Fiber Optics Illustrated Dictionary - Part 71 pptx

Fiber Optics Illustrated Dictionary made presentations through influential organizations such as the National Telecommunications Informa- tion Administration (NTIA) conference. In 1996, Bell Atlantic announced a merger with NYNEX, a plan that was carried out in 1997. The announced merger received Federal Communications Commission (FCC) approval to become the second-largest single telephone company, stretching from Maine to Virginia. Nyquist, Harry (1889-1976) A Swedish-born physicist and engineer, Nyquist emigrated to the U.S. in 1907. Nyquist had an early interest in the transmission of pictures, resulting in the development of a historic facsimile system, AT&T's telephotography machine, in 1924. In the 1920s, Nyquist was also active in studying telegraph communications and providing theoretical observations related to transmission speeds and signal values. In 1928, he described principles for the digital sampling ofanalog signals in Certain Topics in Telegraph Transmission Theory. Unfortunately, theory came far ahead of practice; equipment at the time could not practically embody Nyquist's theories, but they are now the basis for digital sound sampling. The Nyquist theorem is named for this work; Claude Shannon who, like Nyquist, worked at the Bell Laboratories, cites Nyquist in his later development of information theory, in the 1940s. In 1927, Nyquist mathematically described Johnson noise, which is important in the understanding of interference in electronics. In the 1930s, he turned his interest to the study of amplifiers. Throughout his career he developed both theory and systems and is credited with more than 100 patents. See Nyquist theorem, sampling. Nyquist frequency See Nyquist theorem. Nyquist minimum The minimum bandwidth that can be used to represent a signal. This measure is used to limit the spectral width of a transmission signal in order to reduce the chance of interference and to maximize efficient use of the signal. See Nyquist theorem. Nyquist theorem The Nyquist theorem is an important principle in telecommunications, where audio samples are used for synthesized voice, "music on hold," videoconferencing, Internet phone, and other multimedia and digital voice communications. Au- dio sampling is a process of taking digital slices of an analog signal in order to store and reconstruct the signal to preserve the original sound. In general, the slower the sampling rate, the coarser the recreated sound; the higher the sampling rate, the better the recreated sound. There are thresholds, however. Above certain thresholds there may be no perceptual im- provement and artifacts and other technical interference will begin to negatively affect the quality of the recreated sound. Below certain thresholds, the sound 692 may not contain enough information to be intelligible. There are also thresholds in the relationship between the frequencies sampled and the sampling rate. The Nyquist theorem is named for Harry Nyquist, who studied and described these important basic principles as they related to communications in the 1920s. The Nyquist theorem describes a sampling quality threshold relationship between the phase of the har- monically related sine and cosine functions over a specified time interval. In practical application then, an analog signal waveform sampling at equal time intervals requires a sampling rate of at least twice the highest frequency component in the analog signal to fully represent the characteristics of the original sound. Or stated another way, the highest frequency that can be accurately represented in a sampled signal is equal to one-half of the sampling rate. This translates to two samples per cycle and is called the Nyquist frequency or Nyquist limit. Thus, a full sample of 10kHz of audio bandwidth would have to be captured at a rate of20 kHz (or higher, within other thresholds) or information would be lost or introduce artifacts. In theory, the sampling rate can be infinitely high and the samples infinitely narrow. In practice, usually sound sampling rates of about 8 to 44 kHz are used. If frequencies in the sample are higher than the Nyquist rate, an artifact known as aliasing will oc- cur. Thus, in theory, ifa sound sample possesses frequencies up to 10kHz, but the sound is sampled at a rate at 18 kHz, then frequencies over 9 kHz should be filtered to prevent aliasing. In practice, signals above the Nyquist frequency may be filtered to reduce aliasing in the recreated sound sample. Theo- retically, the filter would enable us to get back apretty faithful representation of the original frequencies within the sample that are up to 9 kHz. In real life, filters have phase shift and slope characteristics that may interfere with a perfect re-creation. Other limitations in sound sampling and re-creation are the digi tal storage and bus characteristics of the digital sampling system. In most systems, you need at least 8 bits to make decent-sounding voice, and 16 bits for a decent representation of music. Higher capacities are needed to accommodate higher dynamic ranges and more sophisticated sounds. Sound periph- eral cards for computers and synthesizers with 16- or 32-bit sampling capacities did not become widely available until the late 1990s. The Nyquist theorem has also been applied to video sampling, but it has been found that higher sampling frequencies may be needed for video compared to sound, with suggestions that four times the highest frequency may be necessary for a full re-creation of the original image. See Fourier transform; Nyquist, Harry; sampling; Shannon, Claude. © 2003 by CRC Press LLC oA symbol used on many consumer electronics de- vices to indicate "off." On rocker switches, it indi- cates the side of the rocker which turns an appliance or component off. Its complement is "I" to designate " " on. o Series Recommendations Aseries oflTU-T rec- ommended guidelines for specifications of measuring equipment that can be purchased from the lTU- T. Since lTU- T specifications and recommendations are widely followed by vendors in the telecommunications industry, those wanting to maximize interoperability with other systems should be aware of the information disseminated by the ITV-T. 