Dual-pulse phase-OTDR response to propagating longitudinal disturbance

This work presents a detailed review of the development of distributed acoustic sensors (DAS) and their newest scientific applications. It covers most areas of human activities, such as the engineering, material, and humanitarian sciences, geophysics, culture, biology, and applied mechanics. It also provides the theoretical basis for most well-known DAS techniques and unveils the features that characterize each particular group of applications. After providing a summary of research achievements, the paper develops an initial perspective of the future work and determines the most promising DAS technologies that should be improved.

Section: Das In Geophysics (Boris G Gorshkov)mentioning

confidence: 99%

Scientific Applications of Distributed Acoustic Sensing: State-of-the-Art Review and Perspective

Gorshkov

Yüksel

Fotiadi

et al. 2022

“…Another disadvantage of DAS with coherent probing pulses is the inherent nonlinearity of its response to an external disturbance. The question of the linearity of the DAS response was first considered in [ 16 , 36 ], and further contributions to the development of this concept were made in [ 11 , 12 , 13 ]. The nonlinearity of the DAS response is its intrinsic property, which is based on the fact that the phase increment of the full backscattered field of the scattering fiber segment nonlinearly depends on its strain.…”

Section: Fading and Nonlinearity Of Dasmentioning

confidence: 99%

“…These values can be recalculated to the particle velocity of the medium, which is measured by conventional geophones. A more detailed analysis shows that phase-OTDRs measure the phase difference between the fields formed by two separate scattering fiber segments formed by optical pulses in the fiber medium [ 11 , 12 , 13 ]. The distance between the scattering segments is referred to as the gauge length [ 14 ], this parameter defines the spatial resolution of DAS.…”

Section: Introductionmentioning

confidence: 99%

A Cost-Effective Distributed Acoustic Sensor for Engineering Geology

Gorshkov

Alekseev

Simikin

et al. 2022

A simple and cost-effective architecture of a distributed acoustic sensor (DAS) or a phase-OTDR for engineering geology is proposed. The architecture is based on the dual-pulse acquisition principle, where the dual probing pulse is formed via an unbalanced Michelson interferometer (MI). The necessary phase shifts between the sub-pulses of the dual-pulse are introduced using a 3 × 3 coupler built into the MI. Laser pulses are generated by direct modulation of the injection current, which obtains optical pulses with a duration of 7 ns. The use of an unbalanced MI for the formation of a dual-pulse reduces the requirements for the coherence of the laser source, as the introduced delay between sub-pulses is compensated in the fiber under test (FUT). Therefore, a laser with a relatively broad spectral linewidth of about 1GHz can be used. To overcome the fading problem, as well as to ensure the linearity of the DAS response, the averaging of over 16 optical frequencies is used. The performance of the DAS was tested by recording a strong vibration impact on a horizontally buried cable and by the recording of seismic waves in a borehole in the seabed.

“…Nowadays, many tasks can be solved in science and technics with the help of FOSs. They are useful for measuring deformation [ 9 ], temperature [ 10 , 11 , 12 ], vibration [ 13 ], concentration of substances [ 14 ], rotation speed [ 15 ], refractive index [ 16 ], pressure [ 17 ], liquid level [ 18 ], acceleration [ 19 ], acoustics [ 20 , 21 , 22 ], and other parameters [ 2 , 23 , 24 , 25 ]. Additionally, new types of fiber promise to open new opportunities for such monitoring devices [ 26 , 27 ].…”

Section: Introductionmentioning

confidence: 99%

Study of Intra-Chamber Processes in Solid Rocket Motors by Fiber Optic Sensors

Zhirnov

Stepanov

Sazonkin

et al. 2021

In this study, an experimental study of the burning rate of solid fuel in a model solid propellant rocket motor (SRM) E-5-0 was conducted using a non-invasive control method with fiber-optic sensors (FOSs). Three sensors based on the Mach–Zehnder interferometer (MZI), fixed on the SRM E-5-0, recorded the vibration signal during the entire cycle of solid fuel burning. The results showed that, when using MZI sensors, the non-invasive control of solid fuel burnout is made possible both by recording the time of arrival of the combustion front to the sensor and by analyzing the peaks on the spectrogram of the recorded FOS signal. The main mode of acoustic vibrations of the chamber of the model SRM is longitudinal, and it changes with time, depending on the chamber length. Longitudinal modes of the combustion chamber were detected by MZI only after the combustion front passed its fixing point, and the microphone was unable to register them at all. The results showed that the combustion rate was practically constant after the first second, which was confirmed by the graph of the pressure versus time at the nozzle exit.