Fiber Bragg grating (FBG) sensors

B-SENS designs and develops fully-customizable FBG sensing solutions that can yield quasi-distributed measurements and communicate the processed data to the end user.

These developments encompass the production of the FBG sensors (1), their functional coating, protection or packaging (2) and the read-out unit (3).

1. FBG

FBGs are produced in telecommunication-grade optical fibers (outer diameter of 250 µm) by local laser irradiation transversely to the optical fiber axis.

They are usually short in length (<1 cm) and act as bandpass filters in reflection around the so-called Bragg wavelength.

They are inherently sensitive to temperature changes and axial strain, which induces a shift of their Bragg wavelength. Tracking this shift allows to determine the actual temperature or strain value after calibration.
Nominally, they can reflect the temperature value at +/- 0.1 °C and the strain value at +/- 1µε.

This emerging technology brings the following advantages that are decisive in numerous applications:

  • Small dimensions (<1/4 mm for bare fibers, flexibility with high integration and embedding capabilities)
  • Quasi-distributed sensing (up to 40 sensors cascaded in 1 fiber and connected to 1 device, much less cables, easy installation)
  • Long-haul measurements (20+ km)
  • High fatigue resistance
  • Reliability (passive devices, life time > 20 years, stability over time, no corrosion, use of telecommunication-grade cables/connectors)
  • Use of light (immunity for electromagnetic radiation & radio frequency interference, immune for high voltage discharge, explosion safe, suitable for use in harsh environment)

2. Coating/Protection/Packaging

Specific coatings can be applied to the optical fiber surface at the FBG location to widen the sensing modalities. We have solutions to enable hydrogen sensing and early fire detection.

Our expertise in this field is quite unique and multifold. We make use of organic, inorganic & metal coatings. Their synthesis is ensured by various physical/chemical processes.

Depending on the target application, a specific protection and/or packaging can be applied around the FBG. Metal layers, glass, aluminum, ceramic or Teflon tubing are some prominent examples.

3. Read-out unit

The read-out unit is the measurement device that launches light within the optical fiber cable and collect the FBG spectrum. While optical fibers can be considered the nervous system of the sensing solution, the interrogator is its core.

We have developed two complementary devices:

Both solutions are very competitive in terms of performance and cost. They are provided with a user-friendly interface (Labview or Python) that can be adapted depending on customer’s requirements.

Communication can be provided through Ethernet, WiFi, Bluetooth or LoRa.