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., K Series Recommendations. See 0 Series Recommendations chart. O&M, 0 & M operations and maintenance. O-band A transmission band specified by the lTU for optical transmissions in the 1260 - 1310-nm range. OIP output. OIR Originator/Recipient. Aconcept associated with the X.400 Message Handling System (MHS). The OIR address is used by the MTS for routing. OAI See Open Application Interface. OALC4 A family ofrelatively small-diameter fiber optic submarine cables developed by Alcatel. These cables are specifically intended for repeater-equipped systems. They can house up to 16 optical fibers within a welded steel tube. A gel substance protects the fibers from moisture and hydrogen effects. A steel wire vault surrounded by aseam-welded copper tube provides additional protection. High-density polyethyl- ene provides abrasion resistance. Cables of the OALC4 family are suitable for use at sea depths of between 0 and 7000 to 8000 m, depending upon the ohms per kilometer rating. OAM operations, administration, and maintenance. Various related management functions often associated with telephone and computer networks. In telephone networks, significant management and ac- counting tasks are associated with maintaining a dynamic environment in which subscribers all request different types and levels of service, and where the subscriber population is very mobile, thus changing their locations on a continual basis. Some systems have computer networks and entire facilities associated with just these aspects of the business. With mobile communications on the rise, these management tasks become even more intricate, and computer systems are used to facilitate the administrative tasks. OAM Operations And Maintenance. Preventive maintenance information which, in an ATM B-ISDN environment, is included in the transmitted cells. OAM&P operation, administration, maintenance, and provisioning. OAM&P ANSI standards There are a number of important American National Standards (ANSI) of Committee Tl related to OAM&P, which are available from ANSI and described in the fonn of abstracts on the Web. See the ANSI Standards OAM&P chart for examples. OAO orbiting astronomical observatory. Since 1966, a series of OAOs has been launched from Cape Canaveral to explore and measure astronomical phe- nomena that can more easily be seen from outside the Earth's atmospheric envelope. OA See office automation. OAS See Organization of American States. OBI See Open Buying on the Internet. object 1. Athing, article, entity, or unit of information. 2. An individually identifiable part, entity, or component. 3. In programming, an entity, often com- partmentalized, that stores or receives data, e.g., a byte, block, register, segment, etc. 4. In the X Win- dows System, a software concept practically implemented as private data with private and public rou- tines to operate on that data. 5. In typed objects, an entity that interacts as part ofa defined operation. object, programming In object-oriented programming, a reusable, modular, ''wrapped up" collection of software characteristics, functions, and parameters at a basic level. For example, a button may be designed with certain visual and operational characteristics and stored for reuse in various applications, so that the code for the object isn't constantly reinvented. An object may consist ofa collection of other objects to serve some related or higher function. See class. Object Database Management Group ODMG. An independent standards organization now called the Object Data Management Group to reflect the broader 693 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary lTU-T 0 Series ReeommendatioDs 0.1 Scope and application of measurement equipmentspecifications covered in the O-series Recommendations 0.3 Climatic conditions and relevant tests for measuring equipment 0.6 l020-Hz reference test frequency 0.9 Measwingarrangementstoassess the degree of unbalance·about "Earth 0.11 Maintenance access lines 0.22 CCITT automatic·transmission measuring and signaling testing equipmentATMENo.2 0.25 Semiautomatic in-circuit echo suppressor testing system (ESTS) 0:27 In-station echo canceller testequipment 0.31 Automatic measuring equipment for sound-program circuits 0.32 Automaticmeasuring·equipment for stereophonic pairs of sound-program circuits 0.33 Automatic equipment for rapidly measuring stereophonic pairs and monophonic sound-program circuits, links, and connections 0.41 Psophometerfor use on telephone-type circuits 0.42 Equipment to measure nonlinear distortion using the 4-tone intermodulation method 0.51 Volume meters 0.61 Simple equipment to measure interruptions on telephone-type circuits 0.62 Sophisticated equipment to measure interruptions on telephone-type circuits 0.71 Impulsive noise measuring equipment for telephone-type.circuits 0.72 Characteristics of an impulsive noise measuring·instrument for wideband data transmissions 0.81 Group-delay.measuring equipment for telephone-type circuits 0.82 Group-delaymeasuring equipment for the range of 5 to 600 kHz 0.91 Phase jitter measuring equipment for telephone-type circuits 0.95 Phase and amplitude hit counters for telephone-type circuits 0.111 Frequency shift measwingequipment roruse on carrier. channels 0.131 Quantizing distortion measuring equipment using apseudo-random noise test signal 694 0.132 Quantizing distortion measuring equipment using a· sinusoidal test signal 0.133 Equipment for measuring the perfonnance ofPCM encoders and decoders 0.150 General requirements for instrumentation for performance measurements on digital transmission equipment 0.151 Error perfonnance measuring equipment operating at the primary rate and above 0.152· Errorperfonnance measuring equipment for bit rates of 64 Kbps and N x 64 Kbps 0.153 Basic parameters for the measurement of error performance at bit rates below the primary. rate 0.161 In-service code violation monitors for digital systems 0.162 Equipment to perform in-service monitoring on 2048-, 8448-, 34,368- and 139,264-Kbps signals 0.163 Equipment to perform in-service monitoring on 1544-Kbps signals 0.171 Timing jitter and wander measuring equipment for digital systems based upon the plesiochronous digital hierarchy (FDB) 0.172 Jitter and wander measuring equipment fordigitalsystems based upon the synchronous digital hierarchy (SDH) 0.181 Equipment to assess error performance on STM-N interfaces 0.191 Equipment to measure the cell transfer performance of ATM· connections Supplements O.Sup3.1 Measuring instrumentrequirements - sinusoidal signal generators and level-measuring instruments 0.Sup3.2 Noise measuring instruments for telecommunication circuits 0.Sup3.3 Principalcharacteristics of volume indicators 0.Sup3.4 Consideration ofinterworking between different designs of apparatus for measuring quantizing distortion O.Sup3.6 Crosstalk test device for carrier- transmission on coaxial systems O.Sup3.7 A measuring signal (multitone test signal) for fast measurement of amplitude and phase for telephone type circuits O.Sup3.8 Guidelines concerning the