Possibility of Bending-Induced Fracture in Curved Double-Clad Fibers

Yoshito Shuto

doi:doi:10.11648/j.jeee.20221003.17

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Possibility of Bending-Induced Fracture in Curved Double-Clad Fibers

Yoshito Shuto

Published in Journal of Electrical and Electronic Engineering (Volume 10, Issue 3)

Received: 12 June 2022 Accepted: 24 June 2022 Published: 29 June 2022

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Abstract

Rare-earth-doped optical fibers are one of the most promising solid-state lasers. In these fiber lasers, a cladding-pumping scheme using large-mode-area double-clad fibers (DCFs) is utilized to increase the overall conversion efficiency of pumping light and to overcome the restriction owing to the onset of stimulated Raman scattering. On the other hand, it is extremely challenging to increase the fiber core size while retaining the excellent beam quality because fibers with large core size allow propagation of several higher-order modes (HOMs), except for the fundamental mode (FM). In order to suppress HOMs, DCFs are bent with a relatively small bend radius. For the bent DCFs, the fracture behavior, including delayed fracture, was investigated on the basis of the fracture mechanics concept. When a bent DCF is subjected to a high applied stress, failure occurs by the extension of a crack from the surface of the inner cladding (silica glass) layer of the DCF. When DCFs with core diameters of 20 and 40 μm were curved to be stored in the apparatus to maintain large bending radii of > 245 and 275 mm, respectively, it was found that both instantaneous and delayed fracture of bent DCFs could not occur in either air or distilled water. When a DCF is homogeneously curved in air and in water, bending loss occurs in the core and the optical power lost in the core is emitted from the outer interface (or boundary) between the inner cladding (silica glass) and outer cladding (low-index polymer) layers. As the transmittance of the polymer is not 100%, the leaked light is absorbed and heat accumulates in the polymer. The heat generated in the polymer through the absorption of optical power is transferred to the neighboring cladding (silica glass) layer. When the temperature of the outer wall of the cladding layer is higher than that of the inner wall, tensile stress is generated on the inner wall and compressive stress is generated on the outer wall. The thermal stress generated on the inner wall was estimated. It was concluded that the instantaneous fracture of curved DCFs could not occur in air or in distilled water under high-power laser operation.

Published in	Journal of Electrical and Electronic Engineering (Volume 10, Issue 3)
DOI	10.11648/j.jeee.20221003.17
Page(s)	121-127
Creative Commons	This is an Open Access article, distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution and reproduction in any medium or format, provided the original work is properly cited.
Copyright	Copyright © The Author(s), 2024. Published by Science Publishing Group

Keywords

Double-Clad Fiber, Bending, Fracture Strength, Time to Failure, Fracture Mechanics

References

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Yoshito Shuto. (2022). Possibility of Bending-Induced Fracture in Curved Double-Clad Fibers. Journal of Electrical and Electronic Engineering, 10(3), 121-127. https://doi.org/10.11648/j.jeee.20221003.17

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ACS Style

Yoshito Shuto. Possibility of Bending-Induced Fracture in Curved Double-Clad Fibers. J. Electr. Electron. Eng. 2022, 10(3), 121-127. doi: 10.11648/j.jeee.20221003.17

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AMA Style

Yoshito Shuto. Possibility of Bending-Induced Fracture in Curved Double-Clad Fibers. J Electr Electron Eng. 2022;10(3):121-127. doi: 10.11648/j.jeee.20221003.17

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@article{10.11648/j.jeee.20221003.17,
  author = {Yoshito Shuto},
  title = {Possibility of Bending-Induced Fracture in Curved Double-Clad Fibers},
  journal = {Journal of Electrical and Electronic Engineering},
  volume = {10},
  number = {3},
  pages = {121-127},
  doi = {10.11648/j.jeee.20221003.17},
  url = {https://doi.org/10.11648/j.jeee.20221003.17},
  eprint = {https://article.sciencepublishinggroup.com/pdf/10.11648.j.jeee.20221003.17},
  abstract = {Rare-earth-doped optical fibers are one of the most promising solid-state lasers. In these fiber lasers, a cladding-pumping scheme using large-mode-area double-clad fibers (DCFs) is utilized to increase the overall conversion efficiency of pumping light and to overcome the restriction owing to the onset of stimulated Raman scattering. On the other hand, it is extremely challenging to increase the fiber core size while retaining the excellent beam quality because fibers with large core size allow propagation of several higher-order modes (HOMs), except for the fundamental mode (FM). In order to suppress HOMs, DCFs are bent with a relatively small bend radius. For the bent DCFs, the fracture behavior, including delayed fracture, was investigated on the basis of the fracture mechanics concept. When a bent DCF is subjected to a high applied stress, failure occurs by the extension of a crack from the surface of the inner cladding (silica glass) layer of the DCF. When DCFs with core diameters of 20 and 40 μm were curved to be stored in the apparatus to maintain large bending radii of > 245 and 275 mm, respectively, it was found that both instantaneous and delayed fracture of bent DCFs could not occur in either air or distilled water. When a DCF is homogeneously curved in air and in water, bending loss occurs in the core and the optical power lost in the core is emitted from the outer interface (or boundary) between the inner cladding (silica glass) and outer cladding (low-index polymer) layers. As the transmittance of the polymer is not 100%, the leaked light is absorbed and heat accumulates in the polymer. The heat generated in the polymer through the absorption of optical power is transferred to the neighboring cladding (silica glass) layer. When the temperature of the outer wall of the cladding layer is higher than that of the inner wall, tensile stress is generated on the inner wall and compressive stress is generated on the outer wall. The thermal stress generated on the inner wall was estimated. It was concluded that the instantaneous fracture of curved DCFs could not occur in air or in distilled water under high-power laser operation.},
 year = {2022}
}

