Optical Cable Research Articles

Feasibility study on sinkhole monitoring with fiber optic strain sensing nerves

Anthropogenic activity-induced sinkholes pose a serious threat to building safety and human life nowadays. Real-time detection and early warning of sinkhole formation are a key and urgent problem in urban areas. This paper presents an experimental study to evaluate the feasibility of fiber optic strain sensing nerves in sinkhole monitoring. Combining the artificial neural network (ANN) and particle image velocimetry (PIV) techniques, a series of model tests have been performed to explore the relationship between strain measurements and sinkhole development and to establish a conversion model from strain data to ground settlements. It is demonstrated that the failure mechanism of the soil above the sinkhole developed from a triangle failure plane to a vertical failure plane with increasing collapse volume. Meanwhile, the soil-embedded fiber optic strain sensing nerves allowed deformation monitoring of the ground soil in real time. Furthermore, the characteristics of the measured strain profiles indicate the locations of sinkholes and the associated shear bands. Based on the strain data, the ANN model predicts the ground settlement well. Additionally, micro-anchored fiber optic cables have been proven to increase the soil-to-fiber strain transfer efficiency for large deformation monitoring of ground collapse.

Three-dimensional distributed acoustic sensing at the Sanford Underground Research Facility

Distributed acoustic sensing (DAS) is a valuable tool for monitoring seismic signals as it provides high spatial and temporal resolution strain sensing along the length of a fiber-optic cable. DAS records the seismic wavefields essentially synchronously at each sensing location (i.e., sensing channel with gauge lengths) because the interrogator senses the distributed strain at the speed of light in the fiber. Unlike traditional seismic sensors, DAS has an intrinsic directional sensitivity to the axial strain change along the fiber, leading to difficulties when using standard seismic analysis and interpretations that rely on 3D particle velocity sensing. In addition, cable deployments on the surface can be dominated by high-amplitude wind or urban noise, impeding the detection of low-amplitude distant seismic sources. Here we investigate the capabilities of a unique 3D array with spiral-like portions in the Sanford Underground Research Facility (SURF), the former Homestake Mine, between 1250 m (4100 ft) and 1488 m (4850 ft) in depth for detecting local, regional, and teleseismic sources of ground vibrations. Our pilot array finds that DAS records high frequency (above 5 Hz) vibration sources well, such as mine activities and local and regional blasting events. Furthermore, our deployment method (fiber resting on the surface with rocks placed every meter or so) may contribute to low-frequency noise that contaminates the interpretation of teleseismic waves, particularly lower frequency S-wave arrivals. Nevertheless, this 3D DAS array provides significant data for future analysis as well as the basis for improving and expanding the array in SURF.

Long-term monitoring and analysis of Brood X cicada activity by distributed fiber optic sensing technology.

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.

Inversion method for soil moisture content based on a distributed fiber optic acoustic sensing system.

The traditional measurement method can't achieve real-time monitoring of soil moisture content (SMC) within a two-dimensional area. To solve the above problems, we propose a rapid SMC monitoring method for two-dimensional area based on distributed acoustic sensing (DAS). DAS demodulates the backward Rayleigh scattering signal containing seismic wave sound velocity information from the active seismic source. The folding ruler approximation is employed to calculate the sound velocity of the soil, which is then inverted to determine the soil moisture content. The experiment measured the soil within a two-dimensional area formed by the seismic source and the acoustic sensing optical cable. The sensing optical cable and the active seismic source are organized into a two-dimensional area and the measurement range is 3 × 10 m with 33 points. The SMC ranges from 15% to 40%. The experiment shows that the absolute error between the measured values obtained by DAS and the water cut meter is 7%. This experiment verifies the feasibility of using the Rayleigh scattering properties to invert SMC and provides a new method for real-time monitoring of SMC in a large area.

