# Quantum-Secure Coherent Optical Networking for Advanced Infrastructures in Industry 4.0
## 6 Optical Network Security Framework  
This final section synthesizes the vulnerabilities documented in Section 3 with the comparative insights from Section 4 to propose a layered security framework. Developed through an iterative case-based method [32], this framework was first conceptualized as a theoretical design that combines physical-layer encryption (notably optical phase mask encoding with multi-homodyne coherent detection, MHCD) and quantum key distribution (QKD). The combination of advanced approaches using MHCD or meta-holograms presents potential solutions to unite classical-quantum security standards, although the necessary infrastructure must resolve precision and operational problems [40]. The analysis shows that one method does not adequately tackle the vulnerabilities found in Section 3 without being future-proof against quantum attacks. The current cryptographic methods demonstrate either strong throughput capabilities or post-quantum security but must compromise with hardware complication procedures. The analysis demonstrates why integrated architectures must be put into practice because Section 5 builds upon this requirement. Networks become stronger by establishing a systematic union between physical-layer optical encryption and quantum key distribution because each method addresses different weaknesses and conceals other limitations [13; 31]. This modification enhances the framework in a way that not only provides details of the most suitable physical layer implementation technique but does it within the context of the general hybrid security framework. The proposed architecture in Figure 8 has one major advantage, namely the two-tier security model. At the physical layer, MHCD offers a detailed data channel encryption mechanism suitable for high-speed optical networks while QKD establishes secure working keys through the principles of quantum mechanics. This integration achieves two critical objectives: the paper focuses on achieving the high efficiency of the optical networks in use today while at the same time enhancing their resilience to both classical and quantum \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Method** & **Mechanism** & **Strengths** & **Weaknesses** & **Bandwidth** \\ \hline Spectral Phase Encoding (SPE) & Encodes data using spectral phase masks. & High resilience to brute-force attacks; suitable for high-speed networks. & Vulnerable to cryptanalysis; requires precise phase alignment. & Up to 400 Gbps per channel \\ \hline Optical Double Random Phase Encoding (DRFE) & Employs random phase keys in spatial and Fourier domains. & Dual-layer encryption; resistant to plaintext-ciphertext & Sineptible to ciphertext-only attacks enabled by advanced machine learning techniques. & Up to 100 Gbps per channel \\ \hline Phase-Change Metasurfaces & Utilize reversible amorphous crystalline phase transitions for encryption. & Ultrafast operation; integrate directly into physical layer infrastructure. & Complex fabrication requirements; sensitive to thermal variations. & Up to 200 Gbps per channel \\ \hline Reprogrammable Meta-Holograms & Use programmable incident light with metasurfaces to create dynamic holograms. & Infinite encryption channels; support dynamic configuration updates. & Require precise phase-matching between metasurface and incident beam. & Theoretical \textgreater{}400 Gbps per channel; practical implementations currently limited to 100 Gbps \\ \hline Optical Phase Mask Encoding with MHCD & Uses noise-protected spectral phase encoding with coherent detection. & High-speed operation; quantum-resistant; real-time protection. & Requires precise optical phase control. & 400 Gbps demonstrated \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Comparative analysis of network-applicable optical encryption methods. attacks. Our framework presents a new way of integrating Layer 2 security on the direct link between MACsec-enabled encryption systems and optical transceivers.