An optical fibre dynamic instrumented palpation sensor for the characterisation of biological tissue

AbstractThe diagnosis of prostate cancer using invasive techniques (such as biopsy and blood tests for prostate-specific antigen) and non-invasive techniques (such as digital rectal examination and trans-rectal ultrasonography) may be enhanced by using an additional dynamic instrumented palpation approach to prostate tissue classification. A dynamically actuated membrane sensor/actuator has been developed that incorporates an optical fibre Fabry–Pérot interferometer to record the displacement of the membrane when it is pressed on to different tissue samples. The membrane sensor was tested on a silicon elastomer prostate model with enlarged and stiffer material on one side to simulate early stage prostate cancer. The interferometer measurement was found to have high dynamic range and accuracy, with a minimum displacement resolution of ±0.4μm over a 721μm measurement range. The dynamic response of the membrane sensor when applied to different tissue types changed depending on the stiffness of the tissue being measured. This demonstrates the feasibility of an optically tracked dynamic palpation technique for classifying tissue type based on the dynamic response of the sensor/actuator

Soliton microcomb based spectral domain optical coherence tomography

Spectral domain optical coherence tomography (SD-OCT) is a widely used and minimally invaive technique for bio-medical imaging [1]. SD-OCT typically relies on the use of superluminescent diodes (SLD), which provide a low-noise and broadband optical spectrum. Recent advances in photonic chipscale frequency combs [2, 3] based on soliton formation in photonic integrated microresonators provide an chipscale alternative illumination scheme for SD-OCT. Yet to date, the use of such soliton microcombs in OCT has not yet been analyzed. Here we explore the use of soliton microcombs in spectral domain OCT and show that, by using photonic chipscale Si3N4 resonators in conjunction with 1300 nm pump lasers, spectral bandwidths exceeding those of commercial SLDs are possible. We demonstrate that the soliton states in microresonators exhibit a noise floor that is ca. 3 dB lower than for the SLD at identical power, but can exhibit significantly lower noise performance for powers at the milliWatt level. We perform SD-OCT imaging on an ex vivo fixed mouse brain tissue using the soliton microcomb, alongside an SLD for comparison, and demonstrate the principle viability of soliton based SD-OCT. Importantly, we demonstrate that classical amplitude noise of all soliton comb teeth are correlated, i.e. common mode, in contrast to SLD or incoherent microcomb states [4], which should, in theory, improve the image quality. Moreover, we demonstrate the potential for circular ranging, i.e. optical sub-sampling [5, 6], due to the high coherence and temporal periodicity of the soliton state. Taken together, our work indicates the promising properties of soliton microcombs for SD-OCT

Comparison of Small Baseline Interferometric SAR Processors for Estimating Ground Deformation

The small Baseline Synthetic Aperture Radar (SAR) Interferometry (SBI) technique has been widely and successfully applied in various ground deformation monitoring applications. Over the last decade, a variety of SBI algorithms have been developed based on the same fundamental concepts. Recently developed SBI toolboxes provide an open environment for researchers to apply different SBI methods for various purposes. However, there has been no thorough discussion that compares the particular characteristics of different SBI methods and their corresponding performance in ground deformation reconstruction. Thus, two SBI toolboxes that implement a total of four SBI algorithms were selected for comparison. This study discusses and summarizes the main differences, pros and cons of these four SBI implementations, which could help users to choose a suitable SBI method for their specific application. The study focuses on exploring the suitability of each SBI module under various data set conditions, including small/large number of interferograms, the presence or absence of larger time gaps, urban/vegetation ground coverage, and temporally regular/irregular ground displacement with multiple spatial scales. Within this paper we discuss the corresponding theoretical background of each SBI method. We present a performance analysis of these SBI modules based on two real data sets characterized by different environmental and surface deformation conditions. The study shows that all four SBI processors are capable of generating similar ground deformation results when the data set has sufficient temporal sampling and a stable ground backscatter mechanism like urban area. Strengths and limitations of different SBI processors were analyzed based on data set configuration and environmental conditions and are summarized in this paper to guide future users of SBI techniques

State-of-the-art in studies of glacial isostatic adjustment for the British Isles: a literature review

