Abstract: An integrated photonic circuit has a semiconductor tunable laser with two tuning elements and an output port providing a first laser output, and a calibration structure The calibration structure has a first reference element having a first reference wavelength response (a primary peak or valley at a first reference wavelength) as the semiconductor tunable laser is tuned by adjusting at least one of the tuning elements. The calibration structure also has a first photodetector. At least part of the laser output from the output port is coupled to the calibration structure. At least part of the first laser output is coupled within the calibration structure to the first reference element; and at least part of the first laser output leaving the first reference element after being coupled thereto is coupled to the first photodetector.