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Abstract

A method for controlling excess fiber length (EFL) in a loose tube optical fiber buffer tube which includes traversing a just extruded plastic buffer tube, containing optical fibers and a filling compound, through a vertical cooling tower along a buffer tube path of travel in the cooling tower where the cooling tower contains a water blocking device disposed at a predetermined point along the buffer tube path of travel and the water blocking device has a body containing (a) a chamber with inlet and outlet ports, defining a buffer tube path of travel aligned with the cooling tower path of travel, a conical shaped portion circumscribing a part of the buffer tube path of travel and an annulus shaped portion circumscribing the buffer tube path of travel and a portion of the conical shaped portion; (b) a device disposed near the outlet port for providing a stream of gas directed at the buffer tube path of travel; and, (c) a drain port to remove accumulated water from the annulus-shaped portion. The loose tube optical fiber buffer tube is at a predetermined elevated temperature upon emerging from the water blocking device and without EFL. Subsequently, the fiber is coupled to the loose tube interior and then cooled to ambient temperature to form EFL.