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Position Sensor Using Fiber-Optic Interferometer

IP.com Disclosure Number: IPCOM000044265D
Original Publication Date: 1984-Nov-01
Included in the Prior Art Database: 2005-Feb-05
Document File: 2 page(s) / 33K

Publishing Venue

IBM

Related People

Hodgson, RT: AUTHOR [+3]

Abstract

Coating an optical fiber with a magnetic film, which can "squeeze" the fiber selectively along its length and cause a reflection at the stricture, permits an interferometric length measurement useful in locating a precision mechanical device, such as a robot arm. Fiber-optic interferometers offer economic and performance improvements over interferometers using frequency stabilized gas lasers and delicate optics for distance measurement. A fiber-optic interferometer makes use of a stretched optical fiber coated with a magnetic film that can squeeze the fiber. Light from laser 11 is coupled into a single-mode fiber 12, and coupled out with lowest possible back-reflection in a beam dump 13.

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Position Sensor Using Fiber-Optic Interferometer

Coating an optical fiber with a magnetic film, which can "squeeze" the fiber selectively along its length and cause a reflection at the stricture, permits an interferometric length measurement useful in locating a precision mechanical device, such as a robot arm. Fiber-optic interferometers offer economic and performance improvements over interferometers using frequency stabilized gas lasers and delicate optics for distance measurement. A fiber-optic interferometer makes use of a stretched optical fiber coated with a magnetic film that can squeeze the fiber. Light from laser 11 is coupled into a single-mode fiber 12, and coupled out with lowest possible back-reflection in a beam dump 13. The fiber 12 is coated with a layer of magnetostrictive material 14, which, when placed in a constant or alternating magnetic field from moving carriage magnet 15, suffers a changed localized stress field. This localized stress field transfers the fiber 12, and causes a small light reflection signal at the point of localized stress. The reflection signal interferes with a reference wave arranged at the fiber input (for example, by reflection from the fiber input face), and the interferogram is detected via a bulk or fiber beamsplitter 16. For a movement of one half of the effective light wavelength in the fiber 12, one cycle of the interferogram is detected. Appropriate phase detection schemes allow counting of the fringes, and hen...