  The IceCube Neutrino Observatory at the geographic South Pole instruments a
gigaton of glacial Antarctic ice with over 5000 photosensors. The detector, by
now running for over a decade, will be upgraded with seven new densely
instrumented strings. The project focuses on the improvement of low-energy and
oscillation physics sensitivities as well as re-calibration of the existing
detector. Over the last few years we developed a Precision Optical Calibration
Module (POCAM) providing self-monitored, isotropic, nanosecond, light pulses
for optical calibration of large-volume detectors. Over 20 next-generation
POCAMs will be calibrated and deployed in the IceCube Upgrade in order to
reduce existing detector systematics. We report a general overview of the POCAM
instrument, its performance and calibration procedures.