measurement of jitter © 2003 by CRC Press LLC efforts of the organization to support Universal Ob- ject Storage Specifications (DOSS). See CORBA. http://www.odmg.org/ ObjectDefinition Alliance ODA. Avendor associa- tion established by Oracle which aims to promote and develop new interactive TV and other multimedia services and networks that will operate over a variety of platforms. aDA seeks to establish associated technical standards for these products. Vendors in- clude a number of high-profile financial institutions and retailers, and computer and media developers including Time-Warner, Apple Computer, Xerox, and Compaq. See video-on-demand. object encapsulation Atechnique for combining related data and functions into an operational bundle, thus simplifying its use within a larger framework. The purpose is not to hide the intrinsic components of an encapsulated object, but to create a common superset of characteristics thatwork together and may be frequently used and reused. This technique is one type of modular approach to programming. See encapsulation, obj ect-oriented programming. ANSI Standards OAM&PAbstracts ANSI Standard ANSI Document Title T 1.118-1992 G Interface Specification for Use with the Telecommunications Management Network T 1.204-1997 Lower Layer Protocols for Telecommunications Management Network Interfaces, Q3 and X Interfaces Tl.208-1997 Upper Layer Protocols for Telecommunications Management Network, Q3 and X Interfaces T 1.209a-1995 Supplement - Network Tones and Announcements T1.214-1990 A Generic Network Model for Interfaces between Operations Systems and Network Elements T1.215-1994 Fault Management Messages for Interfaces between Operations Systems and Network Elements T1.221-1995 In-Service, Nonintrusive Measurement Device Voice Service Measurements T 1.224-1992 Protocols for Interfaces between Operations Systems in Different Jurisdictions T 1.226-1992 Management of Functions for Signaling System No.7 Network Interconnections T1.227-1995 Extension to Generic Network Model for Interface between Operations Systems across Jurisdictional Boundaries to Support Fault Management Tl.228-1995 Services to Interfaces between Operations Systems across Jurisdictional Boundaries to Support Fault Management (Trouble Administration) T 1.229-1992 Performance Management Functional Area Services for Interfaces between Operations Systems and Network Elements Tl.233-1993 Security Framework for Telecommunications Management Network (TMN) Interfaces T 1.240-1996 Generic Network Information Model for Interfaces between Operations Systems and Network Elements Tl.243-1995 Baseline Security Requirements for the Telecommunications Management Network T 1.240-1996 Generic Network Information Model for Interfaces between Operations Systems and Network Elements T 1.244-1995 Interface Standards for Personal Communications Services (withdrawn) Tl.246-1995 Operations Systems across Jurisdictional Boundaries to Support Configuration Management - Customer Account Record Exchange T1.247-1995 Performance Management Functional Area Services and Information Model for Interfaces between Operations Systems and Network Elements T 1.250-1996 Extension to Generic Network Information Model for Interfaces between Operations Systems and Network Elements to Support Configuration Management - Analog and Narrowband ISDN Customer Service Provisioning Tl.252-1996 Security for the Telecommunications Management Network Directory 695 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary objectinheritanceA concept in object-oriented programming (OOP) which describes a hierarchical passing on of characteristics down through associated objects. Object Linking and Embedding OLE. A software system developed by Microsoft Corporation which allows various applications programs that are OLE- compatible to share and exchange information. It is an interoperability system that lowers the distinction between various applications developed by different vendors so users can integrate the applications files and environments, and use them more as a suite of tools than as separate items. It further provides specification guidelines for the interface for accomplish- ing these tasks. OLE is a very good concept, in principle, and works well a lot of the time. Unfortunately, the various implementations are not yet perfect, as the OLE-compliant programs and OLE software programs installed on a system sometimes will clobber some of the other programs that don't support OLE, causing odd behaviors and situations where software has to be reinstalled, or OLE disabled temporarily. As OLE-capability must be incorporated into each software application by individual developers, there is some variation as to the completeness and depend- ability of these implementations. When it works, OLE is a good for developing documents that take elements from a variety of text, image, sound, and other programs and combine them via links and drag and drop. Spreadsheet totals or statistics can be incorporated into stock offering documents, images can be incorporated into proposals, sounds can be incorporated into multimedia presentations, etc. without constantly opening and closing applications and converting various file formats with external utilities. OLE does more than just provide a way to insert information from one source into another; it further keeps a record of the links so that if source information in one document is updated, it will also be updated in subsequently linked documents. OLE is used by various applications in Windows and Macintosh operating systems. See ActiveX. ObjectManagementArchitecture OMA. An architectural framework developed by the Object Manage- ment Group (OMG) to lower the complexity and cost of developing new software applications. See CORBA, Object Management Group. Object ManagementArchitecture Board OMAB. A group established in 1996 by the Object Manage- ment Group (OMG) to oversee the OMG Technical Process, including the tracking and revision of technical specifications. See CORBA, Object Manage- mentGroup. ObjectManagement Group OMG. Anonprofit organization of over 800 software developers, vendors, and end users whose aim is to establish the wide- spread use ofCORBA through global standard specifications. Headquartered in Massachusetts and established by eight companies in 1989, OMG promotes the theory and practice of object technology for the development of distributed computing systems through a common architectural framework. OMG 696 seeks to establish industry guidelines and object management specifications to further the development of standardized object software, which it hopes will encourage a heterogenous