Fiber Optic Monitoring System Research Articles

Investigations of the functional role of connexin36 in sensory and sympathetic systems in adult mice

Electrical synapses formed by gap junctions composed of connexin36 (Cx36) occur between neurons in widespread areas of the mammalian central nervous system and enable neuron-to-neuron electrical coupling. We previously reported that dorsal root ganglia (DRG) sensory neurons containing transient receptor potential (TRP) channels, including TRPV1 and TRPM8, and those containing substance P in nociceptive DRG neurons express high levels of Cx36. It has also been reported that Cx36 is expressed in sympathetic preganglionic neurons (SPNs). Here we examined the functional roles of electrical synapses in primary afferent and SPN neural networks by using mice with global knockout (ko) of the Cx36 gene (Cx36 ko mice) and their wildtype (Wt) counterparts. Based on previous evidence showing that spinal neurons in Cx36 ko mice have attenuated responses to nociceptive stimulation when examined ex vivo; our hypothesis was that responses to nociceptive stimulation would be attenuated in vivo in intact Cx36 ko mice compared to Wt. To examine the role of coupling between DRG neurons, in vivo imaging was used to measure the fluorescence signal of Evans blue dye extravasation in skin of live animals after nociceptor activation. The extravasation levels relative to baseline fluorescence were 61.7±4% in Wt mice and 33.2±7% Cx36 ko mice (n=5 matched pairs, all males) after hind paw pinprick. Xylene applied topically on one of the ears induced more extravasation in the wt (255.4 ±3%) than in the Cx36 ko mice (204.6 ±1%). Using a fibre optic blood pressure monitoring system, we found that topical xylene application under isoflurane anesthesia changes the blood pressure, the heart rate, and the respiratory rate additionally to evoking the plasma extravasation. The attenuated extravasation response in the Cx36 ko mice suggests that electrical synapses known to occur between peripheral unmyelinated sensory fibers impact signal transmission from peripheral nerve endings and release other mediators that cause this response. To examine functional roles of coupling between SPNs, we compared physiological responses to colorectal distension (CRD) in Wt and Cx36 ko) mice in mice under isoflurane anesthesia. Mean arterial blood pressure during CRD increased to 108 ± 8% of baseline in Wt mice (n = 7), while this parameter did not change significantly in Cx36 ko mice (n = 12), but did show a tendency to decrease (to 97 ± 2%). Heart rate did not show significant changes, but we found that respiratory rate changes also occurred as part of the systemic response to CRD in both lines of mice. These data show differential regulation of sympathetic activity associated with electrical coupling between SPNs in Wt vs. Cx36 ko mice. In Wt mice with mid-thoracic complete spinal transection (n = 2), CRD also increased blood pressure when tested at 6-8 days after injury. The results taken together, point to the possibility that Cx36 in DRG and SPNs of adult mice has a significant functional role and warrant further research to understand how the presence of Cx36 in DRG and SPNs influences pain processing and associated autonomic responses.

