The manufacturing process consists of major steps, including glass deposition, preform fabrication, and fiber drawing, shown schematically below: Each step applies specialized techniques to realize the stringent requirements of optical signal transmission over transcontinental. The manufacturing process consists of major steps, including glass deposition, preform fabrication, and fiber drawing, shown schematically below: Each step applies specialized techniques to realize the stringent requirements of optical signal transmission over transcontinental. Optical fiber sensors are devices that use optical fibers to detect and measure various parameters such as temperature, pressure, strain, and refractive index. They work on the principle that the light transmitted through the optical fiber is affected by the parameter being measured. The aim of the SPIE Field Guides is to distill this information, providing readers with a handy desk or briefcase reference that provides basic, essential information about optical princi-ples, techniques, or phenomena, including definitions and descriptions, key. The review covers various fiber-optic sensors, including Bragg gratings and interferometers, detailing their principles and applications. Recent advancements focus on enhancing sensitivity and performance, especially in biomedical and environmental applications. Ultra-pure chemicals -- primarily silicon tetrachloride (SiCl4) and germanium tetrachloride (GeCl4) -- are converted into glass during preform manufacturing.