Tensile and temperature tests of the optical fiber cable were carried out. Results of these tests showed proper cxcess fiber length selected during the cable production.SEM and DTA investigations of the standard PBT tubes disclosed a finely dispersed crystalline phase of ca.29%.The value is much lower than the maximal content of the crystalline phase liable to develop in PBT

estimated at 66%.It is very probable that greater quantity of the crystalline phase in tubes

selected during losse tube extruding

could reduce post shrinkage

thus reducing fiber attenuation

and improving mechanical strength of the tubes.