Norton Company

Fitel USA Corporation

Kanishka Tankala

Rakesh Kapoor

Malcolm C Smith

John D Prohaska

David J Mazzarese

Ronald D Grieger

Gary E Johnson

The present invention discloses a method of fabricating rare earth-doped preforms for optical fibers. A silica soot is deposited as a layer with high porosity on an inner surface of a silica-based tube by a modified chemical vapor deposition (MCVD) process at a temperature high enough to produce the silica soot but low enough to avoid sintering of the soot into the silica-based tube. The silica-based tube is then immersed in a solution including a rare earth element and a codopant element for impregnation. The excess solution is drained and the silica-based tube is dried in a stream of chlorine and inert gas at an elevated temperature. Then, the rare earth element and the codopant element are oxidized under an oxygen partial pressure at a temperature high enough to overcome kinetic limitations against oxidation. Finally, the soot layer is consolidated while flowing a mixture of chlorides of a second codopant element and oxygen at a sintering temperature at which the second codopant element reacts with oxygen to form codopant oxide which is delivered around the rare earth element oxide deposited in the soot layer. In the method of the current invention, one or more rare earth elements are codoped with preferred codopants including but not limited to Ge, Al, P and/or B to enhance the performance of the rare earth ions. Other dopants may also be used in conjunction with the preferred dopants for modifying the refractive index of the core.

Method of fabrication of rare earth doped preforms for optical fibers

The present invention provides an optical fiber for use in fiber lasers and amplifiers wherein the optical fiber has a core member surrounded by a cladding member for receiving pump energy and transferring the pump energy to the core member. The optical fiber also has an outer layer surrounding the cladding member. The cladding member has a circular exterior periphery and a predetermined refractive index (n ). The cladding member has an index modified region that directs light to the core member. The index modified region has a stress field portion with a predetermined refractive index (n ). The difference between the refractive index of the cladding member and that of the stress field portion (n &minus;n ) is within such a range that the stress field portion does not affect the polarization properties of the light traveling in the core member. Preferably, the difference between the refractive index of the cladding member and that of the stress field portion (n &minus;n ) is less than 10 , and more preferably 10 .

Cladding member for optical fibers and optical fibers formed with the cladding member

A drill bit is provided with a cylindrical body portion fabricated from a plastic material. The body portion is fastened in concentric, end to end relation to a cylindrical cutter fabricated from a metallic material and having an array of cutting elements disposed thereon. The body portion and cutter are preferably tubular, wherein the cutting elements are disposed in an annular array, to facilitate core or crown drilling operations. The wall thickness of the tubular body portion may be increased relative that of the cutter to compensate for wear during drilling. The tubular body portions also may fabricated from a composite polymer including wear resistant particles, whiskers, fibers and the like disposed on inner and outer surfaces of the polymer body, or dispersed throughout the body.

Method for improving wear resistance of abrasive tools

A drill bit is provided with a cylindrical body portion fabricated from a plastic material. The body portion is fastened in concentric, end to end relation to a cylindrical cutter fabricated from a metallic material and having an array of cutting elements disposed thereon. The body portion and cutter are preferably tubular, wherein the cutting elements are disposed in an annular array, to facilitate core or crown drilling operations. The wall thickness of the tubular body portion may be increased relative that of the cutter to compensate for wear during drilling.

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Southbridge, MA, United States of America

Kanishka Tankala