Optical Fiber Preform With Improved Air/Glass Interface Structure

Abstract

An optical fiber preform comprising a plurality of longitudinal air holes is subjected to a thermal treatment (i.e., heating), coupled with the application of a compressive force on either end of the heated preform to compress the entire preform structure a predetermined amount. The thermal compression treatment has been found to smooth any roughened glass surfaces and heal microcracks that may have formed during the preform fabrication process, essentially “knitting” the glass material back together and forming a preform of improved quality over the prior art microstructured preforms.

1 . A microstructured optical fiber preform exhibiting minimal air-glass interface imperfections formed by:
 heating a selected longitudinal portion of the microstructured optical fiber preform; and   longitudinally compressing the heated, selected portion of said preform using a force sufficient to heal air-glass interface imperfections along the microstructured optical fiber preform.   
     
     
         2 . An optical fiber preform as defined in  claim 1  wherein the preform exhibits an air/fill fraction greater than 75%. 
     
     
         3 . An optical fiber preform as defined in  claim 1 , wherein the preform comprises a polarization maintaining optical fiber preform. 
     
     
         4 . An optical fiber preform as defined in  claim 1  wherein the preform further comprises a plurality of longitudinal air holes. 
     
     
         5 . An optical fiber preform as defined in  claim 4  wherein the preform further comprises a plurality of glass rods extending through selected ones of the plurality of longitudinal air holes. 
     
     
         6 . A microstructured optical fiber exhibiting minimal air-glass interface imperfections formed by:
 a) heating a selected longitudinal portion of the microstructured optical fiber preform;   b) longitudinally compressing the heated, selected portion of said preform using a force sufficient to heal air-glass interface imperfections along the microstructured optical fiber preform;   c) longitudinally stretching the compressed, healed preform of step b) to a diameter suitable for subsequent drawing of the preform into a microstructured optical fiber; and   d) drawing the preform of step c) into a microstructured optical fiber.