Optical Fiber Preform-Oxymoron

Optical Fiber Preform

Optical fiber material from which an optical fiber is made, usually by drawing or rolling.

Optical Fiber Ribbon

A cable of optical fibers laminated in a flat plastic strip.

Optical Fiber Splice

A permanent joint whose purpose is to couple optical power between two fibers.

Optical Fibre

British spelling. In an optical fibre transmission system, the data is carried by pulses of light along glass fibres. This method of transmission has a much higher bandwidth than copper cables and is less subject to distortion and interference. It is safer than copper because it provides electrical isolation and as it carries no current can be used in flammable areas. See Optical Fiber for a longer explanation.

Optical Interconnection Panel

An interconnection unit used for circuit administration and built from modular cabinets . It provides interconnection for individual optical fibers. Unlike the optical cross-connect panel, the interconnection panel does not use patch cords.

Optical Internetworking Forum.

See OIF.

Optical Isolator

A component used to block out reflected and unwanted light. Used in laser modules, for example. Also called an isolator.

Optical Line Interface Unit


Optical Line Terminal

OLT. Also known as Optical Network Unit (ONU). See ONU.

Optical Link Loss Budget

The range of optical loss over which a fiber optic link will operate and meet all specifications. The loss is relative to the transmitter output power.

Optical Loss Test Set

A source and power meter combined to measure attenuation in optical fiber.

Optical Modulator

An active optoelectronic component, typically made from lithium niobate or gallium arsenide, that turns an optical signal on and off to encode and transmit data throughout the network. Modulation can be achieved directly by turning a source laser on and off or externally by altering a continuous source laser signal to achieve a similar on/off effect. Long-distance and submarine optical networks typically use high-power lasers and external modulators, while shorter-distance optical networks are better suited for direct modulation.

Optical Network Unit

See ONU.

Optical Path Power Penalty

The additional loss budget required to account for degradations due to reflections, and the combined effects of dispersion resulting form intersymbol interference, mode-partition noise, and laser chirp .

Optical Power Meter

A device which measures the light signal transmitted through fiber-optic cable.

Optical Pump Laser

A shorter wavelength laser that is used to pump a length of fiber with energy to provide amplification at one of more longer wavelengths . See also EDFA.

Optical Receiver

The receiver converts the optical signal back into a replica of the original electrical signal. The detector of the optical signal is either a PIN-type photodiode or avalanche-type photodiode.

Optical Repeater

In an optical fiber communication system, an optoelectronic device or module that receives a signal, amplifies it (or, in the case of a digital signal, reshapes, retimes, or otherwise reconstructs it) and retransmits it. See also Optical Amplifier .

Optical Return Loss

The ratio, expressed in units of dB, of optical power reflected by a component or an assembly to the optical power incident on a component port when that component or assembly is introduced into a link or system.

Optical Rise Time

The time interval for the rising edge of an optical pulse to transition from 10% to 90% of the pulse amplitude. Alternatively, values of 20% to 80% may be used.

Optical Scanner

A hardware device that recognizes images on paper, film and other media and converts them into digital form which can be stored in a conventional computer readable magnetic medium, such as floppy or hard disk. Optical scanners are getting better and better but are still not perfect. See OCR.

Optical Spatial Division Multiplexing


Optical Spectrum

Generally , the electromagnetic spectrum within the wavelength region extending from the vacuum ultraviolet at 1 nm to the far infrared at 0.1 mm. The term was originally applied to that region of the electromagnetic spectrum visible to the normal human eye, but is now considered to include all wavelengths between the shortest wavelengths of radio and the longest of X-rays. See Optical Fiber.

Optical Storage Device

Optical storage devices use a source of coherent light ” usually a semiconductor laser ” to read and write the data. There are three big advantages to using a laser ” size, safety and portability. Because you can focus a laser into approximately one micron in size ” a far smaller area for encoding a bit of data than conventional drives ” you can fit more data in.

Optical media are also more stable than metal-oxide disks. They aren't affected by light, normal temperatures or electromagnetic fields. (You can put through as many airport x-ray machines as you wish.) And best, the read/write head doesn't get as close to the recording medium as it does in conventional disk drives. Optical drives are interchangeable, also. You can remove them and store them. That makes them great for archiving.

Optical Time Domain Reflectometer

OTDR. A device that measures distance to a reflection surface by measuring the time it takes for a lightwave pulse to reflect from the surface. Reflection surfaces include the ends of cables and breaks in fiber. The reflectometer measures the ratio of incident and reflected light power, or backscatter. By using this device you can figure precisely where a fiber optic link is broken. This device operates like Radar. It sends a light pulse down the cable and waits for it to return. It measures the time taken and calculates the distance based on the speed of light through the fiber optic cable. The reflectometer usually also displays the reflected waves on a time axis for precise reading of, e.g., the leading edges of the transmitted and reflected waves. The reflectometer is also capable of launching a light pulse into the fiber optic transmission medium and measuring the time required for its reflection to return by backscattering or end reflection, thus indicating the continuity, crack, fracture, break, or other anisotropic features of the medium. See also Backscatter .

Optical Transmitter

The optical transmitter converts an electrical analog or digital signal into a corresponding optical signal. The source of the optical signal can be either a light emitting diode, or a solid state laser diode. The most popular wavelengths of operation for optical transmitters are 850, 1300, or 1550 nanometers.

Optical Transport Network

OTN. The Optical Transport Network is a fancy name for a dream ” an all optical telecommunications network with the flexibility of the present all-electronic one. The idea is that a call ” narrow or broadband ” will be " dialed ," then wend its way to the other end through pure optical pipes and pure optical switching. The so-called optical network of today is actually a collection of dumb wavelength-division multiplexed (WDM) point-to-point links, which are typically converted to electrons at some stage (unless the circuit is an end-to-end leased line.) Telecommunications service providers of tomorrow will provide on-demand lightpath services. For this to happen, we'll need, as a first step, dynamically controllable equipment such as configurable optical add-drop multiplexers and large port count optical cross-connects. The next crucial step is to create a standardized management and control infrastructure to allow all the various optical switching and transmission equipment to interwork with one another. There is some debate as to how much "network" should we place? Since most traffic will be dominated by data in the future, some have suggested using an IP-centric minimalist philosophy to build the OTN. On the other hand, the increasing value of data, driven by the growth of e-commerce and companies running their day-to-day business through the Internet, argues for a more sophisticated network. The debate continues.

