Ever wonder how it works? Fiber optic technology was developed
in the early 1970’s
and is rapidly replacing traditional copper cable for transmitting information
over hundreds to thousands of miles. Rather than send data in the form of electrons,
fiber optic technology uses photons, or light.
Fiber
optic cable is made of many thin strands of coated glass fibers.
Each measures about eight microns - that’s smaller than a strand
of human hair. Digitized information is “coded,” or placed
on to light pulses for transmission. It travels along the glass
fiber at the speed of light - 186,000 miles per second. When it
reaches its destination, a decoder converts the light information
into a picture, audio sound or written material in a form we can
understand.
It takes two copper wires, like the ones in your telephone cord, to carry just
one phone conversation. Fiber optic cable carries much more information than
copper cable. Two strands of optical glass fiber can transmit the equivalent
of 24,000 telephone calls all at the same time.
Fiber optic cables now cross the world’s oceans to connect
many countries together. Whether you are in Mauritius, Australia
or the United States, you are probably viewing Dive and Discover
at the end of tiny, nearly continuous strands of glass that reach
all the way from Woods Hole, Massachusetts to you. To make sure
you receive all the information, the fibers are made of ultra-pure
glass so that the light pulses are not distorted or weakened.
There are two types of fiber optic cable that allow the light to
travel along it in different ways. Today we use “single mode” fiber
that allows the light to follow only one optical path. This makes
it possible to transmit much more information over much longer
distances.
On board RV Knorr, we use fiber optic cable to connect the different
laboratories to the shipboard computer network. But we also use fiber optic cable
to connect the ship to ROV Jason while it is underwater. The fiber optic cable
we use has three glass strands to send commands to Jason as well as to receive
data and images sent from the seafloor back to the ship. Copper wires that send
power to Jason surround the three glass strands.
Jason has two fiber optic cables. The main cable runs from the ship to Jason
and has steel armor on its outside. This gives it over 20 tons of strength. The
other cable is the yellow tether that runs from Medea to Jason. Instead of steel,
it is reinforced with a material called Spectra. This material is strong yet
light in weight so Jason can move easily without dragging a heavy cable through
the water.
Underwater fiber optic cables are used to connect instruments on the seafloor
to shore based labs. Scientists can now send commands to their instruments and
collect data continuously from their office computer.
Email
to friend
A
piece of fiber optic cable unraveled to show the three colored
wires containing the glass fibers. The fuzzy white material is
the Spectra.
One
of the colored wires has been spread out to show the glass fiber. The red arrow
points to the junction between the thin glass strand and its outer plastic
coating. This protects it from abrasion. The several copper wires surrounding
the glass strand are the electrical conductors that carry the 1800 volts used
to power ROV Jason. The yellow plastic jacket around the bundle is insulation. 
DSOG
team member Craig Elder holds the yellow fiber optic tether that connects
ROV Jason to Medea. 