Understanding the effects of glacial isostatic adjustment (GIA) of the British Isles is essential for the assessment of past and future sea-level trends. GIA has been extensively examined in the literature, employing different research methods and observational data types. Geological evidence from palaeo-shorelines and undisturbed sedimentary deposits has been used to reconstruct long-term relative sea-level change since the Last Glacial Maximum. This information derived from sea-level index points has been employed to inform empirical isobase models of the uplift in Scotland using trend surface and Gaussian trend surface analysis, as well as to calibrate more theory-driven GIA models that rely on Earth mantle rheology and ice sheet history. Furthermore, current short-term rates of GIA-induced crustal motion during the past few decades have been measured using different geodetic techniques, mainly continuous GPS (CGPS) and absolute gravimetry (AG). AG-measurements are generally employed to increase the accuracy of the CGPS estimates. Synthetic aperture radar interferometry (InSAR) looks promising as a relatively new technique to measure crustal uplift in the northern parts of Great Britain, where the GIA-induced vertical land deformation has its highest rate. This literature review provides an in-depth comparison and discussion of the development of these different research approaches

Ground-based synthetic aperture radar (GBSAR) interferometry for deformation monitoring

Ph. D ThesisGround-based synthetic aperture radar (GBSAR), together with interferometry, represents a powerful tool for deformation monitoring. GBSAR has inherent flexibility, allowing data to be collected with adjustable temporal resolutions through either continuous or discontinuous mode. The goal of this research is to develop a framework to effectively utilise GBSAR for deformation monitoring in both modes, with the emphasis on accuracy, robustness, and real-time capability. To achieve this goal, advanced Interferometric SAR (InSAR) processing algorithms have been proposed to address existing issues in conventional interferometry for GBSAR deformation monitoring. The proposed interferometric algorithms include a new non-local method for the accurate estimation of coherence and interferometric phase, a new approach to selecting coherent pixels with the aim of maximising the density of selected pixels and optimizing the reliability of time series analysis, and a rigorous model for the correction of atmospheric and repositioning errors. On the basis of these algorithms, two complete interferometric processing chains have been developed: one for continuous and the other for discontinuous GBSAR deformation monitoring. The continuous chain is able to process infinite incoming images in real time and extract the evolution of surface movements through temporally coherent pixels. The discontinuous chain integrates additional automatic coregistration of images and correction of repositioning errors between different campaigns. Successful deformation monitoring applications have been completed, including three continuous (a dune, a bridge, and a coastal cliff) and one discontinuous (a hillside), which have demonstrated the feasibility and effectiveness of the presented algorithms and chains for high-accuracy GBSAR interferometric measurement. Significant deformation signals were detected from the three continuous applications and no deformation from the discontinuous. The achieved results are justified quantitatively via a defined precision indicator for the time series estimation and validated qualitatively via a priori knowledge of these observing sites.China Scholarship Council (CSC), Newcastle Universit

Microwave assisted reconstruction of optical interferograms for distributed fiber optics sensing & characterization of PCB dielectric properties using two striplines on the same board

A new concept, the microwave-assisted reconstruction of an optical interferogram for distributed sensing, was developed to resolve both the position and reflectivity of each sensor along an optical fiber. This approach involves sending a microwave-modulated optical signal through cascaded fiber optic interferometers. The optical spectrum of each sensor can be reconstructed by sweeping the optical wavelength and detecting the modulation signal. A series of cascaded fiber optic extrinsic Fabry-Perot interferometric sensors was used to prove the concept. The microwave-reconstructed interferogram matched well with those recorded individually from a traditional optical spectrometer. The application of distributed strain measurement was also investigated. The wavelength shift of the interferogram increases linearly as a function of the applied strain, and the increasing strain did not incur noticeable loss in the reflection spectra --Abstract, page iv Signal integrity (SI) and power integrity (PI) modelling and design require accurate knowledge of dielectric properties of printed circuit board (PCB) laminate dielectrics. Dielectric properties of a laminate dielectric can be obtained from a set of the measured S-parameters on a PCB stripline with a specially designed through-reflect-line (TRL) calibration pattern. In this work, it is proposed to extract dielectric properties from the measurements of S-parameters on the two 50-Ohm stripline structures of the same length, but different widths of the trace, designed on the same layer of a PCB. The dielectric properties on these two lines should be identical. However, an application of the simplest root-omega technique to extract dielectric properties of the substrate would lead to the ambiguity in the extracted data. This is because the conductor surface roughness affects the measured S-parameters and is lumped in the extracted dielectric data. This problem of ambiguity in the dielectric properties extraction can be overcome using the approach analogous to the recently proposed method to separate dielectric and conductor losses on PCB lines with different widths and roughness profiles --Abstract, page 48

Optical Frequency Domain Interferometry for the Characterization and Development of Complex and Tunable Photonic Integrated Circuits