Optical Unifying Layer

OUL. A heady concept. A theoretical way for carriers to integrate the diverse technologies of their existing network into one physical infrastructure.

Optical Virtual Tributary Group

OVTG contains four DS-1 signals packaged into an optical SONET virtual tributary, or VT.

Optical Waveguide

Technically, any structure that can guide light. Sometimes used as a synonym for optical fiber, it also can apply to planar light waveguides. See also Photoni Crystals.

Optical Waveguide Connector

A device whose purpose is to transfer optical power between two optical waveguides or bundles, and that is designed to be connected and disconnected repeatedly.

Optical Wireless

Optical wireless is a vague term which tries to capitalize on the popularity of optical stocks. Several vendors use the term to create interest in various free- space (i.e., through-the-air) transmission systems, some of which run at microwave frequencies and others of which use infrared (Ir) light. One maker described his product as "providing optical wireless connectivity with data speeds up to 2.5 Gbps, allowing high speed access to customers where the existing last-mile infrastructure, whether based on copper or wireless radio frequency technology, provides inadequate bandwidth. This family of products can be installed and operational quickly and easily on a small rooftop space or in an office behind a window. Installation of two units at a location enables a short mesh configuration, allowing redundancy in the event of a link or equipment failure." The term "optical wireless" certainly would be more meaningful if it were limited to Ir and laser- based WLL (Wireless Local Loop) systems, but not all vendors seem to be as concerned about "meaningful" as I am. Everybody's got his own agenda. See also Agenda and WLL.

Optically Active Material

A material that can rotate the polarization of light that passes through it. An optically active material exhibits different refractive indices for left and right circular polarizations (circular birefringence).


In the stock market, an option is a contract you buy which allows you to buy (a "call") or sell (a "put") a stock at a specified per-share price by a specified future time period (option expiration date).


An ant crawling up an elephant's leg with rape in mind.


Overlapped Phase Trellis-code Interlocked Spectrum. OPTIS is a modulation technique use in HDSL2 (High-bit-rate Digital Subscriber Line). See also HDSL2.

Opto-Electric Transducer

A device which converts electrical energy to optical energy and vice versa. Used as transmitters and receivers in fiber optic communications systems.


The range of materials and devices associated with fiber optic and infrared transmission systems. As there are no practical optical computers, all information originates as an electrical signal. Therefore, opto-electronic light sources convert the electrical signal generated to an optical signal which is transmitted to the receiving light detector for reverse conversion back to an electrical signal. In fiber optic systems, the light sources are in the form of either LEDs (Light-Emitting Diodes) or laser diodes. The light detectors are in the form of either PINs (Photo-INtrinsic diodes or APDs (Avalanche PhotoDiodes). Laser diodes and APDs are matched in high-speed, long-haul networks. LEDs commonly are used in fiber optic LANs and other short-haul, relatively low-speed applications. Optical repeaters, which also are opto-electronic devices, repeat the optical signal. Such repeaters accept the optical signal through a light detector, convert it to electrical energy, boost the signal and clean it up, and reconvert it to an optical signal for insertion to the next link of the optical fiber system. Also, each of these functions requires electrical energy to operate and depends on electronic devices to sense and control this energy. See also Optical Amplifiers, a new breed of amplifiers that doesn't take the light signal back to electrical energy.

Optoelectric Transducer

Electronic components that turn light energy into electrical energy and electrical energy into light energy.


Opt(o-Elect)ronics. See Opto-Electronics.

Optus Communications Ltd

Historically, Australia's second general communications carrier, licensed by the government in 1991 to provide competition to then government-owned Telstra Corporation. Initially formed from a consortium of Mayne Nickless, AMP Society, National Mutual, AIDC Telecommunications Fund, Bell South and Cable and Wireless. Optus provides mobile and fixed network services.


Off Premise Extension. An extension or phone terminating in a location other than the location of the PBX. The station uses a line circuit out of the PBX. OPX is commonly used to provide a company executive with an extension off the PBX in his home. This way he can pretend to be at the office when he's really at home. He can also make toll calls and have them easily charged to the office.

OR Gate

A digital device which outputs a high state if either or both of its inputs are high.

Or Statement

See Not Statement.

Orange Book

The common name for the U.S. Department of Defense's Trusted Computer System Evaluation Criteria (TSEC).


  1. Office Repeater Bay. Mounting and powering arrangement for digital regenerators, such as for T-1 lines.

  2. Object Request Broker. See Object Request Broker and CORBA.

Order Entry

A voice processing application which allows someone with a touchtone phone to buy something, i.e. enter their order.

Order Wire

  1. A circuit used by telephone personnel for fixing, installing and removing phone lines. See also Order Wire Circuit.

  2. Equipment and the circuit providing a telephone company with the means to establish voice contact between central office and carrier repeater locations.

  3. A SONET/SDH term for a connection request, and consisting of one octet contained within the SOH (Section Overhead).

Order Wire Circuit

A voice or data circuit used by telephone company technical control and maintenance personnel for the coordination and control action relating to activation, deactivation , change, rerouting, reporting and maintenance of communication systems and services. See also Order Wire.


See Order Wire.


There are two ways you can grow a company's revenues. You can buy other companies and add their revenues to yours. Or you can grow the revenues in your own business by thinking up and creating new products, then marketing and selling more, adding more customers and selling more to your existing customers. Growing your present business' revenues without acquiring other businesses is called organic growth.

Organic Growth

See Organic.

Originate Mode

The "originate mode" sets the modem to begin a data phone call ” i.e. dial the phone, listen for a carrier tone from a remote modem and connect to that modem. The modem at the receiving end must be set to "Answer" mode. In any asynchronous data conversation, one side must be set to "Originate" and the other to "Answer." Such settings are usually made in software.


The two modes of operation for a modem. Originate and answer states define the frequencies used to transmit and receive. In a two-way communication system, one modem must be set to originate and the other to answer.

Originating Direction

The use of Access Service for the origination of calls from an End User premise to a customer premise.

Originating Office

The central office that serves the calling party.

Originating Restriction

A phone line with this restriction cannot place calls at any time. Calls directed to the phone, however, will be completed normally.


