Fiber Optics Illustrated Dictionary - Part 72 potx

Fiber Optics Illustrated Dictionary and others. The OSN architecture is intended to facilitate the interoperability and accessibility of data via industry-standard networks. Open Trading Protocol OTP. See Internet Open Trading Protocol. Open Video System OVS. A regulatory distinction for video services carried by Local Exchange Carriers (LECs), for example, who are not recognized as local cable service providers perFederal Communica- tions Commission (FCC) guidelines and regulations. Thus, a local exchange carrier (LEC) could become an OVS operator, but was also required to provide nondiscriminatory access on a portion of its channel capacity to unaffiliated program providers. By 2000, 25 OVS operators had been certified to serve 50 areas. The mid-1990s was an important time during which technological advances made it possible for a wider range of types of providers to offer a broader range of telephony and cable programming options to their subscribers. In addition to this, the Telecommunica- tions Act of 1996 opened the doors for tekos to offer ISO/Open Systems Interconnection (OSI) Reference Model From bottom to top, seven layers have been defined for OS I, ranging from physical and data layers through presentationand applications layers, thus following a low-level to high-level an'angementcom- mon in many computerarchitecture models. The selection of the layers was based on subdivisions cho- sen to distinguish well-defined functions and various levels of abstraction. In general, layers are related to services provided by the layers below. In actual implementations, the situation is a little more complex and many variations with sublayers or lesser-used layers exist. Layer Function Number Purpose, Implementation Application Layer 7 User interfaces, applications programs, emulation, and other higher-level software implementations. Presentation Layer 6 Character sets, text handling. Data conversion into standard formats for transmission over a network or conversion from the transmitted format to something that user applications can understand. Encryption and other means of data security are also handled at this layer. Session Layer 5 Connection and session mechanisms for facilitating intercommunication between networks. File transfers, program sharing, data sharing, and basic traffic direction are managed at this layer to provide an orderly exchange of information (e.g., management of simultaneous requests from different users that might affect data integrity). Transport Layer 4 Process-to-process communications, addressing, and a number of end- to-end services. The data are packaged into packets in preparation for transmission. Identification is added so that disassembled packets that may travel different routes can be reassembled at the destination. Local network addresses may be defined at this layer. Error handling not already managed by lower levels may be handled here with respect to reliability and data integrity. Network Layer 3 Host-to-host communications and basic transfer units (packets), network addressing, forwarding, and routing. Addresses may be provided by the Network Layer to the Transport Layer. Data Link Layer 2 Activation, handshaking, interfacing, and other basic communications intended to initiate, regulate, and terminate a communications session. Common functions at this level include the management of wired connections (modems, Ethernet, etc.) orwireless transmissions, although the actual physical medium used is handled by the Physical Layer transparently to the Data Link Layer. Low-level error handling, data synchronization, and flow control are managed at this layer. Physical Layer I The transmission medium, electromagnetic properties, and other physical aspects associated with getting the signal from one place to another such as cables, devices, buses, signaing, etc. The physical layer is independent of the actual medium used and thus the layer model applies equally to electrical voltages in wired lines, radio waves in wireless transmissions, and laser light beams in fiber optic cables. 702 © 2003 by CRC Press LLC video through phone lines, to seek cable franchises, or to develop wireless cable systems. Together, these conditions resulted in blurred distinctions between cable and telephone companies since many services were now being offered over the same media. Thus, regulatory authorities were asked to clarify some of the issues and the FCC Cable Services Bureau became involved in this process. On the other side of the equation, in 1996 the cable providers expressed concerns about telcos not being regulated in the same way as cable companies were by the Cable Act. Organizations such as the National Cable Telecommunications Association argued that the FCC exceeded its authority by preventing cable operators from switching to become Open Video Sys- tems (OVS) providers, as defined by the FCC. In January 2001, the FCC presented its seventh An- nual Report on competition in the video markets. The document confinned that cable TV was still the domi- nant video delivery technology, but with a declining market share ofa couple of percentage points per year. Cable service rates increased slightly more than the rate of inflation in general over the study period. In- terestingly, it was found that few telephone companies had sought OVS certification since 1996. See Telecommunications Act of 1996, Video Dial Tone. operand A quantity or information which is being manipulated. For example, in mathematics, if you divide 200 by 10, then 200 is the operand. In computer algorithms, data, or the address of the data to be operated upon, are passed to an instruction in order for the instruction to act upon the data. operating environment This has two meanings, depending upon the context. It is used in a limiting context to describe an operating system which isn't fully integrated or fully multitasking. It may be task- switching, or it may have a graphical user interface on top of a text-based operating system not fully implemented as multitasking. Many vendors have claimed multitasking operating systems which were not really so. In its second, broader context, it refers to the environment surrounding an operating system, that is, the system, the software that runs it, the periph- erals and applications that support it, etc. An operating environment, in this broad sense, may encompass more than one operating system. operating system OS. The most important software on a computer is that which lies between the user applications and the hardware. It's not possible to control the CPU, manage memory, access a disk drive, send images to a monitor, or transmit data through a network connection or modem without an operating system. The operating system handles interrupts, tim- ing, the movement of data from one register to another, and all the nitty-gritty operations