computing environment across platforms and operating systems. See CORBA, Object Management Architecture, Unified Modeling Language. http://www.omg.org/ ObjectRequestBroker ORB. The communications center of the Common Object Request Broker Archi- tecture (CORBA) standard developed by the Object Management Group (ORG). It provides an infrastruc- ture for program objects to intercommunicate, independent of the techniques used to implement them and the platform on which the software is running. Compliance with the ORB provides portability over many different systems. The ORB administers objects so an application need only request an object by name. There are now many commercial and freely distrib- utable ORBs. See CORBA, Fnorb, Object Manage- ment Group, TAO. There is general information on CORBAat http://www.omg.org/ There is a good list of ORB resources on the Web at http://patriot . net/ -tvalesky / freecorte html Object Serialization Stream Protocol OSSP. A means to represent objects within a stream. Objects are grammatically represented and assigned a handle for use as a reference to the object. See byte-stream protocol, Java. Object Services Management components of the Common Object Request Broker Architecture (CORBA) standard developed by the Object Manage- ment Group (OMG). A set of services for facilitating development productivity and consistency of implementation. The Object Services provide generic environments for objects to perform their functions, interfaces for the creation of objects, control of access to the objects, and administration of the location of objects. See CORBA, Object Management Group. object-oriented programming OOP. A software development approach that follows a more natural and efficient evolution than many older reinvent-the- wheel approaches to programming. To understand the difference between non-object-oriented programming and object-oriented programming in asimplis- tic way, imagine a toy shop in which each elfis working in a separate little room, each with a separate set of tools, creating some kind of toy doll. At the end of the day, the creations are brought into a central room and it is discovered that some toys have been dupli- cated, none have interchangeable parts, and the end result is only ahalf dozen different toys. That's pretty much how traditional programming has been done, with an enormous amount of replication of effort. Every company writes the same sorting algorithms, there are hundreds ofhalf-baked proprietary editors, and file search and retrieval methods are reinvented by thousands of programmers on a daily basis. It isn't very efficient. It isn't even very much fun. Now picture a toy shop in which some general guidelines are set out for joints and limbs, and in which each toymaker has a magic replicator in which his or © 2003 by CRC Press LLC her components can be copied an indefinite number of times. Now imagine one of the toymakers is a mechanical wizard, and another is an artist, able to make beautiful embellishments. At the end of the day, instead of having a dozen toys, a limitless number of heads and feet, bodies and legs can be shared among all the toymakers. Not only that, but some particu- larly intricate mechanical parts and some wonderfully aesthetic ones can be used by all. Since guidelines were set out, the parts are interchangeable. The elves have created the basis for thousands of toys, rather than just a dozen. Assuming unlimited replication of individual parts, there's no limit to how often each component can be used. That's what object-oriented programming is, in the ideal sense. Once you create an eye object and give it certain parameters so that the color, shape, and various eye characteristics (con- tact lenses, eyelashes, ability to track a moving shape, etc.) can be individualized, you don't have to do it again; you can mix and match it with head, nose, and hair objects in thousands of different ways. Similarly, in programming it is possible to create directory, menu, window, and button objects. Object- oriented concepts are not limited to physical at- tributes; the software can also incorporate more ab- stract user security objects, sort or fetch objects, and functions and behavioral characteristics associated with a type or class of objects. Object-oriented programming is amodular approach that allows objects to be mixed and matched, or ar- ranged in hierarchies, and customized to suit an individual application. Once created, they can be reused indefinitely. This can save development time and provides the basis for platform-independent software; it also gives a certain level of consistency to the interface, so users don't have ahigh learning curve for interacting with new applications programs. It further provides the programmer with anumber of levels of interaction with an object. The developer can use the object in atransparent way, with the definition of the object encapsulated (bound together as an attribute or functional unit) by passing messages and parameters without worrying about how it was coded, or the programmer can take apart the object and use its individual components, or combine it with others to create a larger functional unit. This too is different from traditional programming. In many cases using someone else's non-object-oriented code involves a lot of study and adaptation to make it work in another setting, and it's rarely easy to mix and match parts of the code so that the characteristics can be inherited among the different parts. In contrast, program objects can be designed so that their characteristics and behaviors are known, so they can be immediately used without a long ramp-up period or restructuring. Object-oriented programming languages are still evolving. Smalltalk is one of the first object-oriented programming environments, developed 20 years ago, but many common languages currently used in commercial software development are not object-oriented; efforts to create object-oriented versions oftra- ditionallanguages have not been fully satisfactory. Nevertheless, the trend is toward object orientation, given its obvious advantages of portability and effi- ciency in many contexts. F or important and interesting information on taking the object-oriented model to global implementation and distribution, see CORBA and Object Manage- ment Architecture. See Open Systems Interconnect, Smalltalk. ODRA See Omnibus Budget Reconciliation Act. ODS See optical burst switching. obscenity Obscenity, in its everyday sense, refers to actions or materials which are offensive, repellent, or vile. In a legal sense, it is more specific, as individual interpretations of what is offensive vary