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Submarine mass wasting in continental margins poses a significant threat to offshore installations, submarine communication cables, and coastal communities due to tsunamis. Based on the analysis of time-lapse geophysical data, we report a very recent submarine slope failure and associated mass transport deposit (MTD) in the Krishna-Godavari (KG) basin, the Bay of Bengal that occurred between January 2009 and December 2015. The head scarp shows erosion of ~ 160 m thick sedimentary strata with an estimated volume of ~ 11 km3. The fan-shaped MTD, located at water depths of 950 to 1100 m, shows a spatial coverage of ~ 70 km2 (volume is ~ 2.2 km3) with a maximum thickness of ~ 60 m. This is one of the largest submarine slope failures reported from time-lapsed geophysical surveys. We analyzed potential triggers such as floods, earthquakes, and cyclones that could have caused the slope failure. We believe that Cyclone Helen, a category-1 storm, may have contributed to the observed slumping in unstable shelf/slope regions of the KG Basin in November 2013 as the Cyclone eye traversed over the head of the slump. However, we cannot rule out other factors such as the extreme flooding events (2010 and 2013) and a 6.0 magnitude earthquake in the Bay of Bengal in May 2014. The study shows that pre-conditioning of sediments is an important factor in the assessment of deepwater geohazards, and areas with relatively moderate external triggers are also at high risk. [ABSTRACT FROM AUTHOR]

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We present the first controlled-environment measurements of the optical path-length change response of telecommunication submarine cables to active seismic and acoustic waves. We perform the comparison among integrated (optical interferometry) and distributed (distributed acoustic sensing, DAS) fibre measurements and ground truth data acquired by 58 geophones, 20 three-axis seismometers and 7 microphones. The comparison between different seismic acquisition methods is an essential step towards full validation and calibration of the data acquired using novel cable-based sensing techniques. Our experimental data demonstrates broadside sensitivity of integrated optical phase measurements, in contrast to predictions from the prevailing model for this type of sensing. We also present evidence of a fast-wave arrival, which we attribute to coupled energy propagating through the metal armour of the submarine cables at a considerably faster velocity than the subsurface and acoustic waves measured during our tests. The latter process can greatly affect the detected optical signal. The experimental setup allowed us to also observe how sensing measurements on separate optical fibres within the same cable can lead to significantly different detected waveforms. Constraining the effects of the fibre architecture on recorded signals can identify factors that contribute to the non-linear response of such a sensing system. [ABSTRACT FROM AUTHOR]

Turbidity currents carve the deepest canyons on Earth, deposit its largest sediment accumulations, and break seabed telecommunication cables. Powerful canyon‐flushing turbidity currents break sensors placed in their path, making them notoriously challenging to measure, and thus poorly understood. This study provides the first remote measurements of canyon‐flushing flows, using ocean‐bottom seismographs located outside the flow's destructive path, revolutionizing flow monitoring. We recorded the internal dynamics of the longest sediment flows yet monitored on Earth, which traveled >1,000 km down the Congo Canyon‐Channel at 3.7–7.6 m s−1 and lasted >3 weeks. These observations allow us to test fundamental models for turbidity current behavior and reveal that flows contain dense and fast frontal‐zones up to ∼400 km in length. These frontal‐zones developed near‐uniform durations and speeds for hundreds of kilometres despite substantial seabed erosion, enabling flows to rapidly transport prodigious volumes of organic carbon, sediment, and warm water to the deep‐sea. Plain Language Summary: Seafloor avalanches of sediment, called turbidity currents, transport huge volumes of sediment and organic carbon to the deep‐sea, and they break critical seabed telecommunication cables that underpin global data transfer. However, turbidity currents are very difficult to measure directly as they often damage sensors placed in their flow path, so they are poorly understood. Here we show that turbidity currents generate ground vibrations that can be measured using ocean‐bottom seismographs placed outside the flow's destructive path, revolutionizing flow monitoring. These seismographs recorded the longest sediment flows yet measured in action on Earth, which traveled >1,000 km along the submarine Congo Canyon‐Channel offshore West Africa. We use these observations to test fundamental models of turbidity current flow behavior. Our measurements show that the front of the flows contain a fast frontal‐zone with high sediment concentrations, which can be up to ∼400 km long, whilst the whole duration of the flow can last for more than 3 weeks. These frontal‐zones develop near‐uniform durations and speeds, despite extensive seabed erosion that adds sediment into the flow. New information on flow durations shows how turbidity currents rapidly deliver prodigious volumes of organic carbon, sediment, and warm water to the deep‐ocean floor. Key Points: Remote seismic monitoring reveals the duration, internal structure, and evolution of powerful canyon‐flushing turbidity currentsFlows contain dense and fast frontal‐zones (up to ∼400 km long) that maintain uniform durations and speeds despite huge seabed erosionCanyon‐flushing flow frontal‐zones can bring substantial fluxes of organic carbon, sediment, and warm water to the deep‐sea in <24 hr [ABSTRACT FROM AUTHOR]

Deep and ultra-deep oil, which are unconventional oil reservoirs have become an important field for increasing reserves and production in China's oil and gas exploration and development, and pose higher requirements for ultra-deep logging technology and equipment. For addressing the technical challenges faced in the development of 260 °C/210 MPa ultra-high temperature and high-pressure logging equipment, based on the CPLog fast and imaging series instruments, this article originally proposes key core technologies and solutions such as 260 °C/210 MPa electromechanical sensors, 13,000 m cable communication, and large borehole correction processing. Through the design indoor testing of a BS-PT-based ultra-high temperature acoustic transducer, 260 °C/210 MPa instrument pressure-bearing housing components, and field testing of large borehole environment testing and 13,000-m cable 8000-m deep well data transmission, it will help develop a prototype of 260 °C/210 MPa ultra-high temperature and high pressure logging equipment. The key technology research of 260 °C/210 MPa logging equipment has laid the foundation for the development of ultra-deep logging equipment and provided technical support for the exploration and development of ultra-deep oil and gas at a depth of 10,000 m. [ABSTRACT FROM AUTHOR]