that are typically not seen or understood on a technical level by most users. Microcomputer operating systems began to be developed in the 1970s. The early ones were text-based. One of the first widely used, popular operating systems was CP 1M, designed by Gary Kildall. CP 1M was the forerunner of QDOS, and hence, MS-DOS, and the syntax and commands are very similar. LDOS, TRS-DOS, UltraDOS, and other TRS-80 operating systems shared many common properties with CP/ M. Kildall also later designed a multitasking operating system and a graphical user environment (GEM). In the early 1980s, Apple created proprietary operating systems for their Apple and Macintosh lines of computers, featuring the first widely distributed graphical operating system descended from pioneering work at Xerox PARCo This concept was so successful that it has since been adapted by virtually all subsequent vendors, including Atan, Commodore Amiga, Apollo, Sun Microsystems, Microsoft, SGI, The X Windows System, and NeXT. It's difficult to find a computer now that doesn't have a graphical user interface on top of, or in conjunction with a text operating system, or which is fundamentally a graphical operating system. The various versions of Win- dows are popular on consumer-level, Intel-based systems. A number of multitasking systems were developed in the late 1970s and early 1980s, but the first widely distributed commercially successful preemptive multitasking operating system on a microcomputer was AmigaOS, introduced in 1985. Most of the work- station level computers had multitasking operating systems by the early or mid-1980s, and the other vendors began to follow this lead in the late 1980s, most notably OS/2 (Operating System 2), originally developed jointly by IBM and Microsoft. Many other operating systems released around this time were task- switching rather than fully multitasking. Microsoft Windows has since become widespread on personal computers, with Windows NT, originating out of the OS/2 collaboration, used on many server systems. Unix is one of the most robust, earliest, and most important operating systems. A high proportion of institutional computing operations, much scientific research, and many Internet hosts run on Unix systems. Unix is freely distributable, powerful, flexible, dependable, well-supported, and runs on most computers. Linux is a popular implementation of Unix (as is BSD), available from a number of commercial and free distribution sources. Along with Apache, a freely distributable server software, Unix! Apache systems are used by thousands ofInternet Services Providers to provide gateways to the Internet through the Web. An operating system runs a computer, and computers are increasingly delegated control tasks beyond those humans can handle alone or in cooperation with one another. Navigational aids on aircraft are a good example. Fighter jets traveling at hundreds of miles per hour move too quickly for the human nervous system to react in time to control every aspect of the plane's behavior, so computerized systems handle many functions on the pilot's behalf. Extrapolate that type of control to appliances, houses, security systems, currency exchange, intelligent vehicle systems, and every aspect of human society that will someday be controlled by computers through a 24-hour Inter- net connection to all the other computers in the world. Given this broader outlook on our probable future, 703 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary the importance of carefully choosing a reliable operating system cannot be overemphasized. Buying the cheapest system or the most popular system, or passively allowing the choices to be made by profit- based corporations is, in the long run, a more far- reaching decision than selecting a President or other political leader. Why? Because a President who does abadjob can be voted out. An operating system that does a bad job cannot be disabled if it has been delegated important tasks such as running medical equipment, automated transportations systems, or en- vironmental controls. Once a fighter plane has been designed with a dependency upon computer control, you can'tjust tumoff the software in mid-flight. Simi- larly, if5 or 10 years from now a family's financial transactions, medical prescriptions, education, and travel arrangements are handled by a computer operating system through the Internet, it may no longer be possible to tum off the computer at will. That bears thought and forethought and suggests that open source operating systems coexisting with commercial products can help maintain balance. See BSD, Linux, Mac OS X, Microsoft Windows, NeXTStep, OS/2, Solaris, SunOS, Unix, UNIX. operational load 1. The full power requirement ofa facility, which may be expressed in terms of averages or maximums. 2. The administrative and personnel requirements of an organization when in full op- eration. operatorAn individual with system access privileges hierarchically higher or more powerful than general users. A telephone operator can manage calls and access services and control mechanisms that are not ac- cessible by regular phone subscribers. A chat room operator can include or exclude specific users or set other restrictions or standards of use. A system operator has access to monitors, security devices, software programs, and other computer operations mechanisms not available to regular users. operator, telephone An individual who handles the routing of calls from callers to callees and provides a variety of types of assistance such as directory assistance, long-distance procedures, billing options, etc. Many of these processes have now been automated, but in the early days, the telephone operator had complete responsibility for connecting, monitoring, and disconnecting calls through manual patchcords. He or she was also implicitly expected to provide emo- tional support, emergency information, local news and gossip, and business tips. In fact, the position of the phone operator included so much power (over connections to alternate business options) and information that a direct dial system was invented ex- pressly to bypass the operator! Later switchboard systems required a higher level of concentration and expertise as many more lines would be serviced and the switchboards included lights to indicate connections and incoming calls, switches, cards for recording toll calls, and more. While the names of the very first telephone operators have probably been lost to history, George Willard Coy is generally credited as the first telephone 704 operator and Emma Nutt as the first female telephone operator. Nutt was instated following the relative failure of male telegraph operators to adapt to the task of courteously handling customer voice calls. Nutt apparently moved from a telegraph office to the phone exchange in Boston, hired in September 1878 by A. Graham Bell. She