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Optical-Fiber-Based Spectrum Analyzer

IP.com Disclosure Number: IPCOM000047436D
Original Publication Date: 1983-Nov-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 2 page(s) / 29K

Publishing Venue

IBM

Related People

Young, P: AUTHOR

Abstract

An optical-fiber-based spectrum analyzer is described in which one end of the fiber acts as a reflector of the spectrum analyzer resonator. One end 2 of the optical fiber 1 is polished and a dielectric coating is deposited by evaporation on end 2 to make the end 2 cross-section highly reflective. The fiber 1 can then be paired with a spherical reflector 3 to form a resonator. In this resonator, the distance R between the two elements must be equal to the radius of curvature of the spherical reflector 3, i.e., twice the focal length of the reflector 3. Both the fiber 1 and reflector 3 must be mounted rigidly relative to each other, and the reflector is mounted on a piezoelectric element 4 so that the resonator can be scanned.

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Optical-Fiber-Based Spectrum Analyzer

An optical-fiber-based spectrum analyzer is described in which one end of the fiber acts as a reflector of the spectrum analyzer resonator. One end 2 of the optical fiber 1 is polished and a dielectric coating is deposited by evaporation on end 2 to make the end 2 cross-section highly reflective. The fiber 1 can then be paired with a spherical reflector 3 to form a resonator. In this resonator, the distance R between the two elements must be equal to the radius of curvature of the spherical reflector 3, i.e., twice the focal length of the reflector 3. Both the fiber 1 and reflector 3 must be mounted rigidly relative to each other, and the reflector is mounted on a piezoelectric element 4 so that the resonator can be scanned. One alternative arrangement (lower figure) is to replace the spherical reflector with a positive meniscus lens 5, the concave side of which is well polished and coated with a reflective material. With the alternative arrangement the spectrum analyzer can be made self-focusing. Since the optical fiber is used, the rest of the unit can be remotely located to avoid exposure of the rest of the unit to hostile environments.

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