A theory of unwinding optic fiber's motion for fiberoptic data link bobbin

Recently, development of mobile communications facilities using fiberoptic data link bobbins have been carried out in which highly densely wound, extremely fine, high‐capacity, low‐loss optical fiber is unwound into free space over a long distance from a supersonic platform. In unwinding during high‐speed flight, air resistance, tension, friction, and inertia are applied suddenly to the ultrafine optical fiber. These forces jointly deform the winding shape of the optical fiber suddenly, with the result that transmission loss may be increased and the optical fiber may be broken. For the development of fiberoptic data link bobbins with ultrafine optical fiber, an analysis of the unwinding motion of the optical fiber, systematically taking account of the forces acting on the fiber, is indispensable. In this paper, a spatial unwinding theory is derived that can handle the dynamic behavior of the optical fiber as the basis for design and fabrication of fiberoptic data link bobbins that unwind optical fiber into the air. The solution method and a numerical simulation are compared with the results of an underwater unwinding test, simulating the Reynolds similarity rule with a high‐speed unwinding bobbin fabricated for test. It is shown that the present theory can effectively analyze the unwinding behavior of the optical fiber when a high‐speed unwinding bobbin is used. © 2001 Scripta Technica, Electron Comm Jpn Pt 1, 85(3): 61–73, 2002