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Thirty years ago Boyer’s report Scholarship Reconsidered: Priorities of the Professoriate (1990) inspired the launch of the ‘SoTL movement’ which sought to raise the status of learning and teaching...

A robust multichannel smartphone spectrometer exploiting multiorder diffraction imaging on a smartphone camera is reported. The instrument utilizes a thin film diffractive element generating multiple orders of diffracted light from a broadband visible source (white LED, λ = 400-700 nm). The smartphone's CMOS camera captures all the diffraction orders simultaneously, producing a 2-D image. Each of these diffraction orders can be utilized as a single optical channel for dedicated samples enabling simultaneous multiple sample analysis. The wavelength distribution along the diffraction direction produces a tunable spectral resolution of δλ ~1.6 to 3.0 nm/pixel over the bandwidth of Δλ = 300 nm. A customized app processes each diffraction image into spectra. 3-D printing is used to create the entire instrument prototype. As an initial demonstration, simultaneous absorption measurements of reference and sample cells using the first diffraction orders (m = +1 and -1) is shown. Absorption spectra for a laser dye (Rhodamine B) and a pH-responsive buffer (bromothymol blue) are measured. This offers a low cost (

Approximately 3 million children younger than 5 years living in low- and middle-income countries (LMICs) die each year from treatable clinical conditions such as pneumonia, dehydration secondary to diarrhea, and malaria. A majority of these deaths could be prevented with early clinical assessments and appropriate therapeutic intervention. In this study, we describe the development and initial validation testing of a mobile health (mHealth) platform, MEDSINC®, designed for frontline health workers (FLWs) to perform clinical risk assessments of children aged 2–60 months. MEDSINC is a web browser–based clinical severity assessment, triage, treatment, and follow-up recommendation platform developed with physician-based Bayesian pattern recognition logic. Initial validation, usability, and acceptability testing were performed on 861 children aged between 2 and 60 months by 49 FLWs in Burkina Faso, Ecuador, and Bangladesh. MEDSINC-based clinical assessments by FLWs were independently and blindly correlated with clinical assessments by 22 local health-care professionals (LHPs). Results demonstrate that clinical assessments by FLWs using MEDSINC had a specificity correlation between 84% and 99% to LHPs, except for two outlier assessments (63% and 75%) at one study site, in which local survey prevalence data indicated that MEDSINC outperformed LHPs. In addition, MEDSINC triage recommendation distributions were highly correlated with those of LHPs, whereas usability and feasibility responses from LHP/FLW were collectively positive for ease of use, learning, and job performance. These results indicate that the MEDSINC platform could significantly increase pediatric health-care capacity in LMICs by improving FLWs’ ability to accurately assess health status and triage of children, facilitating early life-saving therapeutic interventions.

To address the challenge of appropriate cementitious materials that can support future optical fibre sensors with reduced strains for smart city infrastructure, reducing structural heterogeneity by integrating diatomous earth is proposed. A series of samples made up of commercial grade instant mortar and an increased percentage of diatomous earth are fabricated and characterised. Mindful of the growing importance of “in-the-field” measurements and diagnostics to wider construction technology evolution, hardness properties are measured using Mohs scratch test and portable field durometers; the latter was shown to be effective in post-plasticity assessment of these cement composites. Within experimental error low added concentrations improve cement hardness whilst making the cement more plastic. Structural colour is introduced by the diatoms and novel characterisation using a smartphone and polymer lens proposed and demonstrated. The implications for CO2 trapping and intelligent structural health monitoring (ISHM) for internet-of-things (IoT) in smart city infrastructure are discussed.

Fiber drawing from a 3D printed perform was recently discussed to go beyond the limitations of conventional optical fiber manufacturing in terms of structure and materials. In this work, the photosensitivity of silica optical fibers to femtosecond laser light, and fabricated by 3D printing a preform, is investigated. The writing kinetics and the thermal performance of Type II modifications are studied by varying the laser pulse energy and investigating the birefringence response of the femtosecond (fs)-laser written structures. Compared with a conventional telecom single mode fiber (SMF28), the fiber made by 3D printing is found to have similar writing kinetics and thermal performance. Additionally, the thermal stability of the imprinted fs-laser induced nanostructures is investigated based on the Rayleigh&ndash, Plesset equation, describing a model of nanopores dissolution underpinning Type II modifications with thermal annealing.

