Method for controlling tension for winding of optical fiber

PURPOSE:To eliminate an increase in the loss of under-wound bobbin by making the lateral pressure applied to the optical fiber of the under-wound bobbin less than the lateral pressure which causes the optical fiber to generate the loss increase. CONSTITUTION:Winding tension is decreased from T1 to T2 as a bobbin take-up radius Ri increases so that when the winding ends, the lateral pressure applied to the optical fiber of the under wound bobbin is less than the value Pc of the lateral pressure which causes the optical fiber to generate the loss increase. Namely, contact pressure (lateral pressure) P applied between the optical fiber of a 1st layer and a bobbin is the sum of its lateral pressure P1 (only between the optical fiber of the 1st layer and the bobbin) and the whole lateral pressure of the optical fiber wound even in several layers. Therefore, when the number (n) of winding layers and the take-up tension T1 in the beginning of winding are determined, the value P is calculated, the take-up tension Tn at the end of the winding with which the value does not exceed the Pc is found, and the tension is varied stepwise from T1 to Tn, so that no increase in the loss of the under-winding of the optical fiber is generated.