| 摘要 |
The blank for a monomodal fibre for operation in the wavelength range from 1.5 to 1.7 mu m is produced by first depositing an optical absorbent layer (31) of silicon dioxide, doped with oxides of boron and/or phosphorus, onto the inner wall of a substrate tube (30) of silicon dioxide. The absorbent layer has a higher refractive index than silicon dioxide. It is then covered by a transparent layer (32), which forms the optical cladding of the fibre and whose refractive index is virtually matched to that of the absorption layer. Finally, the layer (33) forming the optical core of the fibre is applied; the refractive index of this final layer is greater than that of the cladding layer. The bore of the coated tube is then collapsed and forms the optical fibre blank having a full cross-section, from which an optical fibre is subsequently drawn. <IMAGE>
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