Analisis Pengaruh Kedisiplinan Kerja, Keselamatan dan Kesehatan Kerja (K3), Serta Lingkungan Kerja Terhadap Kinerja Karyawan PT. BBIC BERCA CABLES di Kabupaten Tangerang

PT. BIIC Berca Cables is a company that produces electrical cables and fiber optic cables. Supervising employee discipline, safety & health and the work environment is a way to maintain or improve employee performance. In the preliminary survey conducted, it showed that employee performance was considered to have not met the company's expectations, where many failures were still found during the Optic Cable Quality Test process. The aim of this research is to partially analyze (1) the influence of work discipline variables, (2) occupational safety and health (OSH), and (3) the work environment on employee performance and simultaneously analyze the influence of work discipline, occupational safety and occupational health (OSH) as well as the work environment on employee performance. The research design is associative quantitative, which is a depiction of the relationship between one variable and another. Researchers distributed questionnaires to employees as a method of data collection techniques. The analysis technique used is Correlation Test, Multiple Linear Regression Analysis. In the classical assumption test there is a normality test, multicollinearity test and heteroscedasticity test. From the research results it can be concluded that partially the work discipline variable has a significant positive effect on employee performance, the occupational safety and health (OSH) variable has a significant positive effect, and the work environment variable has a significant positive effect. Simultaneously, work discipline variables, occupational safety and health (K3) variables, and work environment variables have a positive and significant effect on the performance of PT employees. BIIC Berca Cables in Tangerang Regency.
 Keywords : Discipline, Safety, Health, Environment, Employee Performance

Experiences with distributed acoustic sensing using both straight and helically wound fibers in surface-deployed cables — A case history in Groningen, The Netherlands

Distributed acoustic sensing has been limited in its use for surface-seismic reflection measurements due to the fiber’s decreased broadside sensitivity when the fiber is deployed horizontally. Deploying the fiber in a helically wound fashion has the promise of being more sensitive to broadside waves (e.g., P-wave reflections) and less sensitive to surface waves than a straight fiber (SF). We examine such claims and compare the responses of SFs and helically wound fibers (HWFs) with different wrapping angles, using standard and engineered fibers. These fibers have been buried in a 2 m deep trench in a farmland in the province of Groningen in The Netherlands, where we performed an active-source survey. We observe in our field data that using HWF has a destructive effect on the surface-wave amplitudes. Our data confirms the effect of the wrapping angle on the polarity of the surface-wave arrival and the dampening effect of the helical winding, behaving in quite a predictable fashion. Apart from the effect of the wrapping angle, the different design choices, e.g., cable filling and material type, do not show a significant effect on the amplitude of the signals. As for P-wave reflections, we observe that engineered SF and HWF provide reflection images comparable with those obtained from simultaneously deployed geophones at the surface despite the SF’s decreased broadside sensitivity. A polarity reversal and an amplitude difference between the SF and HWFs are observed. Finally, we demonstrate that the combined use of SF and HWF proved to be useful because SF showed better sensitivity in the shallower part and HWF in the deeper part.

Super-long-range distributed vibration sensor based on the polarimetric forward-transmission of light.

Undersea earthquake-triggered giant tsunamis pose significant threats to coastal areas, spanning thousands of kilometers and affecting populations, ecosystems, and infrastructure. To mitigate their impact, monitoring seismic activity in underwater environments is crucial. In this study, we propose a new, to the best of our knowledge, approach for monitoring vibrations in submarine optical cables. By detecting vibration-induced polarization rotation, our dual-wavelength fiber-optic sensing system enables precise measurement of acoustic/vibration amplitude, frequency, and position. As a proof of concept, a double-ended forward-transmission distributed fiber-optic vibration sensor was demonstrated with a single vibration source with a sensitivity of 3.4 mrad/µε at 100 Hz (20 m fiber on PZT), limit of detection of 1.7 pε/Hz1/2 at 100 Hz, sensing range of 121.5 km without an optical amplifier, spatial resolution of 5 m, and position error as small as 34 m. The vibration frequency range tested is from 0.01 to 100 Hz. The sensing system has several advantages, including elegant setup, noise mitigation, and super-long sensing distance.