was paid asalary of $1 0per month for a 54-hour work week (minus lunch). This was a year of great expansion, during which the New England Telephone Company was formed to sellli- censes to telephone company operators in the New England area. Ms. Nutt apparently could remember every number in the directory. Preferred Voice has created a synthesized voice speech attendant for delivery of information services named EMMA in honor of Ms. Nutt. Records are spotty, but a small selection of notable first telephone operators for their regions prior to about 1913 is shown in the Selection of Pioneering "First" Telephone Operators chart. See Call Girls, Strowger switch, switchboard, telephone history. Historic Telephone Switchboard & Operator A telephone operator staffing thefirst switchboard in Idaho Springs, Colorado, wearing a headset. Manual switchboards still exist on islands, in remote areas, and in many undeveloped nationas. In North America. the main telephone system operates with high-speeddigital switching circuits. {Denver Public Library Collection; copyright expired bydate.} operator-assisted call Any phone call in which the caller contacts the operator to handle some part of the transaction or connection, rather than direct dialing. There are usually surcharges associated with operator-assisted calls. operatorconsole, computer In computer networks, a console is a computer terminal which allows access to management and administrative functions that monitor and control the network. Common operations carried out on the console include user password as- signments, new user account allocations, virtual configuration of devices and the network topology, selVer configuration, etc. Often the operator console is in a © 2003 by CRC Press LLC separate room for security reasons and, at the very least, is password protected to prevent unauthorized users, or well-meaning but uninformed users from accessing lower level system functions that could in- terrupt the functioning of the network. operator console, phone In telephony, the main console of a multiline phone system. The operator console often is programmable and may include a hands- free earphone set. Operator Service Provider OSP. Previously called Alternate Operator Services. Acompetitive provider of operator-assisted long-distance calls, especially third-party billing, collect, etc., which usually leases the services of existing phone networks. Large ho- tels sometimes provide AOS services to hotel guests for a premium. See splashing. OPRE Operations Order Review. Ops Abbreviation for operations, operators, operator services, and system operators. This is a particularly common abbreviation on Internet chat systems, where the operators (ops) or channel operators . (chops, chanops) enforce accepted behavior on chat channels. See operator. OPS off-premises station. optical amplifier A type of device used as a cable repeater on fiber optic transmission lines, which functions without converting the optical signal. Early versions were based on semiconductor lasers. Most are now erbium-doped fiber amplifiers (EDFAs), that is, directly doped silica fibers, with the principal param- eters defined by atomic composition. optical attenuator A coupling component, usually ofa standardized type (e.g., FC- connector) that at- tenuates the energy of the passing optical signal by a certain amount. OAs are compact, low-power components available in fixed, variable, and computer- controlled models. Multiple OAs may be combined into multichannel arrays to meet the needs of complex networks. Thus, a fixed or variable amount of loss is intention- ally induced in the received optical signal to adjust the signal to the desired level. This is useful for switching, gain tilt, modulation, and power control. optical burst switching OBS. A mechanism proposed in 1999 by Chunming Qiao and Myungsik Yoo for managing bursty network traffic on the Internet. The research, supported in part by a National Science Foundation (NSF) grant, is intended to streamline network switching in anticipation ofhigh-speed end- to-end optical networks of the future. The system combines aspects of optical circuit switching and packet/cell switching. While transition technologies are expected to combine optical networks with electrical switching, at some point there may be second generation all-optical networks that can be established as a layer beneath Internet Protocol (IP). OBS anticipates this evolution in technology. Many broadband transmissions are inherently bursty (e.g., multimedia), as apparently are large numbers ofself-similar traffic streams. Thus, a system more efficient for this situation than optical circuit switching was sought. The researchers have observed that apacket can be sent along with the header, to reduce setup time and overhead, but that this approach has limitations as well. In OBS, a control packet is transmitted to set up a connection, followed by a data burst before the connection acknowledgment is received, essentially a one-way reservation system. In addition, data burst buffering at intermediate nodes is eliminated, reducing the wait for processing of control packets. Signaling is out-of-band. See Just-Enough- Time, Optical-Label Switching. optical bypass In a Fiber Distributed Data Interface (FDDI) token-passing network, port adaptors can be equipped with optical bypass switches to avoid seg- mentation which might occur if there is a failure in the system and a station is temporarily eliminated. Normally, optical signals pass through the bypass switch uninterrupted, but ifa station fails and is eliminated from the ring, the optical bypass can reroute the signal back onto aring before the signal reaches the failed station, thus providing fault tolerance for the system. The optical bypass switch is attached to the FDDI port adaptors between the attachment station and token- passing ring. See A port, dual attachment station. optical carrier OC. 1. In general, a signal carried over optical media that is intended to provide control signals, information, or other signal data. Com- monly lasers are used to provide carrier signals that may be given information content through electro- optical modulators (e.g., a quadrature amplitude modulator). See carrier, modulation. 