A call that is placed by the mobile subscriber, calling either a land-line circuit or another mobile subscriber.

Origination Cablecasting

Programming over which a cable television system operator exercises editorial control. This term includes programming produced by the operator; Non-broadcast local programming produced by other entities and carried voluntarily by the system. Example: PRISM; regional news channels; Satellite-delivered non-broadcast programming carried voluntarily by the system, such as HBO, ESPN, CNN, C-SPAN, QVC, etc.

This term does not include programming over which the operator does not exercise editorial control, including any broadcast signal, including satellite-delivered broadcast "super- stations " (WGN-TV, WWOR, etc.); Any access channel designated by franchise for public, educational, or governmental use; Leased-access channels.

The cable system operator is required by Section 76.225c of the FCC Rules to maintain records, in the PIF, to verify compliance with rules governing commercial matter in children's programming carried on origination-cablecasting channels. See PIF.


The user that is the ultimate source of a message or probe.


Optically Remote Module. A type of switching module made by AT&T which connects directly to the 5ESS switch communications module via optical fibers.


A Windows NT term. A member of a mirror set or a stripe set with parity that has failed in a severe manner, such as a loss of power or a complete head crash. When this happens, the fault-tolerance driver determines that it can no longer use the orphaned member and directs all new reads and writes to the remaining members of the fault-tolerant volume.


Having, meeting or determined at right angles.

Orthogonal Frequency Division Multiplexing



  1. Outage Seconds.

  2. Operating System, as in MS-DOS (Microsoft Disk Operating System), Windows NT, Windowsn 2000, Windows XP, Solaris, Unix, Linux, Symbian or OS/2. See Operating System.

  3. Operator Services. See Operator Services.

  4. Operations System. Includes SCOTS, FMAS, etc.


Operating System/2. An operating system originally developed by IBM and Microsoft for use with Intel's microprocessors and for use with IBM personal system/2 personal computers. OS/2 has pretty well died. Microsoft's various flavors of Windows survive it.

Osborne Effect

Once there was a personal computer company called Osborne Computer Company. One day, the president announced a revolutionary new computer. It was so good not one of his dealers wanted to (or could) sell the existing product and they sent all their inventory back. Meantime, it was six months before the company could deliver the new product. But without any sales in the meantime, it had no money and Osborne went broke. There is a lesson here for companies who are attempting to manage transition between old and new product lines. Be careful, or suffer the horrible consequences of The Osborne Effect.


Holywood gives our Oscars for great movies, performances , etc. Apparently when the first statue was cast, someone quipped, "My God. It looks like my uncle Oscar." Apparently it stuck.


  1. A device for generating an analog test signal.

  2. Electronic circuit that creates a single frequency signal.


Electronic testing device that can display wave forms and other information on a TV-screen-like cathode ray tube. A basic fixture in sci-fi movies.


Optical Spatial Division Multiplexing is a technology developed to improve the efficiency with which SONET (Synchronous Optical NETwork) supports bursty packet data traffic such as LAN traffic. OSDM accomplishes this by dynamically allocating arbitrary levels of bandwidth to such traffic, guaranteeing minimum levels that are supplemented by higher levels of bandwidth as it becomes available. OSDM is a protocol-independent , self- contained technology that adapts to various current and developing physical layer technologies such as digital wrappers and DWDM (Dense Wavelength Division Multiplexing).


Open Software Foundation. An industry organization founded in 1988 to deliver technology innovations in all areas of open computer systems, including interoperability, scalability, portability and usability. The OSF was an international coalition of vendors and users in industry, government and academia that worked to provide technology solutions for a distributed computing environment. In February 1996, the OSF consolidated with X/Open Company Ltd. to form The Open Group. See The Open Group. www.opengroup.org.


Version 1 of the Open Software Foundation's Unix-based operating system


Open Systems Interconnection. A Reference Model developed by the ISO (International Organization for Standardization, as translated into English). The OSI Reference Model is the only internationally accepted framework of standards for communication between different systems made by different vendors. ISO's goal is to create an open systems networking environment where any vendor's computer system, connected to any network, can freely share data with any other computer system on that network or a linked network. Most of the dominant communications protocols used today have a structure based on the OSI model. Although OSI is a model and not an actively used protocol, and there are still very few pure OSI-based products on the market today, it is still important to understand its structure. The OSI model organizes the communications process into seven different categories and places these categories in a layered sequence based on their relation to the user. Layers 7 through 4 deal with end to end communications between the message source and the message destination, while layers 3 through 1 deal with network access.

click to expand

Layer 1 ” The Physical Layer deals with the physical means of sending data over lines (i.e., the electrical, mechanical and functional control of data circuits). Examples include EIA-232 (RS-232), T-carrier and SONET.

Layer 2 ” The Data Link Layer is concerned with procedures and protocols for operating the communications lines. It also has a way of detecting and correcting message errors. Examples include Frame Relay, PPP (Point-to-Point Protocol), and SLIP (Serial Line Internet Protocol). ATM runs at Layers 1 & 2, as do LANs.

Layer 3 ” The Network Layer determines how data is transferred between computers. It also addresses routing within and between individual networks. The most visible example is IP (Internet Protocol).

Layer 4 ” The Transport Layer defines the rules for information exchange and manages end-to-end delivery of information within and between networks, including error recovery and flow control. TCP (Transmission Control Protocol) is an example, as is the OSI Transport Protocol (TP), which comprises five layers of its own. Layer 4 protocols ensure end-to-end integrity of the data in a session. The X.25 packet-switching protocol operates at Layers One, Two, Three, and Four.

Layer 5 ” The Session Layer is concerned with dialog management. It controls the use of the basic communications facility provided by the Transport layer. If you've ever lost your connection while Web surfing, you've likely experienced a session time-out, so you have some sense of the Session Layer.

Layer 6 ” The Presentation Layer provides transparent communications services by masking the differences of varying data formats (character codes, for example) between dissimilar systems. Conversion of coding schemes (e.g., ASCII to EBCDIC to Unicode), and text compression and decompression exemplify Presentation Layer functions.

