https://www.selleckchem.com/products/pf-05221304.html In this Letter, we report a high-power narrow-linewidth Yb-Raman fiber amplifier with a high second-order Raman threshold and high intensity stability. By employing two temporally stable seed lasers, over 2 kW output power at 1120 nm is achieved at a pump power of 2.6 kW with an optical-to-optical efficiency of 76.3%. The 3 dB linewidth of the 1120 nm Raman-signal laser varies slightly from 0.41 nm to 0.53 nm, and the power ratio of the second-order Raman Stokes light is only about $-46.3\;\rmdB$ at the output power of 2 kW. The results further confirm that the technique of employing temporally stable seed lasers is superior to the power scaling of narrow-linewidth Yb-Raman fiber amplifiers. To the best of our knowledge, it is the first demonstration of an over 2 kW narrow-linewidth fiber laser operating at 1120 nm.A novel, to the best of our knowledge, method to extract optical microring resonators' loss characteristics is proposed and demonstrated using optical frequency domain reflectometry (OFDR). Compared with the traditional optical transmission measurement method, the spatial-resolved backscattering optical signals obtained from the OFDR can clearly show the resonance mode's increased optical path length due to its circulation inside the resonator. By further processing the backscattered optical signals, loaded $Q$-factors of several resonators can be accurately determined. A calculation model is proposed to derive the resonance mode's intrinsic $Q$-factor from OFDR measurements of a series of loaded resonators.We numerically demonstrate an all-dielectric approach for magnetically tunable add/drop of optical channels in dense wavelength division multiplexing applications. Our concept comprises a micro-ring resonator, with an inner magneto-optical disk, side-coupled to two waveguides. The simulation results, obtained within the ITU-T G.694.1 recommendation, indicate high performance add/drop of odd and even