Product overview

Sensor fos4Acc

fiber optic acceleration sensor fos4Acc

The fos4Acc 2D FBG sensor is used for acceleration measurement. Due to the optical measuring principle and the associated insensitivity to electromagnetic interference and lightning strikes, it is excellently suited for the vibration analysis of the rotor blades of wind turbines.


In combination with the Blackbird OECD measuring device, it forms the heart of the fos4Blade modular sensor platform.

The robust design of the fos4Acc 2D is designed for use in demanding industrial environments.


In the glass fiber the signal is transmitted over a long run without significant quality losses. Therefore, the sensor is particularly suitable for measurements in rotor blades of wind turbines.


The assembly can be done either by screwing or gluing on the inside of the rotor blade.

The measurable acceleration range of fos4Acc 2D is ± 3g. Overload accelerations are permitted up to ± 40g. The frequency range that can be solved with the sensor is between 0.1Hz and 100Hz. All the frequencies relevant for rotor blade dynamics can thus be determined.


Due to the robust design, the sensor operates without problems at ambient temperatures between -20 ° C and +70 ° C.

Sensor fos4Strain

fiber optic strain sensor fos4Strain

The fos4Strain expert is a fiber-optic sensor according to the FBG principle for strain measurement. It is designed for the investigation of anisotropic composites.


Due to its high elongation capacity, passive temperature compensation and robust construction, it is ideally suited for the blade load measurement of wind turbines. Due to the optical working principle, the sensor is immune to electromagnetic interference and lightning strike.

With the fos4Strain expert, the average strain level is determined over approx. 70 mm. The influence of uneven strain distribution, as usually occurs on the surface in composites such as GRP, is thus minimized.


The temperature compensation of the sensor is based on a mechanical principle. No additional temperature is necessary. The sensor is adapted depending on the coefficient of thermal expansion of the structure to be inspected.

The maximum measuring range of the fos4Strain expert is up to ± 2,000 µstrain. In combination with up to 10^9 load changes and mechanical temperature compensation, the sensor is clearly superior to conventional resistive strain gauges.


With a kick protection of up to 150 kg, it is protected against accidental damage by maintenance personnel. The installation can be carried out at up to -10°C ambient temperature and in less than 20 minutes.

Sensor fos4Temp

fiber optic temperature sensor fos4Temp

The fos4Temp is a fiber-optic temperature sensor based on fiber Bragg grating technology.


It has been specifically designed for use in harsh environments and is immune to electromagnetic disorders due to its operation.


In addition, the fos4Temp is characterized by its high signal-to-noise ratio. Depending on the application, the fos4Temp is also available in other designs.

Fiber-optic temperature sensor, insensitive to electromagnetic interference


High signal to noise ratio

Wavelength: 1510 nm – 1595 nm


Sensitivity: about 40 pm/K (~25 ppm/K)


Temperature range: -40 to 80°C

Sensor fos4Shear

fiber optic shear sensor fos4Shear

The fos4Shear expert is a fiber-optic strain sensor for determining the shear stress of anisotropic structures. The fos4Shear expert measures strains in ±45° direction with only one connection and can be connected to other sensors.


Thanks to its simple handling and robust construction, the sensor has already established itself in the field of rotor blade dimensions.


Like all strain sensors of the expert series, the fos4Shear is intrinsically temperature-compensated and requires no additional temperature sensors.

Fiber optic shear stress sensor, insensitive to electromagnetic interference


Longer service life and larger measuring range than electrical strain gages (»10high8 load cycles with 0.2% strain)


Compensates against temperature influences

Wavelength: 1510 nn – 1595 nm


Cross-sensitivity temperature: < ± 1µstrain/K


Measuring range: approx. ± 1000µstrain

Sensor fos4Twist

fiber optic torsion sensor fos4Twist

The fos4Twist sensor offers the possibility to measure the torsion, ie the angular offset along the rotor blade, between two points. In this way, theoretical torsion models can be validated by torsion curves of real data. This may be useful for pitch control, for example.

Torsion measurement over a distance of more than 60m (peak position must be accessible for installation)


Measurement on different rotor blade radii possible


Enables extended pitch control by rotor blade torsion data

Construction: 2 boxes connected with fibers. Data transfer is fiber-optic in the gondola


The measurement device is located in the gondola


Current box dimensions: 20.5cm x 11.5cm x 2.0cm

Sensor fos4Pressure

fiber optic pressure sensor fos4Pressure

With the fiber-optic pressure sensor fos4Pressure it is possible to validate the aerodynamic profile of a wind turbine over a long period of time.


