Can linear pre-emphasis mitigate the nonlinear distortion of light-emitting diodes?

Area of Science:

• Optical Communications
• Signal Processing

Background:

• Visible Light Communications (VLC) utilize light-emitting diodes (LEDs) as transmitters.
• LEDs exhibit poor frequency responses, limiting VLC system performance.
• Transmitter pre-emphasis is a proposed technique to enhance LED frequency response.

Purpose of the Study:

• To investigate the effectiveness of transmitter pre-emphasis compared to receiver equalization in VLC systems.
• To analyze the impact of pre-emphasis on LED nonlinear distortion.
• To theoretically and experimentally explain the advantages of transmitter pre-emphasis.

Main Methods:

• Theoretical analysis based on communications theory for linear channels.
• Experimental validation of transmitter pre-emphasis and feed-forward equalizer (FFE) performance.
• Investigation of LED behavior at low and high input power/modulation voltages.

Main Results:

• Transmitter pre-emphasis performance is equivalent to FFE in linear regimes (low input power).
• Pre-emphasis demonstrates a clear advantage over FFE at higher modulation voltages.
• Pre-emphasis effectively mitigates nonlinear distortion inherent in LEDs.

Conclusions:

• Transmitter pre-emphasis offers a superior solution for enhancing VLC performance over traditional receiver equalization.
• The nonlinear distortion mitigation capability of pre-emphasis is a key advantage, explained here for the first time.
• Pre-emphasis is a valuable technique for improving LED-based VLC systems, especially under nonlinear operating conditions.