More than often, the term “Fibre-Optic” has become common talk. Recently, there was news everywhere that, East Africa had been connected to the world via the SEACOM Fibre-Optic cable. So far, there is a lot of excitement in many parts of East Africa, people are eagerly waiting or is it anticipating the onset of cheaper Internet connections as well as international and regional phone calls. What is Fibre-Optic any way? You hear about fibre-optic cables whenever people talk about the telephone system, the cable TV system or the Internet. Fibre-optic lines are strands of optically pure glass as thin as a human being’s hair that carries digital information over long distances. They are also used in medical imaging and mechanical engineering inspection; these tiny strands of glass transmit light at an amazing pace that, it is worth figuring out how it all works! First of all, SEACOM is a company that is charged with the laying of this cable. It has so far connected Mombasa to the rest of the world. On the 4th – 7th of August 2009, SEACOM was able to provide a high speed internet connection at the Kenyatta International Conference Centre in Nairobi Kenya. So far, that broadband has been extended to Kampala as well as Kigali. We saw Kigali being excavated left, right and centre, in a bit to have the city covered by the fibre-optic line, now, the long wait is over. The Fibre-optic is to do with transmitting light (optic) through a strand of glass (fibre). Since light travels in a straight line, the signal being transported is beamed from one end to the other. The glass media works like a mirror in transmitting the light from one end to the other. Every time the signal is sent, it will go straight, whenever there is a bend, the light with be reflected from one side to the other in a periscope manner; it hits the bend and bounces off to the other side and then it is straightened out again. Where there are no bends, it travels straight until it gets to the final destination (this could be tens or hundreds of kilometres). A standard fibre cable is made up of two main sections; the external mirror lined cladding and the core (hollow centre) the light in a fibre-optic cable travels through the core by constantly bouncing from the mirror-lined walls, a principle called total internal reflection. Because the cladding does not absorb any light from the core, the light wave can travel great distances. However, some of the light signal may get lost within the fibre as a result of impurities in the glass used in the manufacture of the cable. Imagine two people standing a hundred meters apart, the first one has to prepare the message, code it and maybe make signs (representing the coded message), the second one receives the signs and tries to interpret (de-code) them so that sense is made of the message. If the two were several kilometres apart, they would definitely send the message through a medium that can deliver it. Assuming that the two are connected by fibre, their data must be coded to give it security, it must get transmitted and then received, hence the need for the following processes:- • Transmitter - Produces and encodes the light signals • Optical fibre - Conducts the light signals over a distance • Optical regenerator - May be necessary to boost the light signal (for long distances) • Optical receiver - Receives and decodes the light signals The transmitter is physically close to the optical fibre and may even have a lens to focus the light into the fibre. The most common wavelengths of light signals are 850 nm, 1,300 nm, and 1,550 nm (infrared, non-visible portions of the spectrum). The Optical regenerator is used to fix signal loss that may occur when the light is transmitted through the fibre, especially over long distances. Therefore, one or more optical regenerators are placed along the cable to boost the light signals. The optical receiver takes the incoming digital light signals, decodes them and sends the electrical signal to the end user’s devices. eddie@afrowebs.com
