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Term Definition
Abrasion mark

A flaw on an optical surface usually caused by an improperly polished termination end.

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The loss of power (signal) in an optical fiber resulting from conversion of optical power (specific wavelengths of light energy into heat.Caused principally by impurities,such as water, ions of copper or chromium (transition metals), and hydroxyl ions, and by exposure to nuclear radiation. Expressed in dB/km (decibels per kilometer).Absorption and scattering are the main causes of attenuation(loss of signal) of an optical waveguide during transmission through optical fiber.

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Abstract syntax notation (ASN) 1

Used to describe the language interface standards for interconnection of operating systems, network elements,workstations, and alarm functions.

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Acceptance angle

With respect to optical-fiber cable, the angle within which light can enter an optical fiber core of a given numerical aperture and still reflect off the boundary layer between the core and the cladding. Light entering at the acceptance angle will be guided along the core rather than reflected off the surface or lost through the cladding. Often expressed as the half angle of the cone and measured from the axis. Generally measured as numerical aperture (NA); it is equal to the arcsine. The acceptance angle is also known as the cone of acceptance,or acceptance cone. See also numerical aperture.

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Acceptance cone

The cross section of an optical fiber is circular; the light waves accepted by the core are expressed as a cone. The larger the acceptance cone, the larger the numerical aperture(NA); this means that the fiber is able to accept and propagate more light.

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Acceptance pattern

The amount of light transmitted from a fiber represented as a curve over a range of launch angles. See also acceptance angle.

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Access coupler

An optical device to insert or withdraw a signal from a fiber from between two ends. Many couplers require connectors on either end, and for many applications they must be APC (angled physical contact) connectors. The most popular access coupler is made by the fused biconic taper process, wherein two fibers are heated to the softening point and stretched so that the mode fields are brought into intimate contact, thus allowing a controlled portion of light to move from one core to the other.

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Access method

Rules by which a network peripheral accesses the network medium to transmit data on the network. All network technologies use some type of access method;common approaches include Carrier Sense Multiple Access/Collision Detection (CSMA/CD), token passing, and demand priority.

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Acknowledgment (ACK)

A message confirming that a data packet was received.

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Active branching device

Converts an optical input into two or more optical outputs without gain or regeneration.

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Active coupler

A device similar to a repeater that includes a receiver and one or more transmitters. The idea is to regenerate the input signal and then send them on. These are used in optical fiber networks.

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Active laser medium

Lasers are defined by their medium; laser mediums such as gas, (CO2, helium, neon) crystal (ruby) semiconductors, and liquids are used. Almost all lasers create coherent light on the basis of a medium being activated electronically. The stimulation can be electronic or even more vigorous, such as exciting molecular transitions from higher to lower energy states, which results in the emissions of coherent light.

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Active monitor

In Token Ring networks, the active monitor is a designated machine and procedure that prevents data frames from roaming the ring unchecked. If a Token Ring frame passes the active monitor too many times, it is removed from the ring. The active monitor also ensures that a token is always circulating the ring.

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Active splicing

A process performed with an alignment device, using the light in the core of one fiber to measure the transmittance to the other. Ensures optimal alignment before splicing is completed. The active splicing device allows fusion splicing to perform much better with respect to insertion losses when compared to most connectors and splicing methods. A splicing technician skilled at the use of an active splicing device can reliably splice with an upper limit of 0.03dB of loss.

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Antenna Control Unit

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