With the exploration and development of unconventional oil and gas resources, downhole environmental monitoring and data-analysis technologies are becoming more and more important. Distributed fiber ...optic measurement technology, as a new monitoring technology to obtain accurate data, has a wide range of applications in hydraulic fracturing and production monitoring. It mainly includes: distributed fiber optic temperature sensors (DTSs) to monitor gas lift, identify in-flow fluid types, interpret flow profiles and monitor production enhancement operations; distributed fiber optic acoustic sensors (DASs) to monitor low frequency strain and microseismic and hydraulic fracturing operations; and distributed fiber optic stress sensors (DSSs) to characterize fractures in the near-well area, which have been well applied in the field. This paper describes the current application status of DASs and DSSs in hydraulic fracturing and production monitoring, respectively, from the principle of distributed fiber optic measurement technology. It also points out the limitations of these measurement technologies and the direction of future development. Distributed fiber optic measurement technology has been making technical breakthroughs in recent years, providing strong technical support for the development of unconventional oil and gas resources.
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.
Distributed fiber optic sensing (DFOS) is gaining increasing interest in geotechnical monitoring. By using soil-embedded fiber optic cables, strain profiles as well as deformation patterns of ...geotechnical infrastructures can be captured. Probing the fiber optic cable–soil interfacial behavior is vital to the advancement of DFOS-based geotechnical monitoring and our understanding of the soil–inclusion interaction mechanism. To this aim, laboratory pullout tests were performed to investigate the progressive failure of the interface between micro-anchored cables and the surrounding sand. High-resolution strain profiles recorded using Brillouin optical time-domain analysis (BOTDA) not only elucidated the influence of anchorage on strain measurements, but also allowed the classical soil–inclusion interaction problem to be studied in detail. Interfacial shear stresses calculated from step-like strain profiles provided clear evidence of the contribution of each micro-anchor to the pullout resistance. The cable–soil contact is a combination of overall bonding and point fixation depending on the level of mobilized interfacial shear stress, and therefore the validity of measured strains is correlated to a three-stage process of interface failure. This study also shows that installing heat-shrink tubes on the fiber optic cable is a rapid, low-cost, effective approach to make an anchored DFOS system for deformation monitoring of earth structures.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
We report the development of an all-fiber-optic scanning endomicroscope capable of high-resolution second harmonic generation (SHG) imaging of biological tissues and demonstrate its utility for ...monitoring the remodeling of cervical collagen during gestation in mice. The endomicroscope has an overall 2.0 mm diameter and consists of a single customized double-clad fiber, a compact rapid two-dimensional beam scanner, and a miniature compound objective lens for excitation beam delivery, scanning, focusing, and efficient SHG signal collection. Endomicroscopic SHG images of murine cervical tissue sections at different stages of normal pregnancy reveal progressive, quantifiable changes in cervical collagen morphology with resolution similar to that of bench-top SHG microscopy. SHG endomicroscopic imaging of ex vivo murine and human cervical tissues through intact epithelium has also been performed. Our findings demonstrate the feasibility of SHG endomicroscopy technology for staging normal pregnancy, and suggest its potential application as a minimally invasive tool for clinical assessment of abnormal cervical remodeling associated with preterm birth.
•A new scheme of fiber-optic cantilever enhanced resonant photoacoustic spectroscopy (CERPAS) is presented.•A high sensitive fiber-optic cantilever microphone is designed to match with the resonant ...photoacoustic cell.•The detection limit for acetylene is achieved to be 80 ppt.
A new scheme of fiber-optic cantilever enhanced resonant photoacoustic spectroscopy (CERPAS), combining high sensitive fiber-optic Fabry-Perot cantilever microphone with resonant photoacoustic spectroscopy, is presented for trace gas detection. A fiber-optic cantilever microphone with high sensitivity at the frequency near 1.4 kHz is designed to match with a first-order longitudinal resonant photoacoustic cell, whose resonant frequency is 1402 Hz. For sensitivity improvement, an erbium-doped fiber amplified near-infrared laser, with the central wavelength of 1532.83 nm and the maximum output power of 1 W, is used as the light source for acoustic excitation. The trace acetylene detection experiment demonstrates that, with the wavelength modulation spectrum and second-harmonic detection methods, the gas detection limit is achieved to be 80 ppt, which is at least one order of magnitude improvement compared with other photoacoustic acetylene sensors reported so far.
