CSIS 160

Josh Ancel

Chapter 11

Terms

 

  1. Phantom Circuits –

 

 

 

  1. Frequency Division Multiplexing – a multiplexing technique that uses different frequencies to combine multiple streams of data for transmission over a communications medium. FDM assigns a discrete carrier frequency to each data stream and then combines many modulated carrier frequencies for transmission. For example, television transmitters use FDM to broadcast several channels at once.
  2. Time Division Multiplexing – a type of multiplexing that combines data streams by assigning each stream a different time slot in a set. TDM repeatedly transmits a fixed sequence of time slots over a single transmission channel. Within T-Carrier systems, such as T-1 and T-3, TDM combines Pulse Code Modulated (PCM) streams created for each conversation or data stream.
  3. Wavelength Multiplexing – a type of multiplexing developed for use on optical fiber. WDM modulates each of several data streams onto a different part of the light spectrum. WDM is the optical equivalent of FDM.
  4. Amplitude modulation – is the modulation method used in the AM radio broadcast band. In this system the intensity, or amplitude, of the carrier wave varies in accordance with the modulating signal. When the carrier is thus modulated, a fraction of the power is converted to sidebands extending above and below the carrier frequency by an amount equal to the highest modulating frequency
  5. Frequency Modulation – the frequency of the carrier wave is varied in such a way that the change in frequency at any instant is proportional to another signal that varies with time. Its principal application is also in radio, where it offers increased noise immunity and decreased distortion over the AM transmissions at the expense of greatly increased bandwidth. The FM band has become the choice of music listeners because of its low-noise, wide-bandwidth qualities; it is also used for the audio portion of a television broadcast.
  6. Pulse Code Modulation – PCM can be used to send digital data; audio signals on a compact disc use pulse code modulation. Developed in 1939 by the English inventor Alec H. Reeves, pulse code modulation is the most important form of pulse modulation because it can be used to transmit information over long distances with hardly any interference or distortion; for this reason it has become increasingly important in the transmission of data in the space program and between computers. Although PCM transmits digital instead of analog signals, the modulating wave is continuous. Digital modulation begins with a digital modulating signal. The two most common digital modulating techniques are phase-shift keying (PSK) and frequency-shift keying (FSK).
  7. Bits – Short for binary digit, sets of ones and zeros used to convey information in a pulse code or binary algebraic expression.
  8. Bytes – eight bits equal 1 byte. This is an other measurement of binary algebra. And is used in all digital data communications.

 

 

 

  1. Channel Bank –

 

 

 

  1. Spans –

 

 

 

  1. ESF –

 

 

 

  1. CRC-6 –

 

 

 

  1. SLC –

 

 

 

  1. TASI –

 

 

 

  1. ADSL –

 

 

 

 

 

 

FYI

Dense Wavelength Division Multiplexing, an optical technology used to increase bandwidth over existing fiber optic backbones.

DWDM works by combining and transmitting multiple signals simultaneously at different wavelengths on the same fiber. In effect, one fiber is transformed into multiple virtual fibers. So, if you were to multiplex eight OC -48 signals into one fiber, you would increase the carrying capacity of that fiber from 2.5 Gb/s to 20 Gb/s. Currently, because of DWDM, single fibers have been able to transmit data at speeds up to 400Gb/s. And, as vendors add more channels to each fiber, terabit capacity is on its way.

A key advantage to DWDM is that it's protocol and bit-rate independent. DWDM-based networks can transmit data in IP, ATM, SONET /SDH, and Ethernet, and handle bit-rates between 100 Mb/s and 2.5 Gb/s. Therefore, DWDM-based networks can carry different types of traffic at different speeds over an optical channel.

From a QoS (Quality of Service) stand point, DWDM-based networks create a lower cost way to quickly respond to customers' bandwidth demands and protocol changes.