A study on birefringence compensation of highly asymmetric germanosilicate fibre drawn from a 3D printed preform is carried out. Surprisingly large compensation is locked in when twist is released, amounting to more than 80% compensation. Large bandgap attenuation is observed when gratings are written into this fibre.

A brief assessment is made of existing wireless and photonic sensor networks in buildings. It follows interests in the premium hotel sector to assess the feasibility integrating fibre optic sensors with existing fibre optic based communications

Fiber Bragg gratings are embedded within 3D printed polymer packages. Information about both induced and applied stresses, and operator error, can be determined from the observed spectral shifts and chirping. A novel way to produce packaged broadband gratings, with Δ λ B W > 7 n m / c m , is proposed and demonstrated.

We demonstrate that under appropriate conditions it is possible to build in tolerance to poor design of a structured optical fibre like photonic crystal fibre. During drawing its internal symmetry of the structure is improved.

Combined rocking filters and polarisation balanced fibre Bragg gratings are demonstrated in a 3D printed optical fibre. (E: john.canning@uts.edu.au).© 2020 John Canning

Additive manufacture (AM) offers a simple route to packaging components such as fibre Bragg gratings. Further, polymers with higher solid state densities than liquid state enable a simple approach to tightly fixing optical components with AM packages. With applied load and using printer directionality, chirping fibre Bragg gratings becomes possible. Information about both induced and applied stresses, and operator error, can be determined from the observed spectral shifts and chirping. Broadband gratings with bandwidths, Δλ BW > 7nm/cm, are demonstrated.

© 2020 OSA - The Optical Society. All rights reserved. Based on 3D printing technology, multi-core doped silica optical fibre has been fabricated. The demonstration heralds a new fibre manufacturing milestone one that enables the design of fibres not previously feasible.

A robust multi-channel smartphone spectrometer is reported by utilizing the multiple diffraction orders of an ordinary diffraction grating.

A self-contained smartphone-based colorimetric sensing platform adaptable for multiple analytes is demonstrated. Concurrent variation of multiple optical sensing parameters is addressed using multiple nonlinear regression analysis.

A multichannel smartphone spectrometer exploiting multiple identical diffraction orders of a customized 2D diffractive element is reported. The instrument utilizes diffraction grating holographic imaging to converge and capture the multiple diffraction orders simultaneously within the limited field-of-view of the smartphone’s camera detector. This eliminates the requirement of convergence optics as used in conventional spectrometer systems. Each diffraction order can be utilized as a single optical channel for spectroscopic analysis. As proof of concept, a customized 2D grating composed of two identical thin-film 1D gratings orthogonally stacked together is utilized to diffract the light rays emanating from a broadband visible source and produce four identical 1st orders dispersive diffraction in two orthogonal axes. The smartphone camera captures the diffraction orders within its solid angle – a quad-channel spectrometer exploiting the 2D properties of a CMOS detector is demonstrated. Mindful of losses, further increases in channel numbers is possible by simply increasing the number of gratings (N) within the stack spatially separated by an angle θ N = 180 ° / N between successive grating axes. The instrument offers an ultra-low-cost, lightweight, high throughput, rugged and small form factor multichannel spectrometer ideal for field use as well as a laboratory benchtop alternative. To evaluate the performance of the instrument, three chemically and biologically significant parameters are measured simultaneously: - (a) iron concentration [Fe], (b) chlorine concentration [Cl], and (c) pH of the drinking water.

In this paper, we report the response of Cobalt-60 gamma irradiation on Photonic Crystal Fibre Bragg gratings (PCFFBGs) and standard commercial FBGs (STD-FBGs). Optical measurements were performed to determine the shift of the Bragg wavelength as a function of accumulated dose and relaxation time. To simulate real time conditions of a radiation dosimeter, the FBGs are examined through three consecutive radiation stages followed by very limited recovery times. We were able to obtain a Bragg wavelength shift with both sets of FBGs. The PCF-FBGs response included strong recovery after each irradiation compared to the STD-FBGs. This makes the PCF-FBGs strong candidates as optical fibre FBG sensors in the area of radiation dosimetry.