2. A series of optical network transport levels defined in conjunction with SONET. See SONET Optical Carrier Trans- port Levels chart. optical channel data unitODV. Aunit of data in an optical transmission network. In an ITVT G.709 optical transport network, for example, ODV overhead resides in columns 1 through 14 of three rows of the frame. It provides connection monitoring, path supervision, and client signal adaptation. optical characterrecognition OCR. A software process, or combination ofhardware scanning devices and software, which evaluates marks on a page and determines whether they have the predefined characteristics oftext, symbols, and images, depending upon the software. Most OCR programs use acombination ofintelligent algorithms and character tables to process marks. These marks are typically text and character symbols, although some programs will also recognize math- ematical and logical symbols if these are added to the program dictionary or the user dictionary. Some programs can automatically discern columns oftext and images, and divide the page up appropriately, handling the regions separately. Once the document has been "recognized,' the characters and symbols are converted to a common format, such as ASCn or one of the many flavors of extended ASCII, and stored as a file that can be further edited with a text editor, word processor, or desktop publishing program. In its strictest sense, OCR just recognizes the characters; software which handles images as well is 705 rrg . . :.".:.:.~ .• '.:.~; , :)1 ;:~: © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary called optical document recognition. However, most OCR applications these days have some document processing and image recognition functions, so the phrase is used broadly here. Most of the early work on pattern matching algorithms used in character recognition was done in the late 1950s and the early 1960s. By 1963, ffiM had a system that could recognize Roman and Cyrillic characters at the rate of about 50 words per minute, the speed ofa moderately competent typist, and faster than most typists can type information with many numerals. See optical document recognition, scanner. Sample Optical Choppers Optical choppers range from simple, regular pat- terns, to combinations of two or more blades (top right). High-precision choppers may have hundreds or thousands of chopping segments (upper left). opticalchopperA component for interrupting a beam of light, often at very fast speeds. Chopping can be accomplished with shutters, tuning forks, rotary discs/ blades, or etched crystalline plates. Applications for choppers range from special lighting and art effects to highly-precise scientific applications and experi- ments. Scientific choppers typically have a data interface to a display component or computer. Tuning fork choppers are intended to be used at a specific frequency and have small apertures at high frequencies, compared to rotary choppers. Despite the frequency and aperture limitations, tuning forks are robust and have many applications and can be used in a wide range of operating conditions. Disc or rotary choppers resemble pinwheels in the sense that they have divided segments rotating around a central axis like a rotary fan. Most are mounted with ball bearings, but some are available with magnetic suspension. Choppers can be fabricated as high precision instru- ments with highly accurate divisions in the chopping segments and carefully controlled rotational axes and speeds. The number of "slots" on a chopper may range from 2 to 2000+ and some choppers provide variable speeds for the rotations of the wheels. It is also possible to design chopper blades to chop more. than one frequency at a time by having two sets of slots in the same wheel. It may be possible to option- ally phase-lock the chopper to an internal clock or to auser-supplied external clock. A monochomator for dispersing light waves may be coupled directly to choppers with an appropriate coupling head. Choppers may consist of coated gels or glass or one or more blades, depending upon the application. When there are two blades, one may be fixed while the other rotates. The alignment of the blades determines whether a beam is passed or blocked. The beam need not be completely blocked. With a general purpose scientific chopper with just two blades, it is possible to have chopping frequencies ranging from about 4 to 5000 Hz. With a gel chopper, different types or colors of coatings may selectively pass or chop certain frequencies. Piezoelectric choppers are small enough to fit on a chip for use in integrated circuits. In conjunction with a collimated laser source, they may be used as compact optical sensors. SONET Optical Carrier (OC-) Transport Levels Carrier Rate (Mbps) 08-3 08-1 08-0 OC-l 51.84 1 28 672 OC-3 155.52 3 84 2016 OC-9 466.56 9 252 6048 OC-12 622.08 12 336 8064 OC-18 933.12 18 504 12096 OC-24 1244.16 24 672 16128 OC-36 1866.24 36 1008 24192 OC-48 2488.32 48 1344 32256 OC-96 4976.64 96 2688 64512 OC-192 9953.28 192 5376 129024 706 © 2003 by CRC Press LLC Choppers are usually described in terms of their operational frequencies. Disc choppers with inter- changeable blades and rotational speeds can support many applications. See knife-edge focusing, Ronchi grating. Piezoelectric Semiconductor Chopper In thequest.{oreversmallercomponents, piezoelectric choppers have been developed, such as the one illustrated here, designed by H. Tohiyoshi. Incident light (A) encounters a chopper plate (B) madefrom anisotropically etched Z-cut quartz, with chopper slits perpendicular (normal) to the surface of the component. Light passing through the slits ac- tivate photosensitive detectors (C). optical combiner In general fiber optics terms, any system for aggregating optical cables in adjacent waveguides or for combining two or more optical signals for transmission through a single waveguide. Optical cables are typically aggregrated to facilitate installation and maintenance. Optical signals are combined for a variety of reasons. Transmission through a single rather than multiplewaveguides can be cost-effective. Broadcast services available to all service subscribers may be combined with targeted services requested by individual users at appropriate points in the network. Combined signals may be useful for research purposes for studying optical effi- ciency, interactions, and various sources of loss. As a fiber optic network component, the term more specifically refers to devices that combine or combine and regenerate combined optical signals with a minimum of loss and interference in the coupling/ combining process. Combiners may be passive or actively integrated with switching mechanisms. An arrayed waveguide grating (AWG) can combine ( or separate) multiple wavelengths. An active self- switching combiner, as an example, takes signals from two or more ports and physically couples them so they are proximate, then phase-shifts the signals through optical amplifiers and brings them together in a combined signal. See multiplexing. optical combiner, projection A projection surface or component that combines a projected image with other functions, images, or physical environments. For example, in military jets, the windshield may serve as a transparent viewing window as well as a projection surface for certain cockpit status displays. The same concept is applied to head-worn optical display systems, some ofwhich have small transparent screens that enable the viewer to see ahead while at the same time viewing a small projected image (in some systems, the image may pass through the combiner to be projected on the viewer's retina). Combiner projection technologies are useful any- where information needs to be superimposed on a transparent surface so that the viewer can see both the projected image and the environment behind the projected image. Thus, they could be used with a video camera to project an image of the area behind a viewer so the viewer could see front and back at the same time or they could project status information over a video image or real-life environment. In terms of innovative networking possibilities, they could project a Web page coupled with a GPS reader that shows a map and local landmarks at the specific site at which aperson is standing with a body-worn computer linked to the Internet. Optical Communications Demonstrator OCD. A NASAlJPL laser-based extraterrestrial communica- tion system capable oftransmitting at speeds up to ~~~p~~l:tJe~~eurct~~?