Laser diode
Generally, laser diode can be modulated digitally or in contiueosly. I n digital application such as OOL, the laser diode will be injected by a current of two values, under threshold and above threshold to get ON OFF pulse. the limitations are many...such as laser line width, temperature of operation, laser FM transfer function and RIN noise and MPN noise in the case of multimode laser diodes. (this is summary) the complete is like a sea, so specified please