Machine-learning-based hybrid random-fuzzy uncertainty quantification for EMC and SI assessment

Modeling the effects of uncertainty is of crucial importance in the signal integrity and Electromagnetic Compatibility assessment of electronic products. In this article, a novel machine-learning-based approach for uncertainty quantification problems involving both random and epistemic variables is presented. The proposed methodology leverages evidence theory to represent probabilistic and epistemic uncertainties in a common framework. Then, Bayesian optimization is used to efficiently propagate this hybrid uncertainty on the performance of the system under study. Two suitable application examples validate the accuracy and efficiency of the proposed method

Long-term effects of thermal variation on the performance of Balanced Twisted Pair Cabling

Remote powering over the Ethernet (including PoE, PoE+ and PoE++) is currently trending as a cost-effective option to power networked devices using balanced twisted pair cabling. As technology advances and Ethernet penetration grows, more devices are deployed, thereby increasing the cabling density to support these devices. Power delivery through Ethernet cables has numerous benefits, including cost and space saving. However, concurrent high-power transmission and installation conditions could induce local heating, and thus, thermal variation may occur in the cable bundles, and these can be exacerbated by the installation conditions, and sometimes by extreme weather conditions. Over a long time, all these could modify the cable properties, thus affecting the performance of the cabling system and thereby impacting the Ethernet signal integrity. Although Joule heating of the cable bundle is primarily assumed to be concomitants of current transmission through the cable, several fundamental questions around these processes are not yet fully answered. They include: Do cable heating and thermal variations influence the designed transmission parameters of the cable? If yes, how can the cause(s) and effects be accurately measured and reliably validated? In answering some of these questions, a series of experiments were developed and adopted to (1) assess cable bundle heating (2) assess the performance of Balanced Twisted Pair cables subject to repeated thermal variation, both within the specified operating range and beyond to account for the situations where high temperature and localised heating might stress the cables beyond the designed or expected levels (3) assess the performance of Ethernet cable dielectrics to understand some of the root causes of Ethernet cable performance degradation. The outcome of the research showed that high power (100 watts) deployment over bundled and insulated unshielded Ethernet cables triggered an extremely high-temperature increase (~ 1400C) that resulted in mechanical failure of the cables’ dielectrics and a short circuit between the copper conductors of the cables. Larger cable conductor size, screening of the twisted pair along with Fluoropolymers as the conductor insulation helped the shielded cables not to reach a point of failure when tested in the insulated environments and at high power levels even though there was a temperature rise on the cables. Moreover, repeated resistive and non- resistive heating have adverse effects on the electrical properties and transmission parameters of Balanced Twisted Pair cables, most notably in the first few cycles. The impact was more pronounced during the cooling phase than the heating phase. Also, the thermal impact was more accentuated in insulated operating condition than in ventilated operating condition. The electrical length of the cable measured by the tester decreased by 0.7 m 5 due to the effect of repeated non-resistive heating in an insulated environment and at a high temperature of ~1200C but decreased by 0.4 m with ~700C in a similar insulated environment. Phase drifts in Balanced Twisted Pair cables were observed to be dependent on the combined effects of mechanical dimension, dielectric constant and frequency. Thermal variation caused a phase change in the Return Loss (RL) signal from 630 to 900, from 900 to 1350 and from 1350 to 3150 respectively. The RL performance of Category 6 U/UTP CoMmunications Plenum rated (CMP) cable failed at 200C and recovered at 230C initially, but after the electrical length of the cable had decreased, subsequent failure and recovery temperatures accelerated towards higher temperature (400C). Similarly, the transition temperatures of the bandwidth of the cavity loaded with the Fluorinated Ethylene Propylene (FEP) from the Category 6 U/UTP CMP cable accelerated during the prolonged thermal cycling. The maximum reduction in the RL value of Category 6A F/UTP cable due to the 40 thermal cycles conducted was observed to be 5 % per degree, whereas the maximum Insertion Loss (IL) increase was 5.8 % per degree. Moreover, for the 24 thermal cycles conducted on Category 6 U/UTP CMP cable, an increase in IL of ~8.3 % per degree was observed while RL decreased by ~6.8 % per degree. Using the Features Selective Validation technique, the comparison between the baseline performance and long-term performance of Category 6A F/UTP permanent link (PL) showed a fair agreement, which implies degradation in the performance of the cable. Furthermore, results showed that impedance varied significantly along the length of the cable due to localised heating of the cable. The impedance along the unheated sides of the cable reverted at every 2 (0.4 m) and 4 (0.2 m) but the impedance profile of the heated middle portion of the cable varied significantly. The results of the Scanning Electron Microscope revealed the deformation in the conductor insulation of a twisted pair sample. Furthermore, the adhesion of the twisted pair conductor insulation to its copper conductor was also observed to be affected near the end of the twisted pair sample. Connector impedance mismatch was observed to be severe on the split pair pins (pair 3,6) than other pairs in the cable. The connector impedance mismatch also dominated the Near End Crosstalk (NEXT) loss at frequencies around 35 MHz. The repeated heating of the cable to a higher temperature of 1200C caused the loss of the PL at room temperature and a DC contact resistance issue which of course resulted in poor intra-pair resistance unbalance between the split pair. The Transverse Conversion Loss (TCL) and Equal Level Transverse Conversion Transfer Loss (ELTCTL) of Category 6 U/UTP CMP PL revealed some imbalances in the structure of the twisted pairs. Also, the equivalent differential mode noise voltages for the TCL values of the cable revealed a voltage spike following the decrease in the electrical length of the cable. More also, Crosstalk performance between the longest and shortest pair in the Category 6A 6 F/UTP cable was also observed to be better due to the heating of the cable in comparison to the crosstalk loss measured due to the cooling of the cable. Crosstalk performance of the portion insulated cables was initially worse during the first few heating and cooling cycles but improved afterwards. In addition, crosstalk, which was not initially present at the reference plane of the permanent link, was observed to increase rapidly from the point where the electrical length decreased. The increase in temperature to ~650C caused an accentuated frequency shift in the resonance of the FEP, which is the probable cause of the immediate performance degradation of the Category 6 U/UTP CMP cable. The dielectric constant of the extracted FEP rod sample from Category 6 U/UTP CMP cable increased as a consequence of prolonged thermal cycling, particularly during the cooling phase, which also suggests the root cause of the poor RL performance observed during the cooling phase. The increased loss tangent of the FEP during thermal cycling also indicates that IL performance degradation of the Ethernet cables will increase during the heating and cooling process in Ethernet cables. Also, on a long-term, IL performance will drift due to thermal cycling. Furthermore, various signal phase transitions were recorded during the heating and cooling of the cable and its dielectric due to the different behaviour of the molecular transitions. As a result, an echo of RL was measured during the transition between the intermittent and prolonged thermal cycling of the cable, of which can be correlated to the spurious resonance, observed in the resonance of the FEP sample during the transition period. Thus, it could be inferred that immediate and longterm effects of thermal variation influence the designed electrical properties and transmission parameters of Balanced Twisted Pair cables. Also, an immediate and long-term effect of thermal variation on the conductor insulation of the cable has a direct effect on the performance of Balanced Twisted Pair Cables

