Distributed acoustic sensing detects polar bears

DAS for bear detectionNowadays cases, when people meet polar bears, have dramatically increased especially in arctic areas because the environment continues rapidly transforming. Thus, there is a need for a structural health monitoring system that allows detecting bears to decrease the number of such meetings. Distributed acoustic sensing (DAS) is an ideal technology to perform this task.

DAS systems are used as an intrusion detection system that is able to operate in environments where temperatures fall to -70 C. Usually, the installation of the distributed acoustic sensing system takes place on the ground, that is why DAS system performance requires its testing in the snow. The DAS has been already tested at similar conditions (deep snow and extreme cold), herewith, people helped to imitate polar bears walking near the distributed acoustic sensing system.

It should be noted that standard DAS system consists of the following components:

  • a sensing fiber optic cable that can be stretched over long distances;
  • a laser central processing unit (DAS).

The operating principle of fiber optic technology is based on mechanical vibrations that undertake fiber impingement, leading to laser beam backscatter and therefore, allowing researchers to measure the signal required. 

The researchers planed to test several opportunities provided by the DAS system: the ability of optical fiber to maintain extreme temperatures, the suitability of distributed acoustic sensing to snow coupling. The performance of the DAS system has been tested at the temperature of the -70C in the MTS environmental control chamber, and it demonstrated good results.

“Launch boxes with 2200m of spooled fiber optic cable were applied on either side of the 150m of distributed acoustic sensing cable to imitate a field deployment of 4.5km.” The researchers pay careful attention to four separate test temperature ranges provided by the DAS system, they even calculate shoe surface area combined with the weight of the participants in order to learn human foot pressure and connect it with polar bear foot pressure to classify bears of different sizes.

Additionally, DAS also allows differentiating humans from polar bears. The thing is that polar bears generally walk with 3 points of ground contact, while people need only one point. Even though the feet of polar bears are quite large, researchers can easily offer similar foot pressures.

Finally, the test results of distributed acoustic sensing demonstrate that fiber optic cables can maintain extreme cold temperatures in the arctic regions, where the temperature is required not to disturb optical fiber performance. The DAS system detects signals at depths of at least 0.65m in the unprocessed data.

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

Distributed fiber optic sensing applies an entangled quantum network

FBG sensors for quantum networkQuantum-enhanced metrology is regarded as a popular area of research for years because of its promising applications, varying from atomic clocks to biological imaging. According to the researches, a non-standard distributed sensing system offers significant advantages compared to traditional fiber optic systems.

These researches help a team of scientists from Denmark to carry out an experiment on distributed fiber optic sensing and the benefits of employing an entangled quantum network to detect an averaged phase shift among numerous distributed sensing nodes. The fiber optic sensing technology uses several methods that enable collecting more accurate measurements in different areas.

The purpose of the new study is based on squeezed light and homodyne detection that is now established distributed fiber optic sensing techniques. The team aims at “measurement of a global property of numerous spatially separated objects and investigate whether probing these objects simultaneously with entangled light led to more accurate results than probing them individually”. 

Thus, the application of a quantum network to probe the objects simultaneously allows distributed sensing systems with far higher accuracy than that attainable when examining probes individually. To be more precise, the team measures the phase shifts (set with wave plates to a known value) by the fiber optic system that sends a weak laser beam through and detects the change in the light’s phase quadrature with homodyne detectors.

The benefit of applying distributed fiber optic sensing plays a really important role when it is necessary to measure the property of numerous objects connected in an optical network. Nevertheless, the losses in the network and detectors are required to be kept low in order to successfully raise the accuracy, alternatively, the quantum benefit of distributed sensing disappears.

The researchers succeeded in the experimental demonstration of the benefits connected with employing multi-mode entanglement for distributed fiber optic sensing. The thing is that the benefits have been previously predicted, however, only highly idealized scenarios and experimentally very difficult probe states or detection methods were taken into consideration. The developed fiber optic system demonstrates that these benefits are available even with current noisy sensing technology.

The fiber optic system finds potential applications in various areas of research and technology development. For instance, they provide a high sensitivity of molecular tracking devices, atomic clocks, and optical magnetometry methods. Moreover, the distributed fiber optic sensing gives valuable information about how quantum-enhanced metrology can be reached utilizing readily accessible technologies, for example, squeezed light generation and homodyne detection.

Optromix is a manufacturer of innovative fiber optic products for the global market. The company provides the most technologically advanced fiber optic solutions for the clients. Optromix produces a wide range of fiber optic devices, including cutting-edge customized fiber optic Bragg grating product line and fiber Bragg grating sensor systems. Moreover, Optromix is a top choice among the manufacturers of fiber Bragg grating monitoring systems. If you have any questions, please contact us at info@optromix.com

Distributed sensors for structural health monitoring of bridges and dams

FBG sensors for bridge monitoringNowadays distributed fiber optic sensors remain a subject of great interest for constant structural health monitoring of huge structures, for instance, bridges or dams. Herewith, the more sensing points there are, the more effective monitoring the sensing system offers. Thus, newly improved distributed sensors with 1 million sensing points provide prominently faster detection of structural problems that are now accessible.

Fiber optic sensors allow accurately detecting of erosion or cracking before a dam fails. Therefore, earlier detection of a problem by fiber optic sensing systems may lead to its possible prevention from later deformation or provision of sufficient time for evacuation procedures. Fiber sensors are considered to be perfect for controlling infrastructure since they suit for use in harsh environmental conditions and in areas that lack nearby power supply.

The operating principle of distributed sensors is based on “changes in the structure at any of the sensing points along with the optical fiber that causes detectable changes in the light traveling down the fiber”. Despite the high popularity of distributed fiber optic sensors, the main applications of sensors include the detection of leaks in oil pipes and structural health monitoring for landslides along railroads.

It should be noted that the novel fiber optic sensing system enables tracing train and temperature changes from 1 million sensing points over a 10-kilometer optical fiber in less than 20 minutes, while the strain parameter demonstrates deformation or mechanical stress on an object of interest. Herewith, the new distributed sensor is regarded as to be about 4.5 times faster than previous fiber sensors with 1 million sensing points. A larger number of sensing points require fewer optical fiber units for structural health monitoring of an entire structure resulting in cost reduction.

A large density of sensing points makes distributed fiber optic sensors suitable for such applications as avionics and aerospace, where every inch of a plane wing has to be controlled properly. According to researchers, the conventional technique of generating the continuous signal in fiber sensors undertakes distortions in the fiber optic system at higher laser powers. This problem has been solved by using the approach known as Brillouin optical time-domain analysis.

The fiber optic sensor has been already tested and showed the opportunity to measure the temperature of a hot spot to within 3 degrees Celsius from the end of a 10-kilometer long optical fiber. Additionally, it is planned to improve the distributed sensor and make it even faster resulting in the further reduction of the acquisition time. Future enlargement of sensing point density will promote the fiber sensors being used in new fields, for example, biomedical applications.

Optromix is a manufacturer of innovative fiber optic products for the global market. The company provides the most technologically advanced fiber optic solutions for the clients. Optromix produces a wide range of fiber optic devices, including cutting-edge customized fiber optic Bragg grating product line and fiber Bragg grating sensor systems. Moreover, Optromix is a top choice among the manufacturers of fiber Bragg grating monitoring systems. If you have any questions, please contact us at info@optromix.com