Patent ID: 8797642

Claim:
A large-mode-area (LMA) optical fiber comprising: (i) a core region having a relative refractive index Δ C wherein 0.02%<Δ C <0.15% and core radius r 1 wherein 10 μm<r 1 <30 μm; (ii) an inner cladding region having an outer radius r IN wherein 50 μm<r IN <500 μm, said inner cladding region including: (a) a first annular region immediately adjacent to and surrounding the core region and having an inner radius r 1 , an outer radius r 2 =r 1 +δr 1 , where 3 μm<δr 1 <15 μm, and a relative refractive index Δ 1 =0%; (b) at least a first ring surrounding said first annular region and having a relative refractive index Δ R1 wherein 0.5Δ C <Δ RI <2Δ C , and Δ RI >Δ I , an inner radius r 2 , an outer radius r 3 , and a ring width W RI , wherein r IN =r 3 +Δr O1 for δr O1 ≧0, and wherein r IN ≧r 3 >r 2 >r 1 ; (iii) an annular outer section immediately surrounding the ring section and having an inner radius r 3 , an outer radius r IN =r 3 +Δr O , and a relative refractive index Δ 3 , wherein Δ 3 ≧Δ 1 ; and (iv) an outer cladding immediately surrounding the inner cladding and having a relative refractive index Δ O ≦Δ 1 .