~y~~~u~;f:::o~~~:rr~~ III flector, which controls the orientation of a Q-switched diode-pumped laser communicating in the downlink direction. The ground station detects the light signal using silicon avalanche photodiodes. This is seen as apossible alternative to radio wave communications that are more apt to be distorted due to Doppler shift effects. See Laser Communications Demonstration System. optical computer A type of processing hardware based on photons rather than electrons. This is a more experimental technology than is usedwith traditional computers, but it has possible advantages, particularly in speed and resistance to interference over current technologies, and may become more prevalent in the future. optical connectorsConnectors specially designed to couple fiber optic cable junctions so they interfere as little as possible with the path of the optical beams passing through the connectors. The connectors are usually used at points where the fibers connect with routing or switching circuitry, or with the optical interface to the system itself. Optical connections have to be well-engineered, as they must handle very precise beams and paths, and often must maintain the proximity and orientation of a bundle of optical fibers. Connectors for blown fiber installations are easier to install and maintain than a number ofother types of fiber attachments. See blown fiber. optical core The light-carrying central region of a fiber optic filament, commonly made from silica and germania. optical coupler See coupler. 707 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary optical coupler module OCM. A component that provides functions in conjunction with coupled fiber optic cables such as branching/joining, multiplexing/ demultiplexing, and filtering. OCMs are often modu- lar and may be customized for operating wavelength and the size and number of fiber filament. optical cross connect OXC. Optical connection components of telecommunications carrier networks that help operators manage the larger amounts of bandwidth enabled by newer capacity-increasing technologies. OXCs began to become generally available in the late 1990s. OXCs can facilitate network administration by en- abling a network to be more readily reconfigured or restored using optical switches. OXCs can handle data streams in the terabit ranges and work with a range of wavelengths and bit rates, making it easier to quickly effect rerouting. Currently OXC components are part of the optical portion of mixed wire and optical fiber networks, but as the optical market grows, demand for OXCs will likely increase. See lambda switching. optical detectorA substance or circuit which detects and converts electromagnetic waves in the form of optical waves. Solar panels contain substances that allow the conversion of light into electricity, which are widely used in the satellite industry to provide power for telemetry adjustment of orbits. See solar panel. optical disc Any ofa number of technologies used to store digital data which is subsequently accessed by light, usually a laser beam pickup. The information on an optical disc is commonly stored in a series of pits, that is, indentations in a metal disc coated with a plastic substrate. The placement, size, and proximity of these pits is defined in part for the specification for the type of optical technology. Newer technologies have been developed to increase the information capacity of a disc, as in digital videodiscs (DVDs) that are slightly thicker, to bring the disc closer to the laser pickup, with slightly smaller, tighter pits. Compact discs, videodiscs, PhotoCDs, and DVDs are popular forms of audio and visual storage media. Optical discs are also used for computer data storage, particularly for backups. optical document recognition ODR. A software process or combination of hardware scanning devices and software, which evaluates the various elements on a page to determine whether they are distinguish- able as text, images, symbols, or lines, and identifies them accordingly. The ODR in its simplest sense does not interpret the text into characters; it merely identifies page layout elements: images, columns, page numbers, text, etc. However, in commercial products, it is commonly combined with optical character recognition (OCR) capabilities in order to optically iden- tify and interpret areas that are text into characters that can be edited with a word processor, text editor, or desktop publishing program. ODR is a somewhat more complex process than OCR; together they com- prise powerful tools which are a part of image document management and processing. 708 ODR is particularly valuable for converting archived image information (e.g., microfiche) into documents that can be desktop published, or archived in data- bases for faster and more efficient search and re- trieval. See image document management, optical character recognition, scanner. optical eye pattern measurement procedure An optical fiber test procedure standardized within TW EIA-526, developed by the Optical Fiber Communi- cations System subcommittee. It describes param- eters for measuring the repetitive temporal characteristics of a two-level intensity-modulated optical waveform at an optical interface. Rise time, fall time, overshoot, and extinction ratio may be determined from the measured eye pattern. The waveform itself may be tested against a reference waveform mask to determine standards compliance. optical fiber A flexible, light-conducting, filamen- tous plastic or glass medium used for optical signal transmissions. Optical fiber is typically from 2 to 125 J.lm thick, and is capable of carrying a variety of high- speed, wide bandwidth transmissions with relatively low loss, when correctly installed. Unlike wire, fiber is not subject to electromagnetic interference or most of the types of radiant eavesdropping techniques that can be used on wire. This has made it very popular