A system to remove cladding light from an optical fiber that includes a core and a cladding that surrounds the core. A volume of an index-matching material contacts an exterior surface of the cladding along a contact length of the optical fiber. The index-matching material has a refractive index that substantially matches a refractive index of the cladding at a predetermined clamping temperature and has a refractive index with a negative temperature coefficient, such that the index matching material distributively removes light from the cladding along the contact length based on the temperature of the index matching material that contacts the cladding.