Flexible factory joint for metallic tubes which enclose loosely inside them optical fibers and its method of construction

Method for making a flexible factory joint for metallic tubes, which enclose loosely inside them optical fibers, comprising the following steps:

• a. Providing first and second metallic tubes to be connected (3, 10), having internal and external diameter, said tubes enclosing loosely inside them optical fibers surrounded by a suitable filling material and further providing a connecting metallic tube (6) having an internal land external diameter, said internal diameter being slightly larger than the external diameter of each of the first and second metallic tubes (3, 10),
• b. Positioning temporarily the connecting metallic tube (6) along its whole length over the first metallic tube to be connected (3)
• c. Cutting out sections at the ends of the metallic tubes to be connected (3, 10) in order to uncover the enclosed optical fibers
• d. Separating the optical fibers in one or more bundles (1,2) each one of them including a maximum number of 12 optical fibers
• e. Cutting each bundle of the fibers at predetermined lengths, depending on the number of the optical fibers enclosed inside the metallic tubes, such that the total length of each bundle after splicing will be the same and the total length of two spliced bundles will be shorter than the length of the connecting metallic tube (6)
• f. Splicing the optical fibers following commonly used methods for this purpose
• g. Arranging the metallic tubes to be connected (3, 10) after the splicing of the optical fibers, so that the fibers are horizontally aligned, and subsequently reducing the distance between them at a predetermined length, such that the optical fibers become loose and this way the desirable excess length of the optical fibers is ensured inside the joint,
• h. Applying a filling material over the optical fibers, same as the one surrounding the optical fibers inside the metallic tubes to be connected (3, 10).
• i. Moving the connecting metallic tube (6) over the first metallic tube to be connected (3), the spliced optical fibers (1, 2) and the second metallic tube to be connected (10) so that it overlaps the ends of the metallic tubes to be connected (3, 10) by equal sections.
• j. Securing the stability of the connection through the creation, by plastic deformation, at the sections at which the connecting metallic tube overlaps the metallic tubes (3, 10) to be connected, of more than one grooved rings (11) which have a diameter smaller than the external diameter of the connecting tube (6) k. Welding (8) circumferentially the ends of the connecting tube (6) to the external surface of the connected metallic tubes (3, 10) so that complete water tightness of the joint is achieved.