Optical margin testing system for automatic power control loops

An optical margin testing system is provided for automatic power control loops. An optical circuit includes a laser diode and a monitor diode coupled to the automatic power control loop. A bias generator circuit generates a control signal. The control signal is applied to the automatic power control loop. The control signal enables an operation point of the laser diode to both increase and decrease by a set percentage value for optical margin testing. The bias generator circuit includes a tri-state receiver. An input signal is applied to the tri-state receiver for selecting one of a normal operational mode, an increased set percentage value operational mode, and a decreased set percentage value operational mode. A current mirror is coupled to the tri-state receiver provides the control signal that is applied to the automatic power control loop.