Patent ID: 7844154

Claim:
An optical fiber for optical power transmission, comprising: an inner isolation region comprising glass having microstructures formed therein and having a relative refractive index Δ 2 , inner and outer radii r 1 and r 2 that define an area A 2 =r 2 2 −r 1 2 , wherein r 1 and r 2 are measured in micrometers and wherein −400≦Δ 2 A 2 ≦−20; an annular power waveguide region surrounding the inner isolation region and adapted to carry power light; an outer annular isolation region comprising glass having microstructures formed therein and having a relative refractive index Δ 4 , inner and outer radii r 3 and r 4 that define an area A 4 =r 4 2 −r 3 2 , wherein r 3 and r 4 are measured in micrometers and wherein −6000≦Δ 4 A 4 ≦−100; and a cladding surrounding the outer annular isolation region.