One of the most exciting prospects for optical fibres made from fluoride glasses is the possibility of providing long distance optical communication systems without the need for repeaters. This objective has stimulated much of the work into fluoride glasses over the past ten years, and has prompted the writing of this book. It has also emerged that fluoride fibres can transmit both visible and infrared energy (from about 0.5 to 5 ,urn) and that they have many applications outside the field of telecommunications. These include optical fibre sensors (particularly in remote infrared spectroscopy), laser surgery and fibre lasers. Several companies are now established in the field, and good quality fluoride fibres are available from sources throughout the USA, Europe and Japan. Moreover, the first commercial instruments based on fluoride fibres are finding their way to the market place and these fibres will undoubtedly form the basis of many more instruments yet to be developed. The work presented in this book represents the field both from an academic understanding of the materials and ways to convert them into fibre, and from a practical and commercial viewpoint. The principal author and some of the co authors are based at the British Telecom Research Laboratories in the UK.

Inhalt
1 Perspective and overview.- 1.1 Introduction.- 1.2 Optical fibre fundamentals.- 1.3 Loss mechanisms in optical fibre materials.- 1.4 Long wavelength fibre materials.- 1.5 Fluoride glasses and optical fibres.- 1.6 Applications for infrared optical fibres.- 1.7 Future prospects.- References.- 2 Properties of fluoride glasses.- 2.1 Introduction.- 2.2 Glass-forming systems, structure and crystallization.- 2.3 Thermal properties.- 2.4 Other properties.- 2.5 Optical properties.- References.- 3 Propagation in optical fibres.- 3.1 Introduction.- 3.2 Multimode fibres.- 3.3 Monomode fibres.- References.- 4 Manufacture of infrared fibres.- 4.1 Materials preparation.- 4.2 Melting techniques.- 4.3 Fibre fabrication.- 4.4 Problems.- 4.5 Fibre results.- References.- 5 Intrinsic loss measurements.- 5.1 Introduction.- 5.2 Rayleigh scattering.- 5.3 IR multiphonon edge.- 5.4 Minimum intrinsic loss.- 5.5 Longer wavelength transmitting fibres.- References.- 6 Extrinsic absorption.- 6.1 Introduction.- 6.2 Spectrometer measurements.- 6.3 Absorption due to water.- 6.4 Absorption due to transition metal ions.- 6.5 Absorption due to rare earth ions.- 6.6 Other impurities.- References.- 7 Extrinsic scattering.- 7.1 Introduction.- 7.2 Identification of scattering centres.- 7.3 Scattering theory.- 7.4 Scattering solutions for limiting cases.- 7.5 Solutions for metallic (absorbing) spheres.- 7.6 Applications to practical examples.- 7.7 Calculations of scattering loss.- 7.8 Scattering loss in fibres.- 7.9 Conclusions.- References.- 8 Measured losses in fibres.- 8.1 Introduction.- 8.2 Available techniques.- 8.3 Total loss.- 8.4 Absorption.- 8.5 Scattering.- 8.6 Recent results.- 8.7 Predicted minimum loss.- References.- 9 Mechanical properties.- 9.1 Introduction.- 9.2 Fracture and glass parameters.- 9.3 Strength measuring methods.- 9.4 Fibre strengths.- 9.5 Identification of flaws and effect on strength.- 9.6 Ultimate strength and maximum practical strength.- 9.7 Strength and homogeneous crystal growth.- 9.8 Durability.- 9.9 Conclusions.- References.- 10 Applications.- 10.1 Mid-IR communication systems.- 10.2 Active fibres.- 10.3 Laser surgery.- 10.4 Infrared fibre sensors.- References.