Fiber optic position sensor

The device which measures the position of an object by utilizing principles of fiber optics is called fiber optic position sensor. It consists of an optical fiber that acts as sensing element and detects changes in position based on modulation of light within the fiber. This sensor helps to measure vibration, position and displacement of objects and offers high precision in the most demanding environments.

Working principle

Let us explore functions of different components used in fiber optic position sensor to understand its working principle.
Optical fiber : It is usually made of glass or plastic. It is capable to transmit light through its core.
Light source : It emits light pulses into one end of optical fiber. LEDs or laser diodes are used as light source. Light pulses emitted by these light sources travel along the core using total internal reflection phenomenon.
Reflection point : At certain point along the length of fiber, there is a reflection point or reflector attached to the object whose position is to be measured. The reflector can be small mirror or reflecting surface.
Position modulation : When object moves, the position of reflector changes with respect to fiber. This leads to variations in time it takes for light to travel from source to reflector and back to receiver. The movement causes shift in phase of the light pulses.
Light detection : The other end of the optical fiber is connected to light detector. This can either be photodiode or photodetector. The detector measures returning light pulses and detects any phase shift caused by movement of reflector.
Signal processing : The signal detected by light detector device is processed to extract phase shift information. This is converted into displacement or position value. This represents movement of object relative to the fiber optic sensor.
Output : The final output can be represented in various forms as per design such as analog voltage, digital signal or any suitable format. This is precise position information of object to be monitored or measured.

Example : ODP fiber optic position sensors from ALTHEN offers high precision sensing. The other manufacturers include Micronor Inc., Honeywell, Hansford Sensors, Micro Optics Inc., FiberSensing, Optocon AG, FISO Technologies Inc., Opsens Solutions Inc. and so on.

Advantages of fiber optic position sensors

Following are the benefits of this fiber optic sensor type.
• High accuracy and resolution
• Immunity against EM (ElectroMagnetic) interference
• Can work in harsh environments such as high temperatures, corrosive conditions etc.
• Long distance measurement capabilities
• Compact in size and light in weight

Conclusion : Traditional position sensors such as potentiometers and magnetic sensors have limitations in certain scenarios. Fiber optic position sensors are commonly used in various industries and applications where accurate and reliable position sensing is needed such as robotics, aerospace, automation and scientific research.

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