Patent ID: 7305166

Claim:
A method of fabricating an optical fiber having a radially graded refractive index profile, the method comprising: providing an elongated glass core rod fabricated from a first material containing a distribution of high refractive index ions; providing an elongated glass cladding tube fabricated from a second material containing one of (i) a zero and (ii) a relatively low concentration of the high-refractive-index ions present in the core rod, the cladding tube being adapted to axially receive the core rod; introducing the core rod into the cladding tube to create a preform having a longitudinal preform axis passing through the center of the core rod; orienting the preform such that the longitudinal preform axis extends along a vertical axis; and heating and drawing, simultaneously, the preform along the vertically oriented preform axis such that, as a result of the simultaneous heating and drawing, (i) the tube collapses and fuses around the core rod and (ii) a quantity of the high-refractive-index ions in the core rod material is permitted to diffuse radially outwardly with respect to the preform axis and into the cladding material.