A hollow optical fiber is usually a glass or plastic tubing with a diameter less than 1 mm and an inner coating of metal and dielectric is formed on the inside of the tubing. Light is prpagated in the bore of the tubing as being reflected on the inner surface and the inner coating enhances the reflection at the inner suface to reduce the propagation loss of the fibers.

By choosing a proper coating material, the hollow optical fibers transmitts electromagnetic wave with any wavlengths from X-ray to terahertz-wave with low transmssion losses. Hollow optical fibers also devlier short laser pulses with high-peak power that usually causes damages on the common silica-glass fibers.