Abstract: An all-glass multi-clad polygon-shaped convex optical fiber comprises a core having a core refractive index, a first glass cladding disposed around the core and having a first cladding refractive index that is lower than the core refractive index of the core, and at least a second glass cladding disposed around the first glass cladding and having a second cladding refractive index that is lower than the first cladding refractive index. The first and second claddings each have a convex polygonal cross-section, e.g. octagonal cross-sections. A method for fabricating such an optical fiber comprises the steps of: (i) mechanically machining an all-glass optical fiber preform having a core and a first cladding into an optical fiber preform having a convex polygonal cross-section; and (ii) fusing at least another glass cladding to the optical fiber preform, thereby resulting in the all-glass multi-clad polygon-shaped convex optical fiber.

Abstract: Machine for the abrasive machining of cylindrical parts, on which the parts to be machined are driven in rotation and in axial translational motion by supporting and driving means. The machine comprises a plurality of bands (17) of abrasive cloth having grains of increasing fineness in the direction of axial translational motion (A) of the parts to be machined, advancing means for unwinding each band (17) from a reel of new cloth continuously during the machining and for rewinding it onto a reel of worn cloth, bearing means for applying each band (17) with a predetermined pressure onto the parts to be machined, and oscillation means (18, 19, 20) for driving the said bearing means in an oscillating movement in axial translational motion.The invention is used, for example, for the superfinishing of shock-absorber rods, of cylindrical rollers, etc.