4-bit DAC based 6.9Gb/s PAM-8 UOWC system using single-pixel mini-LED and digital pre-compensation

Area of Science:

• Underwater wireless optical communication (UOWC)
• Optical communication systems
• Wireless networking

Background:

• Low-cost, high-speed underwater wireless optical communication (UOWC) is crucial for unmanned vehicles and underwater applications.
• Existing systems often face limitations in cost and speed, hindering widespread adoption.

Purpose of the Study:

• To demonstrate a high-speed and low-cost UOWC system.
• To overcome limitations of low-resolution components using digital pre-compensation (DPC).

Main Methods:

• Utilized a low-resolution digital-to-analog converter (DAC), a mini-sized light-emitting diode (mini-LED), and a digital pre-compensation (DPC) scheme.
• The DPC included digital pre-distortion (DPD), digital pre-emphasis (DPE), and digital resolution enhancer (DRE) to compensate for system impairments.
• Optimized the trade-off between inter-symbol interference and signal-to-noise ratio by tuning DPE levels.

Main Results:

• The digital resolution enhancer (DRE) improved the in-band signal-to-quantization noise ratio by 6.8 dB with a 4-bit DAC.
• Achieved a 21.1% higher data rate compared to using only digital pre-emphasis (DPE).
• Successfully demonstrated 6.9 Gb/s PAM-8 signal transmission over a 2-m distance using a single-pixel mini-LED and a 4-bit DAC.

Conclusions:

• This work reports the first cost-effective UOWC system employing a low-resolution DAC and DPC.
• The developed system offers a promising pathway for establishing low-cost underwater optical wireless networks.