Layer 7 ” The Applications layer contains functions for particular applications services, such as file transfer, remote file access and virtual terminals. TCP/IP application protocols such as FTP (File Transfer Protocol), Simple Mail Transfer Protocol (SMTP), SNMP (Simple Network Management Protocol) and TELNET (TELecommunications Network) take place at Layer 7.

See also OSI Standards, which compares Layers 1 through 2 on OSI to making a phone call on the public switched telephone network. .

OSI Model

Open Systems Interconnection Model. See OSI.

OSI Network Address

The address, consisting of up to 20 octets, used to locate an OSI Transport entity. The address is formatted into an Initial Domain Part which is the responsibility of the addressing authority for that domain and a domain-specific part which is the responsibility of the addressing authority for that domain.

OSI Presentation Address

The address used to locate an OSI Application entity. It consists of an OSI Network Address and up to three selectors, one each for use by the Transport, Session, and Presentation entities.

OSI Standards

The International Standards Organization (ISO) has established the Open Systems Interconnection (OSI) Reference Model is to provide a standar network design framework to allow equipment from different vendors to be able to communicate. Standards allow us to buy items such as batteries and light bulbs . Many of us have learned "the hard way" that the lack of computer standards can make it impossible for computers from different vendors to talk to each other. Because a major goal of a LAN (Local Area Network) is to connect varied systems, standards have been developed to specify the set of rules networks will follow. The OSI Model is a design in which groups of protocols, or rules for communicating, are arranged in layers. Each layer performs a specific data communications function. The concept of layered protocols is analogous (but not identical) to the steps we follow in making a phone call:

Step 1 ” Listen for dial tone.

Step 2 ” Dial a phone number.

Step 3 ” Wait for a ring.

Step 4 ” Exchange greetings to check that the connection is made and we're speaking the same language.

Step 5 ” Talk, i.e. communicate messages back and forth.

Step 6 ” Prepare to end conversation. For example, say Goodbye. Step 7 ” Take physical action. Hang up.

Each of these steps, or OSI "layers," builds upon the one below it. Although each step must be performed in preset order, within each layer there are several options. Within the OSI model, there are seven layers. The first three are the Physical (PHY), Data Link (DLL), and Network layers, all of which are concerned with data transmission and routing. The last three ” Session, Presentation and Application ” focus on user applications. The fourth layer, Transport, provides an interface between the first and last three layers. The X.25 Protocol which created a standard for data transmission and routing is equivalent to the first three layers of the OSI Reference Model." See also OSI and X.25.


A test network sponsored by the National Bureau of Standards (NBS) designed to provide vendors of products based on the OSI model a forum for doing interoperability testing.


The science of smells. See Snortal.


Operations System Modifications for the Integration of Network Elements. OSMINE enables equipment used by Regional Bell Operating Companies (RBOCs) and other service providers to be managed effectively from the same software program, helping to ensure multi-vendor interoperability.


Operations System Network.


  1. Operator Service Provider. A new breed of long distance phone company. It handles operator-assisted calls, in particular Credit Card, Collect, Third Party Billed and Person- to-Person. Phone calls provided by OSP companies are often more expensive than phone calls provided by "normal" long distance companies, i.e. those which have their own long distance networks and which you see advertised on TV. You normally encounter an OSP only when you're making a phone call from a hotel or hospital phone, or privately-owned payphone. It's a good idea to ask the operator what the cost of your call will be before you make it.

  2. Online Service Provider. A company that provides content only to subscribers of their service. This content is not available to regular Web surfers. The idea was to build subscription and other revenues from a closed knit group of people. The problem with this idea was the Internet came along and no one any longer could afford a team to compete with the Web's exploding and varied content. So, some online service providers dropped their attempt at content altogether. Others severely limited it. But all were forced to offer (and do offer) access to the Internet. As a result the term "online service provider" has virtually become obsolete, to be replaced by the term, Internet Service Provider.


Open Shortest Path First. My definition is that OSPF is a link-state routing algorithm that is used to calculate routes based on the number of routers, transmission speed, delays and route cost. Here's a longer explanation from Alcatel:

Open Shortest Path First (OSPF) as described in RFC 1245 and RFC 1583 is a routing protocol designed for larger or more complex networks than those typically supported by the Routing Information Protocol (RIP). OSPF uses link state and interior gateway protocols to create a network map on each router and then uses the Dijkstra shortest path algorithm to find the optimum path between network devices. RIP has visibility only to the next hop and uses the distance vector algorithm.

Link state protocol algorithms determine the state of, or status of, each link connected to the router. In a network each router constructs a link state advertisement (LSA) with the status of its links and transmits this to its neighbors. Each router builds a list of all routes to all destinations, based on the compilation of LSAs from each router. Each router identifies which routers and subnets are directly connected to it. Then, it distributes this information to all other routers. OSPF routers take the information and build a table of what the network looks like. Using this table, each router can identify where the sub-networks are located, what routers are in direct connection, and how to get to any specific router.

As an interior gateway protocol, OSPF distributes routing information between routers in a single autonomous system. Once all routers have constructed their databases based on the LSA information, they run the Shortest Path First Algorithm. This results in a tree structure with each router at the "root" of its own tree, and the shortest path to all other destinations mapped out. The selection of the path to these destinations is based on metrics. These metrics may be based on hop count, bandwidth, load, cost, reliability, delay, or controlled statically by the user. This provides the network manager greater control over how routing occurs in the network. Dijkstra's Shortest Path Algorithm is a mathematical process by which it is possible to find the shortest path between points. Essentially , the Dijkstra Shortest Path Algorithm calculates the cost of a path between points beginning with the closest points to the starting point and works its way outward until it reaches the desired end point. A high bandwidth link costs less because more information can be sent across it at one time. Conversely, a lower speed/smaller bandwidth connection costs more because it is not able to send information as quickly. For instance, when sending packets across a 56k point-to-point serial connection there is more delay and overhead than if the same packet was sent over a 100Mbps Ethernet connection. Therefore, it would cost more time to send a transmission over the 56k connection compared to the 100Mbps connection.

OSPF is an excellent protocol in a larger network because it can build a map of large complex networks and then navigate a path between two of the network devices with visibility of the entire network providing the most efficient routing paths possible. Because of its ability to handle large complex networks, OSPF can be complex for the network manager to configure and set up and requires greater computing power within the router. However, OSPF is often the routing protocol of choice when configuring larger networks due to its ability to quickly adapt to network changes (faster route convergence), larger network metrics, area-based topology, low traffic overhead and the ability to support complex address structures and route summarization. Such speed and efficiency means minimized bandwidth usage, faster routing compared to other comparable protocols (RIP, RIPv2), lower network latency and better overall network performance, which is especially useful in networks where bandwidth is at a premium such as in a WAN.