This paper presents the first time studies on chemical sensing characteristics of HF etched thermally regenerated fiber Bragg grating (FBG). No shift in Bragg wavelength, λ B ragg , of the FBG during HF etching has been observed for thermally regenerated FBGs. This contrasts with etching of conventional Type-I gratings both with and without annealing at temperatures, T ∼ 600 °C for which the regeneration does not occur. These HF etched FBGs are studied for refractive index sensing of four media i.e. air, methanol, ethanol and ethylene glycol for the chemical sensing applications. The regenerated grating has a variation in reflection intensity with little shift in λ B ragg , i.e. Δλ B ragg B ragg > 1 nm. For the annealed FBGs at 600 °C, the change in reflected power of the FBG was higher than the non-annealed FBGs while Δλ Bragg was comparable. For chemical sensing based on etched regenerated grating, the removal of the wavelength shift from measurements greatly reduces sensor interrogation complexity allowing for simple amplitude based detection schemes.

The ‘student voice’ is highly profiled in UK higher education, yet highly under-theorised. Over the past 20 years UK universities have gone from a taxpayer-funded, free at the point of use model, to one supported through tuition fees via Government-backed loans. Subsequently, there is a growth of discourse about universities as businesses and students as paying customers/consumers whose opinions and demands must be considered. This article outlines four possible theoretical lenses (or frameworks) through which student voice can be analysed, enabling an exploration of the vested interests and power relations entailed. These lenses draw on (1) research on student voice and power in compulsory education; (2) regulatory capture from Economics; (3) the notion of students voice as part of an incomplete whole and (4) non-representational theory, developed in Human Geography by Nigel Thrift.

© The Author(s) 2019. Excitation of surface waves on conducting materials provides a near resistance-free interface capable of a material glissade either by plasmon forces or by optical beam tractors. Analogous to an ice hockey rink, as proof-of-principle plasmon-assisted optical traction, or hoovering, of water drops on a gold surface is demonstrated. Changes in the contact angle provide a novel, low-cost nanoscale method of quantifying observable and potentially tunable changes. Variability in thresholds and movement, including jumps, is observed and can be explained by the presence of significant roughness, measured by scanning electron microscopy, with water tension. The demonstration opens a path to directly integrate various optical and plasmonic traction technologies. Implications of the phenomena and ways of improving transport and potential applications spanning configurable microfluidics, antennas, tunable lenses, diagnostics, sensing, and active Kerr and other devices are discussed.

The attendees at the SIGGRAPH Conference run the gambit from indie contractors to multi-million-dollar studios. After attending the conference for the past 7 years, I kept hearing the same thing from many small studios and/or individuals. They feel a lot of the emerging technology that is premiered at SIGGRAPH seems out of reach or impractical for them to utilize. Our panel works to challenge this assumption. By bringing in industry professionals from various disciplines and levels, we can show how anyone from an independent contractor to a large studio can implement new tools and technologies. Specifically, our talk will focus on encounters with AR/VR/MR and how we worked it into our pipeline. Whether someone is out there making the next big movie or trying to pitch to a client in a conference room setting, they will find attending this panel useful. We will talk about the practical applications of AR/VR/MR and how we have explored these technologies over the years.

© 2018 IEEE. Spun Hi-Bi bismuth/erbium co-doped photonic optical fibre (SHB-BEPCF) has been fabricated using preform stacking and draw tower self-pressurization. Results demonstrate broadband and partially elliptical polarized NIR emission under un-polarized 830 nm pumping spanning Δλ ~ 520 nm centred at 1430 nm.

