To provide a process line by a simple and reliable method for obtaining an actual extra length having the homogeneity, regularity and high exactness of a fiber.
The optical fiber 10 is introduced into a protective metallic tube 9 accompanied with the controlled extra length. The protective metallic tube is formed by first working a primary metallic strip 1 to a tubular form, then subjecting the tubular strip to laser welding 6 and reducing the tube in some cases while allowing the tube to travel linearly. The method of obtaining the extra length of the prescribed value consists of subjecting the tube stretched by a capstan 8 operating under specified torque to post-stretching of the prescribed value while surely advancing the fiber in the welded tube, then putting the stretched tube into a relaxed state.
LE GAC RENAUD
COMELLO WALTER
