Patent ID: 8682127
Filing Date: 2014-03-25
Classification: G02B

Abstract:
1. A method of fabricating a silica optical fiber or fiber preform comprising the steps of: forming a first module including a core region and an inner cladding region, forming a second module, surrounding said first module, said second module including an inner trench region, and forming a third module surrounding said second module, said third module including a pedestal region surrounding said inner trench region, an outer trench region surrounding said pedestal region, and an outer cladding region surrounding said outer trench region, wherein said modules are formed so that said outer cladding region has a refractive index less than that of said core region, said inner cladding region has a refractive index less than that of said outer cladding region, said pedestal region has a refractive index approximately equal to that of said outer cladding region, said inner trench region has a refractive index much less than that of said outer cladding region, said pedestal region has a refractive index greater than the refractive indices of said inner and outer trench regions, and said pedestal region is configured to resonantly couple at least one transverse mode of said core region, other than said fundamental mode, to at least one transverse mode of said pedestal region, said core region of said fiber has a radius of r said first module is fabricated by a process selected from the group consisting of vapor phase axial deposition (VAD), outside vapor deposition (OVD) and plasma chemical vapor deposition (PCVD), said second module is fabricated by a process selected from the group consisting of plasma outside deposition (POD), PCVD, high pressure sintering of deposited soot, a down-doped sol-gel tube overcladding process, and a void-containing silica process, and said third module is fabricated by forming said pedestal region from a silica tube or by PCVD, forming said outer trench region from a down-doped silica tube, and forming said outer cladding region from a silica cylinder.