Greetings Marlee:
The diameter of glass optical fibers ranges between 100 and 200
micrometers (40 to 80 micro inches). This about the diameter
of a thick human hair such as hair from eye brows.
The manufacturing of optical fiber begins with the
fabrication of a glass rod called a perform that is
thousands of times larger in diameter than the fiber.
The preform glass has an extremely small amount of impurities
in it so it is very transparent and expensive to make. A typical
preform rod might have an outside diameter of 15 cm (6 inches)
and be 100 cm (40 inches) long. This glass is so
transparent that if we could lay a rod of perform
across the Pacific Ocean we could see some one in
Hawaii from California!
To pull optical fiber from a large, heavy glass
preform, the glass rod is slowly lowered into a
circular doughnut shaped furnace which is also
open at the bottom. As the perform glass is lowered
into the top of a doughnut shaped furnace at a rate
of a fraction of a centimeter (inch) per minute,
the end of the preform begins to melt and it drops
in a long string of glass from the bottom of the
furnace much like a string of melted Mozzarella
cheese or taffy candy behaves. The operator attaches
the end of the long string of melted glass, which is
cooling and becoming solid, and winds it onto a rotating
bobbin, a drum about 50 cm (20 inches) in diameter.
As the take-up bobbin rotates the glass string is
pulled at a fast rate of about 100 cm (40 inches)
per second. The faster the bobbin rotates the thinner
the pulled fiber will be and the slower it rotates
the thicker the fiber will be (just like melted cheese).
It takes several hours to pull the one meter (one yard)
long glass preform rod into hundreds of kilometers
(hundreds of miles)of glass optical fiber!
As the tail end of the perform rod drops into the furnace
the furnace must be turned off so that the glass holding
and moving equipment will not be over heated and damaged.
This leaves a large tail end chunk of ultra transparent,
and expensive glass rod left over. The tail rod can be used
for jewelry, optical lenses and other items that are made by
conventional glass and jewelry manufacturing techniques.
For those readers that want to read more about the
manufacturing of optical fiber search the Mad Science
Archives for my answer to:
Re: How are Fiber Optics made?
Date: Thu Mar 19 18:54:45 1998
ID: 890183300.Eg
Best regards, Your Mad Scientist
Adrian Popa