A glass rod is a cylindrical light-guiding component made from drawn optical glass, featuring low loss, high transmittance, and uniform refractive properties. It utilizes the principle of total internal reflection to efficiently transmit light entering from one end to the other while maintaining beam shape and energy stability. It is commonly used in applications such as laser coupling, medical illumination, sensing and detection, display backlighting, and experimental education. Glass rods offer flexible dimensions (diameters from 0.5–20 mm, lengths ranging from a few millimeters to one meter), and their end faces can be polished, coated with anti-reflection films, or shaped into lens structures to further reduce reflection loss and improve coupling efficiency. Their chemical inertness also allows them to operate reliably in harsh environments over extended periods, making them a simple yet essential core component in photoelectric systems.