The FRS round-to-slit bundle is a fiber optic assembly with a round bundle of six fibers to collect light on one end of the fiber. The other end of the fiber converges in a stacked linear configuration which will align to the spectrometer’s entrance slit. FRS round-to-slit bundles are available with UV or NIR grade fused silica optical fibers with standard fiber core diameters of 100 µm.
This configuration allows for much higher throughput into your spectrometer, as opposed to simply using a larger core fiber. When a large core fiber is placed in front of the entrance slit of a spectrometer, the majority of the light is vinyetted and doesn’t make it into the spectrometer. By contrast, when the smaller fibers are stacked along the entrance slit, significantly more light enters into the spectrometer. This allows for much higher sensitivity and signal to noise, while maintaining resolution, since the slit can remain relatively narrow.
It is important to note that proper alignment of the stacked fiber to the spectrometer’s slit is crucial for the fiber to work correctly and must be done every time the fiber is connected.