Fiber optical signal conditioners

Signal conditioners for fiber optic sensors

Fiber optic signal conditioners form the interface between the optical sensor and the subsequent measurement data acquisition system. They transmit light to the sensor, detect the returning optical signal and convert changes in that signal into a precise measurement value. Depending on the sensor system, they can be used to measure temperature, pressure, strain or displacement, with the resulting values then provided via a display, analog output or digital interface.

Althen fiber optic signal conditioners support different sensor technologies. Systems based on WLPI technology (White Light Polarization Interferometry) are available for interferometric sensors. For fiber optic GaAs temperature sensors, signal conditioners based on SCBG technology (Semiconductor Band Gap) are used.

The product range extends from compact, battery-powered single-channel devices for mobile measurements to multi-channel signal conditioners for laboratory and field applications and modular high-speed systems with synchronized data acquisition. This makes it possible to implement both individual measuring points and extensive monitoring systems with a large number of fiber optic sensors.

A key advantage of fiber optic measurement technology is its high immunity to interference at the measuring point. Since no electrical signal transmission is required there, fiber optic sensors can also be used in environments where strong electromagnetic or radio-frequency fields would interfere with conventional electrical sensors.

Precise, interference-immune and flexibly scalable

Althen fiber optic signal conditioners cover a wide range of applications, from mobile single-point measurements to complex multi-channel monitoring systems.

What to consider when selecting a fiber optic signal conditioner

1. Determine the sensor technology
The signal conditioner must match the technology of the sensor being used. WLPI signal conditioners are intended for interferometric fiber optic sensors. Fiber optic GaAs temperature sensors, on the other hand, require signal processing based on SCBG technology.

Some systems, such as CoreSens, can support both technologies within a modular system.

2. Consider the measured variable
Depending on the connected sensor, WLPI-based systems can measure temperature, pressure, strain or displacement. Other signal conditioners are optimized for a specific measured variable, for example fiber optic temperature measurements or physiological pressure measurements.

3. Determine the required number of measurement channels
Compact single-channel devices are available for individual measuring points. Systems with, for example, 4, 8, 16 or 18 channels can be used for multiple sensors.

For larger measurement systems, a modular architecture provides additional advantages. CoreSens, for example, supports 2 to 26 channels per rack and can be expanded to up to 1,300 measurement channels by combining multiple systems.

4. Determine the required measurement speed
The required sampling rate depends on the dynamics of the measured variable. For conventional long-term monitoring of temperature or strain, comparatively low measurement rates may be sufficient.

For fast processes, signal conditioners with significantly higher sampling rates are available. Depending on the model, measurement rates range from approximately 20 Hz up to 1,000 Hz per measurement channel.

5. Consider synchronization of multiple channels
For dynamic measurements, not only a high sampling rate but also precise time synchronization between the individual channels is essential. Systems with deterministic synchronization via EtherCAT are available for such applications.

This is important, for example, when temperature, pressure, strain or displacement need to be measured simultaneously at several positions and compared with each other.

6. Select the appropriate interfaces
Different interfaces are available depending on the signal conditioner. These include:

• Analog voltage and current outputs
• RS-232
• RS-485
• Ethernet
• EtherCAT

Some systems also feature internal data storage, relay outputs or an integrated web server for configuration.

7. Consider mobile, laboratory or field use
Compact handheld devices such as PicoSens or Pico M are suitable for mobile single-point measurements and can also be operated on battery power.

For laboratory measurements, multi-channel devices with displays and data interfaces are available. For industrial field and long-term monitoring, robust desktop, wall-mounted or rack-mounted systems with multiple measurement channels are appropriate.

8. Define requirements for measurement accuracy and resolution
For high-precision applications, the resolution, linearity and accuracy of the complete system consisting of sensor and signal conditioner should be considered.

WLPI signal conditioners such as FieldSens, for example, achieve an accuracy of up to ±0.01% of full scale. In GaAs temperature measurement systems, accuracy is instead specified directly as a temperature deviation.

9. Consider environmental conditions at the measuring point
Fiber optic sensing offers particular advantages where electrical sensors could be affected by electromagnetic fields or high electrical potentials.

Typical examples include high-voltage installations, transformers, MRI systems, microwave systems, radio-frequency applications and certain applications in energy, research and medical technology.

10. Plan for long-term monitoring and scalability
In Structural Health Monitoring, geotechnical applications or plant monitoring, the number of measuring points may increase over the course of a project. For such applications, the signal conditioning electronics should be designed from the outset for expandability and multi-channel operation.

Our technical expert team will support you in selecting and matching the fiber optic sensor, signal conditioner, interfaces and measurement data acquisition system. Contact our sales team

Typical applications for fiber optic signal conditioners

Fiber optic signal conditioners are particularly suitable where precise measurements with high immunity to interference or long-term monitoring of multiple measuring points are required.

Typical applications include:

• Structural Health Monitoring
• Structural monitoring of bridges and buildings
• Tunnel and dam monitoring
• Geotechnical measurements
• Long-term infrastructure monitoring
• High-voltage installations and power supply systems
• Transformers and electrical installations
• Environments affected by EMI and RFI
• Microwave and radio-frequency applications
• Industrial process monitoring
• Research and development
• Aerospace
• Defense and safety-critical applications
• Wind energy and turbine monitoring
• Oil and gas applications
• Fiber optic temperature measurements
• Fiber optic pressure measurements
• Strain and load measurements
• Displacement and deformation measurements
• Medical and MRI applications
• Physiological pressure measurements

Thanks to different sensor, channel, interface and speed variants, the systems can be used for both individual measurement tasks and extensive long-term monitoring systems.