Utilizing existing telecommunication cables for Distributed Acoustic Sensing (DAS) experiments has eased the collection of seismological data in previously difficult‐to‐access areas such as the ocean bottom. To assess the potential of submarine DAS for monitoring seismic activity, we conducted an experiment from mid‐October to mid‐December 2021 using a 45 km long dark fiber extending from the Greek island of Santorini along the ocean bottom to the neighboring island of Ios. This region is of great geophysical and public interest because of its historical and recent seismic and volcanic activity, especially along the Kolumbo volcanic chain. Besides recording anthropogenic noise and around 1,000 seismic events, we observe the primary and secondary microseisms in the submarine section, the latter inducing Scholte waves in a sediment layer where the cable is well‐coupled. By using the spectral element wave propagation solver Salvus, we compute synthetic strains for earthquakes with varying degrees of model complexity. Despite including topography, a water layer, and a heterogeneous velocity model, we are unable to reproduce the lack of coherence in our observed earthquake waveforms. Backpropagation simulations for four observed earthquakes indicate that clear convergence of the wavefield, and thus the ability to constrain a source region, is only possible when all model complexities are considered. We conclude that, despite the promising emergence of DAS, monitoring capabilities are limited by often unfavorable cable geometries, cable coupling, and the complexity of the medium. Interrogating multiple cables simultaneously or jointly analyzing DAS and seismometer data could help improve future monitoring experiments. Plain Language Summary: Distributed Acoustic Sensing (DAS) can use existing telecommunication cables to measure ground movements along the cable. This is particularly interesting in regions where deploying other sensors is more challenging, like the ocean bottom. We ran an experiment from mid‐October to mid‐December 2021 interrogating a 45 km long underwater cable between the Greek islands of Santorini and Ios to test our ability to monitor seismic events. The region is known for its seismic and volcanic activity, particularly along the Kolumbo volcanic chain. On the underwater section of the cable, we observe ocean‐generated noise, the strength of which correlates with the wind speed in the region. Earthquakes in the observed data show very incoherent waveforms after the first arrivals. Our simulations including topography, a water layer, and a realistic velocity model are unable to reproduce this incoherence. We reinject the recorded earthquake wavefield to estimate earthquake source locations. This works for one particular earthquake with the most realistic model. However, we struggle with other earthquakes and simpler model setups. This highlights the challenges of analyzing DAS data from a complex environment. Future DAS monitoring experiments could be improved by interrogating multiple cables or including seismometer data in the analysis. Key Points: Simulations and backpropagations for various model complexities highlight the challenges of reproducing Distributed Acoustic Sensing (DAS) data in complex environmentsModel complexities include a realistic topography, the water layer, and a heterogeneous velocity modelDespite the promising emergence of DAS, monitoring capabilities are limited by cable geometry, cable coupling, and medium complexity [ABSTRACT FROM AUTHOR]

The former USS Kailua (IX-71), ex-SS Dickenson, is an historic shipwreck resting on the seabed off the Hawaiian island of O'ahu, in what is the defensive zone of Pearl Harbor. The wreck is an artifact of the early-to-mid-twentieth century, serving as a cable ship for the laying and maintenance of telegraphic cables, and as a vessel taken into military service during World War II. It is a significant cultural resource in deep water, with a high level of preservation; it is also a rare surviving example of a specialized form of ship that emerged in the mid-nineteenth century, the cable ship. Cable ships remain an important part of the maritime world in the twenty-first century. [ABSTRACT FROM AUTHOR]

Distributed acoustic sensing (DAS) is an innovative technology with great potential for acquiring seismic data sets in urban areas. In this work, we check the suitability of a DAS data set acquired in Granada (Spain) for retrieving subsurface reflectivity from ambient noise. The fiber‐optic is a pre‐existing underground telecommunication cable that crosses the city from Northwest to Southeast. We use a 10 hr recording of strain rate from a 2020 experiment to obtain seismic reflections using the autocorrelation method. We compare the DAS results with reflections obtained from seismic ambient noise recorded in nine seismometers deployed close to the fiber‐cable for 7 days in November 2022. The novel approach proposed in this study for the identification of the reflections is to use autocorrelations after bandpass filtering for specific central frequencies and to check the stability of the signals over a broad frequency band. Microtremor Horizontal to Vertical Spectral Ratio (MHVSR) measurements at a total of 14 stations, five of them outside the city, help to constrain the reflection interpretation. These include one station at the borehole that reaches the basement in the Granada Basin crossing all the Cenozoic units. We use the legacy sonic log to obtain a relationship between frequencies of MHVSR peaks and depth. Autocorrelation and MHVSR methods give consistent results delineating bedrock depth deeper than 1,000 m in Granada. These results confirm that DAS can provide valuable subsurface information in urban areas. Plain Language Summary: Urban subsurface information is of paramount importance to understand how the underground affects the development of cities (groundwater or hazards such as earthquakes). One of the most useful methods to improve the knowledge of the city underground is seismic technique but installation of vibration sensors can be difficult in an urban area. We use in this work a cutting‐edge technology called Distributed Acoustic Sensing (DAS) that uses fiber‐optic cables in the city, such as preinstalled telecommunication cables, as a high number of seismic sensors. We compare the seismic results obtained from the measurements in the fiber‐optic cable and from conventional seismometers. The analysis of the vibrations acquired with DAS and seismometers provide reflections, like echo signals, from the subsurface changes. In particular we obtain a reflection coming from the contact between sediments and bedrock. The depth of this contact is similar with the two type of measurements reaching 1,400 m depth below the city. This confirms that this new technology can be used in cities to study their subsurface. Key Points: Distributed Acoustic Sensing holds great potential for urban seismic data acquisitionAutocorrelation and Microtremor Horizontal to Vertical Spectral Ratio methods consistently reveal bedrock depth exceeding 1,000 m in GranadaA novel approach is developed to analyze autocorrelation results for retrieving subsurface reflections [ABSTRACT FROM AUTHOR]

In Japan today, aging infrastructures such as dams and bridges are becoming an issue. We considered that the use of a hydrofoil multicopter would be an effective method for inspecting and surveying such facilities. When using a hydrofoil multicopter, it is possible to take off from the shore, land on the water, and dive without using a ship. The aircraft developed in this study has the capability to communicate with the land. The aircraft developed in this study is equipped with a communication buoy, and after landing on the water, a communication cable is extended from the buoy to enable underwater maneuvering via wired communication. We report on the development of a precise control system for flight and diving of this aircraft. [ABSTRACT FROM AUTHOR]

