Playing with fire and fibers

If done properly, the annealing of optical fiber can produce useful fiber components. Annealing a fiber involves raising the glass to a temperature above the strain point for a short time and cooling slowly back to room temperature. This process reduces stress in the glass, but also initiates a number of physical and chemical changes to the glass. This article discusses a few component examples and covers some of the glass chemistry and physics that occur during annealing. Before describing the effects of annealing, the article presents an application that motivated us to anneal optical fiber: the annealed-fiber coil. Then, after discussing some of the glass chemistry and physics, two applications where annealing's detrimental effects can be made beneficial are described: a fiber depolarizer and increased ultraviolet (UV) photosensitivity.