Study Reviews Advances in Downhole Fiber-Optic Modeling and Analytics

This article, written by JPT Technology Editor Judy Feder, contains highlights of paper SPE 200826, “Recent Advances in Downhole Fiber-Optics Modeling and Analytics: Case Studies,” by Derek S. Bale, SPE, Rajani P. Satti, SPE, and Roberto Failla, SPE, Baker Hughes, et al., prepared for the 2020 SPE Western Regional Meeting, originally scheduled to be held in Bakersfield, California, 27 April–1 May. The paper has not been peer reviewed. The upstream industry has witnessed significant breakthroughs in developing and deploying permanent, on-demand, and distributed temperature and acoustic fiber-optic monitoring systems to optimize well completions and enhance production. Beyond steady advances in hardware, challenges associated with the analysis of distributed optical data are being addressed to enable delivery of value-driven solutions and services. The complete paper discusses a methodology for integrating intelligent completion and production systems with a modeling and analytics framework for efficient development of fiber-optic-based data-interpretation services for complex downhole environments. Introduction During the last 30 years, the industry has found novel ways to apply fiber-optic technology to monitor in-well events, operations, and critical parameters. Recently, applications including the need to maximize hydrocarbon recovery, remotely manage assets for improved cost-efficiency and safety, and reduce carbon footprint have accelerated the adoption of fiber-optic-based systems. Specific to wellbore completions, the confluence of increased durability and reliability of downhole fiber-optic systems, computer processing speed, and the ability to couple fiber sensors to completion and production equipment has led to significant growth in several applications. Fiber-optic techniques such as distributed temperature sensing (DTS) and distributed acoustic sensing (DAS) have proved particularly successful for applications such as injection and production profiling, well-integrity monitoring, leak detection, perforation cluster efficiency, and fracture monitoring. For all the benefits delivered by downhole fiber-optic technology, challenges specific to data transmission and storage remain, in particular with regard to data analysis and interpretation, that must be understood to fully enable delivery of value-generating solutions. These challenges are illustrated in Fig. 1 of the complete paper. Philosophy and Description of Solutions The solutions to the challenges described previously need to be downhole-tool-centric, cost-effective, and time-efficient. The complete paper is focused on presenting a methodology that follows a scientific and pragmatic work flow and demonstrating successful applications using a combination of intelligent downhole hardware and advanced modeling and analytics. The methodology begins with designing and developing intelligent downhole tools capable of providing the necessary data to enhance or optimize production, mitigate risk, and improve operational efficiency. Intelligent downhole tools can include interval control valves, downhole pressure and temperature gauges, connectors, control units, and cables, and are deployed into a complex downhole environment. As these smart tools are run downhole, fiber-optic cables are deployed in tandem to acquire continuous, spatially distributed data (i.e., strain, temperature, or acoustic) along the completion.

Research on FBG Technology Applied in Highway Soft Foundation Pore Pressure Monitoring

The pore water pressure monitoring of soft ground pavement is one of the important technical links in highway construction monitoring. The use of traditional electrical measuring instruments to monitor pore water pressure has disadvantages such as low degree of automation, non-real-time data transmission, and high manual monitoring costs. However, fiber grating monitoring technology has developed rapidly due to its advantages of stable data transmission, convenient collection, and dynamic monitoring. . Therefore, relying on the soft foundation pore water pressure monitoring project of Jiujiang Ring Expressway, the monitoring principle of the fiber grating seepage pressure sensor and the buried installation technology in the soft foundation are introduced. Through the long-term monitoring practice on the construction site, it is confirmed that the optical fiber monitoring system is applied to the soft foundation. The stability of base pore water pressure monitoring provides a reference for similar monitoring projects and engineering construction.

Quasi-Distributed Fiber-Optic Monitoring System for Overlying Rock Mass Pressure on Roofs of Underground Excavations

Quasi-Distributed Fiber-Optic Monitoring System for Overlying Rock Mass Pressure on Roofs of Underground Excavations

System and Method of Quasi-Distributed Fiber Bragg Gratings Monitoring Brittle Fracture Process of Composite Insulators

Brittle fracture of the composite insulator is a malignant accident. There is a lack of means to monitor the formation and expansion of stress corrosion cracking in rods, resulting in little understanding of the process of brittle fracture development. First, this article proposes a mechanical model for identifying cracks in rods by the wavelength shift trends of fiber Bragg gratings (FBGs). Second, several FBGs and FBG temperature compensation sensors are pasted on the 10-kV composite insulator rod's surface. Then an optical fiber monitoring system for the brittle fracture process of the rod is established. Finally, the model and system were validated by conducting stress corrosion testing with different tensions. The results show that the surface quasi-distributed FBGs can monitor the temperature and stress in the complete brittle fracture process of a glass-fiber-reinforced polymer (GFRP) rod, which verified the correctness of the mechanical model for wavelength shift identification of cracks in axial cross sections. A temperature difference of 1 °C and the wavelength shift of the FBG on two or more fibers reach 1.1 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">smin</sub> and 0.9 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">smin</sub> can be used as warning thresholds for corrosive heat release, crack initiation, and rapid development of cracks to fracture, respectively. This article provides a quasi-distributed FBGs' monitoring system and method to study brittle fracture of composite insulators in stress corrosion testing. It provides a technical means to evaluate and warn the mechanical properties of composite insulators.

