Linewidth Calibration of SG-DBR Lasers

We propose a simple and quick linewidth calibration method for tunable sampled grating distributed Bragg reflector lasers. Only the voltage across the gain section is measured, which allows the operation point with either highest sidemode suppression ratio (SMSR) or lowest linewidth to be selected. The technique results in a linewidth reduction of up to 80% when compared to techniques that only calibrate for SMSR and output power.