How Do Fiber-Optic Sensors Work?

Fiber-optic sensors are a great technological invention with many industrial and mechanical applications.

Fiber-optic sensors are a great technological invention with many industrial and mechanical applications. 

Depending on the application, optic fibers are used as a result of their size. They are quite small and do not require electrical power, which is why they are an excellent choice for remote sensing. They also do not conduct electricity which means they are adequate for areas with high voltage.

What Are Fibre-Optic Sensors?

They are sensors that use optical fibers to inspect and detect vibrations and chemical concentrations.

Fiber optics are thin strands of fiber that transmit light energy and are a major instrument for photoelectric sensing.

Fiber optic sensors are used in various remote sensing applications as they have resistance to electromagnetic interference. The fiber optic sensor comprises a well-organized system. It consists of three major modes; the diffuse reflective mode, retroreflective, and a through-beam.

Fiber Optics

These are the primary elements that make up a fiber-optic sensor system. A fiber optic sensor system consists of a fiber-optic cable connected to a remote sensor. The fiber optics can be either made up of glass or plastics:

Glass Fiber Optics

Glass optical fibers consist of a core containing a  bundle of fragile glass strands protected by cladding or PVC jackets.

The glass strands are about 0.002 inches or 50-micron in diameter and are highly resistant. 

They are usually used for remote sensing applications in harsh environments. Glass optical fibers can withstand high temperatures, pressure, and moisture. They, however, require great care, precision, and experience when cutting them.

Plastic Fibre Optics 

They are a single optical strand of about  0.254–1.52 mm in diameter. They are used for general applications. They have a flexible working mechanism. Compared to glass fibers, they are flexible enough to bend and cut to a preferred length.

How a Fiber Optic Sensors Works

The working principle of fiber optic sensors involves a system where light is sent from the light source to a modulator passing through the optic fiber.

The fiber optic transports these light rays through the principle of internal reflection. The principle states that “When a light ray  passes through a boundary between two materials of different refractive indices(core and cladding), a part of the wave will be refracted at the surface of the boundary, and another part will be reflected.”

When the light enters the modulation area, frequency, light intensity, wavelength, light index, and other optical properties change. The light signal decreases over a distance depending on the modulation area. The extent of change in light properties is used for measurement.

Applications of Fiber Optic Sensors

Fiber optic sensors are lightweight, have high-temperature resistance, and are resistant to other environmental factors. This has made them applicable in different sectors and industries.

Fiber optic sensors are used in mechanical properties testing to measure mechanical strains, temperature, pressure. Here are some of the industries where they are applied:

  • Military and Space Applications
  • Automotive Industry
  • Mechanical Inspections
  • Internet
  • Cable Television
  • Computer Networking
  • Surgery and Dentistry


According to APL Photonics, optical fiber sensors comprise a $1 billion global market. There have been improvements in the working principle of fiber optic sensors, such as the invention of twisted multicore fiber. Also, optic fibers have been developed to reflect and scatter lights over long distances.


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