Optical fiber, has inner spacing layer provided with certain thickness and formed between core region and cladding region, where numerical aperture of fiber or preform is determined from indexes of refraction of core and cladding regions

摘要

The fiber has a core region (1) comprising a core index, which is increased with respect to an index of refraction level of a glass matrix. A negative cladding region (3) comprises a cladding refraction index, which degrades with respect to an index of refraction level of the glass matrix. An inner spacing layer (4) is provided with certain thickness and formed between the core region and the cladding region. A numerical aperture of the optical fiber or preform is determined from the indexes of refraction of the core region and the cladding region.