Coaxial Cable Sensors Based on Fabry-Perot Interferometers and Their Applications in Distributed Sensing

Aging civic infrastructures in the world has put tremendous pressure in their maintenances because potential failure of the large size civil structures will be catastrophic. Structure health monitoring (SHM) has been proven effective to prevent these failures, and distributed sensing technologies are preferred in SHM as they are effective to provide comprehensive evaluation of the structures. Fiber optic sensors are well developed in the past two decades for distributed sensing, but the lack of robustness and the limited deformability of silica make them not suitable for heavy duty and large deformation applications, which is very common in SHM. To address the above limitation of optical fiber sensors, we change the sensing platform from optical fibers to coaxial cable. Inspired by optical FPI, we created two reflectors on a coaxial cable to form a coaxial cable Fabry-Perot interferometer (CCFPI). The reflectors are commonly made by drilling half way holes or crimp on the cable, which introduce impedance discontinuity and hence partial reflection of EM wave in the cable. The two reflectors can produce interference patterns with multiple resonant frequencies which can be tracked to indicate changes in physical parameters such as temperature and strain. To realize distributed sensing, multiple reflectors are implemented along a coaxial cable, where every two consecutive reflectors will form a low finesse CCFPI. A specific signal process technique is used to reconstruct each individual CCFPI interferogram from the complex frequency domain signal. As examples of the distributed sensing capability of the coaxial cable platform, distributed torsion sensing and 3D beam shape estimation system are demonstrated in this thesis. By modifying the cable material and structure, we can achieve other special function for CC-FPI sensors. By fabricating the cable with ceramics as dielectric material and implanting built in reflectors, a high temperature CC-FPI sensor is developed and tested. Another example is a magnetic field sensor made by filling a cavity in a semi-rigid cable with ferrofluid. When external magnetic field change, the property of the ferrofluid will also change, resulting in spectrum shift of the FPI. The coaxial cable FPI sensors have many potentials to measure different physical parameters in distributed sensing form, which makes it a very good sensing platform for long distance and distributed sensing in harsh environment and heavy duty applications

