Fiber Optic Technology for the earthquake warning

Fiber Optic Technology for earthquake warningA research team from the USA has applied FBG sensors for detecting earthquakes and creating a system for subsurface imaging with the help of fiber optic technology. The sensors were installed above an existing fiber optic cable.

According to scientists, this fiber optic system can register seismic signals produced by trains and automobiles. These signals cause changes in the fiber optics’ length from the very beginning till the very end. This fiber optic system is also known as distributed acoustic sensing or DAS.

Scientists have also installed usual high-resolution seismometers along the fiber optic cable in addition to the new DAS technology. They have aimed to compare these two methods of signal detection. In distributed acoustic sensing the fiber laser light is sent through the fiber optic cable. DAS technology measures the perturbations in the backscattered light along the whole fiber optic cable.

In fact, scientists made a conclusion that the fiber optic system is sensitive enough to detect footsteps. The other research team from one of the US universities proved that fiber optic technology can provide data about street traffic and demonstrated the results of the lockdown 2020. The fiber optic system could locate vibrations from cars and pedestrians above and demonstrated that the pedestrian traffic almost disappeared in April and stayed almost the same in June.

However, according to this scientific research, the fiber optic cable can even detect the jet airplanes that fly by. The scientific work was much easier because DAS systems are easy-to-install devices in comparison with the traditional methods. Scientists just needed to use a single fiber optic cable instead of thousands of geophones to detect ground vibration. Researchers got the same information using fiber optic technology faster. The DAS system continuously monitors the modifications in the fiber optics’ length down to changes in the length of less than 1 nanometer.

Thanks to the DAS technology the research team will calculate the velocity structure in the subsurface by measuring the strain changes. The velocity is a crucial factor in the determination of how the ground and civil infrastructure may respond to an earthquake.

Thanks to the new fiber optic technology, scientists and engineers are going to improve velocity and ground motion models in urban areas by collecting more information. Moreover, they hope to find a better understanding of the seismic risks and assess the resilience of our infrastructure.

Besides, the research team has a plan to spread this fiber optic technology for a vast territory to develop a better early-warning system for earthquakes. This is a totally new way of thinking about monitoring and designing for earthquakes that can give people time to get to shelter.

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Distributed Acoustic Sensing (DAS) and its applications

DAS and its applicationsIn southwest Iceland, there is a fiber optic cable that connects two geothermal power plants. It is used as every casual fiber optic cable for data transmitting. However, in 2015 a research team decided to apply it for detecting seismic waves of earthquakes, so they could draw a map of the underground features including geological faults. And distributed acoustic sensing (DAS) made it possible.

Scientists made their discovery thanks to distributed acoustic sensing (DAS). This technique measures any tiny changes to the phase of fiber optic laser pulses that reflect from many points on fiber optics. The thing is an acoustic or seismic wave stretches and compresses fiber optics when it passes through the ground where the fiber optic is attached. DAS systems can provide the necessary information at a reasonable cost. Moreover, the usual seismometers couldn’t reach such kind of information.

In fact, Iceland is not the first country where the distributed acoustic sensing (DAS) technology was applied. Before that, fiber optic cables were produced in other seismic regions, for example, in the USA. The precise information on earthquakes’ location, nearby faults was got thanks to the fiber optics both on the seabed and on land. Scientists consider that by using a million kilometers of fiber optic cable around the world, we can broaden quake monitoring thanks to the network of seismometers with fiber optic sensors.

Distributed acoustic sensing (DAS) has been previously applied mostly in the fossil-fuels industry. The sensing technology helped to monitor boreholes and image deposits of oil and gas. Nowadays, it has many other applications for extracting data from vibration in the ground. Distributed acoustic sensing can even shed some light on global warming by studying the glaciers’ movements in the Antarctic and Alaska.

Besides earthquakes, researchers proved that they can use DAS systems for studying other natural hazards. The research team from Italy showed that they can detect the strain changes connected to the volcanic phenomena which include explosions. They also discovered seismic waves slowing through presumed fault zones on the volcano.

In the meantime, scientists from Japan demonstrated that DAS technology can monitor submarine volcanoes. The researchers measured the signals from the fiber optic cable on the seafloor. They found out that fiber optic sensors could produce coherent measurements that are needed for underwater eruptions’ recording.

Distributed sensing is an effective instrument that provides us with a lot of data that we can’t observe with the naked eye. Considering how widely fiber optic lines are used, distributed acoustic sensing (DAS) can give many possibilities to scientists and society.

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

Distributed Acoustic Sensing (DAS) in exploring the ocean

DAS in exploring the oceanExploring the underwater environment that covers most of the Earth’s surface is one of the most difficult tasks. The easiest way is the usage of distributed acoustic sensing (DAS) technology. However, the fbgs sensors’ setting is also not so easy because of the environmental conditions. Despite this fact, distributed acoustic sensing has a huge potential for observing processes in the future.

Fiber optic solutions are the new methods of geophysical information registration that can be applied both onshore and offshore. The scientists used transmission time-of-flight of laser pulses inside transoceanic subsea fibers to note seafloor strain. To explore seafloor strain with higher spatial resolution, they utilized a distributed acoustic sensing (DAS) system.

Distributed acoustic sensing technology helps to observe the ocean and solid earth phenomena. The scientists applied a fiber optic cable and a distributed acoustic sensing (DAS) unit operating onshore. DAS technology uses a photonic device that sends short pulses of laser light through fiber optics. DAS detects the backscattering set by strain in the cable caused by stretching.

