD includes both na- tional and international remote-sensing data sets con- tributed by more than 800 U.S. and worldwide orga- nizations, including NOAA, NASA, DOE, NSF, EPA, USGS, educational institutions, and others. It is of interest to anyone interested in planet change, particularly climatic change. The data includes tem- poral and geographic information and some parts are interlinked with relevant external information. The GCMD relational database is now searchable online through the GCMD Web site. The data is ofparticu- lar interest to climatologists, agriculturalists, hydrog- raphers, mineralogists, and others. http://gcmd.gsfc.nasa.gov/ Global Data Processing System GDPS. A system of preparing and disseminating cost-effective meteor- ological analyses and forecasts. The GDPS retrieves, assesses; decodes, sorts, and analyzes the data in pre- paring for making it available for distribution. GDPS is one of three integrated core components of the World Weather Watch (WWW) system. It is ad- ministrated by the World Meteorological Organiza- tion. GDPS data are valuable for weather forecast- ing and meteorologically related agriculture, clima- tology, and aeronautics industries. See Global Ob- serving System, Global Telecommunication System. http://www.wmo.chlweb/www/DPS/gdps.html Global Development Gateway GOG. A major World Bank initiative proposed through the GOG Principles discussion forum hosted by Bellanet. The GDG is sponsored by the World Bank to promote in- formation exchange, access, and development. global directoryAn internetwork computer database that stores various types of information related to the various networks. The information may be user login names and passwords, shared database resources, group member lists, device directories that can be ac- cessed by more than one network, or pointers to vari- ous applications or documents common to the vari- ous networks. The Internet has a number of global directories of file databases, archives, etc. See Go- pher, Archie, Veronica. GlobalEnvironmentalMonitoringSystem GEMS. Administrated by the United Nations Environment Programme (UNEP), GEMS was established as part of the Earthwatch program in 1975 to support and strengthen environmental monitoring in participating countries and to improve the collection and evalua- tion of environmental data. Computer-acquired and -processed infonnation is an important part of this effort. See Global Resource Information Database. global function plane GFP. An architecture within which the modular functionality for Intelligent N et- work (IN) services may be globally constructed. The GFP functions are described as service-independent building blocks (SIBs). The IN is viewed as a single entity within the GFP. GFP is defined in ITU- T Q.1201 which describes a generic IN GFP model, service-independent building blocks, and services and features offered through a global service logic. Global Incident Analysis Center GIAC. A SANS Institute center that creates and disseminates reports of malicious activity on the Internet submitted by system administrators and network security profes- sionals worldwide. GIAC maintains a large archive of security-related papers available for free download. http://www.sans.org/giac.htm global informationinfrastructure GIL A term used since the mid-1990s by international standards com- mittees with regard to goals, standardization, and de- velopment of global interconnected telecommunica- tions systems, including the technology, applications, and related services. Global Information Infrastructure Commission GIIC. An independent, nongovernmental initiative inaugurated in July 1995 to promote leadership in the private sector and cooperation between private and public sectors in developing information selVices and networks. GIIC fosters economic growth, education, and quality of life through activities such l as devel- oping an accessible and diversified global informa- tion infrastructure. The GIIC operates as a project of the Center for Strategic and International Studies (CSIS). CSIS is a U.S based private organization founded in 1962 to conduct research in global public policy. http://www.giic.org/ http://www.csis.org/ GlobalInternetLibertyCampaign.A human rights group that includes the American Civil Liberties Union (ACLD), the Electronic Freedom Foundation (EFF), and other member organizations. Global Internet Project GIP. Aprivate sector orga- nization founded in 1996, consisting of senior level managers representing global software and telecom- munications industries with high stakes in Internet development. As part of its activities, GIP encourages the education of world decision-makers in the poten- tial evolution and uses of the Internet. http://www.gip.org/ Global Land Information System GLIS. An inter- active database system developed by the U.S. Geo- logical Survey (USGS). It provides data that is