From Richard Ely
Nicola Jones reports on attempts to communicate data with light (9 January, p 30). What took you so long? My thesis – submitted for a BSc in electrical engineering at the University of Nottingham, UK, in 1968 – was titled A line-of-sight communication channel based on a light-emitting gallium arsenide diode. The department had only three diodes with a capacity of 1 ampere. After burning out two I could foresee doom, so I tried pulse amplitude modulation. The transmitter worked a treat.
Incidentally, my thesis referenced a New Scientist article titled “Light from semiconductors” (12 December 1963, p 666).
Horton, Northamptonshire, UK