dra- matically. Questions involving obscenity often con- flict with individuals' rights and opinions regarding freedom ofspeech, and thus are important issues on the global Internet. See Communications Decency Act of 1996, Electronic FrontierFoundation. OC operator centralization. OC-n See optical carrier for definition and chart. OCC See Other Common Carrier. Occam's Razor A maxim well known to scientists, attributed to William of Occam in the 1300s, that it is vain to do with more what can be done with fewer (or less). It has been restated in many ways, in many contexts, but essentially, in science and in human spheres of activity, the idea is that the simplest ex- planation or one which doesn't require any additional hypotheses is usually the best, and often correct. occlude To block, to obscure or limit from reaching the sight of the viewer. For example, a continuous stream of light can be pulsed by periodically occlud- ing the beam. See chopper, knife-edge focusing, optical chopper, Ronchi grating. OCIR overcoat-incident recording. OCP operator control pane1. OCR 1. See optical character recognition. 2. Outgo- ing Call Restriction. octal A base eight numbering system utilizing the numerals 0 through 7. See decimal, hexadecimal. octathorp See octothorpe. octet 1. Adata unit widely used in digital networks. An octet consists of a sequence of eight data bits, sometimes called a byte (which is usually but not al- ways eight bits and thus ambiguous). 2. In Internet Protocol (IP), octets are used as data units to describe an address or class designation as four octets (32 bits) separated by delimiters. See IP address, IF class. 3. In RFC descriptions ofpackets, an octet is a data unit for describing packet lengths. octet rule In molecular physics and chemistry, an octet is a completed valance shell of eight electrons as is common to most elements. The octet rule is the manner in which atoms bond to one another as mol- ecules so that valance shells fill to comprise eight electrons. There are exceptions, such as the common element hydrogen (H), which requires only two electrons to complete its electron shell. octopus, hydra A visually descriptive name for a 25-pair cable common in multiple phone system in- stallations. At the far end, the 25-pair wire is organized 697 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary into individual connectors (two, four, six, or eight wires) with phone cord connectors. An octopus is useful for stringing a single wire into a location where several phone connections are planned. octothorpe, octathorp The # symbol, sometimes also called pound, hash, crosshatch, or number sign. It is used as an end signal (or "long" signal) on some touchtone phone menu systems. It represents a number sign in financial contexts, a suite number in postal addresses, and a sharp in music notation. See pound. ODBC See Open Database Connectivity. ODC See Open Development Consortium. ODMG See Object Database Management Group. onp See open distributed processing. ODU See optical channel data unit. OdysseyA medium Earth orbit (MEO) satellite communications system intended to begin service in 1999 with 12 medium Earth orbit (MEO) satellites. Planned services included voice, data, facsimile, and Global Positioning Service (GPS). The project was discon- tinued in 1997 and TRW transferred technical exper- tise to the ICO Global Communications ICONET when it became a leading ICO shareholder later in 1997. TRW Inc. announced that it would tum back the license it had received for the Odyssey program to the U.S. Federal Communications Commission (FCC), in order to make the assigned frequencies available to other communications services. See ICO Global Communications. oersted (symb. - Oe, 0) Acentimeter-gram-second (CGS) unit of magnetic intensity (field strength) equal to the intensity of a magnetic field in a vacuum in which a unit magnetic pole experiences a mechanical force of one dyne in the direction of the field. It can be expressed as 10 3 /4pA m· l . Named after Hans Christian 0rsted (sometimes transcribed as Oersted). See ampere. Oersted (0rsted), Hans Christian (1777-1851) A Danish physicist and educator who demonstrated the effects of current on a magnetic needle to a class of physics students around 1819. He reported on the magnetic effects of electric currents, information that brought together magnetism and electricity as never before, and resulted in a change in scientific think- ing and the development of electric telegraphs in Eu- rope and America. The oersted unit of magnetic intensity is named after him. OFDM See orthogonal frequency division multiplex. off-axis parabolic, off-axis paraboloidal OffAP. In optics, a geometric configuration used in reflectors in which the optical or symmetry axis of the reflector does not pass through the reflector but passes by nearby. The optical axis is parallel to the mechanical axis, in relation to the curved reflective surface, but generally falls outside the region ofcurvature of the reflective surface at a focal point that is accessible to the user. The parabolic surface is shaped to efficiently capture incoming rays within a desired field of view. For scientific applications, the reflectors may be coated with gold to enhance infrared reflectivity. On- axis and off-axis parabolic reflectors are used for broad spectral range illumination and light-collecting 698 applications, sometimes in place of optical lenses. Parabolic mirrors may also guide and focus beams, as in spectrometers. OffAP mirrors can produce apoint image from a co 1- limated beam and eliminate aberrations in very fine diameter optical fibers in spectroscopic applications. Multiple OffAPs may be housed in an assembly. There is a broad range of commercially available OffAPs for many applications and custom OffAPs may be ordered, but common focal lengths range from about 3 to 40 in. and off-axis distances range from about 1 to 20 in. for reflectors between 1 to 8 in. diameter. See monochromator. off-hook On a phone set, the state of having the plunger or switch-hook in the active or "up" position so the circuit is connected. The term comes from the old wall phones on which the earpiece (receiver) was taken off a curved hook when in use (and when the battery power was engaged). When the phone is first taken off-hook, it alerts the switching exchange to the fact that the caller wants to use a line. The switching exchange returns a dial tone to the caller to indicate that the line is available for dialing. See on-hook. off-peak hours Hours oflow usage. In telephony, the hours between 11 :00 P.M. and 7:00 A.M. are designated as off-peak in many areas, and calling rates are lower. The