Abstract: Tension is relieved on a coupling of an optical fiber by crimping a sleeve over an end portion of the tension-resistant sheath of the optic fiber lead to produce a narrowed portion, non-parallel sided in section. This is inserted and entrapped axially rotationally and radially in a retainer which is secured within a backshell by grub screws. A collar is fitted to entrap the grub screws. The lead is supported behind the retainer by a resilient block.