The unwanted coupling of energy between two circuits or channels, crosstalk is a form of co-channel interference that superimposes a transmission occurring on one circuit or channel onto another transmission occurring on another circuit or channel. In a voice scenario, the parties talking on the disturbed channel can hear one or more of the parties talking on the disturbing channel. Near-End CrossTalk (NEXT) occurs at or near the transmitting end of the connection and Far-End CrossTalk (FEXT) occurs at or near the far end. See also FEXT and NEXT. Cladding Normal Light Source Critical Angle Cladding Core