Fiber optic sensors are classified into three main types based on how they detect and transmit light signals through optical fibers. Each type works on a different sensing principle and is used for specific applications in automation, measurement, and control systems.
The first type is the Through-Beam Fiber Optic Sensor. In this design, the transmitter and receiver are placed in two separate housings. The transmitter sends a light beam through one fiber, and the receiver collects it through another. When an object passes between them, it blocks the light beam, and the sensor detects this interruption as the presence of an object. This type provides the longest sensing distance and the highest detection accuracy. It’s commonly used for counting, object detection on conveyors, and detecting small parts at high speeds.
The second type is the Retro-Reflective Fiber Optic Sensor. Here, both the transmitter and receiver are built into the same unit, and a reflective surface (mirror or reflector) is placed opposite the sensor. The light beam travels from the transmitter, reflects off the reflector, and returns to the receiver. When an object interrupts this light path, the sensor detects it. This type offers a simpler setup than the through-beam type but slightly shorter sensing distances. It is used in packaging, labeling, and assembly systems where space is limited.
The third type is the Diffuse-Reflective Fiber Optic Sensor. In this type, the sensor emits a light beam toward the target object, and the reflected light from the object’s surface is received back by the sensor itself. The amount of reflected light depends on the object’s color, texture, and distance. When the object comes close enough, the reflected light triggers the detection signal. This type is ideal for detecting different materials or surfaces without requiring a reflector, making it perfect for detecting colored objects, transparent films, or product presence.
Brands like Omron Fiber Optic Sensor provide all three types — through-beam, retro-reflective, and diffuse-reflective — offering high precision, flexible installation, and stable detection even in tight spaces or harsh industrial conditions. Each type has its advantages, and the best choice depends on the sensing distance, environment, and object characteristics in your application.