| 摘要 |
Cooling of an optical fiber with helium during drawing involves recycling at least part of recovered helium having a determined impurity content into an enclosure containing at least a portion of the optical fiber without prior purification, when the determined impurity content is less than a threshold value. Optical fiber production involves: (a) introducing helium gas containing at least 85-90% helium and preferably 95-99.9999% helium into at least one enclosure containing at least a portion of the optical fiber, to contact the at least one portion of the fiber with the helium; (b) recovering at least part of the impure helium that has contacted the fiber portion; (c) determining at least one value of the content of impurities, selected from nitrogen, oxygen, water vapor, argon, HCl, H2, Si and Ge and their mixtures, contained in the at least one part of the recovered helium, and comparing the determined value with a predetermined threshold value corresponding to an impurity content of 0.001-10 volume %, preferably at most 5 volume %, and more preferably at most 1 volume %; and (d) recycling at least one part of the recovered helium having the determined impurity content into at least one enclosure containing at least a portion of the optical fiber without prior purification when the determined impurity content is less than the threshold value. The enclosure is preferably a heat exchanger having a central passage comprising an inlet port for the fiber to be cooled by contact with the gas, an outlet port for removal of the cooled optical fiber, and gas coolant inlet and outlet ports. The heat exchanger can be used for cooling the optical fiber during drawing. The helium is subjected to at least one purification process when the determined impurity content of the helium is greater than the threshold value. An Independent claim is given for an installation for fabrication of an optical fiber. |