for backbone, hazardous area, and multimedia installations. It also does not present the same potential fire hazard as wire electrical cables. Two common types of optical fiber include step-index fibers and graded-index fibers. Step-index fibers have two layers: a lower refractive outer cladding layer and an inner core with a high refractive index. Graded-index fibers also are less refractive toward the outer edge, but rather than being two layers sand- wiched together, as in the step-index fibers, the re- fractivity in the material overall decreases gradually in relation to its distance from the innermost point of the cylinder. Fiber can be bundled without the electrical interference common to bundled wires; a group of fibers works together to provide greater capacity. Single- mode fiber transmissions, in which the signal can only follow one path through the filament, can travel greater distances without repeaters. See multimode optical fiber, single mode optical fiber. optical fiber cable See fiber optic cable. optical fiber ribbon A bundled fiber assembly in which individual fibers are laid side-by-side to form a flat ribbon or strip. This is convenient if they are to be installed in narrow areas such as inside walls or under carpeting. This way of arranging fibers is less common than bundling them into a cylindrical shape. optical handwriting recognition OHR A specialized form of character recognition designed to separate joined shapes and recognize variations ofparticular letters, in addition to other generalized optical character recognition (OCR) functions. Most OHR systems have to be trained to recognize a particular style of handwriting, since there is so much variation in the letter forms in the way different people write. optical insertion loss OIL. The coupling-associated © 2003 by CRC Press LLC Number Line Rate Frame Rate Speed kbps kHz In commercial implementations, OTUs are built into SONEr optical transport platforms. writable optical storage technology, incorporated in 1992. OSTA develops technology "roadmaps," sta- tistical illustrations of optical storage progress and trends, to define compatible product classes. It is not a standards-development organization per se, but it develops specifications and provides input to other organizations regarding practical implementations of optical storage standards. In July 2001, OSTA an- nounced the development and approval of a new specification for organizing compressed audio files on optical disc, called MultiAudio. The intent is to ensure that discs with compressed audio files (e.g., MP3) are as straightforward and standard Red Book CDs. The format specifies a table ofcontents access mechanism for CD and DVD playlists and media playback. See MultiAudio, MultiPlay. http://www.osta.org/ optical time domain reflectometer OTDR. An instrument for reflecting light through a fiber optic waveguide to determine loss and integrity of the fiber light path. OTDR measurements may be uni- or bidirectional. Unidirectional measurements may be misleading if there are diameter differences from one fiber joint to the next. However, if the light will be traveling only in one direction and the OTDR is measured in the same direction, this may be sufficient. If the light is being alternately transmitted in two di- rections along the fiber optic path, bidirectional averaging (taking measurements from each end of the fiber path) will provide more complete data for as- sessing the lightguide. See bidirectional averaging. optical transport network OTN. As defined in ITU G Series Recommendation G.709, OTN is an interface that builds upon previous SDH and SONET technologies to provide layered network services, but improves upon previous technologies with better optical channel management in the optical domain and forward error correction (FEC) to increase the distance over which data signals can be transmitted. G.709 standardizes the management of optical channels (wavelengths) without conversion to electrical through newer bubble and micro-electromechanical systems (MEMS) technologies. See optical transport unit. optical transport unit OTU. In the ITU-T G.709 framing structure, a frame in which each row con- tains 16 forward error control (FEC) blocks of 16- byte interleaved codecs for atotal of 4 x 16 = 64 FEC blocks. Currently three line and frame rates are defined. 48.971 ms 12.191 ms 3.035 ms 2,666,057.143 20.420 10,709,225.316 82.027 43,018,413.559 329.489 OTUI OTU2 OTU3 loss occurring at joints where optical transmission cables are connected into ports. The loss is due to a number of factors, including the quality of the cable assembly, the diameter and type offiber (some are more subject to loss than others), the snugness of the fit, the amount ofstrain associated with the connection, and the ambient environment. In product litera- ture, low optical insertion loss typically refers to the precision of the fit and resistence to strain in the joint between the connector and the port. There is sometimes atradeoff between ease of use and reconnection and loss. OpticalInternetworking Forum OIP. An open trade organization fostering the global development and deployment ofinteroperable optical data switching and routing technologies. Membership includes service providers, equipment manufacturers, and end users. http://www.oiforum.com/ optical label switching See optical-label switching. optical modulation depth OMD. An expression of the degree ofmodulation in an optical data transmission system. OMD is usually expressed in microme- ters as apercentage per channel (e.g., 4% or 20%) at a specified frequency range. The OMD may have to meet certain standards (e.g., SONET). Fiber optic CATV transmitting components may have controls for operator adjustment ofOMD. Poor adjustment can result in reflections or clipping. See modulation. optical network unit ONU. A device for connecting auser with a fiber optic network. The ONU creates aphysical link and conversion services, if necessary, between the central office optical wavelength and the home or office optical wavelength, which may be different frequencies. Anumber of ONUs are typically aggregated at a host digital terminal. Groups of host digital terminals are similarly aggregated at a control tenninal, located at the central office of the local exchange. In spring 2002, companies such as Salira began of- fering multiple-customer ONUs so that individual units for each customer were no longer necessary. optical scanner See optical character recognition, scanner. Optical Society of Japan OS1. Founded in 1952 as a division of the Japan Society of Applied Physics (JSAP), it is now the biggest division of JSAP with almost 2000 members. OSJ publishes the Japanese Journal of Optics and the Optical Review. It provides educational support, technical working groups, and conferences for its members and sponsors anumber of awards for excellence in the