Thorlabs G608N is a crystal clear, gel-like, optical coupling compound intended to reduce signal attenuation in wave guide assemblies at connections. The presence of air at the junction of two optical fibers causes significant signal refraction due to the large differential optical impedance that exists between air and the signal-carrying wave guides. Optical coupling compound G608N has been formulated with the requisite optical properties of clarity, purity and refractive index to minimize signal losses.