An invaluable text for the teaching, design, and development of gas sensor technology. This excellent resource synthesizes the fundamental principles of spectroscopy, laser physics, and photonics technology and engineering to enable the reader to fully understand the key issues and apply them in the design of optical gas absorption sensors. It provides a straightforward introduction to low-cost and highly versatile near-IR systems, as well as an extensive review of mid-IR systems. Fibre laser systems for spectroscopy are also examined in detail, especially the emerging technique of frequency comb spectroscopy. Featuring many examples of real-world application and performance, as well as MATLAB computer programs for modeling and simulation, this exceptional work is ideal for postgraduate students, researchers, and professional engineers seeking to gain an in-depth understanding of the principles and applications of fibre-optic and laser-based gas sensors.