To provide parallel optical data input to optical information processing systems a choice must be made between highly parallel modulator arrays and (currently) moderately parallel arrays of active sources. Two technologies are compared for suitability to address arrays of differential pairs of PnpN optical thyristors; these are liquid crystal display devices (LCDs) and vertical cavity surface emitting lasers (VCSELs). An 8 x 8 array of thyristor pairs is addressed optically with a LCD and a single thyristor pair is driven with a VCSEL pair. The trade-offs between speed and parallelism are considered in each case and desirable properties for future devices are determined.