Lucent Technologies Inc.

At+t Corp.

Darryl Leneir Brownlow

Lloyd Shepherd

Yussuf Sultan Ali

Howard Edan Katz

Valerie Jeanne Kuck

Marcia Lea Schilling

Robert C Moore

Nicholas James Levinos

Alex Harris

In accordance with the present invention, gratings are written on an optical fiber while the fiber is under a controlled amount of strain provided by two-point bending. When the strain is relaxed, the regions of perturbation become narrower as the fiber contracts and the spacing becomes smaller. The advantage of two-point bending as compared with tension is that the strain is precisely controllable and reproducible.

Method and apparatus for writing Bragg gratings on strained optical

Applicants have discovered that the speed of fiber manufacture can be substantially increased by employing a two-step curing process in which the fiber is drawn, coated and exposed to ultraviolet light on-line at high line speeds to effect a partial cure of the coating. After further cooling, the partially cured coating is fully cured by an on-reel exposure to ultraviolet light. The on-reel exposure can take place on the draw tower take-up reel as it is filing with fiber or it can take place off-line after the take-up reel has been filled and removed from the line. The on-reel exposure advantageously takes place either during filling the take-up reel, or during emptying the reel, so that each layer of fiber on the reel is exposed equally to the ultraviolet light. This method of UV illumination improves the energy efficiency in the second exposure by at least a factor of 10 to as much as a factor of 1000. The fiber primary coating pullout strength and mechanical modulus are enhanced.

High speed method for coating and curing optical fiber

Applicants have discovered that low pullout strength of optical fiber is attributable to volatile, unreacted monomers and impurities which result from the incomplete polymerization of liquid coating materials. They have further discovered that removing these unreacted liquids as by heating in air, heating in vacuum or by application of a solvent mixture improves fiber coating adhesion. By heating cured polymer-coated fiber in air at temperatures of 100.degree. C. or more, the fiber pullout strength is enhanced by 25% or more. This postcure heating can advantageously be clone off-line by placing loosely wound fiber in a heated oven. Alternatively, the postcure heating can be done on-line by reel-to-reel passage of the fiber through a heated furnace. Preferred temperatures are in the range 100.degree. C.-300.degree. C. Even greater enhancement of pullout strength can be effected by heating in vacuum or by solvent extraction.

Method for enhancing the pullout strength of polymer-coated optical fiber

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Bridgewater, NJ, United States of America

Darryl Leneir Brownlow