# Integrated Photonics for IoT, RoF, and Distributed Fog-Cloud Computing: A Comprehensive Review
## 5 PIC-Enabled IoT Sensors  
PICs are revolutionizing the IoT by enabling miniaturized, high-performance, and energy-efficient sensing platforms to be implemented across a wide range of applications. Table 3 summarizes the current implementations of PIC-based sensors for various IoT domains--including smart cities, healthcare, transportation, surveillance, and logistics--and outlines emerging research opportunities [22; 29]. These opportunities highlight the potential for advanced sensing capabilities, such as multi-parameter monitoring, real-time environmental detection, and photonic-enhanced security features in future distributed systems.  
To fully realize their potential in IoT ecosystems, Photonic Integrated Circuit (PIC) sensors must incorporate seamless communication capabilities with mainstream wireless technologies such as Bluetooth, LoRa, WiFi, 5G, and emerging 6G networks. These communication standards are essential for enabling low-power, long-range, and high-speed data exchange across heterogeneous environments, ranging from wearable health monitors to smart city infrastructure and industrial automation [22; 23]. By integrating optical sensing with embedded wireless modules, PIC-based sensors can function as autonomous edge nodes capable of real-time data acquisition, processing, and transmission. This hybridization not only reduces latency and energy consumption but also ensures compatibility with existing IoT architectures and the next-generation, ultra-reliable, low-latency communication demands expected in 6G networks. Therefore, embedding multi-protocol wireless interfaces directly within PIC sensor platforms is a critical step toward building scalable, distributed, and intelligent photonic sensing networks for next-generation cyber-physical systems.  
Table 3 presents a brief overview of IoT PIC sensors. The development of IoT-oriented PIC sensors is expected to expand rapidly due to the growing demand for compact, energy-efficient, and high-speed sensing solutions across diverse application domains. In healthcare, PIC-based biosensors enable real-time diagnostics and non-invasive monitoring at the point of care. In industrial IoT, rugged and high-precision photonic sensors provide accurate measurements of pressure, strain, and temperature in harsh environments. Smart cities benefit from PIC-enabled sensors for traffic monitoring, air quality analysis, and intelligent infrastructure control. Additionally, PICs play a key role in emerging areas such as environmental monitoring, agriculture, and secure infrastructure. A particularly high-impact domain is the automotive industry, where autonomous vehicles rely on an array of PIC-based IoT sensors--including LIDAR, gyroscopes, and high-speed optical communication modules--for perception, localization, and navigation. These vehicles generate massive volumes of real-time data that must be processed locally by Fog computing nodes for immediate decision-making, while also being transmitted to Cloud infrastructures for large-scale learning, analytics, and long-term coordination [21; 23]. As the performance and manufacturability of photonic chips improve, their adoption in next-generation IoT networks will continue to accelerate, driving innovation across critical sectors through seamless Fog-Cloud integration.  
\begin{table}
\begin{tabular}{p{142.3 pt} p{142.3 pt} p{142.3 pt}} \hline
**Application** & **PIC Sensor** & **PIC Research Opportunities** \\ \hline \multirow{8}{*}{Smart Cities} & PhotonFirst Integrated Sensors for strain and temperature monitoring [30] & PIC-based environmental pollution monitoring networks; real-time air quality and particulate matter detection; high-density PIC arrays for urban gas leak detection \\ \cline{2-3}  & Integrated Ammonia Senso for environmental gas monitoring [31] & \\ \cline{1-1} \cline{2-3}  & Ultra-Sensitive Refractive Index Gas Sensor [29] & \\ \hline \end{tabular}
\end{table}
Table 3: IoT PIC sensors and research opportunities.