Patent ID: 9065245
Filing Date: 2015-06-23
Classification: G02B,H01S

Abstract:
1. A double-sheath fiber having a core region ( 1 ) and a sheath region, the sheath region having an inner region ( 2 ) and an outer region ( 3 ), which comprises a refractive index that is lower with respect to that of the inner region ( 2 ) and the core region ( 1 ), wherein the outer region ( 3 ) surrounds the inner region ( 2 ), comprising an internal structure ( 4 ) of the inner region ( 2 ) which effects a spatial overlap of modes of higher order with the core region ( 1 ), which is lower than the spatial overlap of a fundamental mode with the core region ( 1 ), wherein the internal structure ( 4 ) is formed by channels mainly extending in fiber length direction, wherein the ratio of the diameter d of the channels versus the center distance Λ of adjacent channels is less than 0.5, preferably less than 0.3, with the center distance Λ being greater than 20 times a wavelength of an electromagnetic radiation propagating in the fiber.