# A novel space division multiplexing system for free space optical communications

**Authors:** Zhou Hai-long, Dong Jian-ji, Shi Lei, Huang De-xiu, Zhang Xin-Liang  
**arXiv:** [1308.6405](https://arxiv.org/abs/1308.6405)  
**Date:** 2013-08-29  
**Summary page:** https://www.summarizepaper.com/en/paper/1308.6405v1/

## Key points

- The paper proposes a new technique for Space Division Multiplexing (SDM) in free space optical communications using spatial phase encoding.
- This approach enables the multiplexing of orbital angular momentum (OAM), going beyond conventional SDM techniques.
- The proposed scheme involves multiplexing Gaussian beams with a set of spatial phase masks and transmitting them in the Fourier domain via a spherical lens.
- To de-multiplex the corresponding channels, another set of phase masks with matched patterns sandwiched by two lenses are used.
- Three different phase masks are proposed and analyzed: planar linear encoding, radial linear encoding, and hybrid of radial and azimuthal linear encoding.
- Combining OAM multiplexing with radial phase encoding can further increase communication capacity in free space.
- This novel SDM technique has the potential to significantly improve data transmission rates in free space optical communications beyond current conventional methods.
- It provides an efficient way to achieve high data throughput while maintaining low complexity and cost.

## Summary

The paper proposes a novel technique for Space Division Multiplexing (SDM) in free space optical communications using spatial phase encoding. This approach goes beyond conventional SDM techniques by enabling the multiplexing of orbital angular momentum (OAM). The proposed scheme involves multiplexing Gaussian beams with a set of spatial phase masks and transmitting them in the Fourier domain via a spherical lens. To de-multiplex the corresponding channels, another set of phase masks with matched patterns sandwiched by two lenses are used. The paper proposes and analyzes three different phase masks: planar linear encoding, radial linear encoding, and hybrid of radial and azimuthal linear encoding. These approaches successfully implement the multiplexing and de-multiplexing of Gaussian beams using phase encoding. The authors prove that combining OAM multiplexing with radial phase encoding can further increase communication capacity in free space. Overall, this novel SDM technique has the potential to significantly improve data transmission rates in free space optical communications beyond current conventional methods. It provides an efficient way to achieve high data throughput while maintaining low complexity and cost.