OPEN COMMUNICATION
THE LATEST IN NETWORKING AND WIRELESS TECHNOLOGIES
■ BY LOUIS E. FRENZEL W5LEF
FIBER OPTICS — The Invisible
Communications Network You Use Every Day
THE WORLD HAS BEEN REWIRED MANY TIMES over the decades. Telegraph
and telephone wiring came first. Then electrical power. (Yes, electrical power
wiring actually came after the telegraph and telephone wiring. Doesn’t seem
right does it?) Shortly after that came cable TV wiring. Computer network
wiring was next. Then fiber optic cable. There has been some overlap of those,
of course, but that is the general sequence.
Today, there is actually a fiber optic
cable glut. Miles and miles of it
were laid in the early Internet boom
days of 1998-2002, then the crash.
Lots of that cable is still unused or as
they say in the industry, it is “dark”
fiber. With booming Internet activity
going on today and the push toward
TV over the Internet, lots of that fiber
is being brought out of the darkness
and even more new fiber is being laid
for special applications.
Fiber optic communications
systems are not something we think of
every day even though we all use
them. Don’t think so? Consider this.
When you make a long distance call,
the fiber network is used. In fact, in
making any phone call today — wired
or wireless — somewhere in the
telephone system your call is being
carried at least part way by light waves
over fiber. Do you have cable TV?
(Over 80% of the US population does
so you probably do, too.) Most
cable TV systems are what
we call hybrid fiber cable (HFC)
systems meaning that a main fiber
optic backbone cable carries the TV
signals to a box in your neighborhood
where the connection continues from
that box to your home over RG-6/U
75-ohm coax. If you use email or
the Internet, you use fiber because
the backbone of the Internet is fiber.
And most of that fiber is buried and
invisible.
Recently, I attended the Optical
Fiber Conference (OFC) in Anaheim,
CA. I have not been to that conference
in a few years as the early 2000’s were
really rough on the fiber industry.
When the Internet bubble burst in
2001, the fiber industry essentially
collapsed. It did not go away, of course,
but little new equipment was sold, lots
of R & D was abandoned or put on
hold, start-up companies folded, and
lots of other companies were bought
and/or merged. All that consolidation
turned out to be good and business has
emerged even stronger today. The OFC
was booming again this year as the
industry renews its growth cycle. Here
is a look at some of the latest trends
and developments in this field which
affect us all, even if you think it doesn’t.
REMEMBER HOW IT
WORKS
■ A typical optical transceiver or transponder, about the size of
a package of gum. Mounts on the printed circuit boards
of networking equipment like routers. Contains the laser
transmitter and photo diode receiver and all the
related circuitry to perform optical to electrical
conversions and vice versa. This one is called
a small form factor pluggable (SFP+)
for short range (SR). It uses a 850 nm laser
and operates at 10 Gb/s. Photo courtesy of
Picolight (now JDSR).
Fiber optic communications is the
transmission of light over a glass or
plastic fiber cable. The light is generated
by a laser in most cases, but in some
smaller, slower networks an LED is used.
The light is infrared (IR) so you cannot
see it as it is lower in frequency than red
light. The light color or frequency is
usually expressed in wavelengths (λ)
and that is measured in nanometers
(nm). A nanometer is one billionth of a
meter. IR light extends from about 700
to 1,600 nm. The most common IR
operational wavelengths are 780, 850,
1,310, 1,490, and 1,550 nm. The 780
nm wavelength is the common TV
remote control frequency while 1550
nm is the main long distance high speed
operating wavelength.
In any case, since most signals are
digital data today, the binary signals
simply modulate the light by turning
the laser light off and on creating
pulses. This is called on-off keying
(OOK) or amplitude shift keying
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June 2007
