When a semiconductor laser is subject to optical injection, it can enter the period-one dynamics through Hopf bifurcation. Under such nonlinear dynamics, equally and oppositely frequency-shifted optical signals from the injection emerge and are utilized for frequency conversion. Only a typical semiconductor laser is required as the conversion unit, where no pump or probe laser is necessary. The frequency shift can be continuously tuned by controlling the level or frequency of the injection. A bit-error ratio down to ${10}^{-12}$ is observed with no or a slight power penalty for amplitude, frequency, and phase modulation at $2.5\mathrm{Gbits}∕\mathrm{s}$ , suggesting modulation format transparency of the system. Frequency down-, no-, and upconversion can be simultaneously achieved and individually selected, increasing the flexibility and reconfigurability of the system.