Schematic of a graphene-covered microfiber structure and modulation result. (a) Schematic structure of a graphene-covered microfiber. A PDMS-supported graphene covered on the microfiber. Pump light and carrier light (signal) propagate in the waveguide simultaneously and the intensity of carrier light follow the changes of pump light with a modulation speed of (b) 10 kHz, (c) 100 kHz, and (d) 1 MHz. Reproduced from ref. .