Quasi-Distributed Fiber-Optic Monitoring System for Overlying Rock Mass Pressure on Roofs of Underground Excavations

Quasi-Distributed Fiber-Optic Monitoring System for Overlying Rock Mass Pressure on Roofs of Underground Excavations

Development of an Electrical Resistivity Tomography Monitoring Concept for the Svelvik CO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; Field Lab, Norway

Abstract. Within the ERA-NET co-funded ACT project Pre-ACT (Pressure control and conformance management for safe and efficient CO2 storage – Accelerating CCS Technologies), a monitoring concept was established to distinguish between CO2 induced saturation and pore pressure effects. As part of this monitoring concept, geoelectrical cross-hole surveys have been designed and conducted at the Svelvik CO2 Field Lab, located on the Svelvik ridge at the outlet of the Drammensfjord in Norway. The Svelvik CO2 Field Lab has been established in summer 2019, and comprises four newly drilled, 100 m deep monitoring wells, surrounding an existing well used for water and CO2 injection. Each monitoring well was equipped with modern sensing systems including five types of fiber-optic cables, conventional- and capillary pressure monitoring systems, as well as electrode arrays for Electrical Resistivity Tomography (ERT) surveys. With a total of 64 electrodes (16 each per monitoring well), a large number of measurement configurations for the ERT imaging is possible, requiring the performance of the tomography to be investigated beforehand by numerical studies. We combine the free and open-source geophysical modeling library pyGIMLi with Eclipse reservoir modeling to simulate the expected behavior of all cross-well electrode configurations during the CO2 injection experiment. Simulated CO2 saturations are converted to changes in electrical resistivity using Archie's Law. Using a finely meshed resistivity model, we simulate the response of all possible measurement configurations, where always two electrodes are located in two corresponding wells. We select suitable sets of configurations based on different criteria, i.e. the ratio between the measured change in apparent resistivity in relation to the geometric factor and the maximum sensitivity in the target area. The individually selected measurement configurations are tested by inverting the synthetic ERT data on a second coarser mesh. The pre-experimental, numerical results show adequate resolution of the CO2 plume. Since less CO2 was injected during the field experiment than originally modeled, we perform post-experimental tests of the selected configurations for their potential to image the CO2 plume using revised reservoir models and injection volumes. These tests show that detecting the small amount of injected CO2 will likely not be feasible.

Monitoring of CFA pile test using three dimensional laser scanning and distributed fiber optic sensors

The results obtained during a pile test are dependent on a number of factors. However, conventional monitoring systems like vibrating wire strain gauges and the extensometers can only measure the variations of strain and displacement at discrete locations at which they are installed in a pile. In order to identify the behavior of Continuous Flight Auger (CFA) pile, the distributed fiber optic monitoring system and three-dimensional laser scanning collected the strain and point clouds data during the pile test with conventional vibrating wire strain gauges, extensometers. Based on the Brillouin Optical Time Domain Reflectometry (BOTDR) fiber optic strain profile, the profiles of axial load, skin friction, displacement can be obtained. The fiber optic monitoring system was compared with conventional systems, and it was found that the ability to measure the full strain profiles is highly advantageous in determining the performance of the pile and in detecting the behavior of CFA pile. The displacement of the pile was measured by the LVDT at the top of the pile and the results were compared with the laser scanning results. In this study, the negative skin friction was detected by BOTDR fiber optic strain profile near the top of the CFA pile. It was not able to define the reason of the negative skin friction from the other monitoring systems but the laser scanning results show that the ground movement due to the pull-out force of the anchor pile affects the negative skin friction. Although laser scanning is not able to measure the real-time data during the pile test, the extensive information can be taken into account by the monitored data from three-dimensional laser scanning.

Classification of Seismoacoustic Emission Sources in Fiber Optic Systems for Monitoring Extended Objects

A new method is proposed for automatic classification of seismoacoustic emission sources in fiber optic monitoring systems based on the principles of optical reflectometry in a time domain using the time reconstruction of the interference signal phase. The novelty of this approach lies in the original principles of forming a space of classification features and the use of ensemble classifiers. This method works provided that a relatively small training database is used. High practical effectiveness of the proposed approach is shown when working on real data. A classification reliability value previously inaccessible to alternative classification methods implemented in serial fiber optic monitoring systems is evenly achieved for different classes of goals.

