An optical waveguide is a structure that confines and directs light through a material, typically by using differences in optical properties to keep light within a defined path. Fiber-optic cables are a familiar example; waveguides can also be formed in thin films or other materials.
In sensing systems, changes in the light traveling through a waveguide can reveal bending, pressure, or other physical changes. Arrays of waveguides can provide measurements across a surface, such as to estimate its shape or orientation. In cyber security, waveguides are relevant as components of optical communications and sensing hardware: protecting the devices and data systems that interpret their signals helps prevent tampering, misleading measurements, or disruption. Their use in any particular system depends on its design and calibration.