The Concept
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Audio system
installers are always looking for better ways of getting audio and
data distributed around large facilities. One popular transmission
medium is fiber optic cable. Fiber optic cable can be used to transmit
almost any type of signal by converting the electrical signal to light,
then back to electrical at the remote end. Fiber is already used extensively
by telephone companies and is used in many large network applications.
It works well at almost any signal frequency, can be used for very
long distances, and provides total electrical isolation without the
threat of interference. Fiber optic cable, though not used as extensively
in the audio industry, can be a powerful tool when properly integrated
in medium to large audio installations. |
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Applications
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In an IQ Network, there are
two very general applications for fiber optic cable. The first is
transmission of audio from a central source to satellite amplifiers
located in remote equipment rooms. The second is transmission of data
for system control. Depending on various factors, fiber can be used
for either or both, and in some cases audio and data can even travel
over the same fiber strand. |
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Analog vs. Multiplexed Fiber
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There are two basic types of fiber transceiver equipment.
Analog transceivers convert one electrical signal into one light
signal, then back again at the other end. Multiplexing transceivers
can take multiple signals and transmit them simultaneously over
the same fiber strand. This is done by digitally sampling lower
frequency signals at a very high frequency and synchronizing them
for transmission on a time-share basis. The same principles can
be applied to wire, however the high efficiency and small size of
fiber cable makes this a very economical method of getting large
numbers of signal around a large facility.
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Analog Transceivers
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Analog fiber transceivers take a single signal and
converts it to light, then back again at the remote end of the fiber
strand. The most significant advantage of using analog transceivers
in an audio application with IQ is cost and simplicity. This is
particularly true when only the data of the IQ Bus data loop or
RS-232 needs to be transmitted a long distance. There are many off
the shelf fiber transceivers on the market for RS-232. The IQ Bus,
however, is designed for normal operation on twisted pair wire as
a 20 milli-amp current loop. When converted to fiber, special electronics
are required at the transceiver for proper conversion. Crown is
not a fiber optic manufacturer, however, Crown does work closely
with fiber transceiver manufacturers. One company that does have
an analog fiber transceiver designed specifically for the IQ Bus
serial data loop is Fiber Options.
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Multiplexing Transceivers
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Where data and audio need to travel down the same
fiber strand, it is necessary to multiplex multiple channels together.
This can be done with a multiplexing transceiver. Multiplexes sample
several audio and/or data channels and convert all the signals to
high frequency digital information. At the remote end of the strand,
a demultiplexer takes the synchronized data, divides the channels,
and converts the signals back to their original form. Like analog
transceivers, the multiplexers must also be able to receive and
transmit the 20 milli-amp current loop information, thus requiring
similar special electronics. B.E.C. Technologies, an Orlando, Florida,
based company, manufactures such equipment. Multiplexing audio and
data may be more expensive, however the total cost depends on the
type and quantity of signals that need to be shipped around a facility.
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Fiber Optic Cable
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There are at least a dozen fiber transceiver companies
in the U.S. alone. We have mentioned two by name due to their history
of working with the IQ Network. There are probably twice as many
manufacturers of fiber cable. The cable can come in various forms,
with various specifications. For use with IQ, we strongly recommend
that the cable you select be of high quality and durability.
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Fiber Concerns
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Fiber has advantages
and disadvantages. If it were the perfect transmission medium, it
would be far more widely used than it already is. Many of the advantages
are described above. For short cable lengths fiber is often cost prohibitive.
Tools used to terminate wire are general inexpensive and easy to obtain,
whereas fiber tools are usually more expensive. Fiber terminations
should only be made by trained professionals since very special care
must be taken. If the tip of a wire breaks, removing a short length
of sleeving usually takes care of it. If the tip of a fiber strand
breaks, the end must be polished and processed and a new terminator
must be installed. Also, fiber can splinter and be a serious health
hazard if improperly handled.
As it pertains to IQ, the biggest reason most people jump on fiber
for transmission of the IQ Bus is to extend the length of the IQ Bus
long distances, such as between remote equipment rooms. This is a
valid reason to use fiber, but using fiber does not automatically
imply that Crown
IQ-RPT Repeaters are not still needed. Fiber transceivers, like
the wire or loop components, can add degredation to the IQ Bus data
signal. Fiber transceivers do not reconstruct the loop. Repeaters
are often required in installations using fiber to make up for signal
loss in the transceivers and remaining wiring. |
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Fiber Transceiver Manufacturers
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As mentioned before, Fiber
Options and B.E.C. Technologies are two companies that have transceivers
available specially designed for the IQ Bus. For more information
contact: |
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Fiber Options
80 Orville Drive
Suite 102
Bohemia, NY (U.S.A.) 11716-2506
Phone 516-567-8320 or in the U.S.A.: 800-342-3748
Internet: www.fiberoptions.com |
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B.E.C. Technologies
9460 Delegates Drive
Orlando, Florida (U.S.A.) 32837-8346
Phone 407-855-8181
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IQ Compatibility
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The IQ Bus is defined as
a carrier of IQ protocol on a serial data loop. Though it normally
operates as a 20 milli-amp current loop, the definition leaves open
the choice of mediums. Fiber optic cable is one alternative. The type
of transmission media, be it twisted pair wire, fiber optic cable,
or anything else, is without regard to the actual data information
being communicated. It necessarily must meet the fundamental hardware
requirements for interconnection with IQ Network hardware, however
there are no compatibility issues to consider regarding the protocol
itself. |