High-voltage monitoring by the fiber-optic recirculating measuring system

Optical technologies for measuring electrical quantities attract great attention due to their unique properties and significant advantages over other technologies used in high-voltage electric power industry: the use of optical fibers ensures high stability of measuring equipment to electromagnetic interference and galvanic isolation of high-voltage sensors; external electromagnetic fields do not influence the data transmitted from optical sensors via fiber-optic communication lines; problems associated with ground loops are eliminated, there are no side electromagnetic radiation and crosstalk between the channels. The structure and operation principle of a quasi-distributed fiber-optic high-voltage monitoring system is presented. The sensitive element is a combination of a piezo-ceramic tube with an optical fiber wound around it. The device uses reverse transverse piezoelectric effect. The measurement principle is based on recording the change in the recirculation frequency under the applied voltage influence. When the measuring sections are arranged in ascending order of the measured effective voltages relative to the receiving-transmitting unit, a relative resolution of 0,3–0,45 % is achieved for the PZT-5H and 0,8–1,2 % for the PZT-4 in the voltage range 20–150 kV.

Application experience of composite external reinforcement systems and optical monitoring of building structures

This article describes results of the widespread use of external reinforcement systems for reinforced concrete and metal man-made structures based on domestic and foreign polymer composite materials (PCM), as well as fiber-optic monitoring systems, including a network of fiber-optic sensors (FOS) and a hardware-software complex that track the actual state of the control object throughout the entire life cycle. It is shown that for reinforced concrete structures it is advisable to use composite systems of external reinforcement installed directly on the reinforcement object by contact molding using special cold curing binders. In relation to metal structures, this technology is unacceptable due to a significant difference in the coefficients of linear thermal expansion of the metal and the carbon composite. To solve this problem, reinforcement technology has been proposed, which consists in installing discrete mechanical fasteners of finished composite spigots (similar to metal ones) made by autoclave and autoclave-free molding methods. In the event that deviations from the normative indicators for this type of structures are detected, the necessary set of measures is taken to strengthen, after which the monitoring system carries out a similar control, the results of which characterize the quality of the work performed. Thus, the monitoring system can act both as an effective tool for structural control and carry out local time monitoring before or after the relevant works on strengthening and reconstruction, and in real time work throughout the entire period of operation.

Radiofrequency interrogation method in fiber optic nondestructive monitoring systems

This paper discusses the radio-frequency method of interrogation of FBG, its properties, operating principles, and distinctive features. The aim of the work is the consideration and application of FBG interrogation by the radio frequency method. During the work, a theoretical study was conducted, as well as practical modeling of this method. Particular attention is paid to the consideration of fiber-optic sensors and interrogators. Their classification was presented. It describes in detail the various interrogators that are most suitable for the considered method of interrogation. As a result of the work, the dependence of the effect of temperature on the grating shift was revealed.

TECHNOLOGICAL ASPECTS OF CREATING A FIBER-OPTIC NON-DESTRUCTIVE TESTING OF SANDWICH COMPOSITE STRUCTURES

The results of research on the formation of the system of built-in non-destructive testing of linings of composite three-layer structures by an optical method using fiber-optic sensors based on fiber Bragg gratings are presented. The features of creating an input/output zone for fiber-optic sensors as applied to three-layer composite structures are studied. Recommendations for ensuring the integrity and optimal functioning of the fiber-optic monitoring system as applied to a real three-layer composite structure are formulated. The following is shown. The process of creating an integrated control system of three-layer composite structures by an optical method using integrated fiber-optic sensors includes a number of operations to form a topology and to ensure the output of fiber-optic sensors from composite claddings in a single technological cycle of manufacturing the structure according to the standard technological process without significantly adjusting it, which is extremely important in relation to serial technologies. When developing the technology of integrating fiber-optic sensors into a three-layer composite structure, it was experimentally shown that from the point of view of survivability and preservation of the efficiency of the embedded control system, it is necessary to fulfill a number of requirements for the placement and output of fiber-optic sensors taking into account the characteristics of manufacturing, machining, and operation designs. Thus, it is advisable to place fiber optic sensors in the casings at least 5 mm from the intended edge of the structure, at least 2 layers from the outer surface of the structure and not less than 5 layers from the honeycomb core. The fiber bend radius should be at least 30 mm to prevent mechanical burst and sharp bending of the signal when it is bending. Fiber optic sensors are recommended to be placed between layers with a reinforcement scheme in the direction of the fiber optic sensor, however placement is also allowed between the fiber sensors and one layer with a different direction of reinforcement, while in order to prevent fractures, computation fiber optic sensors overlap is unacceptable, thus, between crossover fiber-optic sensors must be at least 2 layers of prepreg.

