Simplified Self-Coherent FSO Transmission Boosted by Digital Resolution Enhancer

The joint application of free-space optics (FSO) transmission with coherent detection has recently appeared to enable unprecedented optical wireless capacity. Nevertheless, due to the associated cost and power consumption, simplified self-coherent FSO links are currently being explored to optimize the performance vs. complexity tradeoff. In particular, the utilization of low-complexity virtual carrier self-coherent transmission provides an appealing cost-effective alternative for high-capacity FSO links. However, this transmission paradigm is associated with quantization noise problems due to limited digital-to-analog converter (DAC) resolution. Following all the stated requirements, this work presents a simplified virtual carrier-assisted self-coherent FSO link supported by a low-resolution DAC and Nyquist rate phase reconstruction using the DC-Value algorithm. The utilization of such a low-resolution DAC is aided by a digital resolution enhancement (DRE) method. Employing this simplified self-coherent approach, we experimentally demonstrated 100 Gbps FSO transmission over an outdoor 42 m link using a DAC with resolution as low as 3 bits.