A robust and adaptive smartphone-based colorimetric sensing platform is reported. It utilizes multiple regression analysis to address nonlinear concurrent variations of multiple sensing variables. The instrument can perform colorimetric measurement with improved accuracy over a wide range where both color and intensity information of a colorimetric signal varies independently often simultaneously. The instrument utilizes the smartphone in-built flash LED (λ = 400–700 nm) to illuminate the test sample and the phone’s CMOS camera as a detector, collecting and digitizing the reflected light from that sample. 3D printing technology is used to fabricate a specially designed optical enclosure that performs as a diffuser, neutral density filter, and reflector to ensure constant and uniform illumination of the sensing platform. Thus, an ultra-low-cost (< 3 USD) portable smartphone-based colorimetric diagnostic system becomes feasible along with an easy-to-use customized android app adaptable for multi-analyte assays. The performance of the colorimetric measurement system is validated by: (a) monitoring the concentration of a laser dye, (b) measuring the pH of drinking water, and (c) quantifying the chlorine concentration of shrimp ponds.

Using induced UV attenuation across a twisted fiber asymmetric core drawn from a 3D printed preform, linear fiber Bragg gratings (FBGs) are produced on one side of the core. By removing the twist, a helical grating with a period matching the twist rate is produced. Balancing the rate with the polarization beat length in a form birefringent fiber allows the production of a combined rocking filter and FBG device with tunable properties. Direct observation of the fiber grating dispersion within the rocking filter rejection band is possible.

© 2020 Elsevier Inc. 3D printing is a disruptive technology that could revolutionise the fabrication of optical fibre by offering greater flexibility and diversity in material and structure designs. This paper reviews the recent research and development of material and fabrication techniques toward 3D printing-based polymer optical fibre (POF) and silica optical fibre (SOF).

© Copyright Materials Research Society 2018. A review of the literature offers an explanation for the large anomalous electro-optic (e.o.) effect reported by Fujiwara et al. in 1994. It is based on the large e.o. coefficient of ordered water at an interface measured in recent years >1000 pm/V. More broadly, the concept of water-based photonics, where water could be a new platform material for devices and systems, is introduced, suggesting that liquid states of matter can allow ready shaping and exploitation of many processes in ways not previously considered. This paper is a commentary on the significance of this new understanding and the broader interest of water in photonics, particularly its consideration as a new platform material.

© 2018 OSA. 3D-printing is changing the way research is being conducted. By enabling the ready demonstration of prototype devices and instruments, 3D printing accelerates the adaptation of IoT technologies going beyond simple, latency-enhancing sensors. Prototyping and custom packaging is easier, rapid and increasingly low cost, circumventing traditional approaches, disrupting manufacture. Direct 3D printing of transmission and optical technologies such as optical fibres and waveguides is revolutionising research, enabling accessible and affordable capability to a much wider audience space.

© 2018 The Author(s). Fibre Bragg grating regeneration involves, at its simplest, the annealing and resurrection of a seed FBG through thermal annealing. Micro-Raman spectroscopy provides evidence that inscribing the seed structure has changed the thermal history of the glass so that whilst the annealing is identical in all areas, the local glass relaxation is different in the UV irradiated regions. Notably, there is a significant decrease of the D1 and D2 defects bands within the core and the inner cladding of regenerated FBG revealing the complex nature of this two- or three materials system.

© 2015 by the authors; licensee MDPI, Basel, Switzerland. The regeneration of UV-written long period gratings (LPG) in boron-codoped germanosilicate “W” fibre is demonstrated and studied. They survive temperatures over 1000 °C. Compared with regenerated FBGs fabricated in the same type of fibre, the evolution curves of LPGs during regeneration and post-annealing reveal even more detail of glass relaxation. Piece-wise temperature dependence is observed, indicating the onset of a phase transition of glass in the core and inner cladding at ~500°C and ~250°C, and the melting of inner cladding between 860°C and 900°C. An asymmetric spectral response with increasing and decreasing annealing temperature points to the complex process dependent material system response. Resonant wavelength tuning by adjusting the dwell temperature at which regeneration is undertaken is demonstrated, showing a shorter resonant wavelength and shorter time for stabilisation with higher dwell temperatures. All the regenerated LPGs are nearly strain-insensitive and cannot be tuned by applying loads during annealing as done for regenerated FBGs.

