Optical gas-sensing technologies offer distinct advantages and limitations, making them essential for applications in environmental monitoring, industrial safety, and healthcare. This review presents a comparative analysis of optical gas sensors classified according to their operating mechanisms (spectroscopic, chemical, and electronic) and technological platforms (fiber-optic, dye-based, carbon-based, and waveguide structures). Sensor performance is evaluated using key metrics, including sensitivity, selectivity, response time, environmental stability, durability, fabrication cost, and calibration requirements. Spectroscopic techniques such as tunable diode laser absorption spectroscopy (TDLAS) and Fourier-transform infrared (FTIR) spectroscopy achieve exceptional sensitivity (<1 ppm) and molecular selectivity, but often require complex calibration procedures and costly instrumentation. Fiber-optic and waveguide-based sensors demonstrate high stability and rapid response times (often <1 s), making them well suited for real-time and remote monitoring. Dye-based and chemical sensors offer cost-effective and selective solutions, although their long-term stability may be limited by material degradation. Electronic and carbon-based sensors, including metal-oxide semiconductors, carbon nanotubes, and graphene, provide high sensitivity and robustness, yet face challenges related to cross-sensitivity and large-scale fabrication. Overall, this comparative assessment highlights the performance trade-offs among different sensing mechanisms and platforms, clarifying their suitability for specific application scenarios. Future research should focus on material engineering, hybrid optical–electrical sensing architectures, scalable fabrication strategies, and advanced signal-processing approaches to enhance long-term stability, reduce system complexity, and accelerate the deployment of next-generation optical gas-sensing technologies.
Davari et al. (Sun,) studied this question.