Gas-insulated equipment (GIE) plays a critical role in modern power systems

where reliable and accurate condition monitoring is essential for operational safety. Optical sensing technologies

benefiting from immunity to electromagnetic interference

high sensitivity

and adaptability to harsh environments

offer promising alternatives to traditional electrical sensors. This review presents a comprehensive survey of optical sensing technologies for GIE

including fiber Bragg gratings (FBG)

fiber-optic interferometry

distributed acoustic and temperature sensing

gas absorption spectroscopy

and electric-field detection based on the electro-optic (EO) effect. The fundamental principles

implementation schemes

and typical applications of each method are systematically analyzed. Despite the demonstrated advantages

challenges remain in sensor packaging reliability

optical coupling efficiency

and long-term stability. Future research should focus on enhancing system robustness

spatial resolution

and integration with digital twins and intelligent diagnostic frameworks. This work seeks to bridge GIE and optical sensing technologies

facilitating the development and deployment of high-reliability optical sensing systems for the monitoring of next-generation GIE.