Optimization of the Monitoring of Coal Spontaneous Combustion Degree Using a Distributed Fiber Optic Temperature Measurement System: Field Application and Evaluation

Coal spontaneous combustion (CSC) in gob not only leads to wasted resources and casualties, but also produces a lot of waste gas that pollutes the underground environment. Mastering the degree of CSC helps ensure that timely and effective control measures are taken. The real-time and accurate monitoring of temperature, as the primary indicator of the extent of CSC, is difficult due to the harsh and hidden environment of gob, resulting in a reduced ability to anticipate and prevent CSC. In this work, a complete distributed optical fiber temperature sensing system (DTSS) set with strong anti-damage ability was developed. The optical cable is protected by internal parallel steel cables and external protective pipes, which greatly improve the system’s reliability and integrity when used in gob. During its application in the Wangyun Coal Mine, an abnormal temperature rise in gob was discovered in time, and the effect of inhibitor spraying was monitored and evaluated. The degree of CSC in the gob was accurately identified, which shows that the work of coal mining can be targeted. This work is expected to improve early warning capability to prevent the risk of CSC in gob, and has promising applications.

Multiplexed fiber-optic photoacoustic sensors for simultaneous detection of multi-point gases

A multiplexing scheme of fiber-optic photoacoustic (PA) gas sensors is demonstrated for simultaneous detection of multi-point gases. By sharing the PA demodulation device, the average cost of single point measurement can be significantly reduced. The passive fiber-optic PA gas sensing probe is integrated by a PA tube and a Fabry-Perot (F-P) interferometric (FPI) cantilever. The laser excited the PA signals is simultaneously incident into two sensing probes. The superimposed F-P interference spectrum containing multi-point gas concentration information is received by a high-speed spectrometer. For synchronous measurement of multi-point gases, a white-light interferometry (WLI) based frequency division multiplexing (FDM) spectral demodulation method is exploited. A multi-point acetylene gas remote monitoring system is established by two PA gas sensing probes with 3 km fiber cable. The experimental results show that the sensing probes have achieved the detection limit of sub-ppm. The crosstalk between the two sensors is characterized by the gas concentrations at the two points, indicating a crosstalk of about − 35 dB. This multiplexing scheme of fiber-optic PA sensing probes has the merits of remote monitoring, low crosstalk, high sensitivity, intrinsic safety and low cost. It can be applied for coal spontaneous combustion monitoring, dissolved gas analysis and gas micro-leakage monitoring.

High-Performance Computational Method for an Extended Three-Coupled Korteweg–de Vries System

This paper calculates numerical solutions of an extended three-coupled Korteweg–de Vries system by the q-homotopy analysis transformation method (q-HATM), which is a hybrid of the Laplace transform and the q-homotopy analysis method. Multiple investigations inspecting planetary oceans, optical cables, and cosmic plasma have employed the KdV model, significantly contributing to its development. The uniqueness, convergence, and maximum absolute truncation error of this algorithm are demonstrated. A numerical simulation has been performed to validate the accuracy and validity of the proposed approach. With high accuracy and few algorithmic processes, this algorithm supplies a series solution in the form of a recursive relation.

Intelligent Network Maintenance Modeling for Fixed Broadband Networks in Sustainable Smart Homes

Due to the emergence of sustainable smart homes, each smart device requires more bandwidth putting pressure on the existing home networks. A very good solution to ensure high-bandwidth home networks is the Fiber-to-the-Home (FTTH) technology. FTTH delivers high-speed Internet from a central point directly to the home through fiber optic cables. This fixed broadband network can transmit information at virtually unlimited speed and capacity enabling homes to be smarter. Hence, a well-monitored and well-maintained FTTH broadband network is necessary to obtain a high level of service availability and sustainability in smart homes. This study aims to develop a predictive model that will proactively monitor and maintain FTTH networks through the use of sophisticated modeling techniques such as machine learning (ML). The predictive model targets to classify the proposed technician resolution based on the historical FTTH field dataset. The results show that the K-Nearest Neighbors (KNN)-based model obtained the highest accuracy of 89% followed by the Feed-Forward Artificial Neural Network (FF-ANN)-based model with 86%. In addition, the identified anomalies from the dataset affecting service degradation and performance include FTTH access issues, ONU issues, and faults in customer premises equipment.

High resolution seafloor thermometry for internal wave and upwelling monitoring using Distributed Acoustic Sensing

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.

