Fitel USA Corporation

Ofs Fitel, LLC

David J Mazzarese

George Edward Oulundsen, Iii

Peter A Weimann

Malcolm C Smith

Kariofilis Konstadinidis

Richard Norris

John D Prohaska

Kanishka Tankala

Joseph T Sledziewski, Jr

Michael Thomas Owsiany

Timothy Francis McMahon, Ii

A bend insensitive fiber optic cable includes a singlemode fiber, a buffer layer surrounding the fiber wherein a thickest component of the buffer layer has an elastic modulus greater than 515 MPa (75,000 psi), and a jacket surrounding the buffer layer, wherein the jacket has a thickness of at least 1.2 mm. In one preferred embodiment, the buffer layer includes a nylonresin with a nominal elastic modulus of approximately 218,000 psi. In this embodiment, an inner thin component of the buffer layer is made of an ethylene/ethyl acrylate resin so as to facilitate stripping of the buffer layer away from the fiber.

Bend insensitive fiber optic drop cable for in-home use

The present invention provides a method of preparing preforms for optical fibers. The invention allows one to remove or significantly reduce undesirable refractive index variations in the central portion of the optical fibers. The method of preparing the preform having a central duct includes the steps of a first collapsing step, an etching step and a second collapsing step. The first collapsing step reduces the size of the central duct without closing the central duct by heating the preform at a first preform collapsing temperature. A portion of the last deposited layer of the core glass layers is etched by flowing an etchant gas through the central duct at a lower temperature than the preform collapsing temperature. The preform is finally collapsed at a second collapsing temperature to close the central duct of the preform and form a solid rod.

Method of collapsing a tube for an optical fiber preform

The refractive index profile of a multimode optical preform, fabricated by MCVD for example, is modified in the longitudinal direction by removing selected amounts of core material from the wall of a central hole through the preform prior to collapse. The amount of core material to be removed is determined by measuring the refractive index profiles of optical fibers drawn from a number of precursor preforms at various locations along the length of the drawn fibers, averaging their profiles, and then comparing those averages with a desired profile. The refractive index profile is indirectly measured by bandwidth measurements, which are related to the alpha value a selected parameter (e.g., bandwidth) at various locations along the length of a fiber drawn from a previously fabricated preform. This parameter is then compared with desired values of that parameter at the various locations, and the differences are used to calculate the amount of core material that needs to be removed. Selective core material removal is accomplished by moving a torch along the length of the preform and flowing an etchant gas, such as a mixture of oxygen and SF , through the central hole in the preform. Selective etching is accomplished by varying the flow rate and/or the concentration of the etchant gas and/or the torch speed as a function of the location of the torch along the length of the preform.

Method of modifying the index profile of an optical fiber preform in the longitudinal direction

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

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Warren, MA, United States of America

David J Mazzarese