Optical fiber mode separation systems
AssigneeHydroacoustics Inc.
InventorsDavid M. Berg, Kenneth J. Teegarden
Life of this patent
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Abstract
When a multimode optical fiber is deformed in accordance with an input signal to be sensed, light from lower order core modes is coupled to higher order core modes. A lens assembly is provided which separates the light in the higher order core modes from the light remaining in the lower order core modes. A spatial filter in the lens assembly enables the lens or lenses therein to couple the separated modes to two different output fibers with high efficiency and low coupling loss. The two signals in the output fibers are processed so that the common components which constitute noise are cancelled, while the signal components are additively combined and appear at the system's output so as to provide a highly sensitive, low noise fiber optic sensor system.
Claims23
An optical wave guide system comprising an optical wave guide from which guided optical power radiates at different angles depending upon the modes of transmission of the power in the wave guide, optical apparatus for selectively separating said power belonging to said modes of transmission, which apparatus comprises means for providing a spatial Fourier transform of said optical power at a plane, and a spatial filter disposed in said plane.
An optical transmission system comprising a wave guide from which different components of transmitted light exit the wave guide at different angles, optical apparatus for separating at least one of said different components, which apparatus comprises means for providing a spatial Fourier transform of the light in a plane, and a spatial filter disposed in said plane.
An optical system comprising an input optical fiber, a pair of output fibers, means for deforming said input fiber to change the modes of transmission of light in said input fiber, and optical means for separating groups of modes transmitted in said input fiber and directing light propagating in said input fiber in one of said groups including lower order modes to one of said output fibers and another of said groups including higher order modes to the other of said output fibers, said optical means comprising means for providing a spatial Fourier transform of light in the path between said input and output fibers, and a spatial filter in said plane.
Dependencies are inferred from the claim text.