Optical fiber fabrication method

Abstract

An objective of the present invention is to provide a method whereby the fictive temperature is sufficiently reduced and it is possible to fabricate with high yield an optical fiber with low loss. In 70% or more of the region in the range from a first location wherein the glass outer diameter of the optical fiber reaches less than 500% of the final outer diameter to a second location wherein the temperature T of the optical fiber reaches 1400°C, the temperature of a furnace (20) is set such that, with n=0 being the first location and commencing from the fictive temperature Tf(0) in the first location, the difference is within ±100°C of a target temperature T(n) at each location n, the target temperature T(n) being the temperature at which Tf(n+1) reaches a minimum, Tf(n+1) being derived by carrying out a calculation by the recursive formula Tf(n+1)=T(n)+(Tf(n)-T(n))exp(-Δt / τ(T(n))), wherein Tf(n)is the fictive temperature of the core at a given location n in a fiber drawing step and an annealing step, Tf(n+1)is the fictive temperature of the core after a unit time Δt has elapsed, and τ(T(n)) is the structural relaxation constant of the material of the core in the target temperature T(n) at the location n.

Description

technical field [0001] The present invention relates to methods of manufacturing optical fibers. Background technique [0002] For high-speed optical communication with a transmission rate above 100 Gbit / s, a high optical signal-to-noise ratio (OSNR) is required. Optical fibers used as optical transmission lines are increasingly required to be low-loss, low-nonlinear optical fibers. Fiber nonlinearity and n 2 / Aeff is proportional, where n 2 is the nonlinear refractive index of the fiber, and Aeff is the effective area of ​​the fiber. The larger the effective area Aeff, the more likely it is to reduce the concentration of light energy to the core, and thereby reduce the nonlinearity. The effective area Aeff of a standard single-mode fiber conforming to ITU-T G.652 at a wavelength of 1550nm is about 80μm 2 . However, preferably, the effective area Aeff of the low nonlinear fiber is 110 μm 2 to 180μm 2 In the range. [0003] Larger effective area Aeff means greater se...

AI Technical Summary

Problems solved by technology

Therefore, this conventional slow cooling technique may not sufficiently reduce the attenuation in the optical fiber, and may deteriorate productivity because the furnace for slow cooling may be longer than necessary, or to ensure a longer The slow cooling time, the drawing speed may be slower

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