Showing papers on "Fiber optic sensor published in 1972"

Distance indicating optical probe

Abstract: An optical probe for monitoring the distance to an object includes at least a pair of fiber optic bundles, each bundle having the image of its end surface focused at a plane preferably located on either side of the normal position of an object. Each fiber optic bundle includes one or more fibers used as a receiver and one or more additional fibers used as light transmitters. When the image of the end of the fiber optic bundle is in focus on the object, the light observed by the receiving fiber is at a minimum. As the focus is changed, light from the transmitting fibers will increasingly cover the area observed by the receiving fibers, the intensity of the received light being a function of the out-of-focus distance. By using a pair of optical fiber bundles, the surface of which are focused at different planes, an unambiguous output may be obtained which can be converted directly into a distance measurement from the probe to an object under observation. Reflectivity of the surface of the object may be compensated for by comparing the light received by the receiving optical fibers. In one alternative embodiment, an image is formed by a single transmitter-receiver combination and the focal distance is modified by means of a high index of refraction material which is periodically interposed in the light path. In other embodiments, a beam splitter is used with two transmitterreceiver combinations and the light sources are separated by a means such as, by alternately switching the lights and detectors on and off, by light filters, or by use of polarized light.

Mode detection and delay equalization in multimode optical fiber transmission systems

Abstract: This application describes a detector-equalizer circuit for equalizing the dispersion produced in a multimode optical fiber. The circuit comprises an array of photodetectors whose physical configurations conform to the radiation pattern at the end of the optical fiber. The photodetectors selectively respond to each of the modes or to groups of modes propagating along the fiber. The several output signals thus produced are delayed an appropriate amount relative to each other, and then combined in time coincidence in a common output circuit.