Animated Optical Glossary
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EXFO Glossary

B (browse from .......... to)
b...............BBUBc...............Bit-Error-Rate Test (BERT)Bits per Second (bit/s or bps or b/s)...............Byte (B)
BBase Station Controller (BSC)BB_Credit
B8ZSBase Transceiver Station (BTS)BB_Credit_CNT
BackhaulBaseband UnitBBER
Backoff DelayBasic-Rate Integrated-Services Digital Network (BRI-ISDN)BBU
BackscatterBaud Rate
from b... to BBU


Acronym for: Bit (one binary digit)


Acronym for: Byte (group of 8 bits)


Part of the network that joins several local-area networks, either inside a building or across a city or country. This is achieved through a cable connection between telecommunication or wiring closets, floor distribution terminals or entrance facilities. In star networks, the backbone cable interconnects hubs and similar devices, as opposed to cables running between hub and station. The backbone is the part of the communications network that carries the heaviest traffic.


Intermediate links (network) between the core network (backbone network) and the small subnetworks at the "edge" of the entire hierarchical network (e.g. FTTH, DSL, DAS, RRH, etc.)

Backoff Delay

In Ethernet transmission, the backoff delay is the length of time that a station waits before retransmitting a frame, after a data collision is detected. This operation applies to carrier-sense multiple access networks with collision detect (CSMA/CD).


The portion of Rayleigh scattered light that returns directly to the source. Backscatter light levels are measured by an OTDR to determine optical power, distance, splice loss and reflection.


The range of frequencies required for proper transmission of a signal. Bandwidth represents the amount of data that can be transmitted through a communications channel in a fixed amount of time. For digital devices, it is usually expressed in bits (or bytes) per second, whereas for analog devices, it is expressed in cycles per second, or in hertz (Hz). The greater the bandwidth, the greater the information-carrying capacity and the faster the speed. A continuous frequency range starting from zero is said to be baseband, while a range starting substantially above zero is considered broadband.

Base Station Controller (BSC)

Provides the intelligence behind the BTSs. Typically a BSC has tens or even hundreds of BTSs under its control. The BSC handles allocation of radio channels, receives measurements from the mobile phones, and controls handovers from BTS to BTS.

Base Transceiver Station (BTS)

Contains the equipment for transmitting and receiving radio signals (transceivers), antennas, and equipment for encrypting and decrypting communications with the base station controller (BSC).


A transmission method in which one single digital signal uses an entire bandwidth. The unmodulated signal is sent directly over the transmission medium. Baseband is simpler, cheaper and less sophisticated than broadband. All Ethernet media types are baseband except for 10Broad36, which is broadband.

Baseband Unit

A baseband unit (BBU) is a unit that processes baseband in telecomm systems.

Basic-Rate Integrated-Services Digital Network (BRI-ISDN)

The basic-rate ISDN interface provides two 56/64 kbit/s channels (called B channels) to carry voice or data and one 16 kbit/s signaling channel (the D channel) for signaling/call information.

Baud Rate

The actual symbol frequency being used to transmit data. The term baud rate is often used incorrectly as an equivalent to bits per second (bit/s, bps or b/s). For example, both ITU-T V.22bis (2400 b/s) and V.22 (1200 b/s) modems transmit data at 600 bauds, but V.22bis modems use four bits per symbol and V.22 modems use two.


Acronym for: Buffer-to-buffer credit count


Acronym for: Background block error


Acronym for: Background block error ratio