Fiber optic sensors for high-temperature measurements on composite tanks in fire

For the purpose of increasing payload and reduce freight cost, lightweight composite tank containers used for transportation have been progressively developed during the last years. Compared to conventionally produced cylindrical steel tanks, the fiber-reinforced solutions allow greater flexibility in the tank design. Despite a number of further material-related benefits of fiber-reinforced composites as non-conductive and non-magnetic behavior as well as corrosion resistance and high strength, the optimization of their thermal degradation properties during combustion is still a challenge. To improve the fire performance of lightweight composite containers, special intumescent fire protection coatings can be applied onto the outside tank surface. This paper presents fire tests on glass-fiber-reinforced plastic transport tanks with complex geometries sheltered with different surface-applied fire protection systems. To evaluate the fire resistance of the tank structures, a fiber optic monitoring system was developed. This system is based on distributed temperature measurements using high-resolution optical backscatter reflectometry and pointwise reference measurements using fiber Bragg gratings. Thereby, all the fiber optic sensors were directly integrated in the composite layer structure of the tanks. The focus of the presented work is on the demonstration of capability of fiber optic monitoring system in such high-temperature application. Moreover, the fiber optic measurements provide new insights into the efficiency of intumescent coating applied for fire protection of fiber-reinforced plastic transport tanks.

Design, Testing, and Realization of a Distributed Fiber Optic Monitoring System to Assess Bending Characteristics Along Grouted Anchors

Grouted steel anchors combined with shotcrete layers at the surface are a common method to stabilize slopes and construction pits. Their design is based on the equilibrium consideration of a rigid body motion, and therefore, only tensile stresses are considered and accompanying forces, such as bending, are neglected. Modern approaches substitute the steel with wooden anchors, which show a sufficient tensile, but poor shear strength capacity. Distributed bending curves along the embedded anchors are required to design the optimal anchoring system, which, however, may not be measured using conventional sensing techniques. This paper reports about a distributed fiber optic sensing approach that enables the assessment of curvature and bending characteristics along grouted anchors. The designed system was tested within comprehensive laboratory investigations, in which various loading scenarios were applied to an instrumented, real-scale steel anchor. The suitability of the fiber optic sensing system was proven using image-based and geodetic total station measurements at the surface as well as by comparisons to theoretical beam models. In addition, three instrumented anchors were installed at a highway construction site and autonomously monitored over several weeks. The presented studies demonstrate the high potential of distributed fiber optic monitoring systems and their capability to extend traditional measurement methods in foundation engineering.

Application of predictive data analytics to model daily hydrocarbon production using petrophysical, geomechanical, fiber-optic, completions, and surface data: A case study from the Marcellus Shale, North America

Predicting gas production from stimulated unconventional reservoirs has always been a challenge to oil and gas companies because the physics of fluid flow through such reservoirs is not well understood. On the other hand, modeling gas production from shale reservoirs is a complex multi-variate problem that requires proper integration of data from multiple disciplines, such as geology, petrophysics, geomechanics, completions, and surface-based measurements, etc. This study demonstrates the application of data-driven machine learning algorithms, integrating geoscientific, distributed acoustic sensing (DAS), distributed temperature sensing (DTS) fiber-optic, completions, flow scanner production log, and surface data to model daily gas production from a 28-stage stimulated horizontal well drilled in the Marcellus Shale of the Appalachian basin in North America. In addition, this study aims to utilize the data from a fiber-optic monitoring system, such as DAS and DTS to evaluate the well performance. We build supervised data-driven machine learning models using Random Forest (RF), Artificial Neural Network (ANN), and Support Vector Machine (SVM) algorithms to understand the well performance and forecast the daily gas production. The study compares the forecasted results, tests the level of accuracy, and addresses different issues with these machine learning algorithms. A spatio-temporal database is constructed and used to perform sensitivity analyses to identify the key drivers for gas production. The results show that RF and ANN algorithms can be used to predict daily gas production with significantly high accuracy; however, RF algorithm is the best predictor in terms of highest accuracy (96%), less computational time and cost. Based on sensitivity analysis, it appears that Poisson's ratio, minimum horizontal stress, DAS, casing pressure, gamma log are the most important parameters to predict gas production.

