This work was supported by the National Key R&D Program of China(No.2020YFB1805900);National Natural Science Foundation of China(NSFC)(No.62005297);Shanghai Sailing Program(No.20YF1455300);Shanghai Science International Cooperation Project(No.18590712900).
In this work, a heavily Er-doped fiber with an 8 μm core diameter and a numerical aperture of 0.13 was prepared by the modified chemical vapor deposition(MCVD) technique combined with the sol-gel method. The backgrou...