The noise of Distributed Acoustic Sensing is suppressed

low-noise DASA technique of noise suppression used f-x deconvolution and the wavelet transform allows reducing jump edges in the phase noise of distributed acoustic sensing. The DAS system has been already tested and demonstrated great results of high performance in terms of increasing the quality level of seismic waves. Distributed acoustic sensing provides relatively stable phase sensitivity as well as better the signal-to-noise ratio, leading to more remarkable features of seismic wave signals.

To be more precise, distributed fiber optic sensing based on Rayleigh scattering is not new and used in various applications to control current assets and employ new resources. It is possible to apply such DAS systems to provide efficient and comparatively inexpensive development of perimeter security systems and produce defensive redundancy.

Different methods have been used to apply Rayleigh scattering in the development of distributed fiber optic sensors. For instance, a distributed sensing technology of optical time-domain reflectometry (OTDR) was used for the first time over three decades ago. Nowadays a noise suppression technique based on f-x deconvolution and the wavelet transform is considered to be the most efficient for distributed acoustic sensors.

The thing is that f-x deconvolution is regarded as a traditional technique of seismic data processing. The application includes the treatment of seismic signals by fiber optic sensors as a two-dimensional (2D) image in terms of time and channel. The DAS system enables us to extract the signal characteristics of each channel with a comparatively stable noise distribution between channels. 

Usually, such techniques as deconvolution or the wavelet transform are applied separately in traditional seismic noise processing but here these techniques are combined in distributed sensing technology to minimize the number of wavelets transform layers and reach effective low-frequency noise suppression. The DAS system offers such benefits as comparatively stable phase sensitivity over the whole sensing range, the reduction of jump edges in phase noise, and more evident features of seismic wave signals.

The operating principle of distributed acoustic sensing used f-x deconvolution is based on “the assumption that desired signals are continuous and predictable whereas random noise is incoherent and unpredictable.” DAS sensors are actively used for oil and gas exploration. Thus, the noise compression technique improves the phase noise performance of the DAS system. Moreover, the jump edges from the noise of fiber optic sensors are reduced with the same peaks and valleys compared to the original signals which play a crucial role in calculating the time delay of peaks and valleys between various channels. 

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

Extremely precise FBG sensors promote smaller chips

FBG sensors for chip developmentAn electrical engineer from the Netherlands has developed a fiber optic sensor based on fiber Bragg grating technology (FBG)with a super-precision of less than the size of an atom. Such FBG sensors favor the production of smaller chips, which in turn are required to develop faster computers.

The developed fiber sensor allows measuring deformations less than the width of an atom is possible to be measured. Thus, these fiber optic sensors offer a highly promising application that enables to improve the accuracy of current machines. It should be noted that even the slightest deformation of the wafers in machines may result in serious problems.

“These wafers are actually quite stiff, but because they are moved about at such great speed, they are subject to g-forces that slightly deform them. Measuring this deformation by FBG sensors gives the opportunity to compensate for it in some or other way, and opens up the possibility of producing even smaller chips.”

This is the main reason why the engineer began developing a fiber sensor based on FBG technology, enabling sensing these deformations of roughly one nanometer per meter. The operating principle of this extremely precise FBG sensor is that it is possible to measure the deviations in the frequency of laser beam light with high precision, as well as the principle used by fiber Bragg grating – an optical fiber of sorts treated in such a way that it becomes opaque for a very specific color of light.

Herewith, such a resonance frequency is dependant on the extent to which the optical fiber is stretched. Therefore, fiber Bragg gratings can be employed here to the moving parts as a way to measure the wafer’s deformation. The fiber optic sensing system based on FBG technology has been already tested in the lab. Although modern machines require dozens of such fiber sensors, it is not a challenge because FBG sensors are not expensive and light-weight.

The engineer claims that it succeeded in achieving the accuracy of 5 nanometers per meter, thus, the fiber optic sensor of a few centimeters in length allows measuring the deformation of a couple of dozen picometers, herein, that is less than the diameter of an atom. Nevertheless, several challenges have to be overcome before this incredible level of precision could be reached due to fiber Bragg gratings.

The first challenge is a need for sophisticated stabilization techniques to provide that the laser beam light has the right frequency. However, the main problem is considered to be the resonance frequency of the FBG sensor that depends on not only the deformation but also the temperature. 

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

Fiber optic seismic sensors from submarine cables

FBG sensors in seismologyA team of researchers from France proposes for the first time the opportunity to detect the propagation of seismic waves on the seafloor by fiber optic seismic sensors made from submarine telecommunications cables. The researchers confirm that the potential application of such seismic sensors includes the use of existing infrastructure for the detection of earthquakes, as well as swell and underwater noise.

It should be noted that about 1.2 million kilometers of telecommunications cables cut across the ocean floor that is equal to three times the distance from the Earth to the Moon. The cables consist of optical fibers leading to simple communication by phones, SMS, or e-mail. Herewith, the optical fibers could soon find a new application, that of detecting acoustic and seismic waves.

To be more precise, the researchers apply a 41 km-long fiber cable installed at the coast of Toulon in southern France for their tests to obtain data from the fiber optic sensors of the underwater observatory that is at a depth of 2500 m. Moreover, a special technique based on small impurities in the optical fibers is used for sending light back to the transmitter.

The thing is that “by stretching or contracting the optical fiber, the passage of a seismic or acoustic wave alters the distance between these impurities, and thus the backscattered signal, by a tiny amount.” Nonetheless, the researchers have to prove the opportunity to detect these differences in submarine fiber optic cables because of the insulating layers that surround the optical fibers.

Thus, the pulses of light put at the optical fiber and allow analyzing the backscattered signal. The researchers use the 41 km of optical fibers for tests and change them into more than 6000 fiber optic seismic sensors. Moreover, such fiber sensors enabled to detect a magnitude 1.9 earthquake that happened during the test at each of the sensing areas with a sensitivity close to that of a coastal seismic station, even despite the fact that it was located over 100 km from the fiber optic cable.

Nevertheless, the benefits of seismic sensors do not complete: the sensing points of fiber cable are highly sensitive to waves that go through the ocean, for instance, those created by the swell. The influence of waves on the seafloor near the coast, as well as the effect on the abyssal plain, where they produce “seismic background noise” was captured.

Finally, the fiber optic seismic sensors make it real to find out for the first time how the tiny vibrations that permanently interact with the Earth’s interior are created, allowing specialists in geophysics to examine its structure. Also, such fiber sensors may overcome a wide range of scientific and societal challenges like earthquakes, coastal erosion, the interaction between life, the oceans and the solid Earth, etc.

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