XO Communications 2009 Annual Report Download - page 22

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T1. A data communications circuit capable of transmitting data at 1.544 Mbps.
Tbps (terabits per second). 10
12
bits of information per second. The information carrying capacity of a
circuit may be measured in Tbps.
Time Division Multiplexing, or TDM. A technique used to combine multiple signals into one single
high-speed transmission path. TDM assigns each signal (voice, data or video) a time slot within a set that
enables multiple lower-speed signals to be transmitted simultaneously over one high-speed transmission.
Unbundled Network Elements, or UNE. The telecommunications network that the ILECs are required to
make available to CLECs. Together, these parts make up a local loop that connects to a digital subscriber
line access multiplexer, a voice switch or both. The loop allows non-facilities-based telecommunications
providers to deliver service without laying network infrastructure, such as copper wire, optical fiber, and
coaxial cable.
Universal Service Fund, or USF. The USF was created by the FCC in 1997 as part of the goals
mandated in the Telecommunications Act of 1996. USF’s creation requires telecommunications service
providers to contribute to support USF’s programs which involve making quality services available at
affordable rates throughout the country and especially targets low-income, rural health care, schools,
libraries and high cost areas.
Voice over Internet Protocol, or VoIP. The technology used to transmit voice conversations over a data
network using the Internet Protocol.
Virtual Private Network, or VPN. A private network that operates securely within a public network by
means of encrypting transmissions.
Wave Division Multiplexing, or WDM. Equipment that effectively multiplies the carrying capacity of
fiber by integrating multiple signals or channels onto a single fiber strand, with each channel correspond-
ing to a unique wavelength of light, typically in the 1530-1565 nanometer range (infrared). WDM
equipment is classified as Dense Wave Division Multiplexing (“DWDM”) or Coarse Wave Division Mul-
tiplexing (“CWDM”), depending on the spacing between wavelengths and hence the density of
wavelengths.
Wave Division Multiplexing Transmission. The conveyance of multiple communications signals using
WDM equipment.
Wavelength. A point-to-point communications channel provisioned on a fiber optic network built using
WDM equipment.
Wireless Backhaul. Movement of telecommunications traffic between cell sites and points of connection
to wired networks.
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