Method and system for optical communication
In various embodiments of the present invention data is transmitted in light emitted by a light source by generating a continuous-time data signal and generating, based thereon, a drive signal that provides power to the light source, thereby causing the light source to emit light; variations in the amplitude of the drive signal represent information in the continuous-time data signal. A change in average power delivered to the light source as a result of the variations in the amplitude of the drive signal is detected and power to the light source is adjusted to compensate.
1. A system for transmitting data via light emitted by a light source, the system comprising:
a continuous-time data-signal source for generating a continuous-time data signal, the continuous-time data signal including at least a sinusoidal signal;
a driver circuit for generating a drive signal, the drive signal having a drive voltage and a drive current, that provides power to the light source, thereby causing the light source to emit light, wherein variations in the amplitude of the drive signal represent information in the continuous-time data signal; and
circuitry for (i) detecting a change in average power delivered to the light source as a result of the variations in the amplitude of the drive signal and for (ii) causing the driver circuit to vary the power delivered to the light source to compensate for the change in average power.
2. The system of claim 1 , wherein the light source comprises a light-emitting diode.
3. The system of claim 1 , wherein the variations in the amplitude of the drive signal comprise frequencies less than 100 kHz, 10 kHz, or 1 kHz.
4. The system of claim 1 , wherein the continuous-time data-signal source comprises a pulse-width modulator generator for generating a pulse-width-modulated representation of the continuous-time data signal and a filter or digital-to-analog converter for removing a high-frequency component of the pulse-width-modulated representation of the continuous-time data signal to create the continuous-time data signal.
5. The system of claim 1 , wherein the continuous-time data-signal source comprises an oscillator and a mixer.
6. The system of claim 1 , wherein the continuous-time data-signal comprises a signal blending a plurality of frequencies.
7. The system of claim 1 , wherein the continuous-time data-signal comprises a plurality of symbols, each symbol represented by changes in frequency modulation.
8. The system of claim 1 , wherein the circuitry for detecting the change in average power comprises a comparator for comparing input power to power delivered to the light source.
9. The system of claim 1 , wherein the circuitry for detecting the change in average power comprises a current sensor to measure a current flowing in the light source.
10. The system of claim 1 , wherein the circuitry for causing the driver circuit to vary the power delivered to the light source comprises circuitry to change a DC offset of the drive signal or circuitry to change pulse widths of a pulse-width-modulated representation of the continuous-time data signal.
11. A method for transmitting data via light emitted by a light source, the method comprising:
generating, using a continuous-time data-signal source, a continuous-time data signal, the continuous-time data signal including at least a sinusoidal signal;
generating, using a driver circuit, a drive signal, the drive signal having a drive voltage and a drive current, that provides power to the light source, thereby causing the light source to emit light, wherein variations in the amplitude of the drive signal represent information in the continuous-time data signal;
detecting a change in average power delivered to the light source as a result of the variations in the amplitude of the drive signal; and
causing the driver circuit to vary the power delivered to the light source to compensate for the change in average power.
12. The method of claim 11 , wherein the light source comprises a light-emitting diode.
13. The method of claim 11 , further comprising generating a pulse-width-modulated representation of the continuous-time data signal and removing a high-frequency component of the pulse-width-modulated representation of the continuous-time data signal to create the continuous-time data signal.
14. The method of claim 11 , wherein detecting the change in average power delivered to the light source comprises sensing a current flowing through the light source or sensing a voltage applied to the light source.
15. The method of claim 11 , wherein causing the driver circuit to vary the power delivered to the light source comprises changing a DC offset of the drive signal or changing pulse widths of a pulse-width-modulated representation of the continuous-time data signal.
16. The method of claim 11 , further comprising receiving a dimming signal and adjusting the power provided to the light source accordingly.