Fiber Optics Illustrated Dictionary - Part 63 pdf

Fiber Optics Illustrated Dictionary ITV-T M Series Recommendations, conL Monitoring, Maintenance, Performance, Service, Testing, Misc., etc., cont. M.I025 Characteristics of special quality intemationalleased circuits with basic bandwidth conditioning M.I030 Character. of ordinary quality intemationalleased circuits forming part ofprivate switched telephone networks M.I040 Character. of ordinary quality international leased circuits M.I045 Preliminary exchange· of info for provision of intemationalleased circuits and international data traIlsmission systems M.I050 Lining up· international point-to-point leased circuit with· analog•presentation to the user M.I055 Lining up international multiterminal leased· circuit M.I060 Maintenance of international leased circuits M.II 50· .Maintenance aspects ofmaritimel land mobile telecom.· store-and-forward services (packet mode) via satellite M.1160 Maintenanceaspectsofaeronautical mobile telecom. service via satellite M.1170 Maintenance aspects of mobile digital telecom. service via satellite M.1230 Methodto improve management of operations and maintenance processes in IntemationalTelepbone Network M.1235 Use of automatically generated test calls for. assessment of networkperfonnance M.1300 Maintenance of international data transmission systems operating in range 2.4Kbps 00140 Mbps M.1320 Numbering of channels in data transmission·systems M.1340 Perfonnanceobjectives, allocat. and limits for international PDH leased circuits and supporting data transmission I links and systems M.13S0 Setting up, lining up and characteristics of international data transmission systems operating inrange 2.4 to 14.4 Kbps M.135S .Maintenance of international data transmission systems operating in range 2.4 to 14.4 Kbps M.1370 Bringing into-service of international data transmission systems M.1375 Maintenance of international data transmission systems M.1380 Bringing-into-service of international leased circuits that· are supported by international data tnlnsmissionsystems M.1385 Maintenance of international leased circuits that are supported. by intemationaldatatransmission systems M.1400 Designation for inter-operator networks 612 M 1510 Exchange of contact point info forthe maintenance of international services and the international network M.1520 Standardized. info. exchange between administrations M.1530 Network maintenance info M.1532 Network maintenance service perfonnance agreement (MSPA) M.1539 Management of grade of network maintenance services at·maintenance service customer contact point (MSCC) M.l540. Exchange. of info for planned outages of transmission systems M 1550 Escalation proced. M.1560 Escalationproced. forinternational leased circuits M.2100 Performance limits for bringing-into- service andmaintenance of international PDHpaths, sections and transmission systems M.2101 Performance limits andobjectives for bringing-into-service and maintenance of intematiopal SDHpaths and multiplex sections M110l.l Perfonnance limits for bringing-into- service and maintenance .ofintemationaJ SDH paths and multiplex sections M.2102 Maintenance thresholds and procedures for .recovery mechanisms (protection and restoration) ofintemational SDH VC trails (paths) and multiplex sections M.2110 Bringing-into-service of intern at. PDH paths, sections and transmission systems, SDH paths, and multiplex sections M.2120 PDH·path, section and transmission system and SDH path and multiplex section faultdetection·and localization procedures M.2130 Operationalprocedures for the maintenance· of transport network M.2140 Transport network event correlation M.220 1 Performance objectives, allocations.and limits for bringing into-serviceand maintenance of international ATM virtual path and virtual· channel connections M3208.1 Leased circuit services M.32081 Connection management of pre- provisioned service link connections to form leased circuit service M.3208.3 Virtual private network M.4010 Inter-Administration agreements on common channel Signaling System 6 M.4030 Transmission characteristics for setting up and lining up transfer link for common channel Signaling System 6 (analog version) M.41 00·. Maintenance of common channel Signaling System 7 M.4110 Inter-Admini~ationagreements on common channel Signaling System 7 © 2003 by CRC Press LLC Telecom. Management Network (TMN) M.3000 Overview ofTMN Recommendations M.30 10 Principles for Telecom. Management Network (TMN) M.3013 Considerations for Telecom. Management Network (TMN) M.3016 TMN security overview M.3020 TMN Interface Specification Methodology M.3101 Managed object confonnance ~ternents forgene.ric network info model M.3108.1 .TMN managementservices for dedicated andrecorifigurable circuits network: infomodel for management of leased circuitandreconfigurable services M.3108.2TMNmt\nag~J11entservices for dedicated and reconfigurable circuits network:. Info model for connection management of preprovisionedservice link connections to form reconfigurable leased service M.3108.3TMN managementservices for dedicated andreconfigurable circuits network: Info model for management of virtual private network service M.3120 CORBA generic network and NE.level info model M.3180 CatalogofTMN management info M.lmp3100 M.3100 TMN Implementors' Guide- defects and resolutions (M.31 00 Series) M.3200 TMN managementservices and telecom.managed areas: overview M.3207.1 TMN management service: maintenanceaspectsofB-ISDN management M.3210.1TMNmanagementservicesfor IMT-2000 security management M.3211.1 .TMNmanagementservice:Faultand perfonnancemanagement of ISDN access M.3300 TMNF interface requirements M.3320 Management requirements framework for TMN X-Interface M.3400 TMN Management Functions Supplements M.Sup 1.1PreflXes.used ill decimal system M.Sup 1.2 . Transmission measure. conversion tables M.Sup1.3 Normat(or Laplace-Gauss) distribution M.Sup 1.4 . MethodS of quality control M.Sup 1.5 Mathematical processing of measure. results of variations of overall loss of telephone circuits M.Supl.6 Statisticaltheory require. M.Sup2.1Generalobservations concerning . measuring instruments and measunng techniques M.Sup2.10 Method for measuring frequency shift introduced bycanierchannel M.Sup2.11 Rapid verification test for echo control devices M.Sup2.12 Automaticda~acqui~itionand effertive processing proced. for group and supergroup pilot levels M.Sup2.13 Loop method for maintenance of 4-wire telephone-type leased circuits M.Sup2.14 Automatic measuring device for carrier systems with large number of channels M.Sup2.J5 .petectionofcircuit faults M.Sup2.16 Receiving relative levels at renters' premises for intemati<mall~ased circuits used for data transmission M.Sup2.l7 R.esultsofinvestigati~n of service availability performance ofintemattonal leased circuits made in 1982 M.Sup2.2 