Entanglement, an essential feature of quantum theory that allows for inseparable quantum correlations to be shared between distant parties, is a crucial resource for quantum networks
. Of particular ...importance is the ability to distribute entanglement between remote objects that can also serve as quantum memories. This has been previously realized using systems such as warm
and cold atomic vapours
, individual atoms
and ions
, and defects in solid-state systems
. Practical communication applications require a combination of several advantageous features, such as a particular operating wavelength, high bandwidth and long memory lifetimes. Here we introduce a purely micromachined solid-state platform in the form of chip-based optomechanical resonators made of nanostructured silicon beams. We create and demonstrate entanglement between two micromechanical oscillators across two chips that are separated by 20 centimetres . The entangled quantum state is distributed by an optical field at a designed wavelength near 1,550 nanometres. Therefore, our system can be directly incorporated in a realistic fibre-optic quantum network operating in the conventional optical telecommunication band. Our results are an important step towards the development of large-area quantum networks based on silicon photonics.
Fiber-optic sensors based on Vernier effect Liu, Yingxuan; Li, Xuegang; Zhang, Ya-nan ...
Measurement : journal of the International Measurement Confederation,
01/2021, Letnik:
167
Journal Article
Recenzirano
Fiber-optic sensors have developed rapidly because of their excellent sensing performances and abilities to detect in remote and harsh environments. However, on some special occasions with high ...requirements for sensitivity and resolution, the traditional optical fiber sensing mechanism is difficult to meet the detection requirements. Therefore, it is very necessary to explore new sensor sensitization mechanisms. Vernier effect, as a simple and efficient sensitization method, has been extensively researched and applied in fiber-optic sensors in recent years. This review paper firstly presents the working principles and mechanism of the fiber-optic sensors based on the Vernier effect, and then discusses and classifies their common structures. Furthermore, the research progress and applications of such sensors are summarized and discussed. Finally, the further development direction of the fiber-optic sensors based on the Vernier sensitization mechanism is discussed and prospected.
Brillouin scattering in optical fiber describes the interaction of an electro-magnetic field (photon) with a characteristic density variation of the fiber. When the electric field amplitude of an ...optical beam (so-called pump wave), and another wave is introduced at the downshifted Brillouin frequency (namely Stokes wave), the beating between the pump and Stokes waves creates a modified density change via the electrostriction effect, resulting in so-called the stimulated Brillouin scattering. The density variation is associated with a mechanical acoustic wave; and it may be affected by local temperature, strain, and vibration which induce changes in the fiber effective refractive index and sound velocity. Through the measurement of the static or dynamic changes in Brillouin frequency along the fiber one can realize a distributed fiber sensor for local temperature, strain and vibration over tens or hundreds of kilometers. This paper reviews the progress on improving sensing performance parameters like spatial resolution, sensing length limitation and simultaneous temperature and strain measurement. These kinds of sensors can be used in civil structural monitoring of pipelines, bridges, dams, and railroads for disaster prevention. Analogous to the static Bragg grating, one can write a moving Brillouin grating in fibers, with the lifetime of the acoustic wave. The length of the Brillouin grating can be controlled by the writing pulses at any position in fibers. Such gratings can be used to measure changes in birefringence, which is an important parameter in fiber communications. Applications for this kind of sensor can be found in aerospace, material processing and fine structures.
A fiber-Bragg-grating-(FBG)-based sensor is a very popular fiber optic sensor due to its simplicity, mature fabrication technology, and sensitivity to a number of physical stimuli. However, due to ...the stiff nature of optical fiber, it is impossible to heavily stretch a FBG sensor. A stretchable sensor is highly desired in soft robotics, human motion detection, and biomedical applications, which could involve motions like tension, bending, and twisting. In this Letter, we demonstrate a stretchable FBG-based fiber optic sensor by embedding a FBG-written optic fiber sinusoidally in a soft silicone film at an off-center position. This unique structure enables 30% of elongation in length that facilitates tension, bending, and twisting measurement.
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