An optical cavity is a pair of mirrors placed face to face so light bounces back and forth many times. Those repeated reflections trap and reinforce certain wavelengths, making the cavity a core part of lasers, optical filters, and high-precision measurement systems. Because the optical path is so sensitive to mirror spacing and alignment, even tiny physical changes can alter the light that comes out.
In cyber security, optical cavities matter wherever light is part of the system, such as fiber-optic communications, sensor networks, and laboratory equipment used in security research. Their sensitivity can be useful for defense: cavity-based instruments can detect vibration, drift, or tampering with very small signals. It can also create attack surface, because laser-based interference and fault-injection techniques may exploit optical components or disrupt readings. Understanding cavities helps defenders reason about stability, signal integrity, and the physical security of optoelectronic hardware.