Understanding the concept of light-matter interaction in organic-inorganic nanostructures such as graphene and metal-halide perovskites has been explored to realize photonic and optoelectronic devices. The strong light-matter interaction and impressive performance achieved by tuning the optical/electrical properties have enabled them as potential candidates for optoelectronic applications. In this perspective, we report the synthesis of metal-halide perovskite nanocomposites by incorporation of graphene sheets into the perovskite framework, which exhibits a significant enhancement in electro-optic (E-O) switching modulation. The carrier dynamics in the nanocomposite is investigated using time-resolved luminescence and broadband dielectric spectroscopy studies to get insights into the carrier relaxation and transfer mechanisms. The presence of graphene in the perovskite nanocomposites induced dielectric polarization with a strong electrical conduction and a nonlinear dielectric behavior with negative permittivity at the percolation threshold concentration because of the large resonance derived from the plasmonic oscillations of delocalized charges. A custom-designed optical fiber integrated with nanocomposites is scrutinized to explore the light modulation and E-O sensitivity under an applied electrical field. The E-O interference that leads to phase modulation of light by change in the refractive index of the graphene-CsPbBr3 nanocomposites resulted in a higher E-O sensitivity of 18 nm/V than those of CsPbBr3 nanostructures.