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TY  - JOUR
T1  - Possibility of Bending-Induced Fracture in Curved Double-Clad Fibers
AU  - Yoshito Shuto
Y1  - 2022/06/29
PY  - 2022
N1  - https://doi.org/10.11648/j.jeee.20221003.17
DO  - 10.11648/j.jeee.20221003.17
T2  - Journal of Electrical and Electronic Engineering
JF  - Journal of Electrical and Electronic Engineering
JO  - Journal of Electrical and Electronic Engineering
SP  - 121
EP  - 127
PB  - Science Publishing Group
SN  - 2329-1605
UR  - https://doi.org/10.11648/j.jeee.20221003.17
AB  - Rare-earth-doped optical fibers are one of the most promising solid-state lasers. In these fiber lasers, a cladding-pumping scheme using large-mode-area double-clad fibers (DCFs) is utilized to increase the overall conversion efficiency of pumping light and to overcome the restriction owing to the onset of stimulated Raman scattering. On the other hand, it is extremely challenging to increase the fiber core size while retaining the excellent beam quality because fibers with large core size allow propagation of several higher-order modes (HOMs), except for the fundamental mode (FM). In order to suppress HOMs, DCFs are bent with a relatively small bend radius. For the bent DCFs, the fracture behavior, including delayed fracture, was investigated on the basis of the fracture mechanics concept. When a bent DCF is subjected to a high applied stress, failure occurs by the extension of a crack from the surface of the inner cladding (silica glass) layer of the DCF. When DCFs with core diameters of 20 and 40 μm were curved to be stored in the apparatus to maintain large bending radii of > 245 and 275 mm, respectively, it was found that both instantaneous and delayed fracture of bent DCFs could not occur in either air or distilled water. When a DCF is homogeneously curved in air and in water, bending loss occurs in the core and the optical power lost in the core is emitted from the outer interface (or boundary) between the inner cladding (silica glass) and outer cladding (low-index polymer) layers. As the transmittance of the polymer is not 100%, the leaked light is absorbed and heat accumulates in the polymer. The heat generated in the polymer through the absorption of optical power is transferred to the neighboring cladding (silica glass) layer. When the temperature of the outer wall of the cladding layer is higher than that of the inner wall, tensile stress is generated on the inner wall and compressive stress is generated on the outer wall. The thermal stress generated on the inner wall was estimated. It was concluded that the instantaneous fracture of curved DCFs could not occur in air or in distilled water under high-power laser operation.
VL  - 10
IS  - 3
ER  -

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Yoshito Shuto

Ofra Project, Iruma, Japan

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Yoshito Shuto. (2022). Possibility of Bending-Induced Fracture in Curved Double-Clad Fibers. Journal of Electrical and Electronic Engineering, 10(3), 121-127. https://doi.org/10.11648/j.jeee.20221003.17

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ACS Style

Yoshito Shuto. Possibility of Bending-Induced Fracture in Curved Double-Clad Fibers. J. Electr. Electron. Eng. 2022, 10(3), 121-127. doi: 10.11648/j.jeee.20221003.17

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AMA Style

Yoshito Shuto. Possibility of Bending-Induced Fracture in Curved Double-Clad Fibers. J Electr Electron Eng. 2022;10(3):121-127. doi: 10.11648/j.jeee.20221003.17

