Thermal treatment of silica optical fibers with CO2-laser radiation

S Khotiaintsev,A.N Castro-Martinez

doi:10.20535/2312-1807.2011.16.4.246655

Abstract

We investigate theoretically and experimentally the effect of high-power CO2–laser radiation on silica optical fibers. We show that it takes several tens of milliseconds to heat the standard single–mode silica optical fiber to the fusing temperature of silica with the focused radiation of the CO2 laser of an output power of about 5 W. A point by point exposure of the optical fiber to the focused radiation of the CO2 laser under simultaneous axial tension results in a periodic necking of the optical fiber. Such an alteration of fiber parameters constitutes the Long Period Fiber Grating

Highlights

The CO2 laser is used for splicing the optical fibers, fabrication of lenses at the optical fiber tips and fabrication of optical fiber directional couplers [1]
The Long Period Fiber Gratings (LPFG) can be fabricated in silica optical fibers by point-by-point exposure of fiber to the focused beam of the CO2 laser [16–18]
We considered the silica optical fiber of an external diameter D of 125 μm, and a length of the heated section of the optical fiber of 125, 250 and 375 μm

Summary

Introduction

The CO2 laser is used for splicing the optical fibers, fabrication of lenses at the optical fiber tips and fabrication of optical fiber directional couplers [1]. The laser radiation is partially reflected at the fiber surface and the other part is completely absorbed by the material of the fiber (The penetration depth of the optical radiation of a wavelength of 10.6 μm in silica is of few microns [24]). Under these assumptions, the evolution of absolute temperature T of the heated section of the optical fiber in time, t, is governed by the following equation: P0ηζαt = Eh + Ec + Ehc + ET ,. 2,700 kg/m3 0.7 @ λ=10.6 μm Emissivity, ε Specific Heat, cp Thermal Conductivity, k

Results of the mathematical modeling

Experiment

Conclusions