Functions of the Three Parts of a Fiber Optic Sensor

The three main parts of a fiber optic sensor are the light source, the optical fiber (including the sensing element), and the detector.1. Light Source

The light source generates the optical signal that travels through the fiber. Common light sources include LEDs and laser diodes, which provide stable and coherent light. The light serves as the carrier of information, and its properties—such as intensity, wavelength, phase, or polarization—can be modulated by the sensing element to reflect changes in the measured physical quantity .

2. Optical Fiber and Sensing Element

The optical fiber acts as the transmission medium, guiding light from the source to the sensing region and back to the detector. In intrinsic sensors, the fiber itself is the sensing element, where environmental changes like strain, temperature, or pressure directly modulate the light traveling through it. In extrinsic sensors, the fiber merely transmits light to and from an external transducer that interacts with the measurand . Hybrid sensors combine both approaches, using the fiber for transmission and partial sensing.

3. Detector

The detector receives the modulated light and converts it into an electrical signal that can be analyzed. Detectors measure changes in light intensity, phase, polarization, or wavelength caused by the sensing element. This conversion allows the sensor system to quantify the physical parameter being monitored, such as temperature, pressure, or current . These three components work together to form a complete fiber optic sensing system, enabling precise, remote, and interference-resistant measurements in applications ranging from structural health monitoring to high-voltage current sensing .