Open Shortest-Path First Internet Gateway Protocol. An experimental replacement for RIP. It addresses some problems of RIP and is based upon principles that have been well- tested in non-internet protocols. Often referred to simply as OSPF. See OSPF.


Optical Shared Protection Ring.


An AT&T word for Operator Services Position System.


Operations Support System. Methods and procedures (mechanized or not) which directly support the daily operation of the telecommunications infrastructure. The average LEC (Local Exchange Carrier) has hundreds of OSSs, including automated systems supporting order negotiation, order processing, line assignment, line testing and billing.


Operator Services Signaling System Number 7.


Operations Support System Interface. An element of DOCSIS (Data Over Cable Service Interface Specification), a project intended to develop a set of specifications for high-speed data transfer over cable television systems. At the head-end of the network, the OSSI provides the interface between the cable modem system and the OSSs. The OSSs, according to the OSI (Open Systems Integration) model, provide for the management of faults, performance, configuration, security and accounting. See also DOCSIS and OSI.


The Optical Storage Technology Association. An international trade association dedicated to promoting the use of writable optical technology for storing computer data and images. With a membership of more than 60, OSTA helps the optical storage industry define practical implementations of standards to assure the compatibility of resulting products. www.osta.org.


Over The Air. See also Preferred Roaming List.


Over-The-Air Service Provisioning. The ability of a wireless carrier to provision new services over the network, rather than requiring the customer to bring the terminal device into a shop for programming.


Operating Telephone Company.


Optical Time Domain Reflectometer, a test and measurement device often used to check the accuracy of fusion splices and the location of fiber optic breakers. See GR.196 and Optical Time Domain Reflectometer.


Operations Technology Generic Requirements.

Other Common Carrier

OCC. In the early days of long-distance competition, providers of long distance telephone service other than with AT&T were called Other Common Carriers. All long distance carriers ” including AT&T ” are now called interex- change carriers.


NTIA's Office of Telecommunications and Information Applications (OTIA) assists state and local governments, educations and health care entities, libraries, public service agencies, and other groups in effectively using telecommunications and information technologies to better provide public services and advance other national goals. This is accomplished through the administration of the Telecommunications and Information Infrastructure Assistance Program (TIIAP), the Public Telecommunications Facilities Program (PTFP) and the National Endowment for Children's Educational Television (NECET). The Telecommunications and Information Infrastructure Assistance Program promotes the widespread use of advanced telecommunications and information technologies in the public and non-profit sectors. The program provides matching demonstration grants to state and local governments , health care providers, school districts, libraries, social service organizations, public safety services, and other non-profit entities to help them develop information infrastructures and services that are accessible to all citizens , in rural as well as urban areas. The program was specifically created to support the development of the National Information Infrastructure. The Public Telecommunications Facilities Program supports the expansion and improvement of public telecommunications services by providing matching grants for equipment that disseminate noncommercial educational and cultural programs to the American public. The main objective of the program is to extend the delivery of public radio and television to unserved areas of the United States. Under the program's authority, funds are also allocated to support the Pan-Pacific Educational and Cultural Experiments by Satellite (PEACESAT) project. PEACESAT provides satellite-delivered education, medical, and environmental emergency telecommunications to many small-island nations and territories in the Pacific Ocean. The National Endowment For Children's Educational Television supports the creation and production of television programming that enhances the education of children. The program provides matching grants for television productions , which are designed to supplement the current children's educational program offerings and strengthen the fundamental intellectual skills of children. In addition, a ten-member national Advisory Council on Children's Educational Television provides advice to the Secretary of Commerce on funding criteria for the program and other matters pertaining to its administration. See www.ntia.doc.gov/otiahome/otiahome.html.

Otlet, Paul

A Belgian lawyer who in his 1934 Traite de Documentation conceived the idea of a Universal Network for Information and Documentation in which access would be gained through multimedia workstations that had not even been invented yet.


See Optical Transport Network.


Abbreviation for "On The Other Hand;" commonly used on E-mail and BBSs (Bulletin Board Systems).


Operations Technical Support. See also Office Telesystem.


Organizationally Unique Identifier: The OUI is a three-octet field in the IEEE 802.1a defined SubNetwork Attachment Point (SNAP) header, identifying an organization which administers the meaning of the following two octet Protocol Identifier (PID) field in the SNAP header. Together they identify a distinct routed or bridged protocol.

Out-of- Band

A LAN term. It refers to the capacity to deliver information via modem or other asynchronous connection.

Out-Of-Band Network Management

A method of managing LAN bridges and routers that uses telephone lines for communications between the network management station and the managed devices. This type of management is normally in addition to the conventional method which uses the LANs and WANs that are being connected by these devices. The principal advantage is that in the event of a system failure (which may take a LAN or a WAN down), a network supervisor can bypass the failed system and use a telephone link to reach a bridge/router to diagnose a network problem. Bridges and routers must have built-in telephone modems for this to work.

Out-Of-Band Signaling

Signaling that is separated from the channel carrying the information. Also known as NFAS (Non Facilities Associated Signaling). In the cellular domain, it is known as NCAS (Non Callpath Associated Signaling). Out-Of-Band Signaling is non- intrusive , as it is carried over separate facilities or over separate frequency channels or time slots than those used to support the actual information transfer (i.e., the call). Thereby, the signaling and control information does not intrude on the information transfer. SS7 (Signaling System 7) is an example of NFAS. The signaling information includes called number, calling number, and other supervisory signals. See also In-Band Signaling, NCAS, NFAS and SS7.


In T-1 transmission, an OOF (Out Of Frame) error occurs when two or more of four consecutive framing bits are in error. When this condition exists for more than 2.5 seconds a RED alarms is sent by OOF detecting unit. Equipment receiving this RED alarm responds with a YELLOW alarm.

Out-Of-Order Tone

A tone which indicates the phone line is broken.

