Abstract: A system is described for measuring the distance to an object by comparing a first component (18) of a light pulse that is reflected off the object (14), with a second component (20) of the light pulse that passes along a reference path (26) of known length, which provides great accuracy with a relatively simple and rugged design. The reference path (26) can be changed in precise steps so that is has an equivalent length approximately equal to the path length of the light pulse component that is reflected from the object. The resulting small difference in path lengths can be precisely determined by directing the light pulse components into opposite ends of a detector (70) formed of a material that emits a second harmonic light output at the locations where the opposite-going pulses pass simultaneously across one another.

Abstract: Systems are described for coupling a pair of optical fibers to pass light between them, which enables a coupler to be easily made, and with simple equipment, while closely controlling the characteristics of the coupler. One method includes mounting a pair of optical fibers (12A, 14A) on a block (26) having a large hole (28) therein, so the fibers extend across the hole while lying adjacent and parallel to one another. The fibers are immersed in an etchant (40) to reduce the thickness of cladding (20) around the fiber core (18). The fibers are joined together by applying a liquid polymer (16, FIG. 6) so the polymer-air interface moves along the length of the fibers to bring the fibers together in a zipper-like manner, and to progressively lay a thin coating of the polymer on the fibers.