Therandomphaseerrorsoftheopticalcarriersarediscussedandcontrolledforpassivemillimeter-wavesparseaperture(PMMWSA)upconversionimaging.Atwo-channelmodelissetupforanalyzingcharacteristicsofthephaseerrors,andanactiveopticalcontroltechniquebasedonstochasticparallelgradientdecentalgorithm(SPGDcontroller)isproposedtocalibratethephaseerrors.TodemonstratethefeasibilityoftheSPGDcontroller,simulationsareperformedandanexperimentalsystemwithatwo-channelfiberarrayissetup.SimulationandexperimentresultsshowthattheSPGDcontrollercaneffectivelyandrapidlycompensatethephaseerrorsoftheopticalcarrier,andtheaccuracyofthephasecontrolissufficientforimagingsystems.
