The Nobel Prize in Physics 2009
Posted on October 8, 2009 Comments (1)
The 2009 Nobel Prize in Physics honors three scientists, who have had important roles in shaping modern information technology, with one half to Charles Kuen Kao and with Willard Sterling Boyle and George Elwood Smith sharing the other half. Kao’s discoveries have paved the way for optical fiber technology, which today is used for almost all telephony and data communication. Boyle and Smith have invented a digital image sensor – CCD, or charge-coupled device – which today has become an electronic eye in almost all areas of photography. The Nobel prize site includes great information on the science behind the research that has been honored:
Optical communication of today has reached its present status thanks to a number of breakthroughs. Light emitting diodes (LEDs) and especially diode lasers, first based on GaAs (800-900 nm) and later on InGaAsP (1-1.7 m), have been essential. The optical communication window has evolved from 870 nm to 1.3 m and, finally, to 1.55 m where fiber losses are lowest. Gradient-index fibers were used in the first optical communication lines. However, when moving towards longer wavelengths and longer communication distances, single-mode fibers have become more advantageous.
Nowadays, long-distance optical communication uses single mode fibers almost exclusively, following Kao’s vision. The first such systems used frequent electronic repeaters to compensate for the remaining losses. Most of these repeaters have now been replaced by optical amplifiers, in particular erbium-doped fiber amplifiers. Optical communication uses wavelength division multiplexing with different wavelengths to carry different signals in the same fiber, thus multiplying the transmission rate. The first non-experimental optical fiber links were installed in 1975 in UK, and soon after in the US and in Japan. The first transatlantic fiber-optic cable was installed in 1988.