| 摘要 |
PURPOSE:To improve the mechanical strength of a fluoride optical fiber by heating a fluoride optical fiber preform in a pressurized dry F-base gas or its mixture with a dry inert gas at a temperature near the glass-transition temperature of the preform and drawing the heat-treated preform. CONSTITUTION:An optical fiber preform 1 such as ZrF4-BaF2-LaF3-AlF3-NaF fluoride glass is attached to a dummy quartz rod 2, inserted into a pressure vessel 3 and closed with a lid 3'. The vessel 3 is filled with a dry F-base gas such as F2 or NF3 or a mixture of the F-base gas and a dry inert gas such as Ar at a pressure of >=1atm and, at the same time, the temperature near the surface of the preform 1 is raised to about 250-300 deg.C with a furnace 4 and maintained to the state for about 30hr. After the above treatment, the preform 1 is introduced into a drawing furnace 7, drawn in a dry inert gas atmosphere to an optical fiber having an outer diameter of about 200mum and coated with an ultraviolet curing resin at a thickness of about 50mum to obtain an optical fiber. As an alternative process, the preform 1 is spun by heating and drying under the conditions same as those of the above process to obtain a fluoride optical fiber. |