concept also applies to transportation systems, and fewer buses, trains, or subway cars may be in service during these hours. off hours The times outside normal operating or working hours. Telephone and Internet services are often discounted in off hours or off-peak hours. off the shelfProducts and services that are ready to use without any customization. Products which can be readily purchased by anyone walking into a store or ordering from a catalog, and run with little or no configuration. Essentially the same as shrinkwrapped products. office automationA catchall term for procedures and systems designed to streamline or increase the effi- ciency of business operations, often by installing technology that mayor may not displace human workers. In some respects office automation has freed people from drudge work; it is no longer necessary to have rooms full of"human calculators" sitting and working out sums by hand, but technology has also introduced greater needs for training, storage of information, information retrieval, and other time-con- suming activities that don't necessarily improve quality of life or shorten the work day. Office ofScience and Technology Policy OSTP. The science policy coordinating group for the Federal Government Executive Branch. The OSTP is led by presidentially appointed directors, organized into four divisions: environment, national security and international affairs, science, and technology. The OSTP provides expert advice to the President of the United States in matters of science and technology. http://www.whitehouse.gov/WH/EOP/OSTP/htmll OSTP Info.htrnl Office-of Telecommunications Along with the Of- fice ofTelecommunications Policy, this organization © 2003 by CRC Press LLC was rolled into the U.S. National Telecommunica- tions and Information Administration in 1978 as a result ofa reorganization. Office of Telecommunications Policy OTP. Office of the Director of Telecommunications Regulation ODTR. The National Regulatory Author- ity for telecommunications in Ireland, established June 1997 under the Telecommunications Miscella- neous Provision Act 1996. The ODTR administers the development of a liberal telecom market in accor- dance with the European Union and Irish law, allo- cates radio spectrum, and regulates broadcast transmissions and telecommunications equipment. OFS Laboratories An international optical lab that has pioneered the production of optical fibers, connectors, cables, and attenuators. The Norcross, Geor- gia, plant began producing optical fiber in 1976 and is now the world's largest fiberoptic manufacturing facility. In addition to design and fabrication, OFS publishes a number oftechnical papers on fiber and photonic bandgap technologies. In 2002, OFS introduced a fiber design that incorpo- rates photonic crystal technology to "tune" the wave- lengths passing through the fiber. See photonic crystal. OFX See Open Financial Exchange. OGT outgoing trunk. ohm A practical unit in the meter-kilogram-second (MKS) system equal to the resistance ofa circuit in which a potential difference ofIV produces a IA current. Thus, if the values of two of these three are known, the third can be calculated. Named after Georg Simon Ohm. In 1908 the International Con- gress established the International ohm as the resistance offered to an unvarying current by a column of mercury at O°C, 106.3 em long, of a constant cross- sectional area of1 square mm, and weighing 14.4521 g. In the U.S. in 1950, Congress defined the ohm as equal to one thousand million units (10 9 ) of resistance. See ampere, electromotive force, Ohm's law, resistance, volt. Ohm, Georg Simon (1787-1854) A German physicist who, in 1820, investigated the conducting prop- erties of various materials. He described the flow of electricity through a conductor and discovered the relationships among current, resistance, and electromotive force, information that greatly influenced sub- sequent theory and application in electricity. See Ohm's law. Ohm's law In any specific direct current electrical circuit, the strength of the current is directly proportional to the potential difference in the circuit and in- versely proportional to the resistance. Thus, current (in amperes) equals electromotive force (in volts) di- vided by resistance (in ohms), or I = EIR. See ampere, ohm, resistance, volt. OHR See optical handwriting recognition. OLE See Object Linking and Embedding. OLIU Optical Line Interface Unit. OLNS Originating Line Number Screening. OLT optical line termination. OM Operational Measurement OMA See Object Management Architecture. OMAT Operational Measurement and Analysis Tool. OMG See Object Management Group. OMSN optical multiservice node. Omnibus Budget Reconciliation Act OBRA. OBRA is a 1993 U.S. Congress amendment to the Communications Act of 1932 which preempts state jurisdiction in such a way that individual states no longer regulate rates and entry by companies offering wireless services. The federally controlled spectrum was transferred to the Federal Communications Commission (FCC). It further organized wireless into two categories: commercial mobile radio services (CMRS), including cellular radio services and personal communications services (PCS), and private mobile radio services (PMRS), including public safety and government services. See Telecommuni- cations Act of 1932. omnidirectional Effective in all directions, radiating in all directions, or receiving from all directions. Functional in many directions without preference to anyone. An omnidirectional antenna is one which is designed to send or receive signals in a maximum number of directions. Atheoretical isotropic antenna is fully omnidirectional and often used as a reference for comparing antenna patterns or effectiveness. An omnidirectional speaker directs sound in all directions. Since this is structurally difficult to achieve, ~~: ~~~:~i~~:~~~~s~ ~~~:~~?