optical network unit (ONU)A network element that is part of a fiber-in-the-loop system interfacing the customer analog access cables and the fiber facilities. [T1.508-1998]
optical path lengthIn a medium of constant refractive index, n, the product of the geometric distance and the refractive index. 2.
optical path power penaltyThe extra optical power required to account for degradations due to reflections, intersymbol interference, and mode partition noise. [T1.646-1995]
optical power budgetIn a fiber-optic communication link, the allocation of available optical power (launched into a given fiber by a given source) among various…
optical power marginIn an optical communications link, the difference between (a) the optical power that is launched by a given transmitter into the fiber, less transmission…
optical receiverA device that detects an optical signal, converts it to an electrical signal, and processes the electrical signal as required for further use.
optical repeaterIn an optical communication system, an optoelectronic device or module that receives an optical signal, amplifies it (or, in the case of a digital signal…
optical return loss (ORL)The ratio (in dB) of optical power arriving at the interface (P1) to the optical power reflected back from the same interface (P2). [T1.106-1988]
optical sectionThe part of the physical plant consisting of the fiber-optic cabling and connectors interconnected to provide the transport function between two adjacent…
optical sourceIn optical communications, a device that converts an electrical signal into an optical signal.
optical spectrumBy custom and practice, the electromagnetic spectrum between the wavelengths of the vacuum ultraviolet at 0.001 m and the far infrared at 100 m.
optical switchA switch that enables signals in optical fibers or integrated optical circuits (IOCs) to be selectively switched from one circuit to another.
optical thicknessThe product of the physical thickness of an isotropic optical element and its refractive index. 2.
optical time domain reflectometer (OTDR)An opto-electronic instrument used to characterize an optical fiber. Note 1: An OTDR injects a series of optical pulses into the fiber under test.
optical transmitterA device that accepts an electrical signal as its input, processes this signal, and uses it to modulate an opto-electronic device, such as an LED or an…
optical waveguideAny structure having the ability to guide optical energy. Note: Optical waveguides may be (a) thin-film deposits used in integrated optical circuits…
optically active materialA material that rotates the plane of polarization of light that passes through it.
opto-electronicPertaining to any device that functions as an electrical-to-optical or optical-to-electrical transducer, or an instrument that uses such a device in its…
orange bookNickname name for the United States Department of Defense "Trusted Computer System Evaluation Criteria", DOD 5200.28-STD [CESG]. Also known as "TCSEC"
orbitThe path, relative to a specified frame of reference, described by the center of mass of a satellite or other object in space subjected primarily to…
orbit determinationThe process of describing the past, present, or predicted position of a satellite in terms of orbital parameters. [JP 1-02]
order of diversityThe number of independently fading propagation paths or frequencies, or both, used in diversity reception.
orderwire circuitA voice or data circuit used by technical control and maintenance personnel for coordination and control actions relative to activation, deactivation…
orderwire multiplexA multiplex carrier set specifically designed for the purpose of carrying orderwire traffic, as opposed to one designed for carrying mission traffic.
OrganizerAny person who discovers, creates, investigates, or initiates the tax shelter investment, devises the business or financial plans for the investment or…
originating connectionThe connection between the termination of a user-network interface and an operator service access point that is used for communication between the user…
originating endpointIn a wideband packet node, the point that receives channelized traffic, packetizes it, and sends it into the wideband packet network. [T1.509-1995]
originating line-side accessThe ability to dial the appropriate 7- or 10-digit test number from a subscriber line. [T1.207-2000]
originating point code (OPC)A part of the routing label in a signaling message that uniquely identifies the originating point of that signaling message in a signaling network. [T1.
originating trunk-side accessThe ability to dial the appropriate test line number with trunk access using the appropriate test equipment. [T1.207-2000]
originating userThe user that initiates a particular information transfer transaction. Note: The originating user may be either the source user or the destination user.
origination networkThe signaling network that initiates a non-circuit-related message containing intermediate signaling network indication (ISNI) information; this network…
originatorThe acronym for the agency that is the original source of the data. The source for nearly all map layers created by OCTO that are not part of the…
orthogonal multiplexA method of combining two or more digital signals that have mutually independent pulses, thus avoiding intersymbol interference.
