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 θ 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 θ, the amount of attenuation is increased; by decreasing the angle θ, the amount of attenuation is decreased. The invention allows continuous tuning of the angle θ.