• Korean Journal of Optics and Photonics
• /
• v.32 no.4
• /
• pp.147-152
• /
• 2021

We report high-power continuous-wave operation of a Yb-doped fiber laser at 1070 nm, pumped by high-power laser diodes at 976 nm. Based on theoretical calculation of the stimulated Raman scattering and temperature distribution in the fiber, we construct a bidirectionally pumped Yb-fiberlaser system incorporating a pair of fiber Bragg gratings and a cladding light stripper. The fiber laser yields 3.0 kW of continuous-wave output at 1070 nm in a diffraction-limited beam with M² ≈ 1.26 for 4.1 kW of incident pump power, corresponding to a slope efficiency of 81.5%. The prospects for further power scaling are discussed.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.40 no.6
• /
• pp.547-553
• /
• 2020

As aging infrastructures increase along with time, the efficient maintenance becomes more significant and accurate responses from the sensors are pre-requisite. Among various responses, strain is commonly used to detect damage such as crack and fatigue. Optical fiber sensor is one of the promising sensing techniques to measure strains with high-durability, immunity for electrical noise, long transmission distance. Fiber Bragg Grating (FBG) is a point sensor to measure the strain based on reflected signals from the grating, while Brillouin Optic Correlation Domain Analysis (BOCDA) is a distributed sensor to measure the strain along with the optical fiber based on scattering signals. Although the FBG provides the signal with high accuracy and reproducibility, the number of sensing points is limited. On the other hand, the BOCDA can measure a quasi-continuous strain along with the optical fiber. However, the measured signals from BOCDA have low accuracy and reproducibility. This paper proposed a multi-fidelity data-fusion method based on Gaussian Process Regression to improve the fidelity of the strain distribution by fusing the advantages of both systems. The proposed method was evaluated by laboratory test. The result shows that the proposed method is promising to improve the fidelity of the strain.