On continental margins, sediments cause significant and spatially variable delays in seismic phase arrival times. The strong impedance contrast of the sediment‐bedrock interface causes P‐wave splitting that is clearly seen on distributed acoustic sensing recordings of earthquakes, resulting in additional phase arrivals that must be picked separately. We introduce sediment corrections to correctly account for those additional phases in the hypocenter localization procedure. Conceptually, the sediment correction method differs from the commonly‐used station corrections; instead of introducing a mathematically optimal constant time delay for each station and each phase, the corrections are derived from a physical, first‐order modeling of the wave propagation in the sediments. To calibrate the sediment corrections, a two‐step procedure is adopted: (a) the delay between the P‐phase and the converted Ps‐phase is taken as a proxy of the sediment thickness; (b) the P‐ and S‐wave speeds are determined through inversion. We show that sediment corrections are able to account for most of the observed bias while considerably reducing the number of free parameters compared to classical station correction. Moreover, the observed local delays are almost fully explained by the presence of the sedimentary layer, rather than by the 3D velocity variations of the bedrock. We retrieve vP ${v}_{\mathrm{P}}$ and vS ${v}_{\mathrm{S}}$ values that are compatible with values commonly found for sediments. Given the simplicity and physical foundation of the proposed method, we recommend the use of sediment corrections over station corrections whenever significant P‐wave splitting can be observed. Plain Language Summary: Loose sediments on the ocean floor strongly affect how seismic waves travel from the earthquake hypocenter to the surface. The most important effect is that sediments slow down the seismic waves, causing them to arrive later at the seismic instruments. These delays can make it difficult to accurately locate the source of earthquakes. This study proposes a new method called sediment corrections. We used the distributed acoustic sensing technology to track delays caused by sediment along a telecommunication cable offshore central Chile, located in a very active subduction zone. Using a simple physical model of how seismic waves travel through sediments, we recovered the main structural features of the sediments beneath the cable. Using the properties of the sediments, we then improved the localization of the earthquake sources. Importantly, this method has the potential to be applied in different sedimentary environments, reducing the challenges associated with interpreting data collected in such geological areas. Key Points: We propose a novel inversion method to account for the presence of shallow sedimentary layers in hypocenter localizationThe inferred sediment properties explain the travel time discrepancies compared to the regional velocity modelThe sediment correction method improves hypocenter localization efforts with a small number of free parameters [ABSTRACT FROM AUTHOR]

Underground telecommunication cables are highly susceptible to damage from excavation activities. Preventing accidental damage to underground telecommunication cables is critical and necessary. In this study, we present field trial results of monitoring excavation activities near underground fiber cables using an intensity-based phase-sensitive optical time-domain reflectometer (φ-OTDR). The reasons for choosing intensity-based φ-OTDR for excavation monitoring are presented and analyzed. The vibration signals generated by four typical individual excavation events, i.e., cutting, hammering, digging, and tamping at five different field trial sites, as well as five different mixed events in the fifth field trial site were investigated. The findings indicate that various types of events can generate vibration signals with different features. Typically, fundamental peak frequencies of cutting, hammering and tamping events ranged from 30 to 40 Hz, 11 to 15 Hz, and 30 to 40 Hz, respectively. Digging events, on the other hand, presented a broadband frequency spectrum without a distinct peak frequency. Moreover, due to differences in environmental conditions, even identical excavation events conducted with the same machine may also generate vibration signals with different characteristics. The diverse field trial results presented offer valuable insights for both research and the practical implementation of excavation monitoring techniques for underground cables. [ABSTRACT FROM AUTHOR]

The deep integration of communication and sensing technology in fiber-optic systems has been highly sought after in recent years, with the aim of rapid and cost-effective large-scale upgrading of existing communication cables in order to monitor ocean activities. As a proof-of-concept demonstration, a high-degree of compatibility was shown between forward-transmission distributed fiber-optic vibration sensing and an on–off keying (OOK)-based communication system. This type of deep integration allows distributed sensing to utilize the optical fiber communication cable, wavelength channel, optical signal and demodulation receiver. The addition of distributed sensing functionality does not have an impact on the communication performance, as sensing involves no hardware changes and does not occupy any bandwidth; instead, it non-intrusively analyzes inherent vibration-induced noise in the data transmitted. Likewise, the transmission of communication data does not affect the sensing performance. For data transmission, 150 Mb/s was demonstrated with a BER of 2.8 × 10−7 and a QdB of 14.1. For vibration sensing, the forward-transmission method offers distance, time, frequency, intensity and phase-resolved monitoring. The limit of detection (LoD) is 8.3 pε/Hz1/2 at 1 kHz. The single-span sensing distance is 101.3 km (no optical amplification), with a spatial resolution of 0.08 m, and positioning accuracy can be as low as 10.1 m. No data averaging was performed during signal processing. The vibration frequency range tested is 10–1000 Hz. [ABSTRACT FROM AUTHOR]

Steel-coped beams are used in industrial structures to accommodate a cluster of water mains, fire hydrants, power cables and telecommunication wires. The coped regions restrict the ultimate capacity and cause unfavorable failure modes. The current study investigates the structural assessment of the coped section in offshore topsides while their use enhances operational safety for drilling and production. The structural evaluation is done through 2D digital image correlation (DIC) experiments to quantify the influence of various cope geometries. The DIC technique illustrated the strain and deformation measurements under different loading conditions for different coped geometry. The primary failure mode observed in local web buckling is characterized by noticeable lateral displacement and the development of buckling lines over the coped web. Studies showed the influence of the cope depth on the load-carrying capacity and buckling processes for different cope geometries. The results of the DIC analysis are strongly aligned with experimental data and finite element numerical results, suggesting this technique to the structural assessment of coped section. [ABSTRACT FROM AUTHOR]

Silica composites with low dielectric constants have broad application prospects in the fields of low dielectric and thermal insulation materials. However, silica composites still face challenges such as strong water absorption and strict storage conditions in practical applications. Modification of SiO2@quartz fiber composites was conducted with hydrophobic modifiers (hexamethyldisilazane HMDS, stearic acid, sodium dodecyl sulfate) to study the effects of type and mass fraction of hydrophobic modifiers on the hydrophobic and dielectric properties of the composites. The hydrophobic-modified composites were made into coaxial cables to study the effect of heat treatment on the performance of the cables. The results show that the 3% HMDS-modified composite have the best hydrophobic modification with contact angle of 151.6°, the lowest contact angle is 132.6° after 240 days of storage, and the dielectric constant is as low as 1.87 after 200 °C calcination. The hydrophobic-modified composites were made into coaxial communication cables, and the cables had a voltage standing wave ratio of 1.48, an attenuation value of 1.56 dB, and a characteristic impedance of 48 Ω. The hydrophobic-modified composite materials exhibit excellent cable performance, demonstrating potential application value in communication cables and other fields. [ABSTRACT FROM AUTHOR]

High-fidelity communication in extreme environments has attracted significant attention due to its potential applications in aerospace, polar, deep-sea exploration, fire rescue, and nuclear industries. Yet, challenges persist in constructing dielectric layers with both low dielectric constant and high-temperature stability in communication cables. Herein, low-dielectric inorganic composites utilizing pure silicon oxide (SiO 2) are employed as a substitute for conventional organic materials or their composites. By incorporating the in-situ growth of SiO 2 microspheres (m-SiO 2) on the quartz fiber structure, the composites exhibit a reduced dielectric constant while improving mechanical performance. The flexural stress of the m-SiO 2 @quartz fiber composites is twice as high as that of the composites prepared by the ex-situ synthesis method. Furthermore, the m-SiO 2 @quartz fiber composites display high-temperature resistance up to 800 °C with a mass loss less than 1 %. With 30 wt% of quartz fibers, 20 nm of m-SiO 2 , and 6 wt% of the foaming agent, the composites exhibit a dielectric constant of 1.95. Based on the low-dielectric m-SiO 2 @quartz fiber composites, the cable demonstrates a voltage standing wave ratio (VSWR) of 1.46, an attenuation of 1.22 dB, and a characteristic impedance of 48 Ω. [ABSTRACT FROM AUTHOR]

