Large core fluoride fibres

A fibre-coupled mid infrared spectrometer would have a very broad range of potential applications. For example it could be used for process control of chemical production processes in micro reactors e.g. in the pharmaceutical industry. Because of the absence of an adequate fibre, we developed preforms and fibres for this purpose using ZBLAN glass (ZrF₄-BaF₂-LaF₃-AlF₃-NaF) by a variation of the build-in casting process. Up to 25 m long coated fibres with cladding diameters up to 660 μm and core diameters of 500 μm have been fabricated. The good mechanical stability of these fibres leads to a low minimum bending radius of 10 cm and below and a tensile strength of up to 160 MPa. The attenuation of the fibres was about 1.0 dB/m at 2.5 μm and 0.7 dB/m at 3.3 μm.