Measurementsofloss M.Sup2.3 Level measurements M.Sup2.4 Measure. ofcrosstalk M.Sup2.5 Measuring errors and differences due to impedanceinaccuraeies of instruments and apparatus.Usepf decoupled measuring points M.Sup2~6 EtrorsinindicatiQns givenbylevel- :=~. ins~en:.due·.0~te~g M.Sup2.7 Measure. of group delay and group-delay distortion M.Sup2.8Measure.ofsudden phase changes on circuits M.Sup2~9 . Vibration testing M.Sup4J 0 l'ransient analog circuit impairments effect on data transmission M.Sup4.1 Stability of overall loss and psophometric noise: results of routine maintenance l1leasurementsfuadeon international network during first l\alfof 1978 M.Sup4 2 Results and analysis of 10th series <of tests of short breaks. in transmission M.Sup4.3 Character. of leased intematiot1al telephone-type circuits M.Sup4.5 Instructions for making future measurements oftransmisisonqualityof cotnplet~co~i~.for.recording.results of measurements . M.Sup4~8 Results and analysi~of tests of impulsive noise M.Sup4.9 Weighting of measurements .relatingto stability of circuits inintemational network according to size of circuit· groups M .Sup4. 7 Instructions for making future measurements·oftransmission quality of international circuits and international centres atidfofrecording results of measurements M.SupS.l Requirements for transmission of televisio11 signals over long distances M.Sup5.2 Setting-up and~stingof intemati011al videoconference studios 613 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary M Series Recommendations A series ofITU-T rec- ommended guidelines for TMN and network maintenance: international transmission systems, telephone circuits, telegraphy, facsimile and leased circuits. These guidelines are available for purchase from the ITU- 1. Since ITU- Tspecifications and recommendations are widely followed by vendors in the telecommunications industry, those wanting to maxi- mize interoperability with other systems need to be aware of information disseminated by the ITU- 1. A full list of general categories is listed in Appendix C and specific series topics are listed under individual entries in this dictionary, e.g., L Series Recommen- dations. See M Series Recommendations chart. M-aryAdesignation useful in assessing relative capacities in multilevel modulation schemes. M is used as the symbol for arithmetic equivalencies to represent the number of bits per symbol. Thus, in M-my signaling, a symbol represents n bits, with M signal states, with M = 2". In tum, the number ofsymbols per second determines the baud rate. This can further be extrapolated to calculate capacity in relation to bandwidth. M-Bone See multicast backbone. M-quad, mini-quad A compact version of a quad antenna used for single or multi band radio communications. See quad antenna for a fuller explanation. M-patch bay According to the Federal Technology Recent and Widespread Macintosh Operating Systems Version Description Mac OS 7.6 A widespread version of the Macintosh operating system still used by millions ofend- users for older Macs and supported by many developers well into the year 2000, even though as 8.6 and its successors had been available for a few years and would even- tually supersede it. One of the reasons for the longevity of7.6 was its relative stability and networking capabilities. Another reason was that honest software buyers, with large installed bases of programs, could not easily move to as 8.x and above without up- grading, a move that could cost hundreds, sometimes thousands of dollars per machine. Mac OS 8.5 Code-named Allegra, and coexistent with the Rhapsody environment, this was a major Macintosh Operating System release (with upgrades and patches to bring it up to 8.6) that became well-established in the late 1990s. This release featured a more pol- ished looking interface, better native graphics support, and increased support for Inter- networking, as well as enhanced memory and file transfer capabilities. It was still being widely used in 2001 concurrently with Mac as 9 and Mac as X. MacOS9.x A new version of the Macintosh operating system announced in 1999 to supersede the as 8.x line. With as 9 came Sherlock 2, a Web-compliant searching tool, multiple- user environments (in the sense that more than one person could use the same Mac and keep preferences, file settings, etc. personalized and protected), voiceprint pass- words, Internet file serving capabilities, Internet AppleScript automation tools, and more. In general, this release of the operating system brought the Macintosh operating system into the world of the Internet and made many aspects of the system cus- tomizable and more secure. Mac as 9.1 was announced in 200 I to provide a transi- tion to Mac as x (which became prevalent by 2002). MacOSX Macintosh Operating System Ten. Announced in May 1998, this new version of the Macintosh as was scheduled to ship to developers in early 1999 with an original planned public release in F all 1999 and an actual release in 200 I. The system supports pre-emptive multitasking, advanced virtual memory, and memory protection, optimized for Apple's G3 PowerPC computers. as x is built upon Darwin, the open source model core based on FreeBSD and Mach 3.0 technologies. Darwin is processor-independent and supports PowerPC- and Intel-based desktop computers. Thus, Open Source developers can create applications capable of running on avariety of hardware platforms. At the time as x was released, the installed base ofMacintosh platforms was over 25 million. Apple expected most existing Macintosh applications to run on as xwithout alteration (though in practice this was not entirely so). Mac as X.l improved printing and networking capabilities as well as CD and DVD authoring capabilities. A new, aesthetically appealing user interface called Aqua was introduced with the Mac as x system. Aqua included a new Finder and NeXT-like Dock to enable the desktop to be customized for quick access to commonly used applications. Aqua is built upon graphics technologies for the multimedia world, including OpenGL, Quartz, and Quick- Time. See QuickTime. 614 © 2003 by CRC Press LLC Service (FTS), a patching system for monitoring and patching (interconnecting) digital data circuits at signaling rates from 1 to 3 Mbps. m-s junction metal-to-semiconductor junction. A mechanism within a semiconductor acting as an electrical contact or as a barrier. See p-n junction. Ma Bell colloq. A term to familiarly describe the Bell telephone system, and later AT&T. The Bell system was so ubiquitous and so well recognized that many came to refer exclusively to the corporation as Ma Bell. MAC 1. See mandatory access control. 2. Media Access Control. In a layered network architecture, the lower half of the data-link layer that governs access to the available IEEE and ANSI LAN media. See Media Access Control for a fuller explanation. 