## 5 Conclusions  
In this paper, we successfully constructed and tested a 4.6 km polarization-multiplexed 2 \(\times\) 2 MIMO photonic-assisted terahertz communication system. The experimental results demonstrate that the synergistic approach of using DNN with iterative pruning based on the standard deviation can significantly reduce system complexity while maintaining or lowering the signal BER. We successfully reduced the BER of dual-polarization signals from 10 Gbaud to 30 Gbaud by more than an order of magnitude, meeting the HD-FEC threshold and achieving the transmission of a 124.8 GHz, 240 Gbps (30 Gbaud) PDM-16 QAM signal. Furthermore, for 10 GBaud and 20 Gbaud data, complexity was reduced by approximately 70%. For 30 Gbaud data, complexity was reduced by about 50%. These results not only underscore the effectiveness of iterative pruning techniques in reducing BER and enhancing system performance but also emphasize their potential applications in practical communication systems. These findings are of significant importance for advancing the development of next-generation communication technologies.  
Conceptualization, J.L., S.X., Q.W., J.Z., J.G., S.W., Z.O. and Y.M.; data curation, W.Z.; formal analysis, J.L.; funding acquisition, J.Y. and W.Z.; investigation, J.L.; methodology, J.L.; project administration, W.Z.; resources, W.Z.; software, J.L.; supervision, W.Z.; validation, J.L.; visualization, J.L.; writing--original draft, J.L.; writing--review and editing, J.Y. and W.Z. All authors have read and agreed to the published version of the manuscript.  
This work is supported by the National Key R&D Program of China (2023 YFB2905600) and the National Natural Science Foundation of China (62127802, 62331004, 61720106015, and 61835002).  
**Informed Consent Statement:** Not applicable.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**V-Pol** & **10G-I** & **10G-Q** & **20G-I** & **20G-Q** & **30G-I** & **30G-Q** \\ \hline Weight Count & 227 K & 227 K & 314 K & 314 K & 479 K & 479 K \\ \hline Pruned Weight Count & 42.5 K & 61.3 K & 71.7 K & 122 K & 241 K & 246 K \\ \hline Prune Rate & 81.3\% & 73.1\% & 77.2\% & 61.0\% & 50.3\% & 48.8\% \\ \hline Complexity (FLOPS) & 86.2 K & 124 K & 145 K & 246 K & 478 K & 492 K \\ \hline Complexity Reduction & 81.1\% & 72.9\% & 77.0\% & 60.9\% & 50.2\% & 48.7\% \\ \hline \hline \end{tabular}
\end{table}
Table 1: Complexity of V-pol before and after pruning.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**V-Pol** & **10G-I** & **10G-Q** & **20G-I** & **20G-Q** & **30G-I** & **30G-Q** \\ \hline Weight Count & 227 K & 227 K & 314 K & 314 K & 479 K & 479 K \\ Pruned Weight Count & 31.6 K & 67.2 K & 81.6 K & 98.1 K & 177 K & 210 K \\ Prune Rate & 86.1\% & 70.4\% & 74.0\% & 68.7\% & 63.1\% & 56.3\% \\ Complexity (FLOPS) & 64.4 K & 136 K & 164 K & 198 K & 455 K & 420 K \\ Complexity Reduction & 85.9\% & 70.2\% & 73.9\% & 68.6\% & 63.0\% & 56.2\% \\ \hline \hline \end{tabular}
\end{table}
Table 2: Complexity of H-pol before and after pruning.  
Data Availability Statement: The raw/processed data required to reproduce these findings cannot be shared at this time as the data also form part of an ongoing study.  
The authors declare no conflicts of interest.