Embodiments are presented herein of an open-loop test system for testing vertical-cavity surface-emitting lasers (VCSELs). A high-speed pulse generator may be used to produce nanoseconds pulses provided to the VCSEL device. A high-speed oscilloscope may be used to measure the resultant nanoseconds pulses across the VCSEL device. The VCSEL device voltage and VCSEL device current may be obtained from the measured nanosecond pulses according to compensation data derived from the system. A pre-test compensation procedure may be used to obtain the compensation data, which may include representative characteristics of each system component. The compensation procedure may also include capturing specified pulse trains under different load conditions of the pulse generator to obtain a scaling relationship between the VCSEL device current and an input voltage used for the pulse generation, and also for obtaining various parameters later used to derive an accurate VCSEL device voltage and an accurate VCSEL device current.