Optical feedback is a loop where light from one stage is returned to influence the next cycle of a physical process. It appears in lasers, photonic sensors, imaging systems, and analog optical machines, including setups that generate patterns by recirculating light. In cyber security, feedback loops matter because they can be highly sensitive: a small change in alignment, intensity, reflection, or timing can alter the output or push the system into instability.
Attackers and defenders both care about that sensitivity. A directed light source can sometimes spoof a detector, bias a sensor, or trigger a fault in an optical control loop. In research on cameras, LiDAR, and fiber-based systems, injected light has been used to test how well devices resist tampering and signal manipulation. Defenses include optical shielding, filtering unwanted reflections, independent sensor checks, and calibration controls that detect unexpected feedback. The core lesson is simple: when light becomes part of the computation, the loop itself becomes an attack surface.