valu- able in the study of the Earth's land surfaces. Samples and information about GLIS products are available online. Topics within the GLIS database include cli- mate, geology, hydrology, land cover, and others. There are aerial photographs, satellite images, and digital line graphs to serve a variety of needs. The aerial photographs, for example, include sources such as the National Aerial Photography Program, Na- tional High Altitude Photography, and various radar systems. http://www.earthexplorer.usgs.gov/ Global Maritime Distress and Safety System GMDSS. A maritime safety system which incorpo- rates automated distress calls using Digital Selective Calling (DSC). In the late 1970s, maritime experts began to develop systems for updating safety and dis- tress communications, resulting in the 1979 draft of the International Convention on Maritime Search and Rescue. GMDSS advocates a global search and res- cue plan and a Global Maritime Distress and Safety 407 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary System (GMDSS) as a communications infrastruc- ture for the overall plan. The system is based upon a combination of Earth-based and satellite-based radio services, emphasizing ship-to-shore marine signaling through relatively user-friendly consoles. GMDSS signaling is quickly superseding the decades-old Morse code-based system. In addition to the automa- tion of distress signals, it calls for the shipboard downloading of maritime safety information as a pre- ventive measure. In 1996, the Telecommunications Act was written to encompass U.S. marine vessels, and ships were re- quired to install GMDSS equipment by I Feb. 1999. All vessels subject to Chapter IV of the Safety ofLife at Sea (SLOAS) convention must be fitted with GMDSS equipment (with stipulated exceptions) as must mobile offshore drilling units (MODUs). Implementation of GMDSS has not been without problems. It has been criticized for false alarms and general reliability problems, and many nations have been slow to adopt the system. See COSPAS/ SARSAT, NAVTEX. global mobile personal communications services GMPCS. A phrase coined by the ITU- T to describe mobile communications through low Earth orbit (LEO) satellite systems but later broadened to include other modes of mobile communications (geostation- ary FSS, MSS, "Little LEOs" and wideband LEOs). GMPCS was the discussion theme of the World Tele- communication Policy Forum (WTPF), resulting in a set of principles and recommendations described in the "WTAC Report to the Secretary-General [of the ITU-T] on GMPCS," January 1996. Global Navigation Satellite System GLONASS, GNSS. A satellite system deployed by the Russian Federation defense department, which has much in common with the American Global Positioning Ser- vice (GPS) in terms of satellite placement and the types of information transmitted. The 24 GLONASS system satellites are orbiting in three planes. Unlike the GPS system, GLONASS claims to plan to use the same levels of signals for civilian (CSA) and gov- ernment use (SA), and civilian use is guaranteed for about the next decade. By the late 1990s, the project had been divided into two stages: (I) GNSS-I, the first generation Russian GLONASS and U.S. GPS system and (2) GNSS-2, the second generation sys- tem including civil access with improved position- ing and services. The MIT Lincoln Laboratory conducts research on the GLONASS system and reports progress and ob- servations on the project on their Web site. http://vega.atc.ll.mit.edu/glonass/ Global Network Navigator GNN. A Web-based in- formation service providing lists of and information about new services, sites, and related resources on the Internet. Global Observing System GOS. A system for ob- taining standardized observations of the Earth's at- mosphere and ocean surfaces from ground, sea, air, and space-based observation platforms. GOS is one of three integrated core components of the World 408 Weather Watch (WWW) system and is administrated by the World Meteorological Organization. GOS data are valuable in weather forecasting and meteorologi- cally related agriculture, climatology, and aeronau- tics. Space data are available through the Environ- mental Observations Satellite (EOS) system com- prised of five near-polar and five geostationary en- vironmental observation satellites with a variety of imaging and sounding sensors. See Global Telecom- munication System, Global Data Processing System. http://www.wmo.ch/web/www/OSY/GOS.hrml Global One An international commercial joint ven- ture of Sprint, Deutsche Telekom, and France Telecom. Global Online Directory GOLD. A commercial product from VocalTec that works in conjunction with their Internet Phone software. Internet Phone lets you plug a microphone into your personal computer and use it as a phone transmitter to communicate with an- other person with Internet Phone capabilities. The