In some embodiments, techniques for secure data entry comprise presenting a data field in a spoof-resistant manner, receiving field data, and securing field data. When the LED module is dimmed off, the voltage across the LED module can be kept at a value around a lighting threshold voltage of the LED module that is a minimum voltage for lighting the LED module. Subsystems on a wafer can be located at some distance apart and communicate via the optical interconnect without adverse propagation delays.