Nowadays 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 firstname.lastname@example.org