Chekhov’s novella A boring story: From an old man’s journal, provides a rich stimulus for reflecting upon the practice of teaching in higher education. The narrator’s beliefs about academia, science and medicine alongside his tacit theories of learning and encounters with students and colleagues are reflected upon and speculated upon in light of contemporary teaching practice and pedagogic literature.

Despite numerous criticisms of the UK National Student Survey (NSS) institutional managers still strongly support its use in informing student choice, quality and assurance and quality enhancement activities. This article outlines a granular and nuanced benchmarking system for the NSS which provides both a ‘raw’ score (weighted student satisfaction score) and a normalised quotient (weighted student satisfaction quotient) to enable users to take a more considered approach to the absolute and relative strengths and weaknesses of individual course programmes.

To evaluate image quality and radiation dose of a state of the art cone beam computed tomography (CBCT) system and a multislice computed tomography (MSCT) system in patients with sinonasal poliposis. In this retrospective study two radiologists evaluated 57 patients with sinonasal poliposis who underwent a CBCT or MSCT sinus examination, along with a control group of 90 patients with normal radiological findings. Tissue doses were measured using a phantom model with thermoluminescent dosimeters (TLD). Overall image quality in CBCT was scored significantly higher than in MSCT in patients with normal radiologic findings (p-value: 0.00001). In patients with sinonasal poliposis, MSCT scored significantly higher than CBCT (p-value: 0.00001). The average effective dose for MSCT was 42 % higher compared to CBCT (108 μSv vs 63 μSv). CBCT and MSCT are both suited for the evaluation of sinonasal poliposis. In patients with sinonasal poliposis, clinically important structures of the paranasal sinuses can be better delineated with MSCT, whereas in patients without sinonasal poliposis, CBCT turns out to define the important structures of the sinonasal region better. However, given the lower radiation dose, CBCT can be considered for the evaluation of the sinonasal structures in patients with sinonasal poliposis. • CBCT and MSCT are both suited for evaluation of sinonasal poliposis. • Effective dose for MSCT was 42 % higher compared to CBCT. • In patients with sinonasal poliposis, clinically important anatomical structures are better delineated with MSCT. • In patients with normal radiological findings, clinically important anatomical structures are better delineated with CBCT.

© 2017 Optical Society of America. Top-down contact angle measurements have been validated and confirmed to be as good if not more reliable than side-based measurements. A range of samples, including industrially relevant materials for roofing and printing, has been compared. Using the top-down approach, mapping in both 1-D and 2-D has been demonstrated. The method was applied to study the change in contact angle as a function of change in silver (Ag) nanoparticle size controlled by thermal evaporation. Large area mapping reveals good uniformity for commercial Aspen paper coated with black laser printer ink. A demonstration of the forensic and chemical analysis potential in 2-D is shown by uncovering the hidden CsF initials made with mineral oil on the coated Aspen paper. The method promises to revolutionize nanoscale characterization and industrial monitoring as well as chemical analyses by allowing rapid contact angle measurements over large areas or large numbers of samples in ways and times that have not been possible before.

© 2017 SPIE. The extrusion nozzles of three low cost desktop 3D printers are characterised using optical fibre Bragg gratings. Temperature profiles show remarkably consistent distributions pointing to operation as good quality micro-furnaces potentially not only for 3D printing but also optical fibre drawing.

We show that the surface properties of Au thin films on a glass prism, typical of the Krestchsmann setup for SPR generation, can be modified or tuned with optical exposure. The wetting properties of the film were investigated by measuring contact angles of water drops at room temperature T=23 °C. These contact angle change with optical irradiation from below the film. This change corresponds to a maximum contact angle reduction of Δθ c ∼ 30° when a surface plasmon resonance (SPR) is excited. The variation in contact angle during drop evaporation is evaluated under different irradiation conditions.

© 2017 SPIE. The use of photonic sensors to monitor horses is presented and reviewed. Results are very promising and can be used in other areas to monitor animals, machines or industrial processes.

