Method of making polarization retaining fiber

Abstract From the Canadian patent

Disclosed is a method of making a polarization retaining single-mode optical fiber. There is initially formed a draw blank having diametrically opposed longitudinal apertures in the cladding glass parallel to the core glass region. The draw blank is drawn into a fiber under such conditions that the apertures close as the fiber is being drawn. The flow of surrounding glass including the core glass region, toward the collapsing apertures, causes the core to assume an elliptical shape. The apertures are of such cross-sectional area and spacing from the core that the core develops the desired aspect ratio.