Provided are an optical modulating device and a system including the optical modulating device. The optical modulating device includes a substrate, and a phase modulator formed on the substrate and including a Fabry-Perot cavity. The Fabry-Perot cavity of the phase modulator includes a first reflective layer, a second reflective layer, and a tunable core formed between the first reflective layer and the second reflective layer, wherein the tunable core is formed of a semiconductor material and is configured to modulate a phase of light corresponding to modulation of a refractive index of the tunable core according to electrical control.