| Fig 1: RG transceiver | Fig 2: GR transceiver |
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The devices shown above are based on existing LED technology. At the time of writing, there is no known instance of any being used in this way. The two devices are a spectrally matched pair, one side green, the other red. A single component, the size of a LED would contain both emitter and photo transistor receiver. This means that each device transmits using a different colour from the one it is sensitive to. By placing two matched devices opposite each other (or via fibreoptic cable), they can both transmit and receive data simultaneously with no interference on either channel.
To bring about this effect, standard red and green LED emitters may be used. To distinguish transmitted light from received, there is a chemical layer covering the photo transistor's sensor area. The composition of this layer determines what type of light will pass through and reach the sensor. That is why transmitted light does not interfere with what is received. This simple system would result in a type of LED device with 3 leads: Common; LED; RX. Although they share a common lead, the two parts function independantly.
By extension, the addition of more coloured LED emitters along with sensors coated with different compounds would add more independant channels to each paired device. In fact, the limit on how many channels may operate independantly is only restricted by the number of emitter colours and the selectivity of the chemical coatings used on the photo sensors. There may also be limits on how far some colours will travel in different fibre optic cables, as the glass may absorb some colours more than others.
COPYRIGHT STATEMENT: This concept was originated by John Spencer Durham in 1989, and posted on the internet in July 24 2000. Anyone with the means and desire to develop this principle into a commercial system is free to do so providing the originator is acknowleged by name along with the product, its packaging and manuals.NEXT
