Optical fiber is composed of a light carrying core and a cladding that traps the light in the core, causing total internal reflection. Fiber has two basic types, multimode and singlemode. Multimode fiber means that light can travel many different paths (called modes) through the core of the fiber, which enter and leave the fiber at various angles. The highest angle that light is accepted into the core of the fiber defines the numerical aperture (NA).Two types of multimode fiber exist, distinguished by the index profile of their cores and how light travels in them. |
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