When using a fiber-coupled light source, such as a LED light source from our COB series or a SLED light source from our FJORD series, it is essential to select carefully the right fiber to use with. We all have in mind the differences between single mode and multimode fibers (core/cladding diameters) and optical fiber configurations (bifurcated fibers, splitters, couplers, etc.) among our bunch of fibers. Nevertheless, it is a common mistake not to take into account the differences among the fiber materials when working with light sources at ultraviolet (UV), visible (VIS) or near infrared (NIR) regions. Here, the use of one or another fiber will be defined mainly by the led light source and the amount of light that we need to couple into the fiber for the specific application.

In particular, when handling silica fibers for our setup we should take care with their hydroxyl ion (OH) content because it can dramatically alter our results. For example, high OH content fibers are preferred for UV-VIS operation since they can provide lower absorption at UV wavelengths than low OH content fibers. However, the utilization of low OH for VIS-NIR is recommended for the elimination of undesired OH absorption peaks at larger wavelengths as it is shown in the figure below.

All in all, a wrong fiber choice can cause unexpected or contradictory results, so special attention must be paid during the fiber selection. Contact with the vendor or technical expert for more information about the fiber if necessary.

For more information about this topic: https://www.rp-photonics.com/fibers.html

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