Fibre Optic Sensors

The geological subsurface can help to provide heat as part of the energy transition. It can also store substances such as hydrogen. Fraunhofer IEG is developing the technology needed to take advantage of this: first, the subsurface needs to be explored and evaluated; boreholes must be fitted with suitable sensors; and subsurface usage must be monitored. Fraunhofer IEG is developing fibre optic sensors designed specifically for this task: coupled light is scattered within the fibres, allowing conclusions to be drawn about the environmental temperature, vibrations, or pressure with high spatial and temporal resolutions. When the optical fibres are installed accordingly, these scattering signals can also provide information about drilling operations, as well as cementation and the properties of the geothermal reservoir during extraction and operation.

Applications of fibre optic sensors

The development and use of fibre optics as distributed or point sensors is constantly growing in geoscientific and geotechnical applications. Above all, the introduction of distributed temperature sensing (DTS), distributed strain sensing (DSS), and distributed acoustic/vibration sensing (DAS/DVS) is allowing spatially and temporally continuous monitoring of (geo-)technical systems and facilities. Distributed chemical sensing and distributed pressure sensing (DPS) methods have also been demonstrated in test environments. Point sensors, on the other hand, are advantageous in applications involving high-resolution monitoring of specific system components.

Fields of application of fibre optic sensors

Fraunhofer IEG is adapting fibre optic technologies to the needs of specific technical and geotechnical applications that will need to be newly implemented or further expanded in the coming years. Efficient and effective continuous monitoring is a key building block for the safe operation of underground infrastructure. Typical applications include:

• Exploration of geological horizons and structures
• Microseismic monitoring of geothermal systems
• Monitoring of technical components in boreholes
• Monitoring of pipelines and technical systems