attenuation
The decrease in signal strength along a fiber optic waveguide caused by absorption and scattering.
Attenuation is usually expressed as dB/km.
attenuator
A passive device that reduces the amplitude of a signal without distorting the waveform.
automatic power shutdown (APSD)
A technique (procedure) to automatically shutdown the output power of optical amplifiers to
avoid exposure to hazardous levels.
automatic protection switching (APS)
A network survivability method in which traffic is automatically switched to a protection route
when a failure is detected on a working route.
autonomous message
Message sent by the system to the CIT to notify it of any state change in the system. Autonomous
messages are not responses to a CIT-initiated command. Examples of these messages include
alarms, events (non-alarmed condition), notification of connections that are added or deleted, and
changes in the system database.
avalanche photodiode (APD)
A photodetector that can be regarded as the semiconductor analog to photomultipliers. By
applying a high reverse bias voltage (typically 100-200 V in silicon), an APD shows an internal
current gain effect (around 100) due to impact ionization (avalanche effect).
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B back reflection
See “Fresnel reflection” (p. GL-11).
background block errors (BBE)
Errors identified through OTN performance monitoring.
backward defect indication (BDI)
The OT port has detected a Backward Defect Indication at the ODUk Path layer. This defect
indicates that the peer OTUk port has detected condition that is treated as Server Signal Failure.
band optical filter (BOF)
A band-dependent optical card.
bay
An aluminum steel enclosure for rack-mounted equipment. Also know as a rack.
BB
See “broadband” (p. GL-4) for definition.
BBA
See “broadband amplifier” (p. GL-4) for definition.
Glossary
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1830 PSS-36/PSS–32/PSS-16/PSS-4
8DG60888CAAA Release 3.6.0 and 3.6.1
Issue 1 June 2011
GL-3
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