3. See Message Authentication Code. 4. See multiplexed analog component. MAC Access Arbitration MAA. In a layered network operating as a broadband fiber network (e.g., cable modem services), the Media Access Control (MAC) Access Arbitration is a sub layer which, along with associated sublayers, facilitates multiplexing and Quality of Service (QoS). See Media Access Control. MAC address Media/Medium Access Control address. A network location identifier. See Media Ac- cess Control. MACE Macintosh Audio Compression and Expan- sion. MACE is built into the Macintosh OS Sound Manager utility. Mach line, Mach surface The division between regions of supersonic and subsonic flow. Mach-Zehnder interferometer See interferometer. machine dependent Software or peripherals designed to work on a specific system or architecture, and not readily usable on other systems (although sometimes modifications can be done). Low-level routines written to take advantage ofaparticular chip architecture or peripheral card are machine dependent. Most software executables are machine dependent, since they have usually been compiled from a higher level language down into low-level machine code for a specific system. machine language A symbolic computing machine control language that functions at the lowest level possible on a system, in symbols readily understood by the computer, but inscrutable to most people. Ma- chine language involves the most basic movement and processing of data, in terms that are specific to the computer architecture (usually binary). Thus, move and add instructions are used frequently in machine language programs. A move instruction transfers data between registers, and an add instruction performs a math operation (add, multiply, sub- tract, etc.). Because machine language programs are cryptic, long, difficult to follow, difficult to read, and difficult to debug, assemblers were developed to codify and organize instruction sets so software could be written and debugged more quickly. Assembly language or assembler was a step up from machine language in that it used symbols to encode instructions that would then be translated into machine language. Assembler was easier to code and debug than machine language, but the listings were long and many people had difficulty with the symbology and tedium. Later, higher level languages such as FORTRAN, BASIC, LISP, C, Modula, Perl, Java, etc. were added to make the task of programming easier still, and to adapt programming languages to specific types of tasks. Some higher level languages are compiled into machine language executables that can be run directly thereafter, and others are interpreted into machine language at the time an instruction is processed. Com- piled languages typically run many times faster than interpreted languages because the conversion to machine instructions happens only once, prior to writing the program. This machine language compiled executable is then stored as a file and used as needed. With faster processors, interpreted languages, which also have some advantages, such as direct feedback without compilation waiting times, have remained popular. Machine language coding is rare these days except for specialized coding. Macintosh Plus - Apple Computing Platfonn The Historic Macintosh Plus, released in the mid- 1980s, had a portable all-in-one design, featuring a monochrome monitor, two serialports, SCSI control- ler, graphical user interface, mouse, and networking capabilities through AppleTalk as standardfeatures. Macintosh, Mac A family of Motorola 68000-based personal computers developed and distributed by Apple Computer, Inc. The first of the Macintosh line was the Lisa computer, introduced in 1983. Its graphical operating system was described as radical by many. There were also vocal detractors who said "graphics interfaces will never be accepted in office environments." A graphical interface may not seem unusual now, but at the time, computers were almost exclusively text-based, and this new graphical user interface, which was accessed with a mouse, seemed extraordinary. Many business and computing profes- sionals recoiled in suspicion. In retrospect, now that virtually all computers have graphical user interfaces, the harsh criticisms leveled at the Macintosh graphics now appear shortsighted. 615 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary The Macintosh graphical operating system was inspired by some of the brilliant research and development that was occurring in the 1970s and early 1980s at the Xerox PARC facility in California. The fledg- ling founders of Apple Computer were given a tour of the facility, and Steve Jobs came away energeti- cally inspired by what he had seen, determined to add a new line of computers different from the Apple II line. Unfortunately, while the Lisa was a good machine and most of its characteristics were later incorporated into the more familiar Macs, the initial price tag was high and it didn't sell well. The early Macintosh computers familiar to most people started with the Mac in 1984, followed by the Mac Plus and various sub- sequent Macs (there are now dozens of models). The 1984 release of the 128K 32-bit4.7 MHz "little Mac" was accompanied by a significant product in 1985, the Apple Laserwriter. This new laser printer changed the way many people thought about computers. Since 10-pin dot matrix printers with extremely limited fonts were prevalent at the time, few had considered the potential of personal computers as publishing tools. With the Laserwriter and Adobe Systems Post- Script fonts, publishers sat up and took notice and the desktop publishing industry was born, with very sub- stantial repercussions to the traditional layout and printing industry that are still reverberating today. Newall-digital presses are completely changing the way printed information is produced. The Macintosh line became the preferred system in print publishing service bureaus in the late 1980s, and many of the high-end desktop publishing and graphics programs were available only for the Mac. It was not until the early 1990s that some of these important software programs were ported to Intel-based machines, and service bureaus began to use both platforms. Almost 30 million Macintosh computers had been shipped since 1984, 79% of which were still in use, yet detractors continued to predict the demise of Apple and the Macintosh line (a prediction begun with the first introduction of the Mac line 14 years earlier). The first major change in the Macintosh line was the changeover to PowerMacs in the 1990s. In 1997, to the surprise of many, Steve Jobs took the position of interim CEO and later CEO and injected a sense ofexcitement into what had become an almost lackluster company. This change came about with the evolution from PowerMacs to G3s late in 1997. With the introduction of the iMacs in avariety of designer colors and styles, the Macintosh attracted a new generation of users. By 2000, Macintosh lap- tops had become competitive with the introduction of new models, including the iBooks and full-featured Titanium model. In July 2001, the G41ine was introduced, along with updates to the Mac OS X operating software. The portable models are particularly important to telecommunications since they are often integrated with handheld communications devices for business communications and favored for writing and reporting by journalists. 