leaky wave - technical definition

In an optical fiber, an electromagnetic wave that travels outside the core and in the cladding or even beyond, usually as a result of an incident wave injected into the core at a severe angle less than the critical angle. Leaky waves are detached from the main body of the signal, are not guided, and, therefore, are valueless. Leaky waves travel high-order modes; waves traveling low-order modes generally remain confined within the core. See also cladding, core, critical angle, high-order mode, and low-order mode.