In this study, we provide a dynamic and energy-optimized task offloading approach for MFC. Our method takes into account how much energy FNs, cell phones, and communication cables use. We employ a dynamic programming technique to choose the job offloading strategy that minimises energy use while satisfying the application's latency requirements. We conduct a simulation-based experiment to assess our suggested strategy. The results show that our solution performs better than others in terms of energy consumption and delay efficiency. Additionally, our method may balance energy usage and delay performance while adapting to dynamic changes in the network topology.Our proposed energy-optimized and dynamic design for task offloading in MFC can enable efficient and effective utilization of computational resources in mobile devices and FNs, This may result in better functionality and longer battery life for portable electronics. [ABSTRACT FROM AUTHOR]

Subsea infrastructure is typically out of sight, but in recent times, seldom out of mind. The sabotage of the Nord Stream pipelines in October 2022 has magnified the vulnerability and critical importance of subsea infrastructure. It also exposed a lack of understanding on how subsea networks operate, how they are regulated, who controls them and how they are protected. Ireland matters in this context. Despite its official policy of neutrality, Ireland occupies an important strategic position in terms of transatlantic telecommunications cables between the United States, Britain and continental Europe. The conflict in Ukraine has amplified tensions in this context in terms of the increased threat of grey-zone/hybrid warfare activity. This article will consider for the first time how a global connectivity hub on the western periphery of Europe governs critical underwater infrastructure. It will discuss the context and agencies involved in subsea cable governance in Ireland and identify the gaps in this protection before formulating suggestions for the long-term improvement of Ireland's maritime security capacity. The Irish case is important as it can help inform defence policy and security practice in other island states with large maritime jurisdictions and in particular states with small navies. [ABSTRACT FROM AUTHOR]

Despite significant recent technological advances, oceanographic observations on horizontal scales of meters to a few kilometres prove challenging. Exploiting legacy seafloor cables presents a disruptive prospect to address this gap, as it may provide low‐cost sustained observations with high space‐time resolution, enabled through novel opto‐electronic interrogation of optical fibers within the cables. Here, we demonstrate this approach in a renewable tidal energy cable embedded within a region with a strong barotropic tide. By making remote measurements continuously over 12 hr, we obtain the distributed differential strain experienced by 2 km of offshore cable from a diverse range of oceanic flow processes, with an along‐cable resolution of 2.04 m. We successfully identify: (a) nearshore wave breaking and its modulation by changes in water depth; (b) along‐cable tidal velocity, shown to be linearly related to the differential strain; and (c) high‐frequency motions consistent with 3‐dimensional turbulent processes, either of natural origin or from flow‐cable interaction. These inferences are supported by nearby conventional measurements of water depth and velocity. Plain Language Summary: While new marine observational tools have greatly improved our understanding of the oceans, a gap in our ability to observe processes occurring on scales of meters to a few kilometers still persists. In this study, we demonstrate the use of a legacy seafloor cable as a disruptive observational platform to enable oceanic velocity measurements on such scales. Using this cable, we measure: (a) surface wave breaking at the beach; (b) the along‐cable water‐velocity from the stretching and compression of the cable; and (c) fast motions associated with small‐scale ocean turbulence. These observations are supported by conventional oceanographic measurements in the same region. Our results highlight the potential of legacy seafloor cabled infrastructure, comprising both energy and telecommunications cables, for sustainably obtaining high‐resolution observations of ocean circulation at low cost. Key Points: A fiber optic embedded within a legacy energy cable is interrogated using distributed sensing techniques for 12 hrThe cable strain data captures the modulation of near‐coast wave breaking by tidal changes in water depthStrain is shown to be linearly related to the local velocity, highlighting the potential for high space‐time resolved velocity sensing [ABSTRACT FROM AUTHOR]

In this study, remote control application of an ultrasonic motor (USM) has been achieved over the power line communication (PLC) system. Fast, practical, affordable and effective operating mode is essential for the USM. This study aimed to develop an original, efficient, effective and economical method. Drive and control of USM control has been succeeded with the developed PLC control system. A two-phase high-frequency inverter, a power line transmitter, and a power line receiver circuits have been designed to drive and control of the ultrasonic motor. Required measurements are acquired from the power line to select the most suitable communication frequency and coupling circuit impedance for the PLC system. For the communication frequency and impedance value measurements the receiver and the transmitter circuits have been designed. The PLC-controlled system has been tested for different operating conditions of the ultrasonic motor. USM control has been accomplished over the existing power line without using extra cables and interfaces for communication. The obtained results show that the PLC-controlled system is practical, reliable, cost-effective, and feasible for the remote control of the USM. This research contributes a new and essential perspective for the PLC-based remote control studies in addition to the USM drive and control strategies. [ABSTRACT FROM AUTHOR]

This letter delves into the influence of drain wire design on electromagnetic radiated emission (RE) from a commercial universal serial bus (USB) cable operating in a high‐speed data transfer mode. The investigation involves an experimental comparison of measured RE across various retrofitted cables. Notably, it is demonstrated that the distribution of contact points on the drain‐shield has negligible effects on RE. Conversely, relocating the drain wire externally to the shields and minimizing the distance with respect to the grounding connector leads to a significant reduction in RE, particularly within the sub‐MHz frequency range. Consequently, regulatory proposals are put forth to diminish overall RE and enhance the RE compliance of USB cables. [ABSTRACT FROM AUTHOR]

The development of the digital society has led to an urgent demand for high-temperature-resistant, low-dielectric cable insulation materials. In order to meet the stable high temperature service performance, it is necessary to use inorganic materials instead of the traditional organic insulating materials as the cable insulation layer. Silicon dioxide (SiO 2) as a widely used inorganic dielectric material has great potential for application, and quartz fiber is another wave-transparent material with good dielectric properties. The combination of SiO 2 and quartz fiber can provide a feasible path for pure inorganic composite insulation materials. In this work, the high-throughput (>50 g) synthesis of SiO 2 was investigated to explore the factors affecting the dielectric properties. The effects of different quartz fiber composite amounts and sintering temperatures on the dielectric properties of the composites were investigated by testing the dielectric properties of the composite powders after pressing. The composite powders doped with 20 wt% quartz fibers at 600 °C sintering temperature were found to have better dielectric properties with dielectric constant of 2.48 and dielectric loss of 0.0109 at 20 M Hz. Furthermore, the composite powders were filled into the cables and measured for electrical properties by a network analyzer. And dielectric properties of the cables preliminarily meet the performance requirements for the applications of high temperature (900 °C) radio frequency (RF) communication cables with dielectric constant of 1.731 and insertion loss of 2.02 dB at 18 G Hz. Therefore, this inorganic composite material can be used as the insulation layer for RF high-temperature-resistant communication cables for aerospace, nuclear power plants and energy fields. [ABSTRACT FROM AUTHOR]

