Fiber and lens preform with deep radial gradient layer and method of manufacturing same

A process of forming a fiber preform of fixed length, suitable for use in the production of a glass fiber or lens, wherein said fiber preform is characterized by an annular region having a continuous radial gradient extending along a cylindrical axis of said fiber preform, said process comprising the steps of:

• a) providing a glass tube having a first predetermined fixed length on a glass core having a second predetermined fixed length to form an initial preform structure having a third predetermined fixed length;
• b) supporting said initial preform structure in a heat resistant case to substantially maintain the uniform radial shape of said initial preform structure;
• c) heating said initial preform structure to form a deeply placed radial bonded layer at the interface between said glass tube and said glass core;
• and
• d) rotating said initial preform structure about a predetermined axis during said step of heating, whereby said initial preform structure becomes said fiber preform of fixed length.

A method of forming a cylindrical fiber preform suitable for use in the production of glass fiber or lenses wherein the material properties of said fiber preform are consistent at equivalent radii for cylindrical cross-sections taken along substantially the entire axial length of said cylindrical fiber preform, said method comprising the steps of:

• a) providing a glass core that is cylindrical in form and that has a first predetermined length, said glass core being characterized as having a first predetermined radial profile of material properties;
• b) providing a glass tube that is annular in form and that has a second predetermined length, said glass tube being characterized as having a second predetermined radial profile of material properties;
• and
• c) rotating said glass core and glass tube around a common cylindrical axis oriented orthogonal to any applied gravitational field, said step of rotating being performed in an environment heated sufficient to support radially driven interdiffusion between said glass core and said glass tube.