Structure diagram of fiber optic displacement sensor

A displacement fiber optic sensor typically consists of a light source, transmitting fiber, reflective target, receiving fiber, detector, and signal processing unit arranged to measure displacement via light intensity changes.Core Components and StructureLight Source: A laser diode or He-Ne laser emits light into the transmitting fiber. The light is modulated in some systems to reduce ambient interference and improve sensitivity .Transmitting Fiber: This fiber directs light toward the target. In extrinsic sensors, the transmitting fiber is separate from the receiving fiber, and its axis can be adjusted to optimize sensitivity .Reflective Target: The moving object whose displacement is measured reflects the light back toward the receiving fiber. The distance between the fiber tip and the target determines the intensity of reflected light .Receiving Fiber: Collects the reflected light and transmits it to the detector. The receiving fiber may have a larger core to capture more light, improving linearity and sensitivity .Detector: Converts the optical signal into an electrical signal, typically using a photodiode. The output voltage is proportional to the displacement of the target .Signal Processing Unit: Includes amplifiers, lock-in amplifiers, or data acquisition systems to process the electrical signal and provide a displacement reading. Virtual instrument platforms like LabVIEW can be used for real-time monitoring and control .Structural ArrangementThe transmitting and receiving fibers are usually mounted perpendicular to each other and positioned close to the reflective surface for maximum sensitivity .The reflected light intensity decreases as the target moves laterally or axially away from the fiber axis, producing a measurable voltage change at the detector .A block diagram of the system typically shows: Light Source → Transmitting Fiber → Target → Receiving Fiber → Detector → Signal Processing → Output Display .Optional EnhancementsReflective films can be added to the target to increase light reflection and improve measurement accuracy .Piezoelectric micrometers or stepping motors can precisely control the fiber-to-target distance for calibration and testing .Virtual instrumentation allows real-time visualization of displacement versus voltage curves, enabling precise analysis of sensor performance . This configuration allows the sensor to measure axial and lateral displacements with high sensitivity, non-contact operation, and a linear response over a defined range, making it suitable for industrial, medical, and precision engineering applications .