Open AccessTheory and modeling of photodarkening-induced quasi static degradation in fiber amplifiers
Author(s) -
Benjamin G. Ward
Publication year - 2016
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.24.003488
Subject(s) - photodarkening , optics , photonic crystal fiber , materials science , grating , amplifier , coupled mode theory , mode volume , optical fiber , graded index fiber , refractive index , optoelectronics , fiber laser , physics , fiber optic sensor , cmos
A theory of photodarkening-induced quasi-static degradation in fiber amplifiers is presented. As the doped core of a fiber photodarkens and continues to absorb more power converting it to heat, the intensity grating created by higher order mode interference with the fundamental mode moves toward the input end. This creates a persistent absorption grating that remains phase-shifted from the modal interference pattern. This leads to power transfer from the fundamental mode to a higher order mode with a very small frequency offset that occurs on a time scale of minutes to hours. This process is modeled in large mode area step index and photonic crystal fibers and is found to produce reasonable threshold values.