~ ~~:~~~~~.POint omnidirectional antenna An antenna designed to transceive signals through a wide range of directions. Since an antenna's capabilities are detennined by shape and location, it is rarely completely omnidirectional, but broad omnidirectionality is achieved by maintaining equal field strength through the horizon- tal plane, and radiating in or out through the vertical plane. See isotropic, omnidirectional. omnidirectional microphone A microphone designed to capture sound from all around its location. This is actually less common than directional microphones. Tape players, camcorders, digitizing sound sample microphones, phoneset microphones, and others have directional microphones to zero in on the crucial input, so they can screen out extraneous noises and conversations. Omnidirectional micro'phones can be said to capture sound "environments.' OmniWeb One of the earliest commercial Web Browsers, OmniWeb 1.0 was released in March 1995 for NeXTStep platforms by Lighthouse Design, Ltd. In spite of being a first release, it was a well-designed, full- featured browser, utilizing the Display PostScript and object-oriented capabilities of NeXT Step. It had flexible bookmark and other accessory capabilities not available in other popular browsers until about a year later. OmniWeb was subsequently ported to run on Macintosh Systems by The Omni Group and con- tinues to be enhanced to take advantage of evolution- ary changes in HTML and related Web languages. OMSG optical multiservice gateway. on-hook On a phone set, the state of having the plunger or switch-hook in the inactive, depressed, or 699 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary "down" position to interrupt the circuit, so it is not active while the phone is not being used. The term comes from the old wall phones on which the earpiece (receiver) was cradled on a curved hook when not in use (to conserve battery power). See off-hook. on-line See online. on-axis parabolic, on-axis paraboloidal OnAP. A geometric configuration used in reflectors in which the optical or symmetry axis of the reflector passes through the reflector. On-axis parabolic reflectors are used for collimating beams and off-axis paraboloidal reflectors are used for broad spectral range illumination and light-collecting applications. Paraboloi- dal reflectors are sometimes used in place of or in conjunction with optical lenses. Paraboloidal mirrors may be used to guide and focus beams and OnAPs have been used in experimental laser propulsion research. Higher-precision reflectors may be coated with gold. See off-axis parabolic. on-ramp colloq. Access to a main communications link, such as highway, phone trunk, or networking service. The on-ramp is the link between the user's system and the main system. An Internet Access Pro- vider (lAP) can be considered an Internet on-ramp. on/off keying A type of modulation scheme similar to frequency shift keyin~ (FSK), except that no signal is used for binary "0' (zero). See frequency shift keying, phase shift keying. ONA See Open Network Architecture. ONAC Operations Network Administration Center. ONAL Off Network Access Line. online 1. Having access to a system which is at least minimally functioning, and is largely automated.ln- teracting with aproceduralized system. Auser is said to be online when he or she logs into a computer or a network, or accesses an automated phone system. 2. To bring a system online is to connect or power it up so that it is at least minimally functioning. 3. To bring an employee online refers to fitting the person into an organizational structure within an established system ofpriorities and procedures. Online Public Access Catalog OPAC. An online service for providing access to bibliographic records. OPAC can be used to search records based upon author, title, subject, title keywords, and other search criteria. Many libraries worldwide offer access to OPAC through Telnet, Web interfaces, or internal Libsys systems. Similar to OPAC is the British Li- brary Public Catalogue (BLPC); COPAC is a publicly accessible catalog from 20 of the largest research libraries in Ireland and the U.K. who are members of the Consortium of University Research Libraries (CURL). ONT optical network terminaVtermination. ONU See optical network unit. OOP See object-oriented programming. OPAC I. See Online Public Access Catalog 2. See outside plant access cabinet. open I. Unbounded, having no barriers or extents, unconcealed, exposed, uncovered, unobstructed. 2. An open circuit is one not currently connected, usually because no power is coming to it (as when it is 700 turned off). Acircuit breaker or blown fuse may create an open circuit. 3. An open transmission channel is one that is not currently in use or with channels available so that it may be used with appropriate facilities and authorization. An open channel may also imply one that is unsecured, where others can hear any communication that occurs. open-space cutout In telephone wiring, aprotective grounding mechanism, often used in conjunction with fuses and heat coils to guard against possible danger to people and equipment from large power fluctua- tions. Ifvoltage is too high, the wire grounds by arc- ing across a small air gap between carbon blocks mounted on an insulator such as porcelain. Open 56k Forum Aconsortium oftelecommunications vendors promoting K56flex modem technology. open air transmission A type oftransmission which either depends on air for the propagation of the signals or which is commonly broadcast through the air. Radio, shortwave, and microwave transmissions are primarily open air systems. open applications interface OAL An interface built into a system and documented in such a way that third-party vendors can develop equipment and software applications that tie into that system. Open Buying on the Internet OBI. An open, ven- dor-neutral, scalable, securable, business-to-business standards effort for the support of electronic commerce. The effort was initiated by around-table dia- logue by a number ofFortune 500 companies in Oc- tober 1996. The founding participants included prominent firms such as American Express, BASF Corporation, Ford Motor Company, and others. The goal was the quick and effective implementation of interoperable Internet-based e-commerce solutions amenable to universal, high-speed access and paper- less transactions. In June 1998, CommerceNet as- sumed management of the OBI Consortium to facilitate standardization efforts. The OBI specification supports purchasing solutions for procuring high-volume, low-dollar, indirect products and services. OBI was first publicly demonstrated through the OBI Interoperability Showcase at the CommerceNet 99 conference. The first version of OBI was released in March 1997, with V2.1 released in November 1999. Open Buying on the Internet Consortium OBI Consortium. An independent nonprofit organization dedicated to the development of open standards for business-to-business Internet commerce. http://www.openbuy.org/ Open Collaboration Environment OCE. An environment created by Apple Computer which provides a means for third-party developers to create telecommunications applications that interface with the Macintosh operating system (MacOS). Thus, developers can create Internet phone, facsimile, network, and other telecommunications-related products for Macintosh owners. Open Database Connectivity ODe. Microsoft's telephony software