Mon, 02 Jun 2003

Why fiber optic technology?

Although the telephone was patented by Alexander Graham Bell back in 1876, the first transatlantic telephone cable, called the TAT1, went into operation 80 years later.

But it wasn't until the coaxial cable was invented that it became possible to lay thousands of kilometers of submarine cables underwater -- at times at a depth of three kilometers.

A revolutionary development at that time, the coaxial cable had a number of limitations. First, the electrical signals became weak as the distance increased. Therefore, a lot of repeaters, called cable relays, had to be added to the cable to amplify the signals. Of course, the amplification also increased the noise.

In addition, the capacity of the coaxial cable was very limited. The first transatlantic cable was able to carry about 30 simultaneous circuits between the UK and the U.S., allowing only 60 people to speak on the phones at the same time or 30 on either side of the Atlantic.

Fortunately, as in other technological pursuits, scientists and researchers were always searching for faster, better and cheaper ways of doing things.

In telecommunications and data communication, it was realized that light could also be used to send digital signals over a long distance. Light has many advantages. First, it travels faster than electrons, which means that optical signals can go faster than electrical signals. Second, light signals do not lose their strength as fast as electrical ones while they travel. Therefore, if light was used to carry voice or data signals, fewer repeaters would be necessary.

Researchers also discovered that a certain type of pure glass strand could allow light to travel a great distance without losing its strength quickly. This strand was called an optical fiber, and it is as thin as a human hair. Its outer layer, called the "cladding", is made of a highly reflective material that bounces the light back into its core. That allows the strand to be bent without blocking the "hallway".

As light rays do not interfere with each other as electrons do, a large number of fiber strands can be packed together into one bundle, which increases the carrying capacity tremendously.

Thus, the fiber optic network came into being. It consisted of a transmitter that turned the light source -- a laser or LED (light-emitting diode) device -- on and off to mimic the 0s and 1s of the digital signal, a fiber optic cable with repeaters to boost the light signals, and a receiver that decodes the 0s and 1s into readable digital data.

The first transatlantic fiber optic cable, called the TAT8, became operational in December 1988. Back in the mid 1980s, when the fiber optic cables were beginning to be used to provide high capacity telephone, data or cable TV infrastructure, the challenge was to splice two pieces of strands together so that light could pass through. This was precision work requiring highly specialized skills, and the people who did it earned a handsome wage. Over time, new ways were found to join the two pieces together more easily and properly.

What other advantages does the fiber optic cable have over copper wire? First, because of an absence of electrical interference, we can have a crystal clear conversation when we talk on the phone. Also, unlike the calls that have to go up to the communication satellite in the sky, calls made through a fiber optic infrastructure do not have that annoying echo.

From the infrastructure provider's perspective, fiber optics is the clear choice because it costs less than the coaxial cable to install. It also has a far larger carrying capacity -- more than 120,000 voice channels at the same time. This huge capacity can certainly be used to offer a variety of telecommunications and data communication services.

However, fiber optic technology has found its way into a number of other areas, including medical imaging used in noninvasive surgery and, of course, the computer.

-- Zatni Arbi