computer speaker provides the equivalent of the phone receiver. Long-distance calls can be placed as though they were local calls through your ISP, with- out long-distance charges. Internet Phone connections are full duplex, connect- ing through the TCP/IP transport protocol. In addi- tion to the features ofa conventional phone call, chat lines and other digital enhancements are available. GOLD is the global directory that stores information about Internet Phone users who can be contacted, just as the names of phone subscribers can be accessed through a phone directory. Global Ozone Monitoring Experiment GOME. A satellite-borne ozone European Space Agency (ESA) research project launched in April 1995 on board the European Remote Sensing Satellite (ERS-2). GOME is a nadir-viewing passive spectrometer that senses atmospheric trace constituents by measuring solar ra- diation scattered by Earth's atmosphere. Cloud char- acteristics, aerosols, and surface reflection can also be measured. GOME is designed to sense in the vis- ible and ultraviolet spectra from 240 to 790 nanom- eters. See GOME Data Processor. http://auc.dfd.dlr.de/GO ME/ Global Positioning System GPS. A space- and ground-based 24-hour navigational system originally designed and used by the U.S. military (see Navy Navigation Satellite System), funded and maintained by the U.S. Department of Defense (DoD). It provides the means to monitor, update, and maintain orbiting satellite systems and to determine a location on or around the Earth through information from these sys- tems. GPS uses the known positions ofsatellites as refer- ence points for discerning unknown positions on or above the Earth. There are now over 20 satellites in the system (some are spares), more-or-Iess evenly spaced, orbiting in 12-hour cycles at an altitude of about 10,898 miles (about 400 miles higher than the original NNSS). A system of sophisticated ground stations with antennas, coordinated by a master con- trol station, administers, deploys, and maintains the © 2003 by CRC Press LLC satellites and updates them when needed to correct for clock-bias errors. A variety of types of information can be computed from information from several satellites, including a location or position ofa stationary or moving object, and coordination of time. This information can be in- corporated into software applications in vehicle- mounted or handheld positioning receivers. From military operations, to recreational navigation on the ocean in a kayak, to airline navigation, GPS provides a wealth of data with which to determine latitude and longitude, altitude, and velocity. This information can further be combined with maps to record or suggest routes. GPS satellites transmit timed binary pulses in addi- tion to information constants about the current loca- tion of the satellite. The synchronized atomic clocks aboard the satellites permit the transmission of pre- cise timing tags. The combination of the speed of transmitted electromagnetic waves and the atomic clocks installed in GPS satellites provides remarkably accurate timing pulses. NAVSTAR Global Positioning System NAVSTAR Global Positioning System (GPS) satel- litefrom the 24-unit constellation ofplanes and satel- lites thatprovides militaryandcivilian navigation and positioning data. The nine-ton satellites orbit the Earth every 12 hours, emitting continuous positional sig- nals. The signals can be used to calculate time, loca- tion, and velocity, depending upon the capabilities of the GPS receiver. The system is controlled and oper- ated by the 50th Space Jfing out of Schriever AFB, Colorado. {U.S. Air Force Space Command image.] The GPS Master Control Station (MCS) is operated by the 50th Space Wing's 2nd Space Operations Squadron in Colorado. This squad is responsible for monitoring, controlling, and operating the GPS sat- ellite constellation. The u.S. Air Force Space Com- mand Space and Missile Systems Center in Los An- geles, California, is the executive agent for the De- partment of Defense (000) acquiring GPS satellites and equipment. There are thousands of GPS users worldwide. Per- sonal GPS devices can be purchased for as little as $180 to $450, and more sophisticated ones are used in all industries that rely on location information: air- lines, shipping fmns, ferries, military divisions, etc. F or greater details on individual aspects of GPS, see differential GPS, EAGLE, Intelligent Vehicle High- way Systems, GPS Operational Constellation, GPS Navigation Message, local differential GPS, NAVSTAR, Precise Positioning Service, Standard Positioning Service, wide area differential GPS. Global Resource Information Database GRID. A global network of environmental data centers coop- erating to generate and disseminate key environmen- tal geo-referenced and statistical data sets and infor- mation products. GRID centers are equipped to pre- pare, analyze, and