Russell, P.St.J. and Kazansky, P.G.
Properties and applications of poled glass
At Bunsen Kolloquium, Germany.
23 - 24 Feb 1996.
When glass fibres were first proposed for optical communications in the late 1960's, one attractive selling point was their extreme insensitivity (if not complete immunity) to electromagnetic interference, which - in addition to a much larger bandwidth - gave them considerable advantages over co-axial cable. Early research concentrated on reducing the optical absorption to the lowest possible levels, eventually achieving values <0.1 dB/km in the main communications windows at 1.3 and 1.5µm. At this point there seemed no reason to suppose that germanium doped silica glass of extremely high purity should be anything other than an almost perfect optical transmission medium. Ambitious, however, to extend the capabilities of optical fibres, researchers went on to study whether more complex functions such as amplification, modulation, wavelength conversion and lasing could be incorporated, the idea being to avoid the need for optical-electronic-optical repeaters and modulators. This effort has resulted in the successful demonstration of all-optical diode-laser-pumped in-fibre lasing and amplification by incorporation of rare-earth dopants in the core glass. These developments are already revolutionising communications system design.
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