Vehicle‐induced seismic waves, generated as vehicles traverse the ground surface, carry valuable information for imaging the underlying near‐surface structure. These waves propagate differently in the subsurface depending on soil properties at various spatial locations. By leveraging wave propagation characteristics, such as surface‐wave velocity and attenuation, this study presents a novel method for near‐surface monitoring. Our method employs passing vehicles as active, non‐dedicated seismic sources and leverages pre‐existing telecommunication fibers as large‐scale and cost‐effective roadside sensors empowered by Distributed Acoustic Sensing (DAS) technology. A specialized Kalman filter algorithm is integrated for automated DAS‐based traffic monitoring to accurately determine vehicles' location and speed. Then, our approach uniquely leverages vehicle trajectories to isolate space‐time windows containing high‐quality surface waves. With known vehicle (i.e., seismic source) locations, we can effectively mitigate artifacts associated with suboptimal distribution of sources in conventional ambient noise interferometry. Compared to ambient noise interferometry, our approach enables the synthesis of virtual shot gathers with a high signal‐to‐noise ratio and spatiotemporal resolution at reduced computational costs. We validate the effectiveness of our method using the Stanford DAS‐2 array, with a focus on capturing spatial heterogeneity and monitoring temporal variations in soil seismic properties during rainfall events. Specifically, in non‐built‐up areas, we observed an evident decrease in phase velocity and group velocity and an increase in attenuation due to the rainfall. Our findings illustrate our method's sensitivity and resolution in discerning variations across different spatial locations and demonstrate that our method is a promising advancement for high‐resolution near‐surface imaging in urban settings. Plain Language Summary: Continuous monitoring of near‐surface soil properties is important to various applications, including identifying subsidence and monitoring groundwater levels. Vehicles transiting in city streets excite seismic waves propagating in the subsurface, which can be analyzed to gain insights into the structures beneath the surface. In this study, we develop a novel near‐surface monitoring method utilizing traffic recordings of Distributed Acoustic Sensing (DAS) technology, transforming existing telecommunication cables into extensive ground motion sensors. To harness the vibrations generated by vehicles, our method employs a specialized algorithm, determining vehicle locations and speeds based on the ground deformation they induce. The identified vehicle location is precisely utilized to select specific traffic‐induced seismic waves to explore the subsurface. Our approach allows for the acquisition of clearer and more precise insights into underground structures in urban areas and is more computationally efficient than traditional methods based on ambient noises. Tested at Stanford University in 2023, our method adeptly identified variations in the seismic properties of the subsurface, particularly in non‐built‐up areas, during rainfall events. Such accurate detection is valuable for water resource management and urban development, enabling enhanced understanding and management of urban subsurface environments. Key Points: We utilize a large number of vehicles transiting on city streets as non‐dedicated seismic sources for continuous near‐surface monitoringOur method, tailored for environments with urban and suburban traffic, outperforms conventional interferometry in efficiency and resolution, leveraging selective cross‐correlation of surface wavesWe observed rain‐induced changes in seismic properties using time‐lapse analysis of kinematics and attenuation [ABSTRACT FROM AUTHOR]

Submarine volcanism makes up approximately 85 % of volcanism that occurs on Earth, and its eruptions have the potential to cause several hazards including ash dispersal, pumice rafts, pyroclastic density currents, sector collapses, and tsunamis. Recent examples include the eruptions in Japan and in the Kingdom of Tonga in 2021 and 2022 respectively, but there has been little to no study of submarine volcanism in Southeast Asia and surroundings. Here we provide a compilation of 466 seamounts from the region, from different published sources, through the SEATANI dataset (Southeast Asia, Taiwan, and the Andaman and Nicobar Islands). We use this newly compiled dataset to assess on a regional level the seamount hazard potential and exposure potential as a springboard for future more quantitative hazard studies of the region. The hazard potential was assessed through seamount morphological and structural analyses, to determine the seamount evolution stage and grade of maturity. The exposure potential was evaluated with two different approaches: an areal analysis of the number of assets within a 100 km radius of each seamount and the development of a hazard-weighted seamount density map to highlight potential areas of interest for future more-in-depth studies. Our results show that there are several potentially hazardous seamounts in this region. Taiwan has the highest hazard and exposure potential, for all assets considered, while the Philippines, Indonesia, and Vietnam have relatively high exposure potential for submarine communication cables and ship traffic density. The results from this work serve as a first step towards Southeast Asia and neighbouring countries becoming more resilient against and prepared for submarine volcanic eruptions in the region. [ABSTRACT FROM AUTHOR]

A T‐wave is a seismo‐acoustic wave that can travel a long distance in the ocean with little attenuation, making it valuable for monitoring remote tectonic activity and changes in ocean temperature using seismic ocean thermometry (SOT). However, current high‐quality T‐wave stations are sparsely distributed, limiting the detectability of oceanic seismicity and the spatial resolution of global SOT. The use of ocean bottom distributed acoustic sensing (OBDAS), through the conversion of telecommunication cables into dense seismic arrays, is a cost‐effective and scalable means to complement existing seismic stations. Here, we systematically investigate the performance of OBDAS for oceanic seismicity detection and SOT using a 4‐day Ocean Observatories Initiative community experiment offshore Oregon. We first present T‐wave observations from distant and regional earthquakes and develop a curvelet denoising scheme to enhance T‐wave signals on OBDAS. After denoising, we show that OBDAS can detect and locate more and smaller T‐wave events than regional OBS network. During the 4‐day experiment, we detect 92 oceanic earthquakes, most of which are missing from existing catalogs. Leveraging the sensor density and cable directionality, we demonstrate the feasibility of source azimuth estimation for regional Blanco earthquakes. We also evaluate the SOT performance of OBDAS using pseudo‐repeating earthquake T‐waves. Our results show that OBDAS can utilize repeating earthquakes as small as M3.5 for SOT, outperforming ocean bottom seismometers. However, ocean ambient natural and instrumental noise strongly affects the performance of OBDAS for oceanic seismicity detection and SOT, requiring further investigation. Plain Language Summary: Oceanic earthquakes can produce loud sounds in the ocean. These sounds usually arrive at a seismic station as the tertiary wave, a so‐called T‐wave, following the arrival of the primary P‐wave and secondary S‐wave. T‐waves can propagate thousands of kilometers in the ocean's SOund Fixing And Ranging (SOFAR) channel with little energy loss. Thus, they are useful for monitoring earthquakes and ocean temperature changes. However, currently available instruments for measuring these waves are limited. Recently, a new type of technique, Distributed Acoustic Sensing, provides an opportunity to expand the seismic‐recording capability in the ocean. Ocean bottom distributed acoustic sensing (OBDAS) can effectively turn submarine telecommunication cables into dense seismic sensors that complement conventional seismometers. In this study, we explore the OBDAS potential for T‐wave detection. With a 4‐day OBDAS community experiment offshore Oregon, we demonstrate that OBDAS does a better job than a conventional seismic network for detecting T‐waves when a specifically designed denoising scheme is applied. In addition, OBDAS has the potential to measure ocean temperature changes using more repeating earthquakes of smaller magnitudes, outperforming conventional sensors. However, the accuracy of the OBDAS system can be strongly affected by various types of noise, which requires further research. Key Points: We develop a curvelet denoising scheme for ocean bottom distributed acoustic sensing to enhance T‐wave signalsThe denoised distributed acoustic sensing data detects three times more T‐wave events than cabled ocean bottom seismometersThe improved detection capability makes more small repeating earthquakes useable for seismic ocean thermometry [ABSTRACT FROM AUTHOR]