disseminate environmental data that may be used as the basis for environmental as- sessments. GRID is associated with the Earthwatch program and the Environment Assessment Division of the United Nations Environment Programme (UNEP). It was established in 1985, evolving gradu- ally out of the 1972 United Nations Conference on the Human Environment held in Sweden. Following the conference, UNEP was created to provide a fo- cus for a Global Environment Monitoring System (GEMS) that led to GRID. There are a number of GRID centers around the world, including in the U.S., South America, Europe, Russia, Nairobi (UNEP headquarters), Asia, and New Zealand. For example, the United Nations Environ- ment Programme (UNEP) and 1987 World Commis- sion on Environment and Development project in cooperation with the Government of Norway estab- lished a GRID environmental information center in Arendal, Norway. GRID-Arendal was opened as a nonprofit foundation in August 1989; it communicates and cooperates with other GRID centers. Global Software Defmed Network GSDN. A high- volume commercial virtual private network service from AT&T that utilizes AT&T's Worldwide Intelli- gent Network (WIN) to interconnect networks in the U.S. and other countries. GSDN selects an economi- cal route for external calls and provides internal ser- vices, including order entry, tracking, file transfers, and teleconferencing services. GSDN is aimed at business networks. Global Standards Collaboration GSC. A frame- work for the exchange of information regarding glo- bal standards development for interconnectivity and interoperability of systems and devices. Thus, the GSC has been bringing together senior officials from regional, national, and international standards bod- ies since 1988. Participating bodies include the In- ternational Telecommunication Union (ITU), the In- ternational Organization for Standardization (ISO), the European Telecommunications Standards Insti- tute (ETSI), and others. Focal areas are discussed at large conferences. For example, global radio stan- dardization was the key topic for the 2000 meeting in Sapporo, Japan. Other topics ofcurrent interest in- clude number portability for mobile communications, universal personal telecommunications (UPT), and intelligent networks. http://www.gsc.etsLorg/ 409 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary Global System for Mobile, Groupe Speciale Mo- bile GSM. A digital cellular technology developed jointly by the telecommunications administrations of Europe. The Groupe Speciale Mobile was founded in the early 1980s, and the Global System for Mo- bile (GSM) was first publicly announced in 1991 and has since been standardized in Europe and Japan. GSM was the first fully digital system to provide mobile voice connections, data transfer services, pag- ing, and facsimile at full duplex or half duplex rates up to 9600 bps. GSM operates in two frequency ranges: 890 to 915 MHz for signaling infonnation and 935 to 960 MHz for information transmissions. GSM is a set of standards specifying a digital mobile communications services infrastructure. It is based on a 900 MHz radio transmission technology and specifies related switching and signaling formats. An 1800 MHz Digital Cordless System (DCS) has also been added. Since mobile systems typically support roaming, and since the multicultural makeup of Eu- rope provides a unique challenge in providing com- patible services, interoperability has been emphasized in the GSM specifications. GSM can be described in three categories: commu- nications media, transceiving systems, and informa- tion systems, as shown in the GSM General Catego- ries chart. The GSM subscriber identity module (SIM), also known as a smartcard, is a security feature which handles encryption and authentication. It includes memory storage which can be used for dialing codes or other information related to the service. The SIM is also a means to download and display call-related information. See Future Public Land Mobile Tele- communication System, Personal Communications Network. Global Telecommunication System GTS. A system of terrestrial and space-based data circuits for inter- connecting meteorological telecommunications cen- ters. GTS is one of three integrated core components of the World Weather Watch (WWW) system and is administrated by the World Meteorological Organi- zation. GTS data are valuable in weather forecasting and meteorologically related agriculture, climatology, and aeronautics. The GTS provides rapid and reliable dissemination of observational meteorological data. The GTS is organized into a Main Telecommunica- tion Network (MTN), Regional Meteorological Tele- communication Networks (RMTNs), and the Na- tional Meteorological Telecommunication Networks (NMTNs). The World Meteorological Centres (WMOs) are located in Russia, Australia, and Wash- ington, D.C., and there are