open application processing interface (API), part ofa system that provides interoper- © 2003 by CRC Press LLC ability between Microsoft business-oriented database, spreadsheet, and word processing software, which is especially useful for digital telephony applications. The interface itself is independent of the application that provides the formatted data. In this way, call records and statistics can be stored and manipulated with popular software applications, providing computer-telephone integration and advanced call-recording capabilities. Open Development Consortium ODC. An administrative concept introduced in November 2000 and formed early in 2001 to promote open standards for effective and collaborative exchange of development information. The consortium evolved out ofODC dis- cussion list messages supporting informational concepts related to open development and open source software. open distributed processing ODP. A framework for specifying systems, with an emphasis on distributed systems, defined in ISOIlEC 10746 and lTU- r X.900 as a four-part standardized reference model. It is network-independent and may be implemented with rcP/IP, OSI, NetBIOS, and others. See CORBA. Open Financial Exchange OFX. A specification for the electronic exchange of financial data among busi- nesses, consumers, and financial institutions over the Internet. The specification was jointly developed by CheckFree, Intuit, and Microsoft in 1997. The specification supports a wide variety of types of financial transactions including bill presentation and payment, banking, investment and stock tracking, pension account inquiries, and more. In 2000, the OFX specification was made XML 1.0- compliant and certain tax form capabilities were added. A number of development toolkits are available for creating OFX-compliant applications, including JOFX (Java OFX). By late 2001, OFX was sup- ported by more than 1400 payroll processing, bro- kerage, and banking firms. See JOFX. http://www.ofx.net/ Open Group, The Formerly the Open Software Foundation, The Open Group is an organization which aids in the development and implementation of secure and reliable network infrastructures. The Open Brand is a registration mark (X) awarded by The Open Group to products which conform to the standard specifications. http://www.opengroup.org/ Open Network Architecture aNA. A system developed to encourage third-party vendors to supply public phone network products and services. Under the Federal Communication Commission's (FCC's) ONA, the telephone companies must provide the same service guarantees and levels to outside vendors' products that use the phone lines, as they use themselves. Network services must be stipulated as individual services in order to make them available to unaffiliated Internet Service Providers (ISPs). The Bell Operating Companies are required to comply withONA. open office An administrative and physical structure in which low walls or no walls are favored over high walls, movable walls are favored over fixed walls, and work stations are generally within view of more administrators and employees than in other office designs. Open office concepts are designed to promote flexibility and communication. Open Shortest Path First Protocol OSPF. A TCP/ IP distributed-computing dynamic routing protocol in the Interior Gateway Protocol (IGP) family of protocols, developed by the OSPF working group of the Internet Engineering Task Force (IETF). OSPF dis- tributes routing information within a single autono- mous system based upon link-state technology (a different approach from Bellman-Ford internet routing). OSPF includes explicit support for Classless Inter- Domain Routing (CIDR) and the tagging of exter- nally-derived routing information. OSPF supports routing update authentication and IP multicast update sending/receiving. OSPF is a responsive protocol with low traffic overhead. Routing is based upon destination information in IP packet headers without further encapsulat.ion. OSPF detects and responds to topological changes, calcu- lating new loop-free routes after a short period of convergence. See Hello Protocol, link state advertise- ment. open skies colloq. Regulatory policies that are liberal enough to allow private use. Prior to 1972, the Federal Communications Commission (FCC) did not permit private American satellites to be launched for commercial communications. It then opened the doors on private domestic satellite launchings and operations, a move that created an opportunity for new competitive services to be established. Mel is one of the companies that got its start partly through rec- ognizing and taking advantage of the opportunities presented by these openings. Open Software Foundation OSF. This has now become the Open Group. See Open Group. http://www.opengroup.orgl open system An open computer system is one which has few security barriers. Passwords may not be needed or individual users' directories may be open to all users. In many ways the Unix operating system and the Internet global network have been developed with an effort to keep them open and accessible; some people advocate that all systems should be that way. Open Systems Interconnection OSI. An important layered architecture specification released as a standard by the International Organization for Standard- ization (ISO). OSI is designed to facilitate communications development between computer equipment and network software. Many vendors have opted to support this standard. Essentially, the communication is mapped onto seven layers as shown in the ISO/ Open Systems Interconnection Reference Models chart. See ISO/OSI Reference Model for more information. Open Systems Networking Initiative OSN. A trade organization promoting and supporting open network technologies such as high-capacity storage solutions for enterprise-level systems. The organization was founded by Cisco Systems, Quantum Corporation, 701 © 2003 by CRC Press LLC . below the primary. rate 0.161 In-service code violation monitors for digital systems 0.162 Equipment to perform in-service monitoring on 204 8-, 844 8-, 34,36 8- and 139,264-Kbps signals 0.163 Equipment to perform in-service monitoring. Provisioning Tl.25 2-1 996 Security for the Telecommunications Management Network Directory 695 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary objectinheritanceA concept in object-oriented programming (OOP) which. descriptive name for a 25-pair cable common in multiple phone system in- stallations. At the far end, the 25-pair wire is organized 697 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary into individual

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