Abstract:
A single mode optical waveguide fiber having a refractive index profile comprising not less than four segments (16, 18, 20, 22) provides waveguide properties well suited to undersea or other long haul telecommunications systems. The novel refractive index profile is characterized by a core segment having a negative relative index, in which, the reference index is that of silica. Another feature of the invention is a cladding layer which contains refractive index increasing dopant at least in the cladding portion adjacent the outermost core segment.
Abstract:
An optical fiber including: (i) a silica based, rare earth doped core (12) having a first index of refraction n1; (ii) a silica based inner cladding (14) surrounding the core and having a second index of refraction n2, such that n1>n2, the inner cladding having a plurality of air holes (24, 26) extending longitudinally through the length of the optical fiber; (iii) a silica based outer cladding (16) surrounding the inner cladding and having a third index of refraction n3, such that n2>n3; wherein the optical fiber supports a single polarization mode within the operating wavelength range.