more than a dozen regional hubs in Asia, South America, Africa, Europe, and other locations. See Global Observing System, Glo- bal Data Processing System. http://www.wmo.ch/web/www/TEM/gts.html Global Title Translation GTT. A telephony and ad- ministration and routing function that enables added feature functionality in commercial systems such as Local Number Portability (LNP), calling card ser- vices, and mobile roaming support. GTT determines destination addresses in Signaling System 7 (SS7) and other relevant network systems. When a call is initiated, GTT detennines the destination and may include additional information, depending on the fea- ture service. GTT may support multiple global title addresses. Global Transaction Network GTN. AT&T's exten- sive 800 service phone network, which was in- troduced in 1993. This service supports enhanced fea- tures, providing more flexible routing and number- ing services which can be used, for example, by air- line reservation systems. Globalstar A system of 48 small bentpipe commu- nications satellites orbiting at 1400 kilometers (LEO), for providing voice and data services (data files, pag- ing, facsimile). Globalstar was established in 1991 as ajoint venture of Lora I Space & Communications, Ltd., QUALCOMM, Inc., and a number of corporate partners. Launching began in February 1998. In 1999, G lobalstar launched four more systems, bringing the Global System for Mobile (GSM) General Categories Category Notes Media GSM works over frequency-modulated (FM) signals using a combination of time division multiple access (TDMA) and frequency division multiple access (FDMA). Peak output power varies with the type of transmitter (mobile station class), ranging from 0.8 to 20 watts. Frequency hopping is used to reduce interference and multipath fading, and encryption increases security. The data rate is 270 Kbps. Transceiving There is a base transceiver station (BTS) associated with each cell operating on fixed frequencies unique to its region. Honeycomb-like clusters are handled by base station controllers (BSC), which, in tum, are controlled (routed, switched, handed over) by Mobile Service Switching Centers (MSC). Information There are databases associated with GSM that aid in the administration of subscriber information and those that aid in the administration of security and associated authentication mechanisms. There is also an equipment identity register (EIR), which keeps track of equipment types and configuration, and can block calls on stolen units. 410 © 2003 by CRC Press LLC total satellites to 12. By 2000, the system was opera- tional and the number of satellites increased to 48 over the next two years. Globalstar services can be accessed with vehicle- mounted or handheld devices resembling cellular phones, and the system is integrated with cell phone services through dual-modem handsets. Remote us- ers can access the system through Globalstar service providers, with fIXed-position and wire line phones. Globalstar is intended to enhance rather than replace existing cellular and other phone services. Services are aimed at international business travelers, commer- cial vehicle operators, marine craft, field scientists, and others. The competitive aim is low cost for ser- vice and accessories. GLONASS Global Navigation Satellite System. A Russian Federation Global Positioning System simi- lar to the U.S. NAVSTAR system. GLONASS is managed by the Russian Space Forces. GLONASS provides all-weather positioning coordinates, veloc- ity references, and time information from virtually any point on or near the globe. More specifically, the GLONASS system aids in managing air and marine traffic, in supporting emer- gency and safety systems, geodesy, cartography, and ecological monitoring. Like the American GPS sys- tem, GLONASS is two-tiered. It provides standard precision navigation signals (SPs) with horizontal accuracy to about 63±6 meters and high-precision navigation signals (HPs) with authorization and spe- cialized equipment. The GLONASS system has launched more than four dozen satellites since the first was put into operation in October 1982. Early satellites had a lifespan of about two years, while later satellites lasted about four or five years. In general, the launches have been suc- cessful, although in 1987 and 1988 there were a num- ber of failures. Since 1989, the orbiting platforms have included geodetic reference satellites. In F eb- ruary 1999, the Russian Federation made an open declaration of increasing international cooperation with regard to national satellite navigation technolo- gies and international navigation systems. The con- stellation status is reported, within a few days, on the GLONASS Web site. http://www.rssi.ru/SFCSIC/english.html Glossary of Telecommunications Terms, FCC A short glossary of telecommunications terms related mainly to delivery of broadcast services