Fig. 1. Block diagram of a conventional visible light transmitter using an electrical digital-to-analog converter (DAC).

Fig. 2. Structure of transmitter using optical domain digital-to-analog conversion using an LED array.

Fig. 3. Array of individually switchable LEDs.

Fig. 4. Array consisting of a number of parallel strings of LEDs where each string, but not each LED, can be separately switched.

Fig. 5. Structure of transmitter using a hybrid optical/electrical DAC.

Fig. 6. Structure of the new hybrid optical/electrical DAC.