单词 | cladding |
释义 | cladding 1. A metal coating bonded onto another metal for protective purposes or to alter its conductive properties. Copper-clad aluminum coaxial cables sometimes are used in long-haul CATV distribution networks, for example. Coax cables sometimes are tinned or silvered, as well. See also coaxial cable. 2. The layer or layers of glass that surround the core of a glass optical fiber (GOF).The cladding serves as a waveguide that variously reflects or steers the light signal back into the core, which is the central and primary light conducting portion of a glass fiber. Step-index fiber is characterized by a sharp decrease in the index of refraction (IOR) between the core and cladding, i.e., the cladding is sharply clearer or purer than the core material.This sharp step of approximately one percent in IOR at the core/cladding interface causes any errant light rays to reflect back into the core in a phenomenon known as total internal reflection. Graded-index fiber is characterized by a gradual decrease in the refractive index of the cladding through a great many layers of successively clearer glass.This approach causes the errant light rays to gradually gain in velocity and bend, or refract, back towards the core. Step-index construction is used largely in singlemode fiber (SMF) and graded-index construction in multimode fiber (MMF). See also core, GOF, laser diode, LED, MMF, reflection, refraction, SMF, and total internal reflection. |
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