© 2017 SPIE. Degradation of olive oil under light and heat are analysed using an optical fibre based low-cost portable smartphone spectrofluorimeter. Visible fluorescence bands associated with phenolic acids, vitamins and chlorophyll centred at λ ∼ 452, 525 and 670 nm respectively are generated using near-UV excitation (LED λex ∼ 370 nm), of extra virgin olive oil are degraded more likely than refined olive oil under light and heat exposure. Packaging is shown to be critical when assessing the origin of degradation.

Recently, we showed that femtosecond laser induced “nanogratings” consist of thin regions with a low refractive index (Δn = −0.15), due to the formation of nanoporous silica surrounded by regions with a positive index change. In this paper, we investigate a wide range of laser parameters to achieve very high retardance within a single layer, as much as 350 nm at λ = 546 nm but also to minimize the competing losses. We show that the total retardance depends on the number of layers present and can be accumulated in the direction of laser propagation to values higher than 1600 nm. This opens the door to using these nanostructures as refined building blocks for novel optical elements based on strong retardance.

This paper presents a hybrid baseline (HBL) navigation method for autonomous underwater vehicles (AUVs). In this approach, a floating acoustic transponder is used to augment moving short baseline (MSBL) navigation, in which two transponders are mounted on a source ship. Kinematic information regarding the floating buoy and source ship are communicated via acoustic messages to the AUV fleet. Simultaneously, clock synchronization and a predefined broadcast cycle enables transponder-to-AUV range estimates based on the acoustic message time-of-flight. Using the extended Kalman (EKF) filter formulation, the broadcasted kinematic information and acoustic ranges are combined onboard each AUV in the fleet to estimate the states of the source ship, the floating transponder, and the AUV itself. Simulation was used to optimize the configuration and performance of the HBL navigation, and field tests were performed to evaluate the navigational performance. In post-processing, high-accuracy position and timing data for the source ship and floating buoy was added to the onboard navigation data in an EKF to recreate the path of the AUV. The accuracy of this post-mission localization was evaluated relative to AUV positions independently measured by an acoustic tracking array at the test facility. The resulting AUV position estimation showed a mean error of 1.59 m, an improvement over the previous result (using MSBL navigation only) of 3.30 m.

Silica optical fiber was drawn from a three-dimensional printed preform. Both single mode and multimode fibers are reported. The results demonstrate additive manufacturing of glass optical fibers and its potential to disrupt traditional optical fiber fabrication. It opens up fiber designs for novel applications hitherto not possible.

A commercially available tracked vehicle was modified to make it capable of autonomous operation in a forest environment. The vehicle, of 1364 kg mass (3000 lbs weight), was powered by a 22 kW (30 hp) diesel engine coupled to a hydraulic drive. For autonomous operation, the vehicle was equipped with shaft encoders on the drive wheels, a magnetic compass, three ultrasonic sensors, and a stereoscopic camera. Autonomous operation was enabled by hierarchical fuzzy logic controllers. Two controllers were considered. One controller used shaft encoder counts on the drive wheels, ultrasonic waveform echoes, the magnetic compass for heading, and training data to navigate a forest path. The other controller added stereoscopic vision and dispensed with the training data to reactively navigate the autonomous outdoor vehicle. The vehicle was equipped with GPS, but GPS was only used as an independent measure of vehicle performance in the autonomous mode. Tests using both controllers showed that the autonomous vehicle was able to reliably navigate several forest paths with lengths ranging from 229 to 430 m (750 to 1410 ft) without relying on GPS for navigation. These tests indicate that an industrial-size vehicle may be capable of performing useful forestry functions in an autonomous mode.