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@article{10.11648/j.jeee.20221003.17,
  author = {Yoshito Shuto},
  title = {Possibility of Bending-Induced Fracture in Curved Double-Clad Fibers},
  journal = {Journal of Electrical and Electronic Engineering},
  volume = {10},
  number = {3},
  pages = {121-127},
  doi = {10.11648/j.jeee.20221003.17},
  url = {https://doi.org/10.11648/j.jeee.20221003.17},
  eprint = {https://article.sciencepublishinggroup.com/pdf/10.11648.j.jeee.20221003.17},
  abstract = {Rare-earth-doped optical fibers are one of the most promising solid-state lasers. In these fiber lasers, a cladding-pumping scheme using large-mode-area double-clad fibers (DCFs) is utilized to increase the overall conversion efficiency of pumping light and to overcome the restriction owing to the onset of stimulated Raman scattering. On the other hand, it is extremely challenging to increase the fiber core size while retaining the excellent beam quality because fibers with large core size allow propagation of several higher-order modes (HOMs), except for the fundamental mode (FM). In order to suppress HOMs, DCFs are bent with a relatively small bend radius. For the bent DCFs, the fracture behavior, including delayed fracture, was investigated on the basis of the fracture mechanics concept. When a bent DCF is subjected to a high applied stress, failure occurs by the extension of a crack from the surface of the inner cladding (silica glass) layer of the DCF. When DCFs with core diameters of 20 and 40 μm were curved to be stored in the apparatus to maintain large bending radii of > 245 and 275 mm, respectively, it was found that both instantaneous and delayed fracture of bent DCFs could not occur in either air or distilled water. When a DCF is homogeneously curved in air and in water, bending loss occurs in the core and the optical power lost in the core is emitted from the outer interface (or boundary) between the inner cladding (silica glass) and outer cladding (low-index polymer) layers. As the transmittance of the polymer is not 100%, the leaked light is absorbed and heat accumulates in the polymer. The heat generated in the polymer through the absorption of optical power is transferred to the neighboring cladding (silica glass) layer. When the temperature of the outer wall of the cladding layer is higher than that of the inner wall, tensile stress is generated on the inner wall and compressive stress is generated on the outer wall. The thermal stress generated on the inner wall was estimated. It was concluded that the instantaneous fracture of curved DCFs could not occur in air or in distilled water under high-power laser operation.},
 year = {2022}
}

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TY  - JOUR
T1  - Possibility of Bending-Induced Fracture in Curved Double-Clad Fibers
AU  - Yoshito Shuto
Y1  - 2022/06/29
PY  - 2022
N1  - https://doi.org/10.11648/j.jeee.20221003.17
DO  - 10.11648/j.jeee.20221003.17
T2  - Journal of Electrical and Electronic Engineering
JF  - Journal of Electrical and Electronic Engineering
JO  - Journal of Electrical and Electronic Engineering
SP  - 121
EP  - 127
PB  - Science Publishing Group
SN  - 2329-1605
UR  - https://doi.org/10.11648/j.jeee.20221003.17
AB  - Rare-earth-doped optical fibers are one of the most promising solid-state lasers. In these fiber lasers, a cladding-pumping scheme using large-mode-area double-clad fibers (DCFs) is utilized to increase the overall conversion efficiency of pumping light and to overcome the restriction owing to the onset of stimulated Raman scattering. On the other hand, it is extremely challenging to increase the fiber core size while retaining the excellent beam quality because fibers with large core size allow propagation of several higher-order modes (HOMs), except for the fundamental mode (FM). In order to suppress HOMs, DCFs are bent with a relatively small bend radius. For the bent DCFs, the fracture behavior, including delayed fracture, was investigated on the basis of the fracture mechanics concept. When a bent DCF is subjected to a high applied stress, failure occurs by the extension of a crack from the surface of the inner cladding (silica glass) layer of the DCF. When DCFs with core diameters of 20 and 40 μm were curved to be stored in the apparatus to maintain large bending radii of > 245 and 275 mm, respectively, it was found that both instantaneous and delayed fracture of bent DCFs could not occur in either air or distilled water. When a DCF is homogeneously curved in air and in water, bending loss occurs in the core and the optical power lost in the core is emitted from the outer interface (or boundary) between the inner cladding (silica glass) and outer cladding (low-index polymer) layers. As the transmittance of the polymer is not 100%, the leaked light is absorbed and heat accumulates in the polymer. The heat generated in the polymer through the absorption of optical power is transferred to the neighboring cladding (silica glass) layer. When the temperature of the outer wall of the cladding layer is higher than that of the inner wall, tensile stress is generated on the inner wall and compressive stress is generated on the outer wall. The thermal stress generated on the inner wall was estimated. It was concluded that the instantaneous fracture of curved DCFs could not occur in air or in distilled water under high-power laser operation.
VL  - 10
IS  - 3
ER  -

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