Optics: measuring and testing – By dispersed light spectroscopy – Utilizing a spectrometer
Patent
1992-10-28
1994-11-15
Turner, Samuel A.
Optics: measuring and testing
By dispersed light spectroscopy
Utilizing a spectrometer
385 12, 385 14, 25022727, 356345, G01B 1972
Patent
active
053653378
ABSTRACT:
An interferometric fiber-optic gyro system includes a light source and a plurality of optical fiber rings employed to measure angular displacement along three axes. Optical circuit elements interposed between the source and the rings include an optical switch for periodically applying the optical signal to each of the rings individually along three separate optical transmission paths. Included in each of the optical transmission paths is a modal filter, including a polarizer, and a beam splitter which provides two separate beams to the optical ring for counter-propagation through the ring. Compensating birefringent devices are added in the optical circuits to compensate for a residual birefringence introduced by the various optical elements in the circuits. The characteristics of the compensating devices consist of predetermined lengths of polarization preserving, single-mode optical fiber. The birefringence of each of the optical devices is characterized in terms of a total number of beat lengths. A plus or minus sign is assigned to the value of the beat lengths, depending upon the optical axis of the optical device being measured. The birefringent compensating optical fiber is selected so as to cancel the net birefringent effect of the other optical elements in the optical circuit expressed in beat length. The compensating fiber may be distributed in the optical circuit subject to the requirement that each section of optical fiber has an minimum length to assure single-mode transmission.
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Bina David R.
Lynch Daniel R.
Otten William G.
Page L. Jerry
Smiths Industries Aerospace & Defense Systems Inc.
Turner Samuel A.
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