Cargille Optical Gels Codes 0607 and 0608 have two primary uses. First, as an optical coupling for optical fibers and optical components. They reduce or eliminate internal reflectance thus increasing transmittance of light; they do this by having a refractive index and dispersion that is similar to many glasses and optical plastics, and closely matches the refractive index and dispersion of fused silica.
A second primary use is as a mode stripping gel. When one of the gels is coated on a silica fiber that has cladding, it will remove the signal from the cladding. This is useful when evaluating fiber systems ;using only short fiber lengths, in that the signal that is carried for a short distance in the cladding can be eliminated from the system and detectors will record only the signal propagated by the fiber core. This is quicker and easier than mechanically stripping away the cladding and is non-destructive.
These gels have several very desirable properties. They are transparent to radiation in the near UV, the visible, and the near infrared. We know of no other liquids, gels, or greases with significantly better transmittance. Each has wide temperature stability. Freezing points are below -67°C and boiling point exceeds 400°C. This means a more stable refractive index than some other liquid, gel or grease couplants.