# guided ray

**guided ray:** In an optical fiber, a ray that is confined primarily to the core. *Note:* A guided ray satisfies the relation given by where _{r} is the angle the ray makes with the fiber axis, *r* is the radial position, *i.e.* , radial distance, of the ray from the fiber axis, *n*_{r} is the refractive index at the radial distance r from the fiber axis, and *n*_{a} is the refractive index at the core radius, a, *i.e.* , at the core-cladding interface. Guided rays correspond to bound modes, *i.e.* , guided modes, in terms of modes rather than rays. (188) *Synonyms* **bound ray, trapped ray.**

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**This HTML version of FS-1037C was last generated on Fri Aug 23 00:22:38 MDT 1996
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