Radius of curvature

Nominally, a polished ferrule will have a dome-shaped surface, permitting two coupled ferrules to come into contact over a small surface area in the region of the fiber.  A small radius of curvature indicates a smaller contact area between the ferrules.  Radius of curvature for a UPC connector should fall between 7 and 25mm, whereas for an APC connector, the range of acceptable radii is from 5 to 12mm.