Out-Of-Paper Reception

The ability to receive a facsimile transmission into memory when the facsimile machine is out of paper. The facsimile paper will be printed when you put in new paper.


Or Used. A term used in the secondary telecom equipment business. Equipment taken from service. Can be in any condition. Expected to work and be complete. May not be.


Using a vendor to perform specific network management tasks ; as opposed to "outsourcing" where the whole operation is turned over to an outside vendor. See also Outsourcing.


Service interrupted .

Outage Ratio

The sum of all the outage durations divided by the time period of measurement.

Outdoor Jack Closure

Closures that protect jacks from moisture, dirt and the elements.

Outgoing Access

A ITU description of the ability of a device in one network to communicate with a device in another network.

Outgoing Calls Barred

A switch configuration option that blocks call origination attempts. Only incoming calls are allowed.

Outgoing Line Restriction

The ability of the system to selectively restrict any outgoing line to "incoming only."

Outgoing Sender

Equipment used to transmit call completion information on an interoffice call.

Outgoing Station Restriction

The ability of the system to restrict any given phone from making outside calls.

Outgoing Trunk

A line or trunk used to make calls.

Outgoing Trunk Circuit

Used to carry traffic to a connecting ( distant ) office. depending on the traffic in an individual office. The types of outgoing trunks used will vary depending on the traffic in an individual office.

Outgoing Trunk Queuing

OTQ. Extensions can dial a busy outgoing trunk group, be automatically placed in a queue and then called back when a trunk in the group is available. This feature allows more efficient use of expensive special lines such as WATS or FX. Instead of having to redial the trunk access code until a line is free, the caller can activate OTQ. See also Off-Hook Queuing.

Outgoing WATS

An outgoing WATS (OUTWATS) trunk can only be used for outgoing bulk-rate calls from a customer's phone system to a defined geographical area via the dial-up telephone network. Originally WATS lines came in only lines that could receive calls or lines that could make calls. Now, you can buy a WATS line that handles both incoming and outgoing lines. See WATS.


A set of openings containing electrical contacts into which an electrical device can be plugged. See Outlet Telecommunications.

Outlet Box

A metallic or nonmetallic box mounted within a wall, floor, or ceiling and used to hold telecommunications outlets/connectors or transition devices.

Outlet Cable

A cable placed in a residential unit extending directly between the telecommunications outlet/connector and the distribution device.

Outlet Connector

A connecting device in the work area on which horizontal cable terminates.

Outlet Telecommunications

A single-piece cable termination assembly (typically on the floor or in the wall) and containing one or more modular telecom jacks. Such jacks might be RJ-11, RJ-45, coaxial terminators, etc.


An ATM term. A node whose exclusion from its containing peer group would significantly improve the accuracy and simplicity of the aggregation of the remainder of the peer group topology.

Outline Font

Font is the design of printed letters , like the ones you see on this page. The first type was produced with raised metal or wooden blocks. Put ink on the blocks. Put paper on the inked blocks. Lift paper off. Bingo you have type on paper. Blocks came in fonts ” styles of type, which has neat names like Times Roman, Helvetica, Souvenir, etc. Blocks also came in various sizes ” 10 point, 12 point, 14 point, 36 point, etc. "Point" is simply the name for a way of measuring the size of type, like miles measure distance. When computers came along, they simply copied this technique. You picked type and you picked the size. Printers with print cartridges still work this way. They have to. They could- n't simply take one size font and enlarge or contract it because type enlarged or contracted doesn't look "right." Then two men, John Warnock and Martin Newell, said there had to be a better way and they came up with the idea of an outline font, originally called JaM, then Interpress and now PostScript. In PostScript letters and numbers become mathematical formulas for lines, curves and which parts of the character are to be filled with ink and which parts are not. Because they are mathematical, outline fonts are resolution independent. They can be scaled up or down in size in as fine detail as the printer or typesetter is capable of producing. PostScript outline fonts contain "hints" which control how much detail is given up as the type becomes smaller. This makes smaller type faces much more readable than they otherwise would be. Before outline fonts can be printed, they have to be rasterized. This means that a description of which bits to print where on the page has to be generated. And this is one reason printing outline fonts is so consuming of computer power (whether the power is in the computer or in the printer ” usually it's in both). But it's also the reason why outline fonts, of which PostScript is the most successful and the most common, look so great.

Outpulse Dial

A pushbutton dial which allows rotary dial users the convenience of "Touch-Tone" dialing. Pushing the buttons makes the phone pretend to be a rotary dial phone. This is necessary because touch-tones are not recognized everywhere.


The process of transmitting address information over a trunk from one switching center to another.


Data that flows out of a computer to any device.

Output Device

A device by which a computer transfers its information to the outside world. For example, a monitor, a printer and a speaker.

Output Impedance

The impedance a device presents to its load. The impedance measured at the output terminals of a transducer with the load disconnected and all impressed driving forces taken as zero.

Output Return Loss

A measure of the accuracy of the impedance match between a signal source (such as a cable) and its terminating load. An unequal impedance match causes some of the power from the source to be reflected back to the source, resulting in signal distortion. The ratio of the signal voltage at the load to that voltage reflected back to the source is defined as the return loss. This ratio is generally expressed in decibels (dB).

Output To Output Isolation

The ratio of attenuation provided by the output stage to an interfering signal driving one output compared to a second output. The ratio is measured at the second output. A good specification protects output signals against incorrect cabling, such as accidental untermination or double termination.


Outsourcing software coding jobs to countries like China and India where high tech labor is cheaper.

Outside Line

A term used by PBX users to denote a line connected to the outside world, as opposed to a station line, which essentially is an intercom line. In the US, you usually dial "9" for an outside line to call home to check on the kids. In South Africa, you dial "0." Either way, the kids usually don't appreciate your calling to check on them.

Outside Link

An ATM term. A link to an outside node.

Outside Node

An ATM term. A node which is participating in PNNI routing, but which is not a member of a particular peer group.

Outside Plant

The part of the LEC (Local Exchange Carrier) telephone network that is physically located outside of telephone company buildings . This includes cables, conduits , poles and other supporting structures, and certain equipment items such as load coils. Microwave towers , antennas, and cable-system repeaters traditionally are not considered outside plant. Outside plant includes the local loops from the LEC's switching centers to the customers' premises, and all facilities which serve to interconnect the various switches (e.g., central office and tandem) in the carrier's internal network. Dedicated outside plant comprises physical local loop facilities which are dedicated from the switching center to the customers' premises. See also Dedicated Outside Plant and Inside Plant.

