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Measurement of the Absorption Coefficient of Yb-Doped Fibers by a Side Light Analysis
New Physics: Sae Mulli 2017; 67: 499~503
Published online April 28, 2017;
© 2017 New Physics: Sae Mulli.

Min OH1, Jonghoon YI*1, Uihyeon SEO2, Hojae LEE2, Hyunjoon CHO2, Minseung HWANG2, Kyungyung KIM2

1 Department of Physics, Yeungnam University, Gyeongsan 38541, Korea

2 Deagu Science High School, Daegu 42110, Korea

Correspondence to:
Received December 1, 2016; Revised January 8, 2017; Accepted January 9, 2017.
cc This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
A device was used to integrate side light from a Yb-doped optical fiber. The integrated side-light spectrum was analyzed by using a spectrometer. The side light from the fiber was measured as a function of the distance from the input end of diode-pumped fiber. Diodes with 915 nm or 976 nm wavelengths were used for pumping. When the pump power was very low, an exponentially decreasing fluorescence signal was observed. the absorption coefficient of the Yb-doped fiber at the pump diode's wavelength was measured by fitting the exponentially decreasing fluorescence signal. The measured results were compared with the results obtained by using the cutback method. When the pump's power intensity was larger than 2 W, the 976 nm fluorescence signal deviated from a simple exponentially-decreasing behavior due to amplified spontaneous emission in the case of the optical fiber with a 10 $\mu$m core diameter. The fluorescence signal increased with increasing distance from the fiber input end and reached a maximum, after which it decreased with increasing distance. The maximum position depended on the pump's power.
PACS numbers: 42.55.Wd, 42.55.Xi, 42.81.Cn
Keywords: Fiber laser, Absorption coefficient, Fluorescence

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