field of optics. http://annex.jsap.or.jp/OSJ/index -e. shtml opticalspectrum analyzer OSA. A desktop diagnos- tic instrument for measuring the power of a light signal at each of its emitted frequencies. It incorporates a diffraction grating to split out the wavelengths (in much the same way a prism splits white light into its constituent colors) and measures the power level of each wavelength. See reflectometer, tracer. OpticalStorage TechnologyAssociation OSTA. An international trade association promoting the use of 709 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary In "digital wrapper" implementations as introduced by Lucent Technologies, data is encapsulated in an optical transport unit frame similar to a SONET protocol frame so that any type of network traffic (ATM, IP, etc.) may be handled and forwarded over existing SONEr networks. The OTU provides FEC information at the end of the frame to ensure the suitability of the optical signal for high-speed transmission. optical-label switching OLS. A network switching system developed under the direction ofSJ. Ben Yoo through a DARPA ITO-sponsored research project. It was first proposed by Yoo in 1997 and developed independently at around the same time as Multi- protocol Label Switching (MPLS). OLS is a means of implementing packet-switching protocols over optical media. OLS is a scalable ul- tra-low-latency multiprotocol optical routing/switching system that shares some characteristics with MPLS. Underlying OLS is the packet-switching fab- ric comprising rapidly tunable wavelength conversion capabilities and scalable arrayed-waveguide grating. OLS is built upon this with a forward look to next generation all-optical Intemetworks. OLS routing uses an optical header with a label in the header to determine the packet forwarding. The data are held in the fiber path while the header is ex- amined and may be replaced for the next leg in the transmission path. OLS project goals as of 2000 included router con- nectivity in excess of 1024 x 1024 and aggregate switching bandwidth of almost a peta-bits-per-second. The multi protocol optical routing is intended to be interoperable with circuit-, burst-, flow-, and packet-switched networks. See label switching, Multiprotocol Label Switching, optical burst switching. OQPSK offset quadrature phase shift keying. See quadrature phase shift keying. Orange Book A set of standards for Compact Disc readable (write once) optical media. The previous Red and Yellow Book standards established the basic standards for recording audio and computer data to a Compact Disc. The Orange Book extended these capabilities to enable multisession recordings to be created (though they are not recommended as mas- ters). Red and Yellow Book data can be combined on one disc in whatever order is desired. See Blue Book. ORB See Object Request Broker. ORBCOMM Orbital Communications. orbit The path described by a moving body in more- or-less stable balance with the gravity of the body being orbited so that it continues in that path for a significant period of time (usually at least a few hours or days, although orbits ofartificial satellites can last for years in a stable orbit). The Earth is in orbit around the Sun, and the Moon is in orbit around the Earth. When the balance is lost and the orbit becomes smaller as the orbiting body is drawn inward, it is said that the orbit is decaying. Many types of orbits (orbits at different heights, with differently shaped paths) are used in telecommunications with artificial satellites. 710 Early communications satellite orbits tended to be circular or low and somewhat flatly elliptical (and tended to decay quickly). Communications were hin- dered by the necessity oflocating the orbiting satellite and keeping it in range before it passed around to the other side of the Earth. Later satellites were put into higher, more stable orbits, which were often geostationary; that is, the orbit was synchronized with the movement of the Earth so that the location of the satellite was roughly above the same location at all times. The amount by which an orbit deviates from a circle is referred to as its eccentricity. See geostationary, satellite. Elliptical Orbit Satellite orbits tend to be circular or more flatly elliptical, and may be further controlledso that the satellite spends agreaterpart of the orbitover ocean or land masses, depending upon whether it is serving marine or terrestrial communications needs. The orbits are often described in terms of their dis- tancefrom the Earth as low, medium, and high Earth orbits (LEO, MEO I HEO). Geostationary orbits are a type of high Earth orbit in which the satellitesmove- ment is paced such that it remains in the same position relative to the Earth. Orbital Sciences Corporation Commercial devel- opers of global satellite communications services. Orbital Sciences is a space and information systems company which designs, manufactures, and markets space-related infrastructures and products. See OrbLink. OrbLink A global broadband commercial satellite communications network being developed by Orbital Sciences Corporation for deployment around 2002. The designers intend to use the newest technology to construct broadband services that can be offered at lower prices than existing services. OrbLink is based on seven medium Earth orbit (MEO) satellites orbiting at 9000 kIn in an equatorial orbit, transmitting in extremely high frequency radio bands. Ser- vices will include digital voice, data videoconferenc- ing, computer networking, imaging, and other broadband applications. Pending Federal Communications Commission (FCC) approval, intersatellite communications will be at 65.0 to 71.0 GHz at speeds up to 15 Gbps, sup- porting high-capacity intercontinental trunking. Two- way digital connections will be between 37.5 to 38.5 GHz and 47.7 and 48.7 GHz bands up to about 1.5 Mbps. The seven satellites, plus one spare, are based on © 2003 by CRC Press LLC Orbital's STARBus, a small, lightweight, geostationary technology, acquired through a purchase of CTA Incorporated's space system business. Each satellite will support 100 spot beams. As an economic note on the dynamics of new telecommunications technologies, the total cost ofbuilding and deploying the orbital network, according to Orbital Sciences, com- pares to the cost ofinstalling two transatlantic fiber cables, which provide only about 10% of the trunking capacity of the proposed satellite system. OrckitCommunicationsA developer and manufac- turer of high-speed local loop communications systems and participant in a number of network standards working groups. Orckit partners with Fujitsu Network Communications, Inc. order entry The inputting, usually by voice or key- board, ofa customer request for aproduct or service. On the World Wide Web, Web forms are often available for customers to put in their own order entry. These Web