Alleviating the incompatibility between the PCPE algorithm and odd-bit QAM signals through an element-wise addition pre-processing method

The pivotal role of Photonic Integrated Chips (PIC) has become increasingly prominent in modern telecommunications, especially in data center interconnects and high-speed optical networks, which demand enhanced energy efficiency from these devices. Researchers continually strive to explore more efficient algorithmic approaches to meet this power consumption challenge. The Principal Component Phase Estimation (PCPE) algorithm stands out due to its inherent advantage of low computational complexity, low cycle-slip rate and better Mutual Information (MI) performance, making it a promising solution for reducing Digital Signal Processing (DSP) chip operational energy. However, limitations exist in current PCPE algorithm when dealing with specific modulation formats like odd-bit QAM, thereby limiting its full application potential. Addressing this issue, this work focuses on proposing an innovative Element-wise Addition pre-Processing (EAP) scheme that enhances the clarity of principal component in odd-bit Quadrature Amplitude Modulation (QAM) signals at the phase recovery stage, subsequently improving the accuracy of the PCPE algorithm. Simulation results demonstrate improved mutual information rates of 0.13 bits/symbol for 32QAM and 0.54 bits/symbol for 128QAM systems after applying the proposed solution. These findings indicate that the suggested EAP method strengthens the PCPE algorithm's performance in handling odd-bit QAM signals, broadening its application scope, and paving the way towards more energy-efficient and high-performance solutions in the field of optoelectronic chips.