[ES] Esta tesis aborda la caracterización de circuitos fotónicos integrados (PIC) usando interferometría óptica en el domino de las frecuencias (OFDI). OFDI tiene una implementación razonablemente simple e interroga al dispositivo bajo test (DUT) proporcionando su respuesta en el dominio del tiempo, en la que los distintos caminos ópticos seguidos por la luz se manifiestan en contribuciones que contienen información de posición, amplitud y fase. Junto con un "setup" OFDI construido en nuestros laboratorios y estructuras de test integradas que involucran anillos resonantes, interferómetros, etc., proponemos e implementamos técnicas para obtener parámetros ópticos cruciales tales como el índice de grupo, dispersión cromática, rotación de polarización y pérdidas de propagación en guías de onda. También para caracterizar acopladores ópticos. Se realizan evaluaciones directas de fase óptica en diferentes experimentos para, entre otras aplicaciones, caracterizar efectos de calor en chips. En la culminación de la tesis, se aborda la integración conjunta de los interferómetros de OFDI junto con el DUT, concibiéndolo como una estructura de caracterización integrada. El uso de guías de onda integradas proporciona una alta estabilidad y adaptación al DUT, además de un mecanismo inherente de compensación de la dispersión. Se realiza un análisis y prueba de concepto experimental caracterizando un "arrayed waveguide grating" en tecnología de nitruro de silicio. Seguidamente, se da un paso adelante proponiendo una arquitectura interferométrica de tres brazos novedosa que permite reducir la complejidad de la medida. Se lleva a cabo una validación experimental amplia usando distintos equipos de laboratorio, acoplamiento horizontal y vertical al chip, y diferentes DUTs en tecnologías de nitruro de silicio y "silicon-on-insulator".[CAT] Aquesta tesi aborda la caracterització de circuits fotònics integrats (PIC) usant interferometria òptica al domini de les freqüències (OFDI). OFDI té una implementació raonablement simple i interroga el dispositiu sota test (DUT) proporcionant la seva resposta en el domini del temps, en què els diferents camins òptics seguits per la llum es manifesten en contribucions que contenen informació de posició, amplitud i fase. Juntament amb un "setup" OFDI construït als nostres laboratoris i estructures de test integrades que involucren anells ressonants, interferòmetres, etc., proposem i implementem tècniques per obtenir paràmetres òptics crucials com ara l'índex de grup, dispersió cromàtica, rotació de polarització i pèrdues de propagació en guies d'ona. També per caracteritzar acobladors òptics. Es fan avaluacions directes de fase òptica en diferents experiments per, entre altres aplicacions, caracteritzar efectes de calor en xips. A la culminació de la tesi, s'aborda la integració conjunta dels interferòmetres d'OFDI juntament amb el DUT, concebent-ho com una estructura de caracterització integrada. L'ús de guies d'ona integrades proporciona una alta estabilitat i adaptació al DUT, a més d'un mecanisme inherent de compensació de la dispersió. Es realitza una anàlisi i prova de concepte experimental caracteritzant un "arrayed waveguide grating" en tecnologia de nitrur de silici. Seguidament, es fa un pas avant proposant una arquitectura interferomètrica de tres braços nova que permet reduir la complexitat de la mesura. Es du a terme una validació experimental àmplia usant diferents equips de laboratori, acoblament horitzontal i vertical al xip, i diferents DUTs en tecnologies de nitrur de silici i "silicon-on-insulator".[EN] This PhD thesis covers the characterization of complex photonic integrated circuits (PIC) by using Optical Frequency Domain Interferometry (OFDI). OFDI has a fairly simple implementation and interrogates the device under test (DUT) providing its time domain response, in which the different optical paths followed by light manifest in contributions with position, amplitude and phase information. Together with a working OFDI setup built in our laboratory and integrated test structures involving devices such as ring resonators, interferometers, etc., we propose and implement techniques to get crucial optical parameters such as waveguide group refractive index, chromatic dispersion, polarization rotation, and propagation loss. Also, to characterize optical couplers. Direct optical phase assessment is made in different experiments permitting, amongst others, the characterization of on-chip heat effects. In the culmination of the thesis, the co-integration of the OFDI interferometers with the DUT is addressed, conceiving it as an integrated characterization structure. The use of integrated waveguides provide high stability and adaptation to the DUT, as well as an inherent dispersion de-embedding mechanism. It is provided analysis and experimental proof of concept with an arrayed waveguide grating as DUT in a silicon nitride platform. A considerable leap forward is then taken by proposing a novel three-way interferometer architecture, reducing the measurement complexity. Wide experimental validation is carried out using different laboratory equipment, horizontal and vertical chip coupling, and different DUTs in silicon nitride and silicon-on-insulator.Bru Orgiles, LA. (2022). Optical Frequency Domain Interferometry for the Characterization and Development of Complex and Tunable Photonic Integrated Circuits [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/181635TESI