Quadrant Folding is a technique or process where the constellation points are confined to a specific quadrant or limited region of the complex plane. This can be achieved through various modulation or shaping techniques to ensure that transmitted signals remain within a designated quadrant.

Controlling the signal constellation within a particular quadrant is desirable for various reasons, such as simplifying signal processing or reducing the likelihood of errors. Techniques like quadrant folding can be employed to confine the transmitted symbols to a subset of the available signal space.


Flex-Rate Transmission using Hybrid Probabilistic and Geometric Shaped 32QAM

A novel algorithm to design geometric shaped 32QAM to work with probabilistic shaping is proposed to approach the Shannon limit within ~0.2 dB in SNR. The experimental results show ~0.2 dB SNR advantage over 64Gbaud PAS-64QAM, and flex-rate transmission demonstrates > 500 km reach improvement over 32QAM.

Universal Hybrid Probabilistic-geometric Shaping Based on Two-dimensional Distribution Matchers

We propose universal distribution matchers applicable to any two-dimensional signal constellation. We experimentally demonstrate that the performance of 32-ary QAM, based on hybrid probabilistic-geometric shaping, is superior to probabilistically shaped 32QAM and regular 32QAM.