Frequency setting of a multisection laser diode taking into account thermal effects

A system in which the controller of a multi section diode laser such as a SG-DBR is configured so that the laser can be swept rapidly in a pre-determined frequency direction through a series of frequency points by asserting a pre-calibrated series of sets of control input values to the sections of the diode laser, wherein the frequency points are obtained from cavity modes in a plurality of different supermodes, and the sets of control input values are pre-determined to take account of thermal transients that are known to arise from jumps in the output modes that occur when sweeping through the pre-calibrated series of sets of control input values in the pre-determined frequency direction.