Tellurite And Fluorotellurite Glasses For Active And Passive

1. Introduction; MDO 1
1. Introduction
1.1. Fibreoptic technology
The idea of guiding light, confined within a medium of higher refractive index than air
(e.g. water, glass rods), or contained in reflective pipes, has existed since the 1800s [1, 2].
The major breakthrough came in the 1950s, when silica (SiO2) glass fibre was clad with a
lower refractive index glass, guiding launched light by total internal reflection [3]. A
large number of these fibres bundled together coherently (arranged in identical positions
relative to one another where light enters and leaves the fibre) were shown to transmit an
image; incoherently arranged fibres could be used to deliver light [2].
Early fibres absorbed a large proportion of the light which was launched into them,
with only around 1 % remaining after 20 m (attenuation or loss of 1 dB.m -1 ). In 1966,
Kao and Hockman published their seminal paper suggesting that most of this loss was
extrinsic [4, 5], which should be eliminated by careful processing, to around 10 %
transmission over 500 m (0.02 dB.m -1 ≡ 20 dB.km -1 ). This prediction was conservative,
as in 1979 10 % transmission was demonstrated over 50 km (0.02 dB.km -1 ) in laboratory
experiments [2], and now in commercial systems attenuation in the field is ≈ 0.18
dB.km -1 , with spacing of amplifiers ≈ 200 km [6]. Significantly, the first laser was
demonstrated in 1960 [7], and these are an intrinsic part of commercial systems.
Fibreoptic communication systems have proved advantageous over other methods of
sending and receiving electromagnetic (EM) radiation for a number of reasons. Electronic