Optics: measuring and testing – For optical fiber or waveguide inspection
Patent
1995-02-15
1996-09-17
McGraw, Vincent P.
Optics: measuring and testing
For optical fiber or waveguide inspection
25022719, G01B 902, G01B 1116
Patent
active
055574009
ABSTRACT:
An apparatus and method for measuring the change in a dimension that characterizes a structure. The apparatus operates by measuring the distance between a plurality of reflective markers located along an optical fiber. The optical fiber is attached to the structure in such a manner that a change in the dimension in question results in a change in the optical delay of the fiber between at least two of the markers. The fiber is illuminated with low coherence light. Each marker reflects a portion of a light signal traversing the fiber from a first end thereof. The markers are located at predetermined distances from the first end. Light reflected from the markers is collected and introduced into an autocorrelator that measures the coherent sum of a first signal comprising the collected light and a second signal comprising the collected light delayed by a variable time delay. The coherent sum is measured as a function of said variable time delay. Various embodiments of the present invention utilize different methods for identifying the specific markers. For example, the markers may be constructed such that each pair of markers reflects light of a characteristic wavelength. In a second embodiment, the distance between each pair of markers is used to identify the pair of markers. In a third embodiment, the reflectivity of each marker is used to identify the marker.
REFERENCES:
patent: 5187362 (1993-02-01), Keeble
patent: 5268738 (1993-12-01), Baney et al.
patent: 5341205 (1994-08-01), McLandrich et al.
patent: 5383015 (1995-01-01), Grimes
Danielson et al "Guided-wave reflectometry with micrometer resolution" Applied Optics, vol. 26 No. 14/15 Jul. 1987 pp. 2836-2842.
Baney Douglas M.
Sorin Wayne V.
Hewlett--Packard Company
McGraw Vincent P.
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