The devastation caused by the January 2022 eruption of Hunga Tonga-Hunga Ha'apai volcano (HTHH) in the Tongan archipelago reminded us of the importance of monitoring shallow-sea volcanic activity. Seismic observations are essential for such monitoring, but there were no operational seismic stations in Tonga at the time of the eruption. There are only a few islands near Tongan volcanoes, and installation and maintenance of seismic stations on remote islands are expensive. Seismic observations based on distributed acoustic sensing (DAS) using a seafloor cable may provide a more practical and economical solution. To investigate the potential of this approach, we made preliminary DAS observations for 1 week using the seafloor domestic broadband telecommunications cable in Tonga. DAS equipment was installed at the landing station of the seafloor cable at Nuku'alofa on Tongatapu, the main island of Tonga. To provide reference data, we installed several seismometers on Tongatapu. The DAS data we obtained showed high noise levels in areas of shallow coral reef, but noise levels decreased greatly in deeper water areas, indicating that DAS is suitable for seismic observations of the deep seafloor. We detected many local and regional earthquakes during our week of observation and determined 17 earthquake hypocenters by picking P- and S-wave arrival times from the DAS and onshore seismic data. Although most of these were tectonic events related to the subduction of the Pacific plate along the Tonga trench, several events were detected around the volcanic chain of the Tongan archipelago including one event beneath the HTHH crater, implying that activity at HTHH has continued since the 2022 eruption. The much lower cost of installation of DAS equipment compared to that for pop-up type ocean-bottom seismometers and the ability of DAS systems to monitor seismic activity in real-time make it an attractive option for monitoring the activity of HTHH and other volcanoes near seafloor cables in the Tongan archipelago. [ABSTRACT FROM AUTHOR]

Owing to the fuzzy structure, small background difference, diverse types and complex data distribution, the defect detection of railway communication cable fasteners is still a challenge. Aiming at the problem that the existing CNN methods are sensitive to the distribution of defect data, the unsupervised GAN is introduced, and a block-reconstruction-GAN-based algorithm is proposed. Firstly, the YOLOv5-M model is used to locate the image of the leaky cable fastener. Then, a block-removing approach based on existing Skip-GANomaly is proposed to split the fastener training samples, which can alleviate the overfitting problem of Skip-GANomaly during the reconstruction process of defect fastener by dispersing fastener features and increasing the number of samples. In addition, the cosine similarity is proposed to calculate the similarity score between the original fastener image and reconstructed image, which will be used to distinguish the defect fastener. The experiments are carried out on the cable fastener dataset collected by the comprehensive inspection vehicle and the experimental results show that the AUC value of the proposed algorithm for multi-type fastener defect recognition reaches 0.961, which is 3% higher than that of Skip-GANomaly algorithm. In addition, the visualization results show that compared with other two classical anomaly scores, the method based on cosine similarity can better distinguish defect fastener from the normal fastener. [ABSTRACT FROM AUTHOR]

High-speed railway communication optical cables carry information such as train dispatching, command and control, which are an important part of ensuring the safety of high-speed railway transportation. Therefore, the analysis and handling of optical cable faults is particularly important. Through the summary of years of on-site maintenance experience, the analysis and handling methods of optical cable faults are derived, which are helpful to quickly judge and solve optical cable faults and are able to provide a reference for the maintenance of high-speed railway communication optical cables. [ABSTRACT FROM AUTHOR]

Distributed acoustic sensing (DAS) using existing optical fiber cables facilitates high‐density seismic observation. However, few studies have examined the reliability of the seismic waveform amplitude recorded by DAS. In this study, a DAS network was connected to optical fiber cables installed over a distance of 75 km along a high‐speed train (Shinkansen) railway in the Kumamoto prefecture, Japan. We successfully observed strong motions of the Mj6.6 earthquake (approximately 150 km from the fiber) on 22 January 2022, in Hyuga‐nada, in addition to several small local earthquakes. The observed strong motions from the Mj6.6 earthquake, using DAS, exhibited cycle skipping (clipping) issues due to dynamic range limitations at numerous channels. To address this, we estimated the shaking map, representing maximum strain distributions for Mj6.6, by replacing the clipped data with information from nearby unclipped channels and scaling their RMS amplitudes based on S‐coda (unclipped). Furthermore, we verified the reliability of the amplitude information obtained from DAS by estimating the distance attenuation of seismic waves while correcting for the differences in the structure type and coupling as much as possible. The distance attenuation property of local earthquakes was consistent with that of the peak ground velocities obtained from seismometers, indicating that DAS data acquired using fibers installed on infrastructure (various structures) can also be utilized to assess the spatial distribution of the relative amplitude values along the fiber. Obtaining high‐density seismic motion distributions is important for earthquake early warning and accurate damage estimation of strong motions. Plain Language Summary: In the past decade, the use of distributed acoustic sensing (DAS) for seismological purposes has grown rapidly. By utilizing existing dark fibers, such as telecommunication cables, high‐density seismic observation networks can be established in residential areas. In this study, DAS was applied to an existing optical fiber cable installed along a railway line, which recorded strong ground motions of Mj6.6 originating from a subduction zone, as well as numerous regional earthquakes. Although the technique uses optical phase differences for strain measurements and therefore has a poor response to strong ground motions, we resolve this issue using the correct data from neighboring stations as a reference and estimated the shaking distribution every 5 m along 75 km of the railway line. Additionally, when we analyzed the distance attenuation of small regional earthquakes, we found that the attenuation characteristics were similar to those obtained from permanent seismometers. These findings will significantly impact society in the future, particularly as the fiber cables replace conventional seismic observation networks. As a result, ultra‐high‐density observation networks will be capable of issuing more accurate earthquake early warnings and estimating damage following earthquakes. Key Points: We successfully observed strong motion from the Mj6.6 earthquake in Hyuga‐nada using Distributed acoustic sensing (DAS) over 75 km along railwayThe shaking map of the Mj6.6 was estimated by replacing the clipped channels with nearby unclipped channels and scaling their RMS amplitudes of S‐codaDistance attenuation property of local earthquakes of DAS consistent with that of peak ground velocities from continuous seismometers [ABSTRACT FROM AUTHOR]

