Distributed Acoustic Sensing (DAS) for glaciated areas

DAS for glaciated area detectionNowadays scientists pay more attention to the process of Alpine microseismicity. The thing is that the sensing of seismic activity is important for studying landscape-shaping processes and predict dangerous mass movements. Nonetheless, the amount of modern fiber optic sensors is still low in Alpine regions. Therefore, distributed acoustic sensing (DAS) promotes solving the problem.

The application of advantageous fiber cables makes DAS technology very promising in seismic monitoring of glacier movements and natural hazards. Additionally, DAS technology has significantly changed the portability of seismic devices. This is why the performance of seismic monitoring in difficult-to-reach areas becomes more and more accessible.

It should be noted that the purpose of distributed acoustic sensing “focus on processes near the Earth’s surface rather than on traditional seismology subjects like the deeper crust and mantle.” DAS applies fiber optic sensors into which an interrogator enters a sequence of laser beam pulses. Herewith, fiber optic systems as distributed acoustic sensing are widely used in geophone chain deployments.

Fiber optic systems allow for sensing local earthquake signals, which are too weak to be recorded by conventional seismometers. Moreover, DAS enables the record of anthropogenic noise. Even though individual channels of distributed acoustic sensing have some disadvantages as a lower signal-to-noise ratio, they overcome seismometers. The thing is that there are a lot of unused fiber optic systems with unprecedented sensor coverage and density.

Novel DAS technology performs the records of microseismic signals and ambient noise in glacier areas. Compared to standard fiber optic systems, new distributed acoustic sensing offers important improvements in stick-slip event location and determines weak seismic waves. Herewith, the potential and utility of DAS systems are doubtless for sensing glacial processes.

According to scientists, DAS technology performs measuring seismogenic glacier flow and even small Alpine mass movements, for example, rockfalls. The benefits of distributed acoustic sensing include better limitation of static and dynamic properties of the glacier and its surroundings. The most significant thing is DAS technology provides precise arrival time measurements despite spatial averaging.

Finally, the advantages of DAS channels increase the location quality of stick-slip events significantly. The density of distributed acoustic sensing detects numerous reflections and extremely refracted waves. Herewith, spaced seismometer networks can not carry out it.

Optromix is a DAS system manufacturer that provides top of the line distributed acoustic sensing systems suitable for monitoring commerce networks. If you have any questions or would like to buy a DAS system, please contact us at info@optromix.com

Why DTS systems are beneficial to pipelines

DTS for pipelinesAlmost all pipelines suffer from numerous leaks during their operation, therefore, they require systems for fiber optic pipeline leak detection. Despite the fact that there are various techniques for leak detection, distributed temperature sensing systems (DTS) are considered to be an ideal option for the purpose.

Distributed temperature sensing is a technique that has been applied for more than two decades. DTS systems are regarded as the best option when a leak leads to a temperature differential between the ambient air and the escaping liquid or gas. The thing is that “temperature differentials generally occur when the pipeline product is at high pressure, high temperature or low temperature, all relative to ambient, which is characteristic of numerous pipelines.”

The operating principle of DTS is based on fiber optic sensing systems that operate as a sensor and measure temperatures along the entire length of optical fibers. Herewith, the optical fiber is put along the outside of the pipeline within the protective coating. It should be noted that the accurate installation location depends on the relative area(s) of the anticipated temperature differential caused by a leak, and on other reasons such as available mounting space.

To be more precise, DTS systems allow fastly identifying and precisely locating slow leaks at weld points, pipeline fittings, and herewith, sudden leaks. Fiber optic pipeline leak detection system enables detecting the precise location of leaks, often overcoming other distributed sensing technology. The fact is that even a tiny leak leads to a crucial temperature change, one that can be recorded by the DTS system.  Most DTS measures temperatures with a precision of a few degrees, more than sufficient for leak detection.

For instance, a modern leading distributed temperature sensing technology allows measuring temperatures at a distance of 6 km, totaling 6000 points of measurement. The fiber optic sensing system’s transceiver measures “temperatures for 6 km both upstream and downstream of its installation point, for a total coverage of 12 km per each transceiver.” It is possible to employ several transceivers with accompanying fiber optic cables to offer coverage for long pipelines, totaling hundreds or thousands of kilometers in distance.

DTS technology acts as a semi-automatic leak detection system, obtaining data information to enable operators to take action before automation and/or safety system activation. It should be mentioned that a semi-automatic system means that the leak detection occurs automatically, resulting in an alarm signal in a continuously staffed control room. 

Optromix is a fast-growing vendor of fiber Bragg grating (FBG) product line such as fiber Bragg grating sensors, FBG interrogators and multiplexers, Distributed Acoustic Sensing (DAS) systems, Distributed Temperature Sensing (DTS) systems. The company creates and supplies a broad variety of fiber optic solutions for monitoring worldwide. If you are interested in temperature measurement systems and want to learn more, please contact us at info@optromix.com