A prober for measuring the light output of digital devices integrally formed on a single wafer. The prober includes a light-integrating sphere sequentially aligned with selected devices. Each time that a device is aligned with the sphere, the device aligned with the sphere is activated, so that the light output of each device is individually measured. In the disclosed embodiment, the devices are vertical cavity surface emitting lasers (VCSELs) and light emitting diodes (LEDs).