| 摘要 |
<p>PURPOSE:To extend the length of fiber in the system by grasping the transmission loss increasing characteristics of optical fiber due to radiation and evaluating the lifetime accurately, thereby eliminating the need of shortening the fiber length to attain an undue margin. CONSTITUTION:The transmission loss increasing phenomenon under radiation environment is modeled and the lifetime of fiber is evaluated. Assuming that the increase L of transmission loss is caused by generation of defect due to irradiation at dose rate 7, the temporal variation rate is determined and the lifetime (t) of fiber is calculated for an arbitrary dose rate gamma according to a formula; t=(1/b)Xlog{(aXy)/(aXgamma-bXL0)}, where L0: increase of transmission loss determini,nq the lifetime (t), (a) and (b): constant and coefficient determined from experimental results (including temperature). The increase L of transmission loss at a lifetime (t) is determined according to a formula; L={(aXgamma)/ b}X{1-eXp(-bXt)}. When the allowance of initial transmission loss is set at a value obtained by subtracting the increase L from dynamic range or less, the fiber length can be extended without requiring undue margin.</p> |