616 While the early Mac hardware was not inherently suited to video, it was popular for audio applications and many musicians adopted the Mac for the composition ofelectronic music. The Arniga was the preferred platform for video from the mid-1980s to the mid-1990s, until Commodore support for the Arniga dwindled, and then the desktop video market split onto Intel and Macintosh platforms. As the Macintosh hardware evolved, audio/visual capabilities were in- creasingly incorporated into the basic hardware, with high-quality stereo sound capabilities and some video capabilities built into AIV (audio/visual) models. This was important in maintaining the platform's viabil- ity in a market demanding greater graphics and sound capabilities for games, publishing, and multimedia! Web production. MacMICA A Macintosh-based multipoint videocon- ferencing program from Group Technologies, which works over AppleTalk networks. See Cameo Personal Video System, Connect 918, CU-SeeMe, IRIS, Visit Video. MacMiNT A text-based, Unix-like operating system ported from the Atari ST to the Macintosh. It can be used with freely distributable Unix utilities such as GCC, GDB, make, tcsh, perl, etc. macro A programming routine or script that "bundles" or combines anumber of steps, processes, operations, or other actions. Macros are typically used as time-savers for frequently performed functions. Scriptable macros are usually written in text editors, with simple BASIC-like commands. There are many different macro scripting languages, often developed to automate functions in aparticular application such as a database or paint program. Some macros are recordable; in other words, the user turns on a record feature in the software, then performs a number ofoperations which are to be used frequently in the same sequence, then turns record off and gives the macro a name. The sequence of events is stored and can be invoked later with a name or hot-key sequence. Batch and job control languages can be used to write macros. Perl is a good programming language for writing powerful macros for many types ofapplications, including Web site automation. macrobend A significant bend in an optical fiber. Optical fibers are quite slender and somewhat flex- ible, but due to the nature ofthe transmission oflight, they do not have the small-radius 180 0 ( or more) bending capability of many types of wire and care must be taken not to snap or significantly stress the structure of the fibers because this will compromise their transmission capabilities. Macrobends can be found in installations where the fiber must go around comers to reach the locations desired or may occur in fiber splicing trays. The degree of bend possible and considered significant depends upon the radius of the bend and the thickness (core diameter) and composition of the individual fiber(s), on the one hand, and the length of the waves in relation to the diameter of the fiber, on the other. When the radius of curvature of a fiber is large compared to the diameter of the fiber core, © 2003 by CRC Press LLC macrobend losses may occur. See macrobend loss, microbend. macrobend loss Signal attenuation through absorp- tion in an optical fiber transmission caused by curvature or macrobend in the fiber. The amount of loss is due to many factors, including distance, the diameter and composition of the fiber core, and the wavelength of the optical transmission. Slender fibers are generally more susceptible to bend losses than thicker fibers. Longer wavelengths tend to be more susceptible than shorter wavelengths. As the bend increases, the mathematical/physical relationship between the wavelengths "bounced" along within the fiber core is changed and a critical angle is reached at which the light waves exit the fiber and are lost. Macrobend loss may be reduced by increasing the core diameter of the fiber, but there is atradeoffwith fiber sensitiv- ity, weight, cost, and the capability of the fiber to bend physically. See attenuation, loss, macrobend. macroblock samplingA compromise technique used in video phone systems to provide a recognizable image in spite of slow transmission media. Standard telephone modems are too slow for full-screen, full- motion video images. By using an averaging system to sample the image, the image information can be sent more quickly. The smaller the blocks and the more frequent the sampling, the better the image fi- delity, but the slower the processing. An alternative to macroblock sampling is wavelet video compression, which may provide better images through frame-by-frame compression. MAE 1. See Metropolitan Area Ethernet. 2. See Merit Access Exchange. MAE East The largest Metropolitan Area Exchange, located in Washington, D.C. The MAE is a ring system which provides Internet Service Providers (ISPs) with a relay point for exchanging packets with friendly systems through switched and shared Fiber Distributed Data Interface (FDDI) and switched Ethernet communications services. A MAE is, in a sense, a gargantuan wiring closet with thousands of lines of cables, switches, routers, and connections interconnecting many public and private network installations. The MAE system provides access and interconnections, but doesn't provide ISPs with po- litical connections with the other services on the system. These have to be individually arranged by each ISP. See MAE West. MAE West A Metropolitan Area Exchange established in 1988 in San Jose, California, providing switched and shared Fiber Distributed Data Interface (FDDI) and switched Ethernet communications services. Originally operated by Metropolitan Fiber Sys- tems, MFS merged with Worldcom Communications in the mid-1990s to provide expanded nationwide services. MAE West interconnects with the Ames Inter- net Exchange (NASA) and well-known networks like CERFnet, BBN Planet, MCI, and others. See MAE East. magic signatureA file integrity mechanism built, for example, into PNG graphics files to detect file corruption. The signature is typically incorporated into the file header or the early part of the file image. Dif- ferent levels ofsophistication can be designed into magic signatures, with different byte lengths. See cy- clic redundancy check. Magic Wand In navigation and location applications, an electronic device proposed by Egenhofer and Kuhn for geographical information system applications. The Magic Wand would incorporate a Global Positioning System (GPS) receiver and a gyroscope to provide location and orientation information relative to the position and orientation of the wand. This information could be cross-referenced with a knowl- edge base including adigital terrain base enabling the user to find information on a topographic feature (e.g., a specific mountain). With a cell phone connection to the local area network or the Internet, the possi- bilities become vast, with the capability ofuser public information servers to fill in further details on fea- tures pointed to with the Wand. Magic WAND Magic Wide Area Network Davis. A project to promote wide area networking in the Uni- versity of Cali fomi a, Davis, campus community, especially to off-campus locations that serve its staff and students. The project was initiated in 1997. E:!