A liquid used of Refractive Index similar to Glass used to match the materials at the ends of two fibers to reduce Loss and back reflection. Index matching fluid has an Index of Refraction that nearly equals that of the fibers core. Used to reduce Fresnel Reflection loss at Fiber ends. Also known as index-matching gel, it is used to enhance the Transmission of Light across the joint. Index matching Gel was first used in the Optical Fiber industry in 1978.