METHOD FOR PRODUCING RARE EARTH DOPED OPTICAL FIBER

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PROBLEM TO BE SOLVED : To provide a method for producing a rare earth doped optical fiber effective for suppressing photodarkening. SOLUTION : An optical fiber preform is allowed to contain 10-100 wtppm of an OH group. When the optical fiber preform is drawn to form an optical fiber, the drawing condition satisfies the expression : 0.5≤αf/αp≤0.95, wherein αp represents OH absorption loss calculated based on the OH concentration distribution of the optical fiber preform before drawing and electric field strength distribution, and αf represents OH absorption loss of the optical fiber after drawing. The OH group in the optical fiber preform is preferably distributed in a core part to which rare earth has been added. COPYRIGHT : (C)2010, JPO&INPIT