Effects of impurity dilution in preforms on attenuation and strength of optical fiber

The two-step optical fiber preform process (manufacture of core and clad parts separately) is developed for both cost and performance consideration during the optical fiber technology development. It is expected that the impurity at the step interfaces could be diluted with the increase of preform size which is one of the main methods for cost reduction. However, no specific quantifiable outcomes and formulation results have been reported for this dilute phenomenon. In this paper the water peak (attenuation at 1383 nm) and proof test fiber break rate of optical fiber drawn from PCVD (plasma chemical vapor deposition) core Rod in Cylinder (RIC) preform with different sizes were studied to illustrate the dilute effect. The interface impurity induced loss at 1383 nm of the fibers from the preforms with outer diameter of 185 mm and 200 mm decreased to 80% and 64% of 150 mm concept. The break rates of different preform sizes show the similar performance. This dilute effect is to be appropriate for the OVD and MCVD core technology, VAD and OVD directed over-clad technology and all other preform technology for manufacturing fibers from multi-interfaces preforms.