Performance Assessment of a Newly Constructed Skewed Half-Through Railway Bridge Using Integrated Sensing

© 2018 American Society of Civil Engineers. Half-through steel plate girder bridges are widely used across the United Kingdom's railway network. However, few studies have investigated their real in-service behavior. Concurrently, the use of advanced sensor systems, such as those utilizing fiber-optic sensors, have begun to find widespread use in structural health monitoring due to their high accuracy and long-term stability and durability. In this paper, the real performance of a newly constructed skewed half-through plate girder railway bridge was assessed using an integrated fiber optic monitoring system installed during the bridge's construction. Monitoring data recorded during the passage of 12 separate trains consisted of strains measured along the length of the main steel plate girders and crossbeams. Based on available design and construction information, a three-dimensional finite-element model capable of simulating the railway bridge's response was constructed and used to investigate and provide comparisons with monitoring results of the performance of such bridges under passing trains. The influence of track cant on load distribution between the two main girders was discussed, and the live load utilization percentage of the main girders was estimated to be approximately 37% of its design capacity. In addition, the effect of different transverse crossbeam end-connection details (pinned or moment connected) and the influence of axle load distribution through track ballast on the overall response of the bridge structure were evaluated. The results obtained in this study have not only led to the establishment of a comprehensive performance baseline for the newly constructed bridge for long-term condition monitoring but may also be used for improving the design and in-service structural evaluation of such bridges.

Application of wavelet analysis in distributed optical fiber Brillouin temperature strain monitoring system

In the distributed optical fiber monitoring system, the Brillouin system is a system with the most difficult integration, the weakest signal and the most widely used range. It can monitor the strain and temperature of single fiber cable at the same time, and the monitoring range can exceed 100km. It is widely used in super engineering such as submarine optical cable, submarine tunnel, oil pipeline and so on. It is of great research value since this system can monitor the physical quantity of micro deformation, crack and temperature in real time. After the Brillouin system is built independently, the high precision extraction of Brillouin spectrum is realized by using the high efficiency denoising ability of wavelet. By studying the algorithm, the system can reach the temperature identification accuracy of ± 1 degrees centigrade, and the accuracy of strain reaches ± 20 με.

Study of Intracranial Pressure Monitoring In Traumatic Brain Injury

Intracranial pressure monitoring is considered the standard of care for severe traumatic brain injury and is used frequently. However, the efficacy of treatment based on monitoring in improving the outcome has not been rigorously assessed. We conducted a trial in which we included 26 patients of all types of traumatic brain injury (TBI) and they were monitored for intracranial pressure by Conventional fluid filled system with a manometer (Group 1) and compared with the Fiber optic transducer-tipped intracranial pressure monitoring system (Group 2).The main aim of this study was to examine the relationship between Intracranial Pressure (ICP) monitoring and in-hospital mortality. The median length of stay in the ICU was similar in the two groups (12 days in the conventional pressure-monitoring group and 9 days in the new fiber optic group; P=0.25), the number of days of brain-specific treatments (e.g., administration of hyperosmolar fluids and the use of hyperventilation) in the ICU was similar in both groups. The distribution of serious adverse events was similar in the two groups. We concluded that ICP monitoring (as is any monitoring modality) is a useful guide for management. The outcomes are decided by the differences in management protocols that the knowledge of the said parameter brings about. ICP monitoring is recommended for the better management of traumatic brain injury and fiber optic ICP monitoring seems to be beneficial than using the conventional methods of ICP monitoring with manometer.Nepal Journal of Neuroscience, Volume 15, Number 2, 2018, page: 23-29

Fiber Optic Microseismic Monitoring System Used in Underground Coal Mines

A fiber optic microseismic monitoring system for underground coal mines is proposed in this paper. The technical details including overall structure, fiber Bragg grating geophone, and interrogation system are introduced. The results show that the system achieves a bandwidth of 1-300 Hz and a dynamic range of 80 dB. An application example of monitoring cross-border mining activities in underground coal mine is presented at the end.