Side-emitting optical fibre

If the previous conditions are not respected, ie, if the light incidence angle j/ is smaller than the critical angle j/c, the light can leak from the core to the external surface of the fibre this kind of fibre is called side-emitting optical fibre (SEOF). Several approaches are possible to allow SEOFs, including the following ... 

Figure 4.5 Side-emitting optical fibre with tight leakage due to scattering material within the cladding.

Figure 4.6 Side-emitting optical fibre with light leakages due to miciDperfusion of the cladding.

UV-Vis process analysers can be used in a noncontact mode as the source radiation can be passed though a window in a process pipe, for example, and the emitted radiation detected on the other side of the pipe. This means that the sample can be subjected to a measurement without its flow being impeded or its composition changed in any way. Optical fibres are used to transmit the radiation to and from the sample, which can be in a distant location, a hazardous area or in a harsh environment such as a high temperature reaction vessel. The most common forms of optical fibre probes used for UV-Vis measurements are of the transmission and ATR types (Figure 9.12). The petroleum and chemical industries use UV-Vis spectroscopy for monitoring many of their processes ... 

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