Observations of Ocean Surface Wave Attenuation in Sea Ice Using Seafloor Cables

AbstractThe attenuation of ocean surface waves during seasonal ice cover is an important control on the evolution of Arctic coastlines. The spatial and temporal variations in this process have been challenging to resolve with conventional sampling using sparse arrays of moorings or buoys. We demonstrate a novel method for persistent observation of wave‐ice interactions using distributed acoustic sensing (DAS) along existing seafloor fiber optic telecommunications cables. DAS measurements span a 36‐km cross‐shore cable on the Beaufort Shelf from Oliktok Point, Alaska. DAS optical sensing of fiber strain‐rate provides a proxy for seafloor pressure, which we calibrate with wave buoy measurements during the ice‐free season (August 2022). We apply this calibration during the ice formation season (November 2021) to obtain unprecedented resolution of variable wave attenuation rates in new, partial ice cover. The location and strength of wave attenuation serve as proxies for ice coverage and thickness, especially during rapidly evolving events.

Conscripting communalism: surveillance and resistance in contemporary Mauritius

AbstractIn this article I explore changing state–citizen relationships in Mauritius. To do so, I outline and provide analysis of the system through which this Indian Ocean island has historically managed its diversity – a process that I call conscripting communalism. Conscripting communalism was formulated at independence in a context of behavioural predictions for the future that the internet era has challenged in powerful ways. To illustrate my argument, I explore three specific moments when ethnic and religious discourses were surpassed by collective concern within a rapidly authoritarianizing state: first, the sinking of the Wakashio oil tanker off the coast of Mauritius in 2020, which resulted in national solidarity towards the environment rather than communal violence; second, proposed legislation put forward by the Mauritian Information and Communication Technology Authority (ICTA) in 2021, which attempted to enable state surveillance of social media and which was soundly resisted by both domestic and external parties. And finally, I explore 2022 accusations that the Mauritian government authorized the installation of digital interception technology by representatives of the Indian state on one of the country’s fibre optic cables. The article argues that Mauritius represents an important site of analysis of the tensions between competing global visions of human rights, political autonomy, surveillance, solidarity and expectations for the future and the role of the internet in shaping these competing visions. I explore how new technologies have become the tools of both repression and resistance. The implications ripple far beyond the island.

Deep clustering analysis for data exploration and anomaly detection in distributed acoustic sensing (DAS) systems

Distributed acoustic systems (DAS) offer a unique opportunity to sense seismic and acoustic waves at high sampling rates and spatial resolutions using fiber optic cables. The prevalence of fiber optic cables crossing seabeds around the world make them particularly attractive sensors of opportunity for acoustical and geophysical applications. However, the high spatial and temporal resolutions of these systems pose significant challenges to efficient data processing and analysis. To overcome this, we propose a two-step exploratory analysis procedure in which the dimensionality of the data is first reduced into a latent space containing its salient information, and then perform clustering analysis of the data in the latent space. Spectrograms of detected events are encoded into the latent space using a convolutional autoencoder, and clustering is performed using Gaussian mixture model clustering. We demonstrate our technique on experimental data collected from a DAS array deployed at a geothermal energy research site. With this technique, we show a data-driven approach to exploratory data analysis, enabling identification of dominant types of detections in the data and identification and removal of anomalous detections due to instrument noise.

Performance of distributed acoustic sensing relative to co-located hydrophone measurements

Distributed acoustic sensing (DAS) is a technology that transforms telecommunication fiber optic cables into dense sensor arrays by continuously transmitting pulses of light down the cable and measuring backscattering from natural inhomogeneities within the fiber cable. The technology can densely sample the acoustic field over long ranges (up to 100 km), providing a means for large scale passive acoustic monitoring. The DAS Calibration Experiment 2022 (DASCAL22) provides 9 days of co-located hydrophone and DAS data in Puget Sound, WA. The DAS data were recorded with a 2kHz sampling rate over ∼3.5 km of cable in a channel reaching close to 100 m depth and with DAS channels spaced 6.38 m. A combination of an active source broadcast from 1, 5, and 10 m depths, and passive signals (primarily boat noise) are used to investigate the capabilities of DAS to sense a range of frequencies and the impacts of the environment on those capabilities.