Novel Specialty Optical Fibers and Applications

Novel Specialty Optical Fibers and Applications focuses on the latest developments in specialty fiber technology and its applications. The aim of this reprint is to provide an overview of specialty optical fibers in terms of their technological developments and applications. Contributions include:1. Specialty fibers composed of special materials for new functionalities and applications in new spectral windows.2. Hollow-core fiber-based applications.3. Functionalized fibers.4. Structurally engineered fibers.5. Specialty fibers for distributed fiber sensors.6. Specialty fibers for communications

Birefringent and diffractive devices for implementing multi-Gbit/s transmission systems using visible WDM over SI-POF technology

Mención Internacional en el título de doctorNew optical devices are indispensable for the development of the future SI−POF high speed short−range communication networks and as well as in many sensors applications based on SI−POFs. These devices are not well established to date due to the physical and multimodal characteristics of the SI−POF technology as well as the characteristics of the SI−POF visible WDM systems. Therefore, the main objective that has been established for this research work is to develop new optical components based primarily on liquid crystals and diffractive elements for applications in advanced optical communication systems with plastic optical fibers, ensuring an optimized power consumption to reduce the carbon footprint of ICTs.Se necesitan nuevos dispositivos ópticos en el rango visible para el desarrollo de las futuras redes de comunicación de alta velocidad y corto alcance basadas en SI−POF. Estos dispositivos también son de gran utilidad en muchas aplicaciones de sensores basados en POF. Los diseños de estos dispositivos no están bien establecidos hasta la fecha debido a las características físicas y multimodales de la tecnología SI−POF, así como las características de los sistemas WDM en el visible. Por lo tanto, el principal objetivo que se ha establecido para este trabajo de investigación es el desarrollo de nuevos dispositivos ópticos basados principalmente en cristales líquidos y elementos de difracción para aplicaciones en sistemas avanzados de comunicaciones ópticas con fibras ópticas de plástico de salto de índice, lo que garantiza un consumo de energía optimizado para reducir la huella de carbono en esta tecnología en el sector TIC.Programa en Ingeniería Eléctrica, Electrónica y AutomáticaPresidente: Rajeev J. Ram.- Vocal: Bruno Fracasso.- Secretario: Javier Mateo Gascó

Flexible Polymer Waveguides for High-Speed Short-Reach Links

This dissertation presents a detailed study of flexible polymer waveguides for used in short-reach communication links. Flexible polymer waveguides enable a wider range of applications as compared to the rigid polymer waveguides, especially for the rack-to-rack links and data bus systems in autonomous car and avionic industry. However, their optical performance including bending and twisting loss, crosstalk, bandwidth and mode coupling behaviour hasn’t been studied in detail when the flexure is applied to the waveguide. This research quantifies those performances when flexible polymer waveguides are being flexed and provides a useful guideline when designing those flexible polymer links in the real world. In addition, some suggestions have been discussed, which can be used to improve waveguide loss performance. A lot simulation work has been done to support the observations from the experimental results. The flexible polymer waveguides are proven to be robust and have low propagation loss (0.03 dB/cm) and high temperature resistance (up to 350 °C). They can be bent down to 2 mm without cracks and the resultant excess bending loss can be less than 2 dB. The excess twisting loss is also shown to be very low, around 0.02 dB for 4 × 360° full twisting turns as long as lateral tension is carefully reduced. The crosstalk results reveal their values are < -25 dB under any launch conditions when waveguides are flexed. The dynamic behaviour study shows that flexible polymer waveguides are robust and can work dynamically for a long-time horizon. In addition, a new design of flexible polymer waveguides has been proposed which can reduce the excess bending loss to around 0.5 dB at 2 mm bending, which is a big improvement. As for the mode coupling behaviour, both simulation and experimental works have been done to investigate how optical modes will evolve due to the small bends, micro bends and rough sidewalls. A better understanding of propagation mechanism inside waveguide is given and discussed. Then, the ultra-short laser pulse measurements are carried out to get the bandwidth length products (BLP) of the waveguides under flexure. The results indicate polymer waveguide can support over 100 GHz×m BLP and small bends have the ability of improving bandwidth performance further. At last, a 40 Gbps transmission over 1-m spiral flexible polymer waveguides under different bending radius has successfully been demonstrated

Investigating Human Achilles Tendon Biomechanics Using Novel Ultrasound Imaging approaches