~~E~!t~~~~~=~~~rl~~~J~ II communications users. It is one of the larger ACTS projects. The project endeavors to specify, demon- strate, and promote standards for a wireless access system that retains the benefits ofmultimedia wired ATM networks. The project was described in the mid- 1990s with trials and workshops conducted in 1998. Communication was aimed to be in the 5-GHz frequency range at transmission speeds of about 20 Mbps at ranges up to about 50 ms. Documents de- scribing the project are available for public download. http://www.tik.ee.ethz.ch/ wandl Magic WAND networkA global community support group, initiated in 1996 in Japan by the mother ofa disabled child to help others in similar situations through mutual support and communication. The network is also called Community-Based Rehabili- tation. Magic Wand SpeakingReaderA Texas Instroments (TI) optical reader product released in the early 1980s. It incorporated text-to-speech capabilities for barcode-readable electronic books for children. As a scanner is passed over the barcode, the Magic Wand Speaking Reader strings stored allophones (speech units) together to generate a spoken message. magnesium oxide Amaterial suitable for insulating against water and heat when compressed around a conducting wire. When used in conjunction with copper wires, it is known as mineral-insulated copper- sheathed (MICS). magnet 1. A body, person, or situation with attract- ing properties. It is called charisma when a person has "magnetic" qualities. 2. A body that produces an external magnetic field which can attract magnetic materials such as iron. Natural magnets are known as lodestone. Magnetic properties were described by 617 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary the Greeks at least as early as 60 B.C. Steel will hold magnetic charges for a long time; iron can be magnetized, but retains the magnetism to a lesser degree than steel, as do nickel and cobalt. Materials that magnetize readily, but lose the property quickly, are useful as cores for various electrical devices. Mag- nets are used in many industrial applications, generators, monitors, speakers, compasses, and many more. See electromagnet, gauss, lines of force, lodestone, magnetic field, solenoid. magnetic bubble memory A form of magnetic storage in which the digital data are stored in "bubbles," small circular regions called magnetic domains on a thin film of magnetic material that is selectively polarized. Since the presence or absence ofa bubble can be used as a binary toggle, ones and zeroes are easily represented. Magnetic bubble memory is nonvolatile through permanent magnets; the stored information is retained when the system is powered off. Magnetic bubble memory was used in the early 1980s when other types of storage were expensive and un- reliable, but was superseded by random access memory (RAM), floppy diskettes and hard drives by about the mid-1980s. Newer forms of bubble memory use circuits associated with crystals, an evolution of the older magnetic bubble memory that is not destruc- tively read and rewritten. See magnetic core memory, random access memory. magnetic circular dichroism MCD. Dichroism means having two colors. Circular dichroism (CD) is a phenomenon occurring when optically active matter absorbs circularly polarized light with a slight difference in left- and right-handed directions. In terms of polarization, it has the character of "ellip- ticity" (a phenomenon distinct from optical rotation) and occurs in certain asymmetric materials. Dichroic minerals may appear to be different colors depend- ing upon the angle at which they are viewed. A spec- tropolarimeter can be used to measure CD. Nunes et al. have suggested the use of coherent laser-induced thermal grates for ultraviolet circular dichroism spec- troscopy. Magnetic circular dichroism is exploited in various spectrometry and X-ray technologies and is useful in exploring the properties and origins of magnetism. magnetic core memory A type of random access memory developed at MIT in the late 1940s and early 1950s. Jay Forrester was head of the Whirlwind computer project, a system built for realtime control applications that spawned core memory technology when vacuum tube systems were still prevalent. Magnetic core memory consists of an array of ferrite toroids (cores) with wires passing through toroids at each junction in the array, each of which represents a bit of memory. These toroid bits can be stimulated by current of sufficient intensity to alter the magnetic polarity ofa specific point in the array, which can thus be made to toggle between two polarized states to represent binary ones and zeroes. The array configu- ration makes it possible to pinpoint a specific toroid by its X and Y coordinates and modify the polarity by running a portion of the current through a wire in 618 each axis, thus not changing the positions surrounding the selected toroid but running sufficient current through the selected toroid to change its state. Like magnetic bubble memory, magnetic core memory is nonvolatile; it retains its data if the system is powered off. By the 1970s, core memory was being gradually re- placed by semiconductor technologies except for a number of specialized scientific applications. See magnetic bubble memory, random access memory. magnetic detectorA device designed to receive electromagnetic waves, pioneered by Rutherford and further developed by G. Marconi. The magnetic detector comprises a small induction coil with primary and secondary coil windings surrounding a glass tube with a soft iron wire, rather than the usual common soft iron core. The wire is connected to itself in a loop that runs outside the glass tube and coil windings and is set to move continuously through the tube. A magnet is installed near the secondary ( outer) winding, adjacent to the circulating