Remote Fiber Optic Sensors For Angular Orientation

J. T. Newmaster; M. R. Brininstool; T. Hofler; S. L. Garrett

doi:10.1117/12.942486

23 March 1988 Remote Fiber Optic Sensors For Angular Orientation

J. T. Newmaster, M. R. Brininstool, T. Hofler, S. L. Garrett

Proceedings Volume 0838, Fiber Optic and Laser Sensors V; (1988) https://doi.org/10.1117/12.942486
Event: Cambridge Symposium on Fiber Optics and Integrated Optoelectronics, 1987, Cambridge, MA, United States

Abstract

Three fiber optic sensor systems designed to remotely determine angular position are described. Two of the systems use a sheet polarizer affixed to a "codewheel" and the third system uses a two-channel digital shaft encoder style "codewheel". The first polarization scheme uses four utical channels, two of which are analog and two digital. The ratio of the two analog channel intensities yeilds tan 6. The four-fold quadrant ambiguity is resolved by the two digital channels which are transected by two semicircular masks on the polarizer codewheel [Ref. U.S. Patent #4,577,414, 25 Mar 1986]. The second polarization scheme again uses quadrant ambiguity masks but only one analog channel which simulates a polarization vector which oscillates through 90°. The oscillating vector is produced by superimposing two sine wave modulated beams at the polarizer codewheel. The modulations of the two beams have a phase difference which is created by time delaying one of the beams in a fiber delay loop. The phase difference between the generated composite signal and electronic reference signal then determines the angle of the codewheel. We have demonstrated experimentally that this type of split analog/digital scheme has a resolution equivalent to a 10-bit digital system (ie ±0.35°). The digital shaft encoder scheme uses only two digital channels and a codewheel which has two concentric masks with 48 equally spaced windows offset with respect to each other by one-half window width. At 0° there is a unique mask which initializes an up/down decoder chip [Hewlett-Packard HCTL-2000]. This system has a resolution better than 7 bits. The supporting electro-optical systems including sources, fibers,lenses, mirrors, couplers, WDM's, polarizers, detectors, and signal processing for all schemes are described and the relative merits of each are compared.

Citation Download Citation

J. T. Newmaster, M. R. Brininstool, T. Hofler, and S. L. Garrett "Remote Fiber Optic Sensors For Angular Orientation", Proc. SPIE 0838, Fiber Optic and Laser Sensors V, (23 March 1988); https://doi.org/10.1117/12.942486

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