Method and apparatus of attenuating an optical signal without adding extra components is presented. The drive current of the optical signal source is set to meet a predetermined bandwidth requirement and exceed a predetermined amplitude requirement. An optical isolator that is used to prevent back-reflections from reaching the optical signal source is used to achieve the desired amount of attenuation. More specifically, the invention includes controlling the attenuation by tuning an angle between the transmission axis of a polarizer that is part of the optical isolator and the original polarization state of the optical signal. By increasing the angle , the amount of attenuation is increased; by decreasing the angle , the amount of attenuation is decreased. The invention allows continuous tuning of the angle .