Ensemble Designs BrightEye 20 Analog and Digital Audio Embedder or Disembedder - Manual (Page 19)

TM BrightEye 20
Multi-mode
Multi-mode fibers have a larger diameter core (either 50 or 62.5 microns), and a
correspondingly larger aperture. It is much easier to couple light energy into a
multi-mode fiber, but internal reflections will cause multiple “modes” of the signal
to propagate down the fiber. This will degrade the ability of the fiber to be used
over long distances.
See also Single mode.
NTSC
The color television encoding system used in North America was originally
defined by the National Television Standards Committee. This American
standard has also been adopted by Canada, Mexico, Japan, Korea, and Taiwan.
(This standard is referred to disparagingly as Never Twice Same Color.)
Optical
An optical interface between two devices carries data by modulating a light
source. This light source is typically a laser or laser diode (similar to an LED)
which is turned on and off at the bitrate of the datastream. The light is carried
from one device to another through a glass fiber. The fiber’s core acts as a
waveguide or lightpipe to carry the light energy from one end to another. Optical
transmission has two very significant advantages over metallic copper cables.
Firstly, it does not require that the two endpoint devices have any electrical con-
nection to each other. This can be very advantageous in large facilities where
problems with ground loops appear. And secondly, and most importantly, an
optical interface can carry a signal for many kilometers or miles without any
degradation or loss in the recovered signal. Copper is barely useful at distances of
just 1000 feet.
Oversampling
A technique to perform digital sampling at a multiple of the required sample rate.
This has the advantage of raising the Nyquist Rate (the maximum frequency
which can be reproduced by a given sample rate) much higher than the desired
passband. this allows more easily realized anti-aliasing filters.
PAL
During the early days of color television in North America, European broadcast-
ers developed a competing system called Phase Alternation by Line. This slightly
more complex system is better able to withstand the differential gain and phase
errors that appear in amplifiers and transmission systems. Engineers at the BBC
claim that it stands for Perfection At Last.
Progressive
An image scanning technique which progresses through all of the lines in a frame
in a single pass. Computer monitors all use progressive displays. This contrasts
to the interlace technique common to television systems
SMPTE
The Society of Motion Picture and Television Engineers is a professional organi-
zation which has done tremendous work in setting standards for both the film
and television industries. The term “SMPTE’” is also shorthand for one particular
component video format - luminance and color difference.
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