to consumers provided by the Federal Communications Commission. Glossary of Telecommunications Terms, Federal Standard Originally introduced in 1976 as MIL- STD-188-120, this archive has evolved through sev- eral revisions to become the Telecom Glossary 2000. It is provided through the u.s. National Communi- cations System in print, CD-ROM, and Web formats, with increasing emphasis on electronic development and dissemination. The Glossary is mandated for use by all federal departments and agencies for the prepa- ration of telecommunications documentation and is available from the National Technical Information Service. Definitions from the previous standard were revised and updated by the FTSC Subcommittee to Revise FED-STD-J037B. The subsequent version, FED- STD-l 03 7C (1996), was further updated to Telecom Glossary 2000, with many of the new definitions drawn from TI Standards and Reports. The Glossary includes standard definitions for tele- communications terms related to antennas, comput- ers, transmissions media (e.g., fiber optics), networks, audio/video technologies, radio communications, etc. Sources include government publications and those of prominent telecommunications organizations in- cluding the lTV, ISO, and the American National Standards Institute. The Glossary has been reviewed by the National Communications System Member Organizations, the Federal Telecommunication Standards Committee members, members of relevant industries and federal agencies, and by the general public. Telecom Glos- sary 2000 was discussed through members of the TIAI Ad Hoc Glossary Group. GMDSS See Global Maritime Distress and Safety System. GMDSS Radio Maintainer License A license granted by the Federal Communications Commission (FCC) to maintain radio communications aboard ships that are equipped to comply with Global Maritime Distress and Safety System (GMDSS) regulations. It further confers the operating authority of the General Radiotelephone Operator License and the Marine Radio Operator Permit. A licensed maintainer is re- quired by ships that conduct at-sea maintenance. The license requires FCC Element 1, Element 3, and El- ement 9 exams to be passed. GMDSS Radio OperatorLicenseA license granted by the Federal Communications Commission (FCC) to individuals deemed capable of handling radiocom- munications aboard ships that are equipped to com- ply with Global Maritime Distress and Safety Sys- tem (GMDSS) regulations. The licensee may oper- ate basic equipment and make antenna adjustments. The license further confers the operating authority of a Marine Radio Operator Permit. Applicants are re- quired to pass the Element I and Element 7 written exams. GMPCS See global mobile personal communica- tions by satellite. GMR See giant magnetoresistance. GMS See Geostationary Meteorological Satellite. GMSK See Gaussian minimum shift keying. GNN See Global Network Navigator. GNOME An open source user software environment and applications framework available to developers as part of the GNU project. GNOME is typically dis- tributed with BSD and GNU/Linux distributions and is available for other platforms as well. The goal of the GNOME project is to provide a user- friendly graphical desktop environment and a devel- oper- friendly base of tools for creating GNOME- compatible software applications to augment or re- place commercial operating systems and develop- ment environments. As the project has evolved, it is 411 : '.:'·.·:.··' ·':.11·:.··:··· ·.·· i~: © 2003 by CRC Press LLC . contribution is sometimes over- looked, as he pulled out of the partnership near its successful completion, due to distrust and disagree- ments with his collaborators, but he was an impor- tant contributor, both to the inception and progress of the project. See Field, Cyrus West; Gooch, Daniel; gutta-percha; transatlantic cable. GITS Government Information Technology Ser- vices. 405 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary Gladstone-Dale law The refractive index ofa sub- stance varies with a change in temperature or volume according to a formula in which the index of refrac- tion (n) plus one, over the density (r), equals a con- stant (k). glassA strong, brittle substance primarily composed of silica, that ranges from transparent to opaque, de- pending upon the quantity and composition. Press LLC Fiber Optics Illustrated Dictionary System (GMDSS) as a communications infrastruc- ture for the overall plan. The system is based upon a combination of Earth-based and satellite-based radio services, emphasizing ship-to-shore marine signaling through relatively. of the glass is not practical because it introduces undesired impurities. It has been discovered that pulling fibers or fiber pre- forms at 0 gravity results in a fine, pure glass with- out the problems of crystallization associated with Earth-based fabrication. See pulling fiber, vapor deposition. glass