# Integrated Photonics for IoT, RoF, and Distributed Fog-Cloud Computing: A Comprehensive Review
## 1 Introduction
[12; 13] has demonstrated the feasibility and performance advantages of integrated RoF architectures for broadband access and 5G fronthaul, highlighting the impact of PICs in next-generation network infrastructures. As silicon photonics and heterogeneous integration continue to evolve, PIC-enabled RoF systems are poised to play a central role in the deployment of cost-effective, high-capacity, and flexible access networks. This review paper presents a comprehensive analysis of the emerging role of PIC technology in the evolution of next-generation sensing and computing infrastructures. Specifically, it highlights the transformative potential of PICs in enhancing the performance, scalability, and energy-efficiency of Internet of Things (IoT) sensor networks, Fog computing architectures, and Cloud-based data-processing systems. By synthesizing recent advancements in integrated photonics, the review identifies how PIC-based solutions enable high-speed, low-latency data transmission and processing at the edge (Fog) and core (Cloud) layers, while reducing the size, cost, and power consumption of sensor nodes. Furthermore, the paper outlines the current challenges and future research directions requiredto fully integrate PICs into distributed intelligent systems, ultimately contributing to the realization of faster, smarter, and more sustainable digital infrastructures. Despite these promising advancements, several challenges persist, such as the need for standardized fabrication processes, effective integration with existing electronic systems, and overcoming scalability constraints in manufacturing. Continued research and industry collaboration are therefore vital for addressing these barriers and fully realizing the transformative potential of integrated photonics in both Cloud and Fog computing networks [14; 15]. To ensure comprehensive coverage, a systematic literature review was conducted. following the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) methodology as a guiding framework. Relevant studies were identified using major scientific databases, including IEEE Xplore, ScienceDirect, and Scopus, focusing on publications from 2012 to 2025. The search strategy employed targeted keywords such as \"integrated photonics\", \"Fog computing\", \"cloud datacenters\", \"photonic integrated circuits\", \"radio over fiber\", and \"IoT sensors\". Inclusion criteria were limited to peer-reviewed journal articles and high-impact conference proceedings directly relevant to photonic integration in distributed computing environments. Although not all PRISMA items were strictly applied, the review process adhered to its core principles to ensure transparency, relevance, and rigor in the selection and synthesis of sources. The remainder of this paper is structured as follows: Section 2 describes the hierarchical architecture of IoT, Fog, and Cloud computing. Section 3 presents the role of Radio-over-Fiber (RoF) in enabling IoT and Fog computing. Section 4 summarizes key Fog computing application scenarios. Section 5 discusses PIC-enabled IoT sensors. Section 6 reviews high-speed network technology enablers. Section 7 highlights current industry implementations. Section 8 outlines future trends and research directions. Section 9 outlines a summary of benefits and Section 10 discusses the implementation challenges and emerging solutions. Finally, Section 11 provides the conclusions.