Patent ID: 7386210

Claim:
A method of making an optical fiber, comprising: providing a longitudinally extending core member comprising a first index of refraction, the core member comprising at least a core having a concentration of boron; providing a longitudinally extending cladding member having an index of refraction that is less than the first index of refraction; forming three longitudinally extending apertures in the cladding member, a first of the three apertures being generally centrally located in the cladding member and the other two apertures being disposed diametrically about the first aperture; providing two longitudinally extending members having a thermal coefficient of expansion (TCE) different from the TCE of the cladding member and an index of refraction that is different than the index of refraction of the cladding member; inserting the core member into the first aperture and the two longitudinally extending members into the other two apertures of the cladding member thereby forming a preform for drawing an optical fiber; and wherein the core has a numerical aperture of less than 0.18.