This article takes up the significant yet understudied issue of belligerent rights regarding submarine communication cables in armed conflict. The article takes up three key questions that have persistently evaded clarity. First, what actually is the law applicable to cables in wartime? Second, how is this law to be applied in practice? And third, is it fit for purpose? The article concludes that, as a matter of lex lata , no lex specialis rules have emerged specific to the protection of submarine cables in armed conflict, either in treaty or customary international law. However, this does not MEAn that belligerents are free to target submarine cables in times of armed conflict. Instead, important international law constraints are to be found in general IHL principles, the law of neutrality, and law of the sea protections that persist in times of armed conflict. Applied to the technical configurations of submarine cables as currently deployed and used, it is far from clear that these rules and principles permit the targeting of submarine cables in wartime. [ABSTRACT FROM AUTHOR]

Introduction. One of the main driving factors of the demand for cable and conductor products is the modern trend of urbanization, which leads to an increase in cities with significantly increased requirements for electrical networks of transportation and distribution of electrical energy. This requires the development of appropriate infrastructure with significant demand for electricity in the commercial, industrial and residential sectors. The construction industry uses a wide range of cables with an appropriate set of electrical and mechanical properties, resistance to the influence of external climatic factors, and, first of all, must meet fire safety requirements. Increasing construction activity is stimulating the market for fire-resistant cables in the construction industry. According to the Construction Products Regulation, power, telecommunication cables, data cables, control and management, fiber optic refer to construction products in the EU member states. These cables are intended for the supply of electrical energy and communication, which are permanently installed in buildings and other engineering structures. Power, telecommunications, data and control cables are considered construction products, and are the only electrical products classified as construction. Over the next 15 years, Eastern Europe is expected to see increased growth in the construction industry, as the end of the war in Ukraine requires nearly $1 trillion in reconstruction. A strategic task in the reconstruction of the country is the use of cable and conductor products with increased operational properties, including in the construction industry. Significant efforts and investments in innovation and certification of cable and conductor products require manufacturers to create construction products of the «Power, control and communication cables» category with a high level of fire safety in accordance with the Euroclassification of cables in terms of reaction to fire depending on the level of safety. Purpose. Analysis of fire safety requirements for cables as a category of construction products and determination of thermal resistance of power cables based on experimental thermal studies of modern electrical insulating compositions. Methodology. The thermal stability of power cables with a voltage of 0,66/1 kV was determined, depending on the design, based on the conducted experimental studies of the thermal stability of electrical insulation materials, between the core filling and the polymer sheath, removed from the cable samples. On the basis of the conducted correlation analysis between thermal resistance and fire load, which are important parameters for confirming the quality and safety of the entire cable, it has been proven that the efficiency of halogen-free compositions to meet fire safety requirements increases with the increase in the cross-section and number of cores in the cable. Practical value. Determining the heat load and fire resistance of cables of various designs and areas of application based on the obtained experimental data on the heat of combustion of polymer cable materials is necessary and justified at the stage of mastering and determining the prospects for the production of cables with modern halogenfree electrical insulation compositions in accordance with fire safety requirements. References 40, figures 6. [ABSTRACT FROM AUTHOR]

For the maintenance of railways on soft soils, accurate knowledge of the subsoil conditions is essential. Soft soils at shallow depths have high variability; thus, high spatial resolution is required. Spare telecommunication fiber-optic cables, known as dark fiber, can be used as an array of sensors to measure waves generated by running trains, which offers a unique opportunity to characterize shallow soils at high spatial resolution. We used dark fiber to measure seismic waves generated by running trains and implemented a seismic interferometry technique to retrieve surface waves. We evaluated the reliability of selected parts of the recorded signals split as bow waves (the train approaching the fiber), train waves (the train passing alongside the fiber), and tail waves (the train leaving the fiber) to retrieve broad-band surface waves. The analysis was performed in two distinctive zones. Zone I consists of a thick–soft (2.0–6.0 m thickness) layer, and Zone II consists of a thin–soft (less than 2.0 m thickness) layer, both overlaying a "stiffer" sand layer. At Zone I, train waves yielded the best results in revealing the thick–soft layer. At Zone II, the bow waves yielded clear high-frequency energy, revealing the overall soil structure but without identifying the shallow thin–soft layer. [ABSTRACT FROM AUTHOR]

Extreme weather events threaten life and property in populated areas. Timely and precise weather event monitoring and risk assessment are critical, but can be hampered by limited meteorological stations in cities. Recent studies have shown that seismic stations are sensitive to storm-induced noise. This study aims to investigate the sensitivity of distributed acoustic sensing (DAS), a technology capable of turning existing optical fibres into dense seismic sensors, for recording storm-induced seismic noise. We analyse 4-month continuous DAS recordings (June–September 2021) from a 4.2-km-long underground fibre-optic array in State College, PA. We calibrate the DAS data by comparing it to various meteorological data (rainfall and wind speed) from nearby weather stations. We first show DAS-recorded low-frequency wind-induced noise (0.5–8 Hz) probably caused by light poles swaying in the wind, as observed resonant frequencies agree with theoretical natural frequencies of nearby light poles. We find a strong linear correlation between DAS energy and wind speed. We further characterize rain-induced noise. Detailed observations from two rain events: a moderate rain and a heavy rain from Hurricane Ida, suggest that rain-induced noise is not generated by direct raindrops hitting the ground. Instead, the low-frequency noise (2–8 Hz) is attributed to the acoustic noise generated by water flow in stormwater drainage systems. Strong high-frequency noise up to 125 Hz is likely related to the rapid rainwater filling from the surface to the drainage system during heavy rain. We show linear relations between rain-induced DAS energy and rainfall rate, where the slopes of relations are related to the volume of rainwater, suggesting the influence of surface water and rainwater flow in the drainage system on DAS signals. Our results show the possibility of using DAS-equipped pre-existing telecom fibre-optic cables for sensing windstorms and rainstorms in urban areas and their interactions with urban infrastructures. [ABSTRACT FROM AUTHOR]

