A technique relates to a self-calibration routine for a laser with respect to a multiplexer. Electrical power is stepped up to a filter within the laser while monitoring transmission through multiplexer to store a current and maximum recorded transmission through multiplexer until minimum operating power is reached. If the current transmission through multiplexer at minimum operating power has fallen by more than predefined amount relative to maximum recorded transmission, the electrical power is stepped up to filter until the current transmission is restored to the predefined amount of the maximum recorded transmission, determining self-calibration for a blue edge of the multiplexer pass band. If current transmission through multiplexer at minimum operating power has not fallen by more than predefined amount relative to the maximum recorded transmission, electrical power is stepped up to filter until the current transmission falls to predefined amount of maximum recorded transmission, determining self-calibration for red edge.