Method for manufacturing an optical fiber preform with improved air/glass interface structure

An optical fiber preform comprising a plurality of longitudinal air holes is subjected to a thermal treatment (i.e., heating), coupled with the application of a compressive force on either end of the heated preform to compress the entire preform structure a predetermined amount. The thermal compression treatment has been found to smooth any roughened glass surfaces and heal microcracks that may have formed during the preform fabrication process, essentially "knitting" the glass material back together and forming a preform of improved quality over the prior art microstructured preforms.