wire. This fairly sensitive detector was used in conjunction with early telephone receivers, but never came into wide use and had almost disappeared by the early 1900s. See detector. magnetic disk A circular device coated on the surface with magnetic particles that can be rearranged to encode information. A number of computer storage devices, including floppy disks, cartridges, and hard drives, use magnetic disks. The disk shape is favored because it allows the disk to be rotated very rapidly under a read/write head. By controlling the position of the read/write head, fast access to any portion of the recording surface can be achieved, called random access. Early magnetic floppy disks were vulnerable to dam- age because they had an opening for the read/write head where the disk might be inadvertently touched or scratched, and pliable coverings that could be bent, thus damaging the disk. With the commercial introduction of the 3.5-in. floppy diskette around 1983, these sources of trouble have been removed. The chief disadvantage of magnetic disks is that they can be damaged by exposure to magnetic sources (be careful to keep them away from monitors and speakers), which gives them a somewhat limited shelf life. See gamma ferric oxide, superparamagnetic. magnetic equator Similar to, but not coincident with, the Earth's geographic equator; also called the aclinic line as it is the point at which a dip needle is at zero (90°), between its two vertical positions. See agonic. magnetic field The region ofexternal influence associated with an electromagnetic body in which these forces can be detected or exhibit a measurable influence on magnetic materials or instruments. The intensity of a magnetic field is described in terms of the number of lines offorce passing through a speci- fied area, although the field is conceptualized as continuous. The influence ofa magnetic field can be seen by holding a magnet near small magnetic objects. A magnetic field can be induced in certain materials by running current through them. See flux, gauss, lines of force. © 2003 by CRC Press LLC magnetic field modulation MFM. A means ofmodu- lating a magnetic field very close to the recording surface of an optical disc such that the polarity of the magnetic field can be switched at very high frequency. This produces marks on the recording portion of the disc that are narrow and tall (crescents), enabling higher bit densities per unit area and, as such, the density is no longer limited by the wavelength of the laser reading the data after it has been recorded. The crescent-shaped aperture is formed between a front and rear (double) mask and cross- talk is reduced by this arrangement. High-speed polarity changes enable the disc to be written in a single pass, thus significantly increasing write speeds. In earlier optical disc writing technologies, the magneto-optical coil had to be larger because of its distance from the recording surface. This limited the switching frequency due to magnetic induc- tance in the coil and hence the recorded marks on the disc could not overlap, limiting areal density. With MFM write mechanisms, the bit density is limited not by the wavelength of the laser, but by the ability of the mechanism to resolve the individual marks in the recorded surface. Heat applied to the read-out layer which magnifies the data in the recorded layer provides higher reso lution and supports increased disc capacity. By using a mask in conjunction with the temperature distribution in the recording layer, individual bits can be isolated even if the laser light covers more than one mark. Newer laser technologies (e.g., blue lasers) will likely increase resolution even further. In combination with MFM, higher-resolution lasers will support very high capacity magnetic super resolution (MSR) discs. See overcoat-incident recording, surface-array recording. magnetic induction The characteristic of certain permeable substances to become magnetized when placed near a magnetic source, without coming in direct contact with that source. Thus, a steel bar does not necessarily have to touch a magnet to be mag- netically influenced by that magnet, or to influence other materials in the vicinity of the bar by induction. See lines of force, magnet, magnetic field, magnetic super resolution. magnetic north The northerly direction in the Earth's magnetic field near, but not corresponding to, the north geographic pole, to which north direction-seek- ing poles of magnets are attracted. Thus, what is called magnetic north is actually Earth's south magnetic pole, located in northern Canada, since the north-labelled compass needle will orient itself to- ward the south pole of the Earth. See declination. magnetic storage A medium designed so magnetic materials within it can be dynamically aligned and realigned to hold encoded data. Floppy diskettes, hard drives, and audio/data tapes are various forms of magnetic storage. Magnetic storage is inexpensive and very convenient in that it can be easily rewritten; how- ever, it is subject to loss over time through superparamagnetic phenomena, and may be damaged by prox- imity to equipment with magnetic components, such as monitors. See bulk eraser, superparamagnetic. magnetic stripe Typically a narrow strip on a portable medium such as a bank card or ill card, which is encoded with information of use to the cardholder. When inserted into a magnetic stripe reader, such as a cash machine, the information is used by the system as authorization for access and various transactions. magnetic super resolution, magnetic-induced super resolution MSRA technology for enabling very high storage capacities on magneto-optical media. MSR capacities can be up to ten times the bit density ofearlier mechanisms. MSR is based on IRIS Ther- mal Eclipse Reading (IRISTER) technology, developed by Sony in 1991. Vendors such as Fujitsu introduced commercial versions in the mid-1990s, based on land groove recording techniques. They could hold 2 Gbytes on a single-sided disc and 4 Gbytes on a double-sided disc and be read by existing magneto-optical drives. See magnetic field modulation for a fuller explanation. See GIGAMO, land groove recording. magnetic tapeA narrow, very long magnetic sequen- tial data encoding medium used for audio tapes and computer data backup tapes. In the late 1970s and into the early 1980s, magnetic tape storage was commonly used on microcomputers for storing and retrieving applications programs and data. Due to its slow, se- quential nature, tape drives were soon superseded by 8-in. floppy diskette drives, except for backups or specialized applications. magnetite A form of iron ore, readily magnetized, called lodestone when it is already magnetic as it comes out ofa mine. See magnet, lodestone. magneto An apparatus in which a magnet is put close to a wound helix or