Outside The Box

As in "He thinks outside the box." This is an expression that means he is creative, whatever that means. Where the expression came from is anyone 's guess.


Outsourcing is the contracting by a company of one or more of its internal functions to an outside vendor, one based in the same country or one based in a low- wage country such as China. There's probably nothing you can't outsource Those functions might include running the company's phone systems and telecom networks and/or running the company's computer system. A company might be motivated to do this because they lack the internal resources (e.g., capital budget or staff), or feel they can bring their phone costs into line and those phone costs (or at least certain of them) might now become able to be budgeted with some precision. This has appeal to senior management, who are trying to reduce their uncertainties. This usually has no appeal to lower level management who might be fired , especially if the new corporate outsourcing manager felt they were useless. See also Out-Tasking. An more contemporary word for what we used to call "facilities management."

See also Offshoring.

Outward Restriction

Phone lines within the PBX can be denied the ability to access the exchange network without the assistance of the attendant. Restricted calls are routed to intercept tone.

Outward Trunk Queuing

A process of holding outgoing long distance calls in queue until the appropriate long distance facility is available. See Off-Hook Queuing.


Outward Wide Area Telephone Service. See WATS.


Ground. See Ground Start.

Over Modulation

Occurs when the level of a modulation signal is so high that the processing amplifiers become saturated resulting in clipping of the signal. When a transmitter is over modulated it can put out spurious interference emissions or create " harmful interference."


Refers to radio or television signals received on a local antenna and processed for re-transmission into a television distribution system.


Overbuild traditionally means building more capacity into a network than you really need. Overbuilding has several potential benefits, depending on which side of the equation you find yourself. First, it provides for anticipated growth in traffic requirements. Second, it yields greater revenues for the vendor, although at the expense of the customer. ILECs (Incumbent Local Exchange Carriers) long have been accused of over- building their networks, as the total investment goes into the rate base, on which the carrier realizes a rate of return guaranteed by the regulator . Overbuilding also is known as "gold- plating ." See also Overbuilder.


An overbuilder is a fancy name for a local phone company which runs fiber to your building and on that fiber runs telephone, phone, TV, and data. The idea of an overbuilder is that it rationalizes service provision. That's the benefit to the customer. The benefit to the overbuilder is that he'll suffer far less churn ” as much as 78%, according to numbers I'm hearing.


Paging calls over and above the standard amount of calls allowed to a subscriber. The customer is charged for overcalls.

Overdrive Processor

Intel's name for its line of single-chip performance upgrade chips. Based on Intel486 DX2 "speed doubling" technology, the Intel overdrive processors allow users of Intel486SX systems to double the internal speed of their computer's CPU by adding a single chip, without upgrading or modifying any other system components.

Overfloor Duct Method

A distribution method that uses metal or rubber ducts to protect and conceal exposed wiring across floor surfaces.


Additional traffic beyond the capacity of a specific trunking group which is then offered to another group or line. For example, overflowing calls from WATS lines to (DDD) direct distance dial lines.

Overflow Calls

Calls sent to other answering groups, other call centers, or outside service bureaus to handle peak calling loads. There are planning, training and scheduling issues involved with handling overflow calls.

Overflow Load

The part of an offered load that is not carried. Overflow load equals offered load minus carried load.

Overflow Tie-Line Enhancement

A call center term. Using Overflow Tie- Line Enhancement, non-ISDN calls diverted to an overflow call center now convey the city- of-origin announcement prior to being connected to an agent.

Overflow Traffic

The part of the offered traffic that is not carried, for example, overflow traffic equals offered traffic minus carried traffic.


In communications, all information, such as control, routing and error- checking characters , that is in addition to user-transmitted data. Includes information that carries network status or operational instructions, network routing information, as well as retransmissions of user-data messages that are received in error.

Overhead Bit

A bit other than one containing information. It may be an error checking bit or a framing bit. See Overhead Bits.

Overhead Bits

Overhead bits are bits assigned at the source. They are transmitted with the information payload and are for functions associated with transporting that pay- load.

Overlap Sending

The process of setting up a call by sending dialed digits one at a time, as they are dialed by the originating device. The term comes from the fact that you can key digits faster than an old pulse telephone set with a keypad can send them. In other words, your dialing overlaps the pulses, as the dialing instructions are held in buffer memory in the set until such time as they can be output in pulses. Overlap sending is the way you normally set up a voice call over an analog circuit. Overlap sending also is used in some ISDN BRI (Basic Rate Interface) implementations. A better approach for ISDN is "en-bloc" sending, in which all call setup information is gathered in a block and sent to the network all at once, as in cell phone calls.

Overlapped Phase Trellis-code Interlocked Spectrum



  1. Typically a piece of cut-out cardboard, which you place over several keys on a phone or console. When you punch in a certain code, the buttons become what's written on the programming overlay. Also called a Programming Overlay.

  2. The ability to superimpose computer graphics over a live or recorded video signal and store the resulting video image on videotape. It is often used to add titles to videotape.

  3. A Northern Telecom definition: Generally used to describe some software that is not always memory resident. It is loaded on request. In the Meridian 1 most configuration, administration and maintenance functions are done from a tty terminal using various overlays. Each overlay is designed for a specific task: For example, Overlay 10 is used to configure PBX (500/2500) sets, Overlay 11 is used to configure proprietary sets. Overlay 17 is used to configure I/O ports, Overlay 15 is used to configure customer data, Overlay 48 is used to configure link maintenance, and so on. The Meridian 1 has some 100 overlays. An overlay is loaded from the tty by typing LD nn where is the overlay number. Overlays are exited by typing ****./

