▎ 摘　　要

A graphene-coated double D-type low loss all-fiber modulator is proposed. The modulator is improved on the basis of standard fiber. Only the cladding is processed without grinding the original core structure. The upper and lower cladding are cut same distance. This can ensure that the mode field does not deviate in one direction, so that most of the mode field is still tied to the core, which greatly reduces the device loss. The existence of the double graphene layer can also ensure a very excellent modulation efficiency. The calculation results show that the mode loss of our proposed dual-D modulator under X polarization is 0.125 dB/mm, and the mode field mismatch loss is 0.25%. The mode loss in Y polarization is 0.033 dB/mm, and the mode field mismatch loss is 0.32%. When the modulation voltage is 5 V, the modulation depth is 78.4% under the condition of five-layer graphene, while the modulation speed can reach 15.38 GHz. Besides maintaining low modulation voltage and higher modulation efficiency, this structure makes full use of the advantages of good fiber coupling, and will be widely used in future fiber communications and all-fiber systems. (C) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement