| 摘要 |
1496788 Optical fibres STANDARD TELEPHONES & CABLES Ltd 27 Aug 1975 [5 Sept 1974] 38826/74 Heading C1M An optical fibre or fibre preform is made by depositing a dopant 40 comprising or consisting of P 2 O 5 in the bore of a tube 41 of silica glass, the dopant diffusing into the inner surface of the tube 41 to obtain a layer 42 of increased refractive index, and heating the tube and collapsing its bore to obtain a fibre or preform having a core zone 45 and a cladding 46. The dopant preferably is deposited by a reaction from which hydrogen and its compounds are excluded (e.g. oxidation of PCl 3 or POCl 3 ). In a preferred embodiment Fig. 2 a layer 21 of pure SiO 2 is deposited in the bore of a tube 20 of impure SiO 2 , before the P 2 O 5 layer 22 is formed. The P 2 O 5 may be doped with an oxide of, e.g. Ge, Al, Ti, As, Ga, Sb, Ta, Sn, Nb, In or Zr. |
