optical transmitter equipment and a semiconductor laser device are provided . in one example , optical transmitter equipment includes a semiconductor laser driven by a direct - modulated method . the optical transmitter equipment comprises at least a semiconductor laser , the semiconductor laser having an active layer for laser oscillation and a clad region for optical confinement ; an emission device capable of supplying optical energy to the active layer in the semiconductor laser ; and a drive circuit for the semiconductor laser . the emission device is configured to supply optical energy corresponding to a bias current in the semiconductor laser to the active layer in the semiconductor laser .