A team of researchers presents a fiber optic technology based on fiber Bragg gratings (FBGs) for sensing to monitor the activity of an active volcano. The monitoring of volcanic activity plays a crucial role in better understanding and even prediction of important and potentially disruptive volcanic events, therefore, the fiber optic sensing system has to maintain harsh environmental conditions.
Nonetheless, the recording process of seismic activity now faces several difficulties concerning both discriminating between various sources of seismic wave, and the design of fiber optic sensing systems that can operate in active volcanic settings without any damages.
The team of researchers from France demonstrates the results obtained from the first high-resolution seismometer based on FBG sensors installed on an active volcano. It should be noted that the lifetime of modern fiber optic systems is quite short during their operation at high temperatures and the billowing, sulfurous, acidic gases near a fumarole.
Additionally, standard FBG sensors can fail in emergency deployment, or repair, even in pre‐eruptive phases. The operating principle of novel fiber optic sensing systems is based on interferometry forms that apply more sensitive fiber optic elements such as fiber Bragg grating resonators that enable to detect the acceleration of the ground as a change in the signal from the FBG sensor.
These fiber optic systems can be used for networking across long distances and monitoring these distance via optical fibers. The FBG sensor is considered to be “a purely optomechanical geophone that is interrogated through a 1.5-kilometer fiber optic cable by a remote, and thus it is a much safer fiber optic system down the volcano’s flank.”
Moreover, the fiber optic sensing system has been already tested and recorded tiny seismic events within the volcano for nine months. The development of new FBG sensors lasts almost a decade, the researchers use previous researches of a high-resolution optical seismometer prototype that includes a 3-kilometer fiber optic cable.
Finally, FBG sensors are regarded as highly reliable, fiber optic technology allow installing the sensors in locations that were not previously practical, providing more data about microseismic events under a volcano’s dome. The researchers claim that such fiber optic sensing systems offer more detailed information about “the fumarole signature, which helps to constrain the geometry and activity of the plumbing system of the dome”.
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