# Quantum-Secure Coherent Optical Networking for Advanced Infrastructures in Industry 4.0
## 8 Conclusions  
The protection of data operations requires advanced and secure solutions because these operations now define how global infrastructure develops. The integration of MACsec and Layer 2 controls with advanced digital signal processing and phase-sensitive detection magnifies the security risks from minor breaches in 400 Gbps and faster links, as predicted at the beginning. This research confirms that ignoring security holes in the optical layer combined with key exchange vulnerabilities makes large-scale infrastructure exposed to both present-day attacks and forthcoming decryption methods. Meanwhile, upper-layer encryption methods like TLS and IPSec have been insufficient over time since quantum computing threats and transmission rate growth require more protection.  
This study establishes comprehensive vulnerability mapping starting from hardware synchronization gaps and OTU4 overhead manipulation through multi-homodyne DSP exploits, and proves that coherent network protection must be fully integrated rather than followed separately. Each element in the series of protocols and framing methods coupled with encryption layers brings forth individual security threats. Post-quantum developments make data collection today more problematic since encrypted communications can later be subjected to successful decryption methods. Studies validate that using MACsec or optical-layer encryption as standalone solutions will not provide lasting confidentiality during quantum computing development.  
For the protection design of national-scale critical infrastructures, global financial systems, and data centers that support cloud-based services, it is crucial to create a security framework that considers throughput performance and latency alongside future capabilities. The proposed dual-layer encryption mode consisting of optical phase mask encoding enabled by physical-layer encryption delivers a viable solution. Networks secure their data effectively through the combination of phase mask encryption at high speeds with quantum-based key distribution methods. When a top security layer encounters an analysis or time-based attack, it is supported by a secondary defense layer that retains privacy or identifies any ongoing intrusion.  
The world's data infrastructure future requires the practical integration of quantum resilience at the physical layer because the findings show the necessity of this approach for developing coherent optical systems. Security measures implemented by stakeholders to tackle hardware and protocol weaknesses as well as cryptographic mechanism flaws enable optical transport systems that are protected from present and future data requirements and quantum security threats.  
Conceptualization, O.J. and I.A.; methodology, O.J. and I.A.; validation, O.J. and I.A.; formal analysis, O.J.; investigation, O.J.; data curation, O.J.; writing--original draft preparation, O.J. and I.A.; writing--review and editing, O.J. and I.A.; visualization, O.J.; supervision, I.A.; project administration, I.A. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.