The researchers could get even more data than expected. They could record underwater earthquakes, volcanic activity, and a range of micro hydrodynamic signals. The scientists monitored the acoustic waves by alterations in laser light along the fiber optic cable. Recordings of a small earthquake wavefield demonstrated several fault zones underwater. Distributed acoustic sensing could picture earthquake hazards in the coastal oceans and give new data about fault orientations and seafloor structures. The DAS system displayed the state of the sea and its changes during a storm cycle. These observations proved the necessity and potential of this method for marine geophysics.

There are still aspects of this distributed acoustic sensing research that should be improved. One of them is the fact that current DAS instruments can only see lower frequencies. However, such frequencies are considered to be low for acoustics, but it is high for seismologists and enough to locate boat signals. The research team also explores the possibilities of tracking mammals, for example, whales with the help of distributed acoustic sensing technology. The second challenge is the fact that the scientists don’t know where exactly the fiber optic cable is. Because seabed bathymetry can affect the signals and influence DAS senses. Nowadays, it is possible to use only the initial part of the fiber optic cable, up to 200 km. But it already allows capturing a number of spheres of science.

As a result of the research, the observations with the DAS system during just a few days helped to create a map of an unknown fault system and detect several dynamic processes in the water. The distributed acoustic sensing technology could help to get rid of a huge gap in ocean sensing.

According to the researchers, the production of fiber optic systems based on the DAS technology can be easily automated. However, there is still a space for developing and finding new ways of optimization.

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

Distributed Acoustic Sensing (DAS) system for Arctic tests

DAS system for Arctic tests The USA researchers started a number of experiments that aim to analyze the first data about seafloor under Arctic sea ice with the usage of a new method. The research team was able to connect a distributed acoustic sensing (DAS) system with a fiber optic cable. The cable vibrations can record the data 24/7. That helped the scientists to get all the activities and changes within the ocean all day long. This was the first time in history when a DAS system was used on the seafloor of the Arctic or Antarctic oceans.

The appliance looks like an electronic box that is attached to the fiber optic cable on land. It uses a laser to send thousands of short pulses of light. The small amount of the light is reflected back. And the reflected light helps the appliance to monitor events along with the fiber and store the data on hard drives.

According to the research, the DAS technology showed the icequakes, different climate signals, and marine life. The researchers are expecting to note other climate signals like ocean wave height, timing, and distribution of sea ice breakup, and ice thickness, etc. The usage of the distributed acoustic sensing system has the potential to record a variety of Arctic phenomena so the scientists can better see the climate change effects and sea life. Moreover, the DAS system makes it cost-effective and safe in comparison with the other methods. The scientists have already recorded a number of events that the traditional hydrophone or ocean bottom seismometers couldn’t even detect. With the help of the DAS system, the scientists hope to also record whale songs.

However, the research team has to face challenges during the first week of the tests. And the most difficult one was the harsh climate. It was really cold, most of the territory is tundra. It’s snowing most of the time and it’s getting dark really early. No wonder, that the team should find new creative ways of data fixing like DAS technology to get everything working.

That’s why the researchers chose a distributed acoustic sensing system to cope with the weather conditions. Fiber optic cable is double-armored with copper and steel. All the network components are created to hold the extreme Arctic environment. They have no need in sending a boat to plant monitors, moving over the sea ice to install the sensors. This fiber optic cable can exist for years or decades without replacing it.

This project of watching the Arctic ocean with the usage of the distributed acoustic sensing system is going to last over the next two years. The research team will collect the data. And the next third year will be spent on its analysis.

According to the researchers, the production of fiber optic systems based on the DAS technology can be easily automated. However, there is still a space for developing and finding new ways of optimization.
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

Distributed acoustic sensors (DAS) are applied underwater

DAS are applied underwater Scientists are looking for new ways of employment for distributed acoustic sensors (DAS). The fiber optic system contains a mandrel with a wounded with sensitized optical fiber. It is the acoustic sensor for a heterodyne that is protected for underwater use.

Nowadays, the DAS system can be used both for military purposes as well as for peaceful life. In the military, they are mostly utilized for submarine locations. While they are also in active use for monitoring sea animals’ life or finding and exploring marine mineral sources. The fiber optic systems based on the DAS technology have more advantages over the other items. First of all, they are thin and reliable. Secondly, there are no underwater electrical devices. And finally, the systems with acoustic sensors are immune to electromagnetic interference.

These devices usually contain an array of DAS sensors along with the fiber. Herewith, the arrays are up to a hundred or even fewer acoustic sensors because of the technical restrictions. The spacing between these acoustic sensors is fixed. That’s why there are some limitations in marine acoustic detection, for example.

The recent researches from China exploited a distributed acoustic sensing based on heterodyne coherent detection and demonstrated its field-testing. The optical cable contains a supporting mandrel, special optical fiber, and cable sheath. Acoustic signals from the fiber optic system disturb the mandrel and the fiber. That all causes phase changes which are the desired signal. The whole model was created to analyze the equivalence and specific character of the acoustic wave response.

With the array signal processing, the DAS device can easily find underwater acoustic signal sources and track motion trajectories. Moreover, the results of the experiments are highly accurate.

There are also obvious benefits of distributed acoustic sensors (DAS) in various industries. Most of which are elements of longer-term goals.

Some of the potential advantages of a distributed acoustic sensing are numbered below:

  • a low-cost acquisition system;
  •  a simple design;
  • no electrical energy required in the fiber optic cable;
  • the fiber optic cable is suitable for harsh environments (dust, temperature, harmful gases);
  • the fiber optic cable is immune to the radiations such as EMI (Electromagnetic Induction) & ESD (Electrostatic Discharge);
  • the fiber optic system can transform several kilometers long sensor that enables it to monitor on a truly distributed basis.

According to the researchers, the production of fiber optic systems based on the DAS technology can be easily automated. However, there is still a space for developing and finding new ways of optimization.

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