1. Is Fiber Optic right for your AV System Design?
Audio video over fiber optics, specifically video, can be a great solution when the need arises. Let’s look
at what it takes to decide on your AV system needs. There’s more to selecting fiber than just the need
for a long run. Let’s look at everything, and help you make the best choice.
Unlike traditional copper cable systems, fiber does not have such severe distance or bandwidth
limitations. Most designers use fiber because they have distance issues that cannot be alleviated using a
traditional copper cable system, however; there is a trend in the market that is shifting towards using AV
over fiber as a complete AV system solution. Security and convenience are also factors, which we will
discuss, but let’s look at limitations first.
In today’s AV world, video has grown exponentially. From standard analog video up to 4K and 8K digital
video signals, bandwidth requirement has increased as well. The advent of higher resolutions has
created a need for additional information, such as deep color, HDCP handshaking, EDID and CEC controls
to name some. Non-video information is just as important in modern systems, RS-232, USB, and of
course audio (which has also expanded in its size and complexity). Copper cable systems have come a
long way, but their threshold is anywhere from 100 to 500 feet. The more information being used in
copper systems, the shorter the length of cable that may be used without anomalies. Fiber optic cable
can take the same set of signals over 15 miles in a single run, depending on the algorithm and cable
used. Using repeaters or proprietary buffers, these distances can be increased almost infinitely. As your
clients needs for bandwidth increases, are you meeting those needs?
There are 2 common methods that manufacturers transmit data through fiber optic cabling, TDM (time
division multiplexing) and WDM (wavelength division multiplexing). TDM combines all of the signals
necessary (AV and control, USB, etc.) and converts them into a single optical wavelength. WDM divides
these signals into separate wavelengths, on different parts of the light spectrum, and separates them
with unused frequencies to keep each signal’s integrity (called channel spacing). Some systems use
either TDM or WDM, and some use a combination of both. TDM is best for unidirectional
communication (like AV streams) while WDM is best used in bi-direction communication. Typically a
TDM system will take (2) cables, one for each direction, and a WDM system will only need one, but a
TDM system has the ability to travel much further than a WDM system.
Skew loss is the main distance limitation when it comes to using AV over fiber. Manufacturer’s have an
acceptable amount of skew loss that they consider acceptable. When designing a fiber optic system, it is
best to try and mitigate any signal losses in the transmission of the signal pathways. This is called a loss
budget. Depending on certain factors, connector loss, splice loss, cable distance, you can calculate your
loss budget to optimize your fiber optic system. Many manufacturers have pre-configured a certain
amount of loss into their system when putting it onto the marketplace, but being cautious of your
controllable losses, you may optimize the distances and the quality of your system. Using the
manufacturer’s recommended cabling and connectors will assist in this mitigation.

2. There are commonly two different calculations required to calculate a loss budget with fiber. Each
assumes that there are known values for different sets of variables. One is the maximum signal loss
across a piece of pre-existing fiber and the other is maximum fiber distance given known budget and
loss variables. The first calculation below will calculate signal loss through a known length of fiber.
Calculating maximum signal loss is simply the sum of all worst case variables within a fiber segment.
The numbers shown in the table above are average losses. Actual losses could be higher or lower
depending upon many factors.
Fiber Loss Formula Example using 10 km run of 1310 SM fiber
Loss = (Fiber Attenuation x km) + (Splice Attenuation x # of splices) + (Connector Attenuation x # of
connectors) + (Safety Margin) = Total Loss
Loss = (0.35 dB x 10) = 3.50 dB + (0.01 dB/splice x 1) = 0.01 dB + (0.75 dB/connector x 2) = 1.50 dB + (3
dB Safety) = 3.00 dB = 8.01 dB total loss
(courtesy http://www.bb-elec.com/Learning-Center/All-White-Papers/Fiber/Calculating-Fiber-Loss/Calculating-Fiber-Loss.pdf)
If you need to have a system extend further than what a manufacturer recommends, you may be able to
utilize repeaters. A repeater, or a buffer, refreshes the signal(s) and allows for a longer run. Depending
on the type of fiber optic system and the manufacturer, you may be able to design a system that is many
times longer than what the original hardware is capable of. TDM will allow for “daisy chaining” of their
hardware, since it is a unidirectional, the signal can simply be buffered and passed along the pathway.
WDM does not have that capability, and it is inherently more difficult to extend bi-directional
communications over fiber because of the massive loss budget of adding additional hardware and
processing. Some manufacturers have been able to overcome that issue while minimizing the
limitations with the extension of WDM signals.
Depending on the type of system that you are designing, you may have the need to simply extend a
single AV signal from point to point. You may also have the need to extend many signals to a single
point or to multiple points. The use of a distribution amplifier or a matrix switcher may become
necessary. There are many DAs and switchers currently on the marketplace that can fill those needs. If
you have multiple inputs and outputs that will require greater distances than a copper cable system will
allow, a fiber optic switcher is a great solution. Because of the diversity of today’s systems, many
products on the marketplace take a “modular” approach. They allow you to start with a frame and only
populate the portions of that frame as you need. Some systems even allow for the mixing of copper and
fiber optic cabling. As your client’s AV needs grow, the frame can be populated without having to
replace the original switch.
The flexibility of today’s fiber optic systems provides yet another reason for jumping on the fiber optic
bandwagon. Convenience. Entire buildings can now have their AV system reside on a single matrix
switch. A good designer can bring any input to any output in a large facility. Because of newer fiber
optic manufacturer’s modularity, this can also be accomplished in phases, or as the client’s needs grow.
Some manufacturers are creating modular switches as large as 512x512. In this information age, getting
these signals throughout a facility at the speed of light is critical. Is this something that your client
would prefer?

3. Security isn’t just for the government anymore. Years ago many government entities discovered using
AV over fiber optics. It was simple, as you cannot tap into a fiber optic cable. Fiber optic cables also do
not emit electromagnetic interference. Their signal cannot be achieved illicitly. Corporations, private
companies, and pharmaceutical manufacturers are just some of the clients who prefer having a secure
AV system. Secure data, spreadsheets and proprietary information can easily end up in the wrong
hands. Fiber optic AV systems are an easy and secure way to ensure that your client’s security needs are
met. Have you talked with your client about their security needs?
There are many different solutions in today’s marketplace when it comes to fiber optic audio video
networks. There are many different types of fiber optic cables and connectors as well. Certain criteria
will decide what type of system you decide to use, depending on your source, your distance required to
carry that information and your budget. Do your diligence when it comes to making fiber optic
selections during the design of audio video fiber networks, and you will be able to make successful
selections that will benefit your client wants and needs, for today and down the road.