coil ofconductive wire (usually copper) to stimulate a momentary electric current that changes direction when the magnet is withdrawn. Similarly, a magnetizable material may be associated with a coil and periodically stimulated by a magnet to produce the same effect. This is a simple magneto- electric machine. An alternator is a common application ofa magneto that employs permanent magnets to generate ignition current for engines. The discovery of magneto effects was an important step in telecommunications history. A. Graham Bell described its significance in aletter written in August, 1875: " the discovery of the Magneto - electric current generated by the vibration of the armature of our electro magnet in front of one of the poles - is the most important point yet reached I feel sure that the future will discover means ofutilizing currents obtained in this way - on actual telegraph lines. I think some steps should be taken immediately towards obtaining a Caveat or Patent for the use of a Magneto-Electric Current specially as a means of transmitting simultaneously musical notes differing in intensity as well as pitch. I can see clearly that the magneto-electric current will not only permit of the actual copying of ~ ken utterance, but of the simultaneous transmission of ~ number of musical notes (hence mes- 619 ······ :·'.:·:··::··.~:.:::··:· •. ·II::··.:· \;i. ;i~f \~ © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary sages) without confusion. The more I think of it the more I see that the method of making and breaking contact so many times per second - is only the first stage in the development of the idea. When we can create apulsatory action of the current which is the exact equivalent of the aerial im- pulses - we shall certainly obtain exactly similar results. Any number of sounds can travel through the same air without confusion - and any number should pass along the same wire. It should even be possible for a number of spoken messages to traverse the same circuit simultaneously; for - an attentive ear can distinguish one voice from another- although a number are speaking together." Historically, this letter shows the transitional period in Bell's thinking about telegraphy and the potential for telephony. Even though he mentions the "copying of spoken utterance," his main focus was sending a variety of coded tones over telegraph wires (a harmonic telegraph), not exclusively sending voice over phone lines. Since there were long debates over who invented the telephone and Bell retroactively claimed to have worked out telephone ideas a year before writing this letter, there are still questions as to whether Bell had actually sent voice transmissions over wires when he filed his famous harmonic telegraph "telephone" patent. Bell's first public demon- stration of intelligible speech was not until 1876, with an instrument that worked in part due to the addition ofa magneto-induction device. Clearly the magneto was recognized by Bell as an important discovery and was likely a key component in turning the harmonic telegraph into a voice-carrying telephone. Bell's interest in magnetos was well-founded and shared by a number ofinventors, some of whom had built magneto machines in the early 1870s. By the late 1870s, magnetos were being developed into small generators to create electricity for low-power appli- ances, including phone bells. The magneto enabled a subscriber to ring the operator by turning a crank on the ph<ilne to provide the necessary power. Tho- mas Edison shared Bell's interest in magnetos, pat- enting a number of dynamo-related technologies and, in 1880, a magneto signaling apparatus. Currently, magnetos have potential for use in crank- powered light beacons or radio devices for back- woods communications and emergency rescues. If someone were lost in the woods with a magneto- based locator or handheld two-way magneto radio, the lost individual wouldn't be dependent upon batteries that wore out as long as he could tum a crank to generate additional current to power the device or to refresh rechargeable batteries. See electromagnet; Faraday effect; Gramme, Zenobe; induction; magneto phone; telephone history. magneto-optical MO. Technologies in which light is used to detect or influence the magnetic characteristics ofa medium. In the context of communications technologies, magneto-optical refers to magnetic phenomena that 620 can be controlled or read with optical technologies. Thus, a compact disc (CD) can be written by influ- encing the magnetic field associated with the materials within the disc and can subsequently be read by an optical laser pickup mechanism that senses the magnetic polarization of the encoded information. Many important data technologies are based on magneto-optical phenomena, including removable high- capacity data storage drives such as the popular CD and DVD formats. Magneto-optical discs do not suf- fer from "bit rot" to the same degree as certain floppy diskette and recordable tape technologies which can experience data corruption over time, or from prox- imity to magnetic sources (e.g., monitors). Because a magneto-optical disc-reading head is optical, there is no direct physical contact with the recorded/recording medium and thus some of the problems of hard drive wear and tear are eliminated. In general, vendors have sought to increase the nu- merical aperture (NA) of an optical lens to decrease the diameter of light incident or spot on the optic media in order to increase the track density and bit density of data on a disc. In other words, developers have worked hard to pack more information in less space in MO storage technologies. The ISO standard NA is 0.55 but companies like Maxoptix have achieved higher NAs (e.g., 0.8) with lower cost components that are readily available. See compact disc, Faraday effect, Kerr effect. Magneto-Optical Filter Development Group MOF. Acollaboration of astrophysical organizations dedicated to achieving high-time cadence synoptic mag- netograms of the Sun. The group provides a public data archive of the synoptic data from the Magneto- Optical Filter installed in the Kanzelhohe Solar Ob- servatory. magneto phone Ahistoric phone mechanism based upon magnetic-electric effects for the generation of low power current. While some magneto phones were handheld with a button to disengage the instrument from the phone circuit, the more common ones were wall or desk mounted and employed a crank handle to generate electricity through a magneto to produce an alternating or "ringing" current. This sent a signal from the subscriber to a switchboard to ring a bell that summoned the operator. The operator would then crank the switchboard to ring the callee and patch together the connection. The power for the conver- sation itself was usually supplied by a "talk battery" connected to each of the phones. Many of the old crank-handle magneto single-wire phone lines gave way to two-wire "common battery" systems in which the battery was located at the cen- tral switchboard. Yet, surprisingly, there were regions in the u.S. where magneto phones were in use right up until the 1980s! Magneto or battery power is no longer used in public phone systems except in some remote areas, because signal current to ring abell or to notify the switching office that the phone is "off- hook" is now supplied through the phone line itself, and the connection is established automatically by dialing the desired number. See magneto. © 2003 by CRC Press LLC Compact Magnetometer for Remote Sensing Top: The Lunar Portable Magnetometer mounted on the back of the Lunar Roving Vehicle during the Apollo 16 lunar exploration mission. Bottom: The Galileo spacecraft incorporated a large number of sensors, includingmagnetometers mountedon the long boom shown on the lower left in this artistsconcept. [NASA/JSC images.