What a switch

A bacterium in optical communications

 
By T V Jayan
Published: Sunday 15 December 2002

a salt- loving bacterium may offer a solution for one of the most nagging problems of optical communications: non-availability of cheap and speedy optical switches. Indian scientists have recently demonstrated that a protein found in the cell membrane of Halobacterium halobium functions as an optical switch, when integrated with lasers.

The scientists -- Sukhdev Roy and C P Singh of Agra-based Dayalbagh Educational Institute, and K P J Reddy of the department of aerospace engineering at the Indian Institute of Science (iisc), Bangalore -- claim that the protein has several advantages over other contending materials for optical switches, such as liquid crystals and organic polymers.

In communications technology parlance, a switch is nothing but a router that directs voice or data messages from its origin source to its destination. It is quite similar to a junction to which too many roads are linked. Unless the traffic is cleared as and when the vehicles reach the junction, it might lead to severe traffic jams. In a similar way, if switches do not route voice and data messages as swiftly as the latter arrive, communication can become dauntingly slow.

The Indian scientists found that bacteriorhodopsin -- the light-sensitive protein of the bacterium -- is quickly able to transmit data. The protein gets activated when it is exposed to a green-yellow beam at a wavelength of 570 nanometre (nm). Thereafter, a series of structural changes take place in the protein that enable it to absorb red light at 640 nm wavelength, which can carry messages. According to Roy, the protein can absorb the red 640 nm beam only when exposed to the green-yellow 570 nm light. Thus, the protein functions as a not logic gate -- when its beam input is low, the output is high.

The researchers claim that bacteriorhodopsin would help in making better and cheaper switches. Some of the indigenous qualities of the protein are its tiny size, low-production cost and very high quantum efficiency. The protein can be coated on anything and can withstand extreme conditions, such as high temperatures. Moreover, the bacterium can be easily cultured and can be genetically modified to incorporate more features.

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