# TIA's Glossary of Telecommunication Terms

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## optical path length

1. In a medium of constant refractive index, *n* , the product of the geometric distance and the refractive index. 2. In a medium of varying refractive index, the integral of *n* *s* , where *s* is an element of length along the path, and *n* is the local refractive index. (188) *Note:* Optical path length is proportional to the phase shift that a lightwave undergoes along a path.

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