Dual loop automatic power control for laser driver

A laser driver. The laser driver comprises a diode driver, a power detector, a first extreme detector, a second extreme detector and a current controller. The diode driver receives bias and modulation currents to control a laser diode for generating light signals. The power detector detects optical power of the light signals. The first and second extreme detectors, both coupled to the power detector, detect the first and second extreme values among detected optical power. The first extreme value is either the maximum or the minimum optical power of the light signals, while the second extreme value is the other.