Optimally doped ironchalcogenide superconductor Fe_1.03Se_0.5Te_0.5 has been investigated under high pressures using synchrotronbased x-ay diffraction and midinfrared reflectance measurements at room temperature. The superconducting transition temperature .(T_c)of the same sample has been determined by temperaturedependent resistance measurements up to 10 GPa. The tetragonal phase (P4/nmm) is found to exist in phaseseparated states where both the phases have remarkably high compressibility. A firstorder structural transition to the orthorhombic phase (Pbnm) is reported above ~10 GPa. For the tetragonal phase, a strong correlation is observed between the Fe(Se,Te)₄ tetrahedral deformation and the sharp rise of T_cup to ~4 GPa, above which T_cshows marginal pressure dependence at least up to ~10 GPa. The evolution with pressure of the optical conductivity shows that with increasing pressure the tetragonal phase approaches towards a conventional metallic state. Above ~6 GPa, the Drude term reduces drastically, indicating poor metallic character of the highpressure orthorhombic phase.