Era Of Optical Fibre

Encyclopedia Britannica can be 
transmitted in a fraction of second, reports Biplab Das 

The earliest sign of innovative thinking dates back to a time when our nomadic ancestors first fashioned stone tools. Gradually, stone age gave way to bronze and iron ages. But, our technologies did not progress much until the last century arrived. 

"During the last century, an orgy of technological innovations swept the globe," said Dr. H. S. Maiti, director, Central Glass Ceramic Research Institute (CGCRI), in his lecture on celebration of the National Technology Day. The programme was organised by The Indian Science Congress Association (ISCA) and Birla Industrial and Technological Museum (BITM) at BITM on May 13. 

Speaking on 'Innovations in Technology Development,' Maiti said, "A simple idea grows into a complex technology." However, technology depends on basic science for new ideas. In this context, he mentioned the discovery of transistor in 1948. "It was only possible after the physicists hit upon the concept of semiconductivity." 

A transistor is a valve, which controls the flow of electricity in the same way as the valves in the fire hose help a fireman control torrents of water. 

"As soon as the transistor was invented, it made giant computers with gears, levers and vacuum tubes obsolete," Maiti said. The original hand-built transistors were, however, crude electrical components about the size of a dime and were connected by wires. 

Soon, this primitive process of making transistors came to an end when scientists found versatile uses of silicon. Now transistors are made by using light beams from a mercury lamp that make microscopic grooves and lines on silicon wafers. Silicon, being a highly malleable element, has miniaturised the electronic devices by million fold. Tens of millions of transistors can now be crammed into an area the size of a fingernail. A silicon chip occupying a tiny area of 1 square centemetre can be encapsulated in a ceramic body harbouring myriad electrical circuits. 

Maiti pointed out other applications of silicon. "Wonderful lenses and prisms can be carved out from silica glass," he said. According to him, transmission of information using copper wires has been a smart idea, but its narrow bandwidth limits the amount of information or bits transmitted in one second. 

The problem, Maiti said, was solved with the help of optical fibre derived from silica glass. The possibility of such a solution was first published in 1966. In optical-fibre technique, light beams travelling inside thin transparent glass fibre are tapped inside. The beam then bounces off the interior walls of a bilayer fibre. 

Optical fibre vibrates more frequently than copper wires and is able to convert more information into signals. The number of independent speech signals transmitted through optical fibre is much higher than that of copper wires. Modern fibre cables can carry 100 billion bits of information per second. Through these cables, it is possible to send the Encyclopedia Britannica in a fraction of second. 

Adding germanium and phosphorous to silica glass reduces its refractive index. Reduction in the refractive index of the glass fibre increases the length of waves which, in turn, speeds up signal propagation. 

Maiti discussed the use of laser, or light produced by manipulating the electrons of atoms jumping from one orbit to another, in optical fibres. "The use of laser have made the electronic amplifier an outcast," he said. "One can always string more optical fibres and expand the bandwidth via new lasers." 

Laser is highly promising for the internet because it is 10 to 100 times more effective than the conventional systems. The capacity may be further enhanced by adding one per cent of an element neodymium. 

At the end of his lecture, Maiti pointed out other applications of ceramic. He gave a brief overview of the works carried out by the CGCRI scientists in this regard. 

Scientists at CGCRI have replaced the ball and socket joint of hip using a ceramic product comprising aluminium and titanium dioxide. Ceramic products can also produce artificial eye. "Using a ceramic product called calcium phosphate, a porous eye implant weighing less than 1.5 gm has been produced at CGCRI," said Maiti. 

The day ended with a brief concluding remark by Dr. Samaresh Goswami, director, BITM. He highlighted the need of basic science for the progress of technology. "Instead of producing mere technocrats, it is better to encourage youngsters to go for basic research," he commented.

    June 3, 2002.