In fiber optic sensors light

Fiber optic sensors utilize visible and infrared light, typically emitted by LEDs or lasers, to detect changes in intensity, phase, wavelength, or polarization.

Fiber optic sensors operate by transmitting light through optical fibers to a sensing element or object and detecting changes in the light that occur due to the physical quantity being measured, such as distance, pressure, temperature, or strain . The light source is usually an LED or laser, with LEDs being common for industrial sensors due to their stability and cost-effectiveness . Visible light (red, blue, or pink) is often used for precise object detection and measurement. For example, red LEDs (~633 nm) provide high process stability even on bright or white surfaces, while blue LEDs (~455 nm) are suitable for detecting glossy, dark, or glowing surfaces because they penetrate less deeply into the object . Pink light combines red and blue LEDs to enhance output and range. Infrared light (wavelengths above 750 nm) is invisible to the human eye, reducing visual distractions and interference. It is ideal for applications requiring longer detection ranges or where the sensor must operate without being noticed, such as on robot grippers or autonomous vehicles . Fiber optic sensors can be intrinsic, where the fiber itself senses changes in light properties, or extrinsic, where the fiber transmits light from a remote source to a detector . The light may be modulated in intensity, phase, polarization, or wavelength, depending on the sensor type and application . In summary, fiber optic sensors rely on LED or laser light in the visible or infrared spectrum, with the choice of wavelength tailored to the sensing environment, object properties, and required measurement precision .