TUBE FOR REINFORCING COATED OPTICAL FIBER

摘要

PROBLEM TO BE SOLVED: To reduce shrinkage due to a temperature change of the environment and to prevent the deterioration of transmission characteristics at low temperature by using a polyester elastomer containing polybutylene naphthalate as a hard segment as a tube material and specifying the average coefficient of expansion in the longitudinal direction. SOLUTION: The tube 1 for reinforcing a coated optical fiber is formed from a polyester elastomer containing polybutylene naphthalate as a hard segment. Since the average coefficient of linear expansion in the longitudinal direction in the range of -40 to +20 deg.C is reduced to <=0.7×10-4(1/ deg.C) by regulating the soft segment contained in the polyester elastomer, shrinkage at low temperature is suppressed and the increase of loss at low temperature is reduced. The tube has a circular cross section, 0.4-0.8mm inside diameter (d), 0.15-0.30 mm thickness (t) and 1-14 kg.mm2 flexural stiffness. The tube is easily bendable and hardly causes buckling.