Novel two-dimensional (2D)-materials-based ultra-fast modulators exhibit significance in extending the fundamental investigations and practical applications of mode-locked fiber lasers. In our work, employing the liquid-phase exfoliation method, a ${{\rm Cr}_2}{{\rm Ge}_2}{{\rm Te}_6}$Cr2Ge2Te6 (CGT) optical modulator with a modulation depth and a saturable intensity of 1.64% and ${6.31}\,\,{{\rm MW/cm}^2}$6.31MW/cm2 was fabricated. Due to its suitable modulation properties and high nonlinear coefficient, a stable bright-dark soliton pair was successfully achieved within an Er-doped fiber laser. Under the pump power of 560 mW, the maximum average output power was 5.36 mW with a pulse repetition rate of 1.835 MHz. Our results fully present the capacity of CGT in designing bright-dark soliton operations and provide a meaningful reference for promoting the ultra-fast modulation applications of ferromagnetic insulators.