Achilles tendinopathy is the most common lower limb tendinopathy, with increasing yearly prevalence. Nonetheless, there remains poor understanding of disease aetiology, and challenges associated with contextualising diagnosis to inform treatment. Imaging highlights that structural changes do not correlate with functional changes. The aim of this thesis is to establish an ultrasound-based imaging method to detect the slip planes, and subsequently to quantify local strain distribution in human free Achilles tendon. A systematic review was conducted to determine state-of-the-art in detecting non uniformity in tendon deformation during functional use and synthesise current best understanding of how non-uniformity varies between individuals, with injury and with ageing. Outcomes identified that no previous studies have looked at slip-planes in tendon, to define sub-tendon boundaries and explore independent loading of each head of triceps surae muscles and resulting tendon deformation behaviour. The thesis subsequently focused on developed a method to address this gap, adapting and optimising an automated algorithm known as slip-elastography (previously developed to investigate slippery boundary of cancerous tissue) to detect and quantifying non-uniform tendon strains and identify slip boundaries. Ultrasound radiofrequency data of the AT was collected while participants performed movement tasks and analysed retrospectively along with electromyography and torque data. Data demonstrated that the deep layer of the AT displaced further than the superficial layer during movement. However, knee position was shown not to influence tendon displacement profile during EL and CL. The technique provided data on lateral shear strains throughout the tendon, as a route to detecting intra-tendon slip-planes. Tendon shear strain was highest during EL, with shear strain significantly dependent on loading type only, with no effect of knee ankle or muscle activity during EL, CL or MVIC. Data indicates that the extent of non-uniformity could be controlled with different exercises, offering a possible future route towards optimising treatment. However, these are not yet detected robustly enough for clinical applicability, challenged by limited resolution and the 3D nature of movements in the AT. Future work needs to improved resolution with higher frequency data acquisition to address these limitations and develop rehabilitation mechanism and injury prediction tools

Contribution to the study of the vulnerability of critical systems to Intentional Electromagnetic Interference (IEMI)

The progress of high power electromagnetic (HPEM) sources during the late 1990s raised the concern in the electromagnetic compatibility (EMC) community that they could be deployed for criminal purposes to interfere with the operation of modern electronic systems. It is well established that sufficiently intense electromagnetic fields can cause upset or damage in electronic systems and therefore, can affect almost every critical infrastructure (CI) that is based on information and communication technologies (ICT). This field of study was initially known as electromagnetic terrorism, but was changed to the more encompassing term of intentional electromagnetic interference (IEMI). This thesis is a contribution to the assessment techniques of the vulnerability of CIs against IEMI. In order to quantify their impact, the electromagnetic environment created by IEMI sources needs to be characterized, the susceptible components and subsystems of the CIs should be identified, and the expected disturbances have to be evaluated. We present a qualitative methodology to carry out the so-called IEMI audit of a facility. Given the complexity of the problem, it was decided that the vulnerability of an infrastructure should be evaluated in a qualitative manner by regarding the consequences of interrupting the normal provision of a service, the probability of occurrence of an IEMI attack, and the preparedness of the infrastructure to withstand an attack. An updated survey and classification of potential IEMI sources that were collected from a large number of scientific publications is presented. The sources have been classified according to their electromagnetic environment, their transportability, technological development, and cost level. The expected disturbances due to a high frequency illumination of representative cabling systems inside an office were studied through measurements performed using a plastic raceway containing several types of cables found in commercial buildings. The tests revealed that at low and intermediate frequencies, low voltage power cables are more susceptible compared to telephone or network cables. At high frequencies, the coupling is dominated by connector apertures and discontinuities and load unbalance. The applicability of the TL theory in evaluating differential mode signals in two-wire lines floating above a ground plane was studied through comparisons with full-wave simulations. The results showed that the validity of the TL theory is conditioned upon an electrically short distance between the differential wires, regardless of the distances above the ground plane. TL theory is also used to assess the effect of conductive and dielectric losses in the dispersion of injected IEMI signals along power and communication cables as a function of the propagation length. A TL model of the low voltage power cabling of the plastic raceway was developed and in order to validate the models, the numerical results were compared against measurements obtained using frequency and time domain techniques. General considerations and guidelines for the application of the TL theory for evaluating the overall transfer impedance of complex cable assemblies are given. The obtained simulation results were found to be in good agreement with the experimental data up to frequencies of about 500 MHz. Finally, an improved model for estimating the transfer impedance of a two-layer braided shield is also proposed and validated using experimental data