TEMPERATURE-DEPENDENT PERFORMANCE OF LOOSE TUBE CABLES: BUFFER TUBE MATERIALS CABLE STRUCTURE ISSUES

摘要

A series of service-affecting field failures in cold weather (-40 ℃ to 0 ℃) initially andrnmore moderate conditions (up to 15 ℃) recently have raised concerns about the temperaturedependentrntransmission performance of loose tube fiber optic cables. First field failures occurredrnin 1550-nm aerial transmission lines while 1310-rim operations failed more recently, Field OTDRrnanalyses and laboratory temperature-cycling measurements of the affected cables established thatrnthe transmission loss resulted from fiber microbending due to random fiber contacts with thernbuffer tube walls caused by the axial shrinkage of the buffer tubes relative to the cable centralrnmember, High resolution thermal expansion/contraction measurements on commonly used PBTrn(Polybutylene terephthalate) buffer tubes indicated that the total axial shrinkage consists of tworncomponents: irreversible shrinkage due to the relaxation of processing-induced stresses and reversiblernthermal contraction/expansion. The magnitude of both components depends strongly onrnbuffer tube material characteristics and processing conditions used to manufacture buffer tubes.rnIn this report, we review our work to date in developing field installation and cable design solutions,rnpresent a comparison of two buffer tube materials, identify key materials issues that determinernbuffer tube dimensional stability, and discuss the implications of these issues on the field installationrnand cable design solutions that we developed to minimize the risk of temperatureinducedrncable loss (TICL) in loose tube fiber optic cables.