Innovations in Micropile Testing Using Distributed Optical Fibre Sensors

Micropiles are primarily used in situations where traditional foundation methods, such as large-diameter bored piles or driven piles, are not feasible due to various constraints, including limited access, low headroom, or the need to work in environmentally sensitive areas. They are often employed in urban areas with restricted space or for underpinning existing structures. Two case studies of instrumented micropiles are presented in this paper, with the aim to showcase innovations in pile testing using Distributed Optical Fibre Sensing (DOFS). In the first project, micropiles were installed as part of an underpinning work where several existing piles were removed to allow safe passage of Tunnel Boring Machine (TBM) underneath the building. An experiment pile was instrumented with conventional and DOFS sensors to measure pile responses due to tunnelling in proximity. In the second project, the micropile was tested to determine its load carrying capacity for buildings constructed in hilly area. In both cases, API pipes were applied and socketed into bedrocks. Optical cables were attached on four sides of the steel pipes and subsequently grouted. During the load tests, DOFS data were able to display precisely the shaft distribution of micropiles when subjected to vertical loads as well as bending behaviour due to the close proximity tunnelling. Interpretations of distributed strain profiles from DOFS have contributed to a better understanding of API-reinforced micropile performance under complex geological and loading conditions.

Assessment of long-range distributed acoustic sensing (DAS) capabilities in controlled environments

Distributed Acoustic Sensing (DAS) is an emerging technology enabling the recording of disturbances along fiber-optic (FO) cables with a wide range of applications, such as monitoring marine fauna, anthropogenic activities, and ocean climate. Despite the extensive research on DAS technology, its long-range capabilities have not been structurally studied yet. We present results of a sequence of purposefully designed experiments of DAS capabilities in (1) a laboratory, (2) a pool, and (3) a marine facility. To simulate long cables, we use combinations of FO coils 10–200 km in length. In the laboratory, realistic strain signals are simulated by an FO stretcher. In the pool, realistic acoustic signals are transmitted by an underwater speaker. At the marine facility, a combination of playback and real sound sources is used. Simultaneously deployed hydrophones allow DAS calibration and performance assessment. In this series of experiments, we measure internal noise, compare different DAS equipment, and successively optimize acquisition parameters for each interrogator performing at different, long sensing ranges in increasingly realistic environments. We show that long-range capabilities are strongly dependent on DAS settings (optical power, pulse repetition frequency, gauge length, pulse width) and vary between different interrogators.

Digital Silk Road; Is it an Anti-Globalization Backlash? Is it Chinese-Style Globalization?

Digital activities of the Belt and Road initiative called the "digital Silk Road" in the post-COVID-19 outbreak era and initially introduced in 2015 as the "information Silk Road," have come under fire. Finding out whether China's technical improvement, which has become evident in many areas thanks to the Digital Belt and Road initiative project, is a backlash against globalization or a new wave of it done in a Chinese form is the main challenge of this study. Data centers—the backbone of the Belt and Road Initiative—undersea fiber optic cables, 5-G cellular data networks, and Turkish investments in these sectors have all been essential in this regard. This method explores China's technological development from the four modernization periods to the present through a chronological descriptive description. This study should be viewed as significantly contributing to the literature because it provides a system-level examination of the digital Belt and Road endeavor.

On the potential of using Distributed Acoustic Sensing (DAS) to build teleseism based ocean-tomography network

The sound from marine teleseisms rank among some of the loudest in Earth’s Oceans, typically radiated into the ocean near the epicenter and propagating across the entire ocean basin. Acoustic sensing on ocean observatories provide a critical path to better understand origins of these low-frequency sound waves known as T-phases, and structure of the ocean over the megameter propagation through the ocean. Of the emerging technologies implemented on these observatories, distributed acoustic sensing (DAS) has the potential to revolutionize marine seismoacoustics. DAS can be implemented on unused oceanic fibers on the continental slopes surrounding an ocean basin could readily enable a teleseism based ocean-tomography network with surprisingly little new infrastructure. In November 2021, a DAS system installed on two runs of fiber optic cable that connect to an ocean observatory measuring offshore volcanic activity, detected a few examples of teleseismic T-phases. Combined with other hydroacoustic ocean observatories in the Pacific Ocean, the T-phase origins are localized to bathymetric features over 100 km from the epicenter, an important consideration when utilizing these T-phases as sources of opportunity to study the ocean.