applications are often in the form of shopping carts in which the customer browses various Web pages and enters each product desired into the shopping cart (order batch). The order is typically pre- processed by a CGI and then sent to the appropriate order fulfillment personnel for shipping and billing. Other automated systems allow customers to carry out a complete ordering transaction over atouchtone phone by using the keypad to enter codes and digits. See Automatic Call Distribution. Organization of American States OAS. The OAS Web site provides information on the group. http://www.oas.org/ OrganizationallyUnique Identifier OUI. A globally unique 24-bit Ethernet address identifier for LAN s and MANs managed and assigned by the IEEE Reg- istration Authority online or by phone. The OUI is assigned as athree-octet field in the SubNetwork At- tachment Point (SNAP) header, identifying an organization which further creates unique six octet numbers. Together they constitute a distinct Media Ac- cess Control (MAC) address or Ethernet address. See Ethernet, IEEE, Token-Ring. originate/answer On acomputer data modem, when the user wants to dial out to connect to another computer, a bulletin board, or an Internet access point, the commands for controlling the phone line and dialing the desired number come from the originating modem. "Originate mode" sets up a sequence of events which checks for a dial tone, dials, and hand- shakes with the receiving modem to establish the connection rate and protocol (or hangs up if the line is busy or is dropped). The receiving modem is set to "answer mode' so it detects an incoming call, an- swers it, and participates in the rate and protocol ne- gotiation. Most of this is automatically handled through a terminal software program, but it may be necessary to set originate or answer through menu selections, or direct commands through the software to the terminal program. originate restriction A secwity or specialized use restriction on a phone line which causes it to work only for incoming calls. Outgoing calls are blocked. This restriction is sometimes set on phones adjacent to public areas to prevent people from monopolizing or misusing a phone line. Sometimes the originate restriction applies only to long-distance calls or calls outside aprivate branch exchange. In some circumstances, the local phone company will partially disconnect a line by setting an originate restriction if the subscriber is behind in the payment of the phone bill. After paying the bill, it is usually necessary to request restoration of full service, as it is seldom done automatically. originator Initiator, caller, inventor, introducer, founder. The person, entity, device, or station that first communicates a message or starts an action or process. Orion A broadband data satellite service provider aiming at international common carriers and individual companies. ortho-correction In satellite imaging, acorrectional adjustment for distortion resulting from t~rrain. orthogonal frequency division multiplex OFDM. Amulticarriermodulation system which is similar to discrete multitone in that it utilizes Fourier transforms of data blocks. OFDM is suitable for Digital Sub- scriber Line (DSL) services. See Digital Subscriber Line, discrete multi tone. OS X See Mac OS X. OS/2 Operating System/2. International Business Machines' 32-bit preemptive multitasking text and object-oriented graphical operating system targeted for Intel-based microcomputers in the late 1980s. It was originally developed for IBM by both IBM and Microsoft Corporation, and version 1.0 was released in 1987 to succeed MS-DOS. When an upgrade to OS/2 was well under way, Microsoft pulled out to concentrate on their own operating system in competition with IBM. Many of the same concepts that were part of OS/2 were incorporated into Microsoft Windows NT, which was marketed as a direct com- petitor to OS/2. In 1991, ffiM released OS/2 version 2.0. Version 2.1 added support for multimedia and Windows 3.1 applications. OS/2 had some commercial success in the early and mid-1990s, but by 1996, through aggres- sive advertising and bundling programs, Windows was better known and more widespread in North America. In spite of this, there are many strong sup- porters of OS/2, including a worldwide network of Team OS/2 Groups. It is still a popular choice in Western Europe and Canada. Team OS/2 information for OS/2 users is available at their Web site. See Team OS/2. OS/2 SMP OS/2 Symmetric Multiprocessing. This version ofIBM's OS/2 supports systems with multiple processors, making it suitable for Internet services, graphics, and corporate applications, particularly those which operate as various types of resource servers in a networked environment. See OS/2. OS/2 Warp Operating System/2 Warp. By version 3 ofmM's OS/2 operating system, their operating system product was called OS/2 Warp. The Warp version added increased support for various peripheral 711 © 2003 by CRC Press LLC . laser source, they may be used as compact optical sensors. SONET Optical Carrier (OC-) Transport Levels Carrier Rate (Mbps) 0 8-3 0 8-1 0 8-0 OC-l 51.84 1 28 672 OC-3 155.52 3 84 2016 OC-9 466.56 9 252 6048 OC-12 622.08 12 336. through the filament, can travel greater distances without repeaters. See multimode optical fiber, single mode optical fiber. optical fiber cable See fiber optic cable. optical fiber ribbon A bundled fiber assembly in which individual fibers are laid side-by-side to form a flat ribbon or strip. This is convenient if they are to be installed in narrow areas such as inside walls or under carpeting. This way of arranging fibers is less common than bundling them into a cylindrical shape. optical. A flexible, light-conducting, filamen- tous plastic or glass medium used for optical signal transmissions. Optical fiber is typically from 2 to 125 J.lm thick, and is capable of carrying a variety of high- speed, wide bandwidth transmissions with relatively low loss, when correctly installed. Unlike wire, fiber is not subject to electromagnetic interference or most of the types of radiant eavesdropping techniques that can be used on wire. This has made it very popular for backbone, hazardous area, and multimedia installations. It also does not present the same potential fire hazard as wire electrical cables. Two common types of optical fiber include step-index fibers and graded-index fibers. Step-index fibers have two layers: a lower refractive outer cladding layer and an inner core with a high refractive index. Graded-index fibers also are less refractive toward the outer edge, but rather than being two layers sand- wiched together, as in the step-index fibers, the re- fractivity in the material overall decreases gradually in relation to its distance from the innermost point of the cylinder. Fiber can be bundled without the electrical

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