Efficiency Enhancement of Optical Tuning for Bragg Gratings in Rare-Earth Doped Fibers

It has been demonstrated that the Bragg gratings in a rare-earth doped fiber can be effectively tuned based on the thermal effect induced by the pump absorption. In this letter, we theoretically and experimentally investigate how to improve the optical tuning efficiency. Through fiber selection, a maximum wavelength shift of 1.14 nm is obtained with a pump power of 216.8 mW in a highly doped Er/Yb codoped fiber. We further propose two methods to enhance the tuning efficiency via weakening the heat transfer from silica fiber to the ambient air: 1) pumping the surrounding air to close to vacuum and 2) depositing a silver film. As a result, the tuning efficiency can be enhanced by 46%.