orthogonal samplingIn digital video, a sampling where the luminance and the color-difference samples are generated from pixels arranged in common, continuous vertical and…
orthomode transducerA device forming part of an antenna feed and serving to combine or separate orthogonally polarized signals.
oscillatorAn electronic circuit designed to produce an ideally stable alternating voltage or current.
other common carrier (OCC)A communications common carrier--usually an interexchange carrier--that offers communications services in competition with AT&T and/or the established U.S.
out callA universal personal telecommunications (UPT) call type that permits a UPT user to make calls from any terminal on any network, and have access to his/her…
out-call registrationA feature that enables the universal personal telecommunications (UPT) user to register for outgoing calls from the current terminal address to allow…
out-of-areaAn area not included in the subscribed service. An area may be defined in terms of a state/province, NPA, LATA, etc. [T1.207-1998]
out-of-band emissionEmission on a frequency or frequencies immediately outside the necessary bandwidth which results from the modulation process, but excluding spurious…
out-of-band notificationIn encryption, notification using a communication means other than the primary communication means. [After X9.49]
out-of-band signalingSignaling that uses a portion of the channel bandwidth provided by the transmission medium, e.g.
out-of-frame-alignment timeThe time during which frame alignment is effectively lost. Note: The out-of-frame-alignment time includes the time to detect loss of frame alignment and…
out-slot signalingSignaling performed in digital time slots that are not within the channel time slot.
outage thresholdFor a supported performance parameter of a system, the value that establishes the minimum performance level at which the system is considered to remain in…
outgoing accessThe ability of a user to originate data calls via an ISDN. [T1.615-1992]
outpulsingThe process of transmitting address information over a trunk from one switching center or switchboard to another.
output1. Information retrieved from a functional unit or from a network, usually after some processing. 2. An output state, or sequence of states. 3.
output ratingThe expression of the stated power available at the output terminals of a transmitter when connected to the normal load or its equivalent. 2.
outside plant1. In telephony, all cables, conduits, ducts, poles, towers, repeaters, repeater huts, and other equipment located between a demarcation point in a…
ovalityThe attribute of an optical fiber, the cross section of the core or cladding of which deviates from a perfect circle. 2.
over-the-air key distributionProviding electronic key via over-the-air rekeying, over-the-air key transfer, or cooperative key generation. [INFOSEC-99]
over-the-air key transferElectronically distributing key without changing traffic encryption key used on the secured communications path over which the transfer is accomplished.
over-the-air rekeying (OTAR)Changing traffic encryption key or transmission security key in remote crypto -equipment by sending new key directly to the remote crypto-equipment over…
over-the-horizon radarA radar system that makes use of the atmospheric reflection and refraction phenomena to extend its range of detection beyond line of sight.
overfillThe condition that prevails when the numerical aperture of an optical source, such as a laser, light-emitting diode, or optical fiber, exceeds that of the…
overflowIn telephony, the generation of potential traffic that exceeds the capacity of a communications system or subsystem. 2.
overhead bitAny bit other than a user information bit.
overhead informationDigital information transferred across the functional interface between a user and a telecommunications system, or between functional units within a…
overlap pulsingAn arrangement for exchange-carrier-to-interexchange carrier (EC-to-IC) outpulsing that allows seizure of the EC-to-IC trunk and initiation of outpulsing…
overlay cellA larger cell that physically overlays one or more smaller cells. For example, intra-building cells may be encompassed by a larger campus cell. [T1.
OverloadTo exceed the design capacity of a device.
overmodulationThe condition that prevails when the instantaneous level of the modulating signal exceeds the value necessary to produce 100% modulation of the carrier.
overrideTo preempt, manually or automatically, a prescribed procedure. Note: For example, one might manually override a prescribed course of action programmed to…
overshootThat portion of an arc digitized past its intersection with another arc. See also dangling arc.
overt channel[A] Communications path within a computer system or network designed for the authorized transfer of data. [INFOSEC-99]
overtoneOf a sinusoidal wave, an integral multiple of the frequency, i.e., the fundamental, of the wave, other than the fundamental itself.
overwrite procedure[The] Process of writing patterns of data on top of the data stored on a magnetic medium. [INFOSEC-99]