| 摘要 |
<p>Optical fiber (10) according to the invention comprises a core (11), with an inner cladding (12) surrounding the core, and an outer cladding surrounding the inner one. The fiber comprises preform-derived glass. The outer cladding comprises a first outer cladding region (41,42,43) between the inner cladding region and a second outer cladding region (14). The first outer cladding region is selected to have an effective refractive index less than 1.35, and such that the optical characteristics of the optical fiber are essentially independent of the second outer cladding, and/or such that the fiber is re-coat insensitive. The first outer cladding typically comprises elongate features (42,43) extending in the fiber axial direction, with a web material (41) joining the inner cladding to the second outer cladding. The elongate features are filled with a low-index material, exemplarily air, but could of course be evacuated. Fibers according to the invention have many uses, e.g., cladding-pumped optical fiber or fiber with a long period grating.</p> |