  4. See Overlay Area Code.

Overlay Area Code

A new area code which overlays an existing area code. New York's Manhattan has always had 212 as an area code. When the local phone company needed more numbers, it simply added an area code, 917. It originally used that area code for cell phones and beepers, but then it ran out of new numbers and used that area code for new business and home phones. Good . Thus no one had to change their phone number and go through all the expense of printing new stationery and contacting all their customers and friends with their new phone number. In contrast, we have something called a "split" area code. The "authorities" simply say the left hand side of town will have a new area code, which means that all the people and companies on the left side of town now get a new area code, and thus a new phone number. This is a "dumb" idea since it forces a huge number of people and companies to reprint all their stationery and all their customers to change their listings. In contrast an overlay area code allows everyone to keep their old phone numbers, forcing only the new area code on new phone numbers. The problem, according to some state public service commissions is that an overlay area code forces some neighbors to dial 1+area code+a number (i.e. eleven digits) when dialing their neighbors. In today's exploding communicating world, this doesn't seem like too high a price to pay for the huge savings and lack of business disruption. Local public service commissions make the split/overlay decision. For example, a few years ago when Dallas, Texas, ran out of numbers, the local phone companies simply wanted to overlay a new area code ” 972 ” on top of the existing 214 area code. But the Texas PUC refused to allow it for whatever dumb reason. The serious problem with splits is that a customer of five years back may no longer be able to find you. If he dials your old number, he will now get some new company who's never heard of you and you'll lose the sale. I recommend to all my friends that when they get clobbered by an area code split they immediately subscribe to their "old" number, put an answering machine on it, directing everyone who calls it to your new number. See Split Area Code.

Overlay Cell

A cellular/PCS term for an additional cell sector which overlays the underlay cell. Overlay cells are used when traffic regularly exceeds the capacity of an individual cell. The overlay cell handles the excess traffic.

Overlay Network

A separate network for a particular service covering most of the same geographical locations as the basic telephone network, but operating independently. Overlay networks typically are deployed on a selective basis to address performance issues in the existing PSTN (Public Switched Telephone Network). For example, developing countries in Asia and Central/Eastern Europe have built digital microwave overlay networks to serve major businesses, educational institutions, and government offices. Those networks overlay the legacy network, bypassing it and its inherent problems resulting from old, overloaded and poorly maintained infrastructure. Such an approach serves as an immediate stop-gap measure, providing state-of-the-technology voice and data communications capabilities. Eventually, such overlay networks will be fully integrated into the PSTN at such time as the PSTN is upgraded.

Overload Class

OLC. The means used to control system access by mobile stations, typically in emergency or other overload conditions. Mobile phones are assigned one or more of 16 overload classes. Which class you get assigned means your phone will or won't work in the next emergency, e.g. the day of September 11, 2001 when most peoples' mobile phones (including mine) simply ceased to be able to make calls.

Overload Control

How a system responds to being overstressed is called Overload Control. When a system is overloaded, frequently there are so many extra events being processed that the system's actual capacity or throughput goes down. Even though it may be rated at, say 10,000 busy hour calls, when overloaded, for example, with 11,000 calls, the computer telephony system may be only able to process only 8,000 calls.

Overload Management

An AT&T term for handling peak demands by selectively delaying, degrading, or dropping only those portions of traffic flow that are tolerant of those particular types of impairments.

Overload Protection

An uninterruptible power supply (UPS) definition. This feature automatically shuts the unit off when the battery is overloaded in order to protect it against overload damage.


When a circuit already in use is seized. For example, when your boss can break into your telephone conversation.

Override Prompts

The ability of callers and users to key over system prompts.


Loss of data because the receiving equipment could not accept the data at the speed at which it was being transmitted.


Time division multiplexing (TDM) technique where each bit from each channel is sampled more than once.


The image fills the screen from bezel to bezel. The bezel is the metal or plastic part ” in short, the frame ” that surrounds a cathode ray tube ” a "boob" tube. NEC's term for overscan is "full scan."


Condition in which the transmitting device runs slightly faster than the data presented for transmission. Overspeeds of 0.1% for data PABXs are typical.


In frame relay, this refers to a situation in which a device is transmitting over a circuit at a rate greater than the target device can receive the data over a circuit. For instance, the transmitter may be pumping data at 128 Kbps over a T-1 circuit, while the receiver has only a 64 Kbps circuit connection to the network. In such an instance, the network will impose flow control, adapting to the rate of reception within the limits of its buffering capability. Once that limit is reached, the network is oversubscribed. In order to maintain its ability to support "normal" traffic requirements of users in the aggregate, the network will mark the excess frames as Discard Eligible and spill them onto the switchroom floor for the night shift to clean up. (Just kidding about the switchroom floor part.) As always, it is the responsibility of the end user equipment to detect the fact that this had occurred and to recover through retransmission of the discarded frames . See DE.

Overtime Period

Those minutes of use of a telephone service beyond the initially defined period for which a basic charge is quoted. The initial period on many calls is one or three minutes. After that, the next minute is overtime.


Proteon's architecture for products conforming to SNMP.


A call center term. To replace the contents of something ” a file or record, for example ” with new data.


Open Video Systems, the successor to Video Dialtone.


See Optical Virtual Tributary Group.


When I take charge of a project, a product, a feature or whatever I "own" it. I am now responsible for it. "Own" is Microsoft jargon. But it's moving into mainstream corporate America.


Microsoft jargon for person in charge. See also Own.


Operator Workstation. See Operator Workstation.


Operator Work Time.


Optical Cross-Connect. A device that serves to physically interconnect multiple optical fibers on an automated basis, thereby allowing optical signals to be directed and redirected from any of many input fibers to any of a number of output fibers without the requirement for a technician to manually connect and reconnect the fibers. In other words, an OXC is much like an automated patch panel, or cross-connect block, for DWDM (Dense Wavelength Division Multiplexing) optical networks. An OXC can take several forms. An FXC (Fiber Switch Cross-Connect) switches all of the wavelength channels from one input fiber to one output fiber. A WSXC (Wavelength Selective Cross Connect) can switch a subset of the wavelength channels from one input fiber to an output fiber, in which case the wavelength channels must first be demultiplexed. A WIXC (Wavelength Interchanging Cross-Connect) is a WSXC with the additional ability to change the wavelength (i.e., optical frequency) of an input channel on an input fiber to another wavelength on an output channel on an output fiber. See also DWDM.


A phrase that contains an obvious contradiction. Examples include jumbo shrimp, gourmet food, military intelligence, accurate billing and constructive criticism.

Newton[ap]s Telecom Dictionary
Newton[ap]s Telecom Dictionary
ISBN: 979387345
Year: 2004
Pages: 133

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