} magnetometer MAG. An instrument for detecting or measuring a magnetic field. A compass is a basic magnetometer. Magnetometers are used as navigation, measuring, and diagnostic instruments. They measure magnetic fields associated with the Earth, with various magnetic substances, and with electrical currents. A Barlington fluxgate magnetometer was installed in the early 1990s in Antarctica to measure magnetic field strength and direction. A magnetometer is one of the many sensors carried aboard the Galileo deep- space mission to the planet Jupiter, launched in 1989. It measures Jupiter's magnetic field, strong magnetosphere, and the characteristics and distortion in the fields caused by the interaction between Jupiter's magnetosphere and nearby bodies (satellites, aster- oids, etc.). Magnetic effects are fascinating to most people and a number of types of magnetometers can be built with simple materials (e.g., a plastic bottle and bar magnet), making this a good instrument to use as an educational tool. More sophisticated laser magnetometers can detect subtle fluctuations in Earth's magnetic field and can be built by more ambitious hob- byists. Thus, a torsion balance, rare-earth magnets, a pair of coils, a laser source, and reflecting mirror, can be combined to create a sensitive Baker-Diverdi magnetometer. magnetometer, induction IMAG. An instrument for detecting temporal variations in a geomagnetic field. An induction magnetometer may have several sensors with different characteristics incorporated into one housing. IMs can be used for a variety of pur- poses, including the study of electromagnetic characteristics of the ionosphere which, in tum, is useful in understanding transmission of radio waves. See magnetometer. magnetomotive force Descriptive of the relationship of magnetic flux and reluctance through a magnetic circuit, somewhat analogous to electromotive force in an electrical circuit, although the magnetic circuit has a region of influence that differs from an electrical circuit in air. See magnet, reluctance. magnetosphere A region within the solar wind flow in which there is an interaction between the solar wind and Earth's magnetic field. Fluctuations and interac- i~~~:~::~i::~~~~::~~~t~i~a~~~iJ:~ • is attributed to Thomas Gold, in 1959. The first image of the magnetosphere, taken by an ultraviolet camera, was captured during the Apollo 16 mission. Solar flares contribute significant energy to the magnetosphere and can substantially influence and disrupt radio communications. Strong flares may even disrupt power systems! The magnetosphere also has its aesthetic aspects. When energy particles react such that electrons are directed into Earth's atmosphere, the result is the Norther Lights (Aurora Borealis) and Southern Lights (Aurora Australis) - eerie, waving emanations in the sky best seen at dusk. NASA's Education Web site offers information on the history and characteristics of the magnetosphere. http://www-istp.gsfc.nasa.gov/Education/ magnetron In its simplest sense, a magnetron is a surface with magnets in or behind it designed to attract and trap charged particles. This basic implemen- tation ofa magnetron is useful in industrial environments where it may be combined with a vacuum chamber to coat surfaces such as metals and alloys in a process called magnetron sputtering. In electron tube applications, a magnetron is a device that uses a magnetic field acting upon a diode vacuum tube to generate microwave frequency power. Mag- netron tubes were especially important in the development ofpractical, long-range radar devices in the 1940s and later improvements on magnetron technology were incorporated into microwave ovens by Percy Spencer (Raytheon) in the mid-1940s. Travel- ing-wave tubes (TWTs) evolved from magnetron tubes in the mid-1940s. Magnetrons are now commonly used to generate continuous-wave (CW) microwave-frequency signals. 621 © 2003 by CRC Press LLC . 2 Results and analysis of 10th series <of tests of short breaks. in transmission M.Sup4.3 Character. of leased intematiot1al telephone-type circuits M.Sup4.5 Instructions for making future measurements oftransmisisonqualityof cotnplet~co~i~.for.recording.results of measurements . M.Sup4~8 Results and analysi~of tests of impulsive noise M.Sup4.9 Weighting of measurements .relatingto stability of circuits inintemational network according to size of circuit· groups M .Sup4. 7 Instructions for making future measurements·oftransmission quality of international circuits and international centres atidfofrecording results of measurements M.SupS.l Requirements for transmission of televisio11 signals over long distances M.Sup5.2 Setting-up and~stingof intemati011al videoconference studios 613 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary M Series Recommendations A series ofITU-T rec- ommended guidelines for TMN and network maintenance:. A graphical interface may not seem unusual now, but at the time, computers were almost exclusively text-based, and this new graphical user interface, which was accessed with a mouse, seemed extraordinary. Many business and computing profes- sionals recoiled in suspicion. In retrospect, now that virtually all computers have graphical user interfaces, the harsh criticisms leveled at the Macintosh graphics now appear shortsighted. 615 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary The Macintosh graphical operating system was inspired by some of the brilliant. LLC macrobend losses may occur. See macrobend loss, microbend. macrobend loss Signal attenuation through absorp- tion in an optical fiber transmission caused by curvature or macrobend in the fiber. The amount of loss is due to many factors, including distance, the diameter and composition of the fiber core, and the wavelength of the optical

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