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Browse Prior Art Database

Acoustically Operated Fiber Optic Switch

IP.com Disclosure Number: IPCOM000075103D
Original Publication Date: 1971-Jul-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 24K

Publishing Venue

IBM

Related People

Smith, MV: AUTHOR

Abstract

An optical fiber guide with refractive index na at its axis has light-focusing properties when its refractive index n(r) decreases over the cross-section of the fiber in a parabolic manner n(r) = n(a) (1-1/2 a(2)r(2)). A light beam with oblique or eccentric incidence shows sinusoidal deviations from the axis of the fiber. This sinusoidal fiber has a defined periodicity length L = 2na(2)/-i/2/.

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Acoustically Operated Fiber Optic Switch

An optical fiber guide with refractive index na at its axis has light-focusing properties when its refractive index n(r) decreases over the cross-section of the fiber in a parabolic manner n(r) = n(a) (1-1/2 a(2)r(2)). A light beam with oblique or eccentric incidence shows sinusoidal deviations from the axis of the fiber. This sinusoidal fiber has a defined periodicity length L = 2na(2)/-i/2/.

Two of such self-focusing fiber guides, running parallel, have inserted a common section of at least twice the diameter d and of half the length of periodicity L/2. The normal connection of fibers is in direction 1-3 and 2-4, respectively. Both light beams cross each other within the insert of an angle 2 theta which can be derived from tan theta = n d/L.

Switching or light dividing between adjacent fibers is achieved by Brillouin- scattering of light with acoustic waves applied laterally to the common fiber section. An acoustic beam impinging normally upon the center portion of the inserted section has its frequency or wavelength chosen such that the Brillouin (Bragg)-scattering condition 2 sin theta = lambda/~ is fulfilled. A glass fiber of d =
0.3 mm diameter, e.g. with axial refractive index n(a) = 1.6 and a parameter of its radial dependence a(2) = 0.15 mm/-2/, requires a section length L/2 = 8.3 mm. A light beam of wavelength lambda = 1 mu can then be scattered with an acoustic beam of ~ = 8.8 mu wavelength. With a sound velocit...