In addition, the sound emission can be measured. The turbine can be regulated to this input size, so that the general acceptance among residents increases.

Fiber-optic Fabry-Pérot Sensor for the static and dynamic pressure measurement of aerodynamic and aeroacoustic effects on the rotor blade

Rectangular fiber feed for plane integration on wings

Insensitive to electromagnetic interference, long life time, high robustness

Dimension: 10x3x2mm^2


Measuring range: 70 to 110 kPa (static), 60 to 140 kPa (dynamic),


Sensor frequency: 300kHz

Measurement Blackbird OECD

fiber optic measurement device Blackbird OECD

The Blackbird OECD measures the wavelength of the attached fiber Bragg grating (FBG) sensors. Broadband light is guided through the optical cables to the connected FBG sensor. The FBG reflects a narrow section of the spectrum. The mean wavelength (or Bragg wavelength) of the reflected signal changes depending on the measured physical quantity (e.g. temperature, strain or acceleration).


It is installed in the rotating hub and is designed for the harsh environmental conditions prevailing there in terms of vibration, temperature (fluctuation) and humidity.

The advantages of fiber optic measurement technology include an extremely high sensor durability without EMI, ESD or insulation problems.


The Blackbird OECD is the first fiber Bragg grating measurement device suitable for both vibration and strain measurements.
The Blackbird OECD combines the advantages of optical signal acquisition with regard to electromagnetic compatibility and the proven handling of conventional electrical measurement technology.

In combination with the FBG sensors fos4Acc 2D and fos4Strain, this measuring device forms the heart of the fos4Blade sensor platform, on the basis of which different applications for the optimization of wind turbines can be built.


These applications can be Rotor Ice Control, Turbine Load Control or Turbine Integrity Control.

Measurement device fos4Test dyn

fiber optic measurement device fos4Test dyn

The fos4Test dyn is a measuring device in which high-frequency optical input signals are converted into electrical output values. It is the first FBG measuring instrument, which is suitable for the determination of vibrations.


In combination with the fos4Acc 2D FBG sensor, this measuring device is the core of the system for ice detection on rotor blades of wind turbines according to DIN 45662.

Only one FBG sensor is connected and read out per measuring channel (no multiplexing). This enables highly dynamic measurements in accordance with IEC 61400-13 (prerequisites for the load measurement of wind turbines).


The fos4Test dyn thus combines the advantages of optical signal acquisition with regard to electromagnetic compatibility and the proven handling of conventional electrical measurement technology.

The fos4Test dyn is used for many applications – especially in the R&D sector in wind energy as well as in other industries. It is installed in the rotating hub and is designed for the harsh environmental conditions prevailing there with regard to vibration, temperature (oscillation) and humidity.


Multiple fos4Test dyn meters can be connected in series (Ethernet) and synchronized for off-line data collection.

Measurement device imc CANSAS-FBG-T8

fiber optic measurement device imc CANSAS-FBG-T8

The fiber optic CAN measurement module imc CANSAS-FBG-T8 based on the Blackbird OECD makes measurements in high-voltage environments safer and easier. Measuring point and measuring technology are completely decoupled thanks to the optical measuring method.


The instrument measures temperatures at any potential at eight optical inputs using the proven fiber Bragg grating sensors (FBG). This data is output via CAN.

Safe and reliable measurement in high-voltage environments
Easy handling due to small cable diameters
Measuring in the winding of electric motors
Easy to use
Easy to integrate

When working on voltages above 50V, comprehensive protective measures are prescribed. This also applies to connected measuring technology if it is electrically connected. With fiber optic measurement technology from fos4X the topic of personal protection is significantly reduced:


Since fiber-optic sensors have no electrical conductivity, neither special safety equipment nor special training of the personnel is necessary. Moreover, cost-intensive high-voltage cable insulation is no longer required.

Blade Physics Library

Blade Physics Library

The Blade Physics Library translates the fiber-optic measured variables into easily usable physical parameters, which are offered for further use via Fieldbus and IIoT interfaces.