This paper aims to discuss the common obstacles detected during the maintenance of railway communication optical cables, and explore the methods to analyze and locate and deal with such obstacles. According to the situation of fiber core blocking, the obstacles of optical cables are divided into several types, such as complete blocking, partial blocking, and excessive fiber attenuation. The causes of optical cable obstacles are analyzed, and are divided into natural disasters, external forces, human factors, and cable defects. For diff erent types of optical cable obstacles, corresponding handling methods are proposed, including the principles for dealing with faults and obstacles, the sequences for achieving emergent reconnection and recovery, and the methods for locating and dealing with cable fault points. This paper emphasizes the importance of day-to-day maintenance management of railway communication optical cable lines, to ensure the safe operation of railway communication equipment, so as to guarantee the safety of railway transportation. [ABSTRACT FROM AUTHOR]

Temperature is an essential oceanographic variable (EOV) that still today remains coarsely resolved below the surface and near the seafloor. Here, we gather evidence to confirm that Distributed Acoustic Sensing (DAS) technology can convert tens of kilometer-long seafloor fiber-optic telecommunication cables into dense arrays of temperature anomaly sensors having millikelvin (mK) sensitivity, thus allowing to monitor oceanic processes such as internal waves and upwelling with unprecedented detail. Notably, we report high-resolution observations of highly coherent near-inertial and super-inertial internal waves in the NW Mediterranean sea, offshore of Toulon, France, having spatial extents of a few kilometers and producing maximum thermal anomalies of more than 5 K at maximum absolute rates of more than 1 K/h. We validate our observations with in-situ oceanographic sensors and an alternative optical fiber sensing technology. Currently, DAS only provides temperature changes estimates, however practical solutions are outlined to obtain continuous absolute temperature measurements with DAS at the seafloor. Our observations grant key advantages to DAS over established temperature sensors, showing its transformative potential for the description of seafloor temperature fluctuations over an extended range of spatial and temporal scales, as well as for the understanding of the evolution of the ocean in a broad sense (e.g. physical and ecological). Diverse ocean-oriented fields could benefit from the potential applications of this fast-developing technology. [ABSTRACT FROM AUTHOR]

Brood X is the largest of the 15 broods of periodical cicadas, and individuals from this brood emerged across the Eastern United States in spring 2021. Using distributed acoustic sensing (DAS) technology, the activity of Brood X cicadas was monitored in their natural environment in Princeton, NJ. Critical information regarding their acoustic signatures and activity level is collected and analyzed using standard outdoor-grade telecommunication fiber cables. We believe these results have the potential to be a quantitative baseline for regional Brood X activity and pave the way for more detailed monitoring of insect populations to combat global insect decline. We also show that it is possible to transform readily available fiber optic networks into environmental sensors with no additional installation costs. To our knowledge, this is the first reported use case of a distributed fiber optic sensing system for entomological sciences and environmental studies. [ABSTRACT FROM AUTHOR]

The Granada Basin in southeast Spain is an area of moderate seismicity. Yet, it hosts some of the highest seismic hazards in the Iberian Peninsula due to the presence of shallow soft sediments amplifying local ground motion. In urban areas, seismic measurements often suffer from sparse instrumentation. An enticing alternative to conventional seismometers is the distributed acoustic sensing (DAS) technology that can convert fibre-optic telecommunication cables into dense arrays of seismic sensors. In this study, we perform a shallow structure analysis using the ambient seismic field interferometry method. We conduct a DAS array field test in the city of Granada on the 26 and 27 August 2020, using a telecommunication fibre. In addition to the existing limitations of using DAS with unknown fibre-ground coupling conditions, the complex geometry of the fibre and limited data recording duration further challenge the extraction of surface-wave information from the ambient seismic field in such an urban environment. Therefore, we develop a processing scheme that incorporates a frequency–wavenumber (f − k) filter to enhance the quality of the virtual shot gathers and related multimode dispersion images. We are able to use this data set to generate several shear-wave velocity (VS) profiles for different sections of the cable. The shallow VS structure shows a good agreement with different geological conditions of soil deposits. This study demonstrates that DAS could provide insights into soil characterization and seismic microzonation in urban areas. In addition, the results contribute to a better understanding of local site response to ground motion. [ABSTRACT FROM AUTHOR]

The degradation of communication cable insulators reduces the availability of the train control system and is caused by the degrading of data transmission line parameters. Due to extremely varying environmental conditions in the railway industry, the effect of data transmission line degradation on the critical parameters of the surge arrester that is used in wayside equipment is not known. The surge arrester module is very important in the railway industry, as it enables the protection of sensitive parts of wayside equipment, especially communication interfaces existing in wheel detectors, evaluators, signals, etc. These are critical to the safe and efficient management of railway infrastructure. The process of selecting a surge arrester component for a two-level voltage input to enable the examination of the degradation impact of a cable insulator used in rail signaling equipment on the performance of the surge arrester is presented in this paper based on the standards, as well as practical experience. To achieve this objective, an innovative design of the goal function that can be adapted to the new requirements of various industry sectors is proposed. The use of a two-stage solution verification is a unique feature of this method. The results indicate that the proper selection of the arrester components ensures the effect of degradation of the communication cable has an insignificant influence on the power dissipation of the surge exposures. [ABSTRACT FROM AUTHOR]

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Early detection of potentially unreliable areas in optical fibers makes it possible to detect degradation of optical fibers of fiber-optic communication lines at an early stage. Early diagnostics of the physical state of optical fibers located in the laid optical cables of telecommunication systems is an important topical task. The paper presents adaptive algorithms that allow one to determine the maximum of the Mandelstam–Brillouin scattering spectrum (Brillouin frequency shift), and then the degree of tension of optical fibers. The process of determining the Brillouin frequency shift, whose values at wavelengths of laser radiation used in telecommunication systems belong to the microwave range, can be significantly accelerated if adaptive algorithms for obtaining and processing data are implemented due to a special choice of the step for the scanning frequency and the time of accumulation of measurement results. The adaptive algorithms considered in this paper make it possible to speed up the process of obtaining output results in Brillouin reflectometers by ignoring readings that do not significantly affect the final characteristics. The construction of approximate graphs of the distribution of the spectrum and tension along the length of the fiber allows the trained user of the Brillouin reflectometer to stop the analysis process in order to make corrections to the measuring process (selection of the scanning range in frequency, change in the scanning step in frequency, choice of the accuracy of the presentation of output results, change in spatial resolution, etc.), which also speeds up the testing of the selected fiber. The measurement process can also be accelerated by adaptively changing the number of averages. With a database of measured Mandelstam–Brillouin scattering characteristics of optical fibers of various types and manufacturers, the speed of obtaining tension plots can also be increased. Since the approximate value of the Brillouin frequency shift is calculated already at the initial steps of the measurement process, preliminary dependences of the tension distribution along the length of the fiber will be constructed rather quickly. [ABSTRACT FROM AUTHOR]