Radiation absorption creates electronic excited states that are trapped by localized defects for extended periods of time. Fiber-optic sensors detect objects and conditions by directing light to a test object and evaluating the intensity change of the returning light. They can detect very small objects, are particularly flexible to mount and are extremely resistant in harsh environments – even in high temperatures. A Fiber Sensor is a type of Photoelectric Sensor that enables detection of objects in narrow locations by transmitting light from a Fiber Amplifier Unit with a Fiber Unit. Fibers have many uses in remote sensing.