A type of glass modifications occurring after femto- second laser irradiation gives rise to strong (10 −2 ). This form birefringence is thought to be related to index nanostructure (called nanogratings). Analyzing induced tracks in fused silica using scanning electron microscopy (SEM) with nm resolution shows that nanostructures are porous nanoplanes with an av- erage index lower than typical silica (� n ∼ -0.20). Their origin is explained as arising from fast decomposition of the glass un- der localized, high-intensity femtosecond laser radiation where strong nonlinear, multiphoton-induced photoionization leads to plasma generation. Mechanistic details include Coulom- bic explosions characteristic of strong photoionization and the production of self-trapped exciton (STE). Rapid relaxation of these STE prevents recombination and dissociated atomic oxy- gen instead recombines with each other to form molecular oxygen pointed out using Raman microscopy. Some of it is dissolved in the condensed glass whilst the rest is trapped within nanovoids. A chemical recombination can only occur at 1200 ◦ C for many hours. This explains the thermal stability

This paper presents the results from field testing of a unique approach to the navigation of a fleet of autonomous underwater vehicles (AUVs) using only onboard sensors and information provided by a moving surface ship. The approach, considered moving short-baseline (MSBL) navigation, uses two transponders mounted on a single surface ship that alternately broadcast acoustic messages containing one of the parameters of the kinematic state of the surface ship. The broadcasts are initiated according to a predefined schedule so that the one-way travel time (OWTT) of the acoustic messages may be used to determine the range to the transponder. Each AUV in the fleet uses the surface ship state measurements and ranges provided by the acoustic messages in two extended Kalman filters (EKFs) for state estimation. The first EKF merges the intermittent surface ship state measurements with a kinematic model to estimate the state of the surface ship. This is necessary because the presented approach uses 13-bit acoustic messages as opposed to the more commonly used 32-byte messages, which allow the full state to be encoded in a single broadcast. The second EKF uses the current surface ship state estimate to properly interpret the acoustic ranges, combining them with a kinematic model to estimate the state of the AUV itself. Numerous MSBL navigation experiments were compared against a more traditional approach using a long-baseline (LBL) array of transponders and OWTT acoustic ranging. The results of all tests were verified by independent LBL measures of position.

Measurement of the magnetic signature of naval vessels allows one to determine their vulnerability to mines, and thus whether the signatures must be reduced. Hypothetically, a formation of magnetometer-equipped AUVs could be used to perform a magnetic signature measurement. In this work, a formation of three magnetometer-equipped AUVs was used to assess the feasibility of performing a magnetic signature measurement on a moving surface vessel. The AUVs used localization from acoustic transponders fixed to the bottom, data contained in acoustic communications, an inertial measurement unit, and other onboard sensors to navigate during the experiments. A surface vessel with a fiberglass hull was outfitted with a permanent magnet at the bow, and directed to travel on a straight course. The AUVs navigated in the opposite direction, passing underneath the surface vessel. Position estimates for individual magnetic field measurements using AUV-acquired navigation data were found to be accurate to within an average of 1.2 m. Magnetic fields of 100–300 nT were clearly measured, consistent with the 5–10 nT noise floor of the AUV/magnetometer unit. In the measurements that were performed, total uncertainty in signature measurement was estimated to be ∼250 nT in the presence of a magnetic field gradient of ∼200 nT/m.

While soldering fiber Bragg gratings into ferrules may allow them to overcome their inherent mechanical and chemical weaknesses, the high temperatures required to achieve reliable encapsulation can result in decreased grating reflectivity. In this paper, finite element models and data from on-line temperature measurements of regenerated gratings during induction heating are analyzed. The results are used to design and implement an optimized methodology, which allows standard, type-I gratings to be brazed into ferrules with high-temperature solders, while ensuring low reflectivity losses. © 2001-2012 IEEE.

© 2016 Optical Society of America. Optical fiber is drawn from a dual-head 3D printer fabricated preform made of two optically transparent plastics with a high-index core (NA ∼ 0.25, V > 60). The asymmetry observed in the fiber arises from asymmetry in the 3D printing process. The highly multimode optical fiber has losses measured by cut-back as low as α ∼ 0.44 dB/cm in the near IR.

This paper describes field testing of state estimation and navigation for autonomous underwater vehicle (AUV) operation in the presence of water currents. In the presented approach, an extended Kalman filter (EKF) is used to estimate the water currents in the north and east directions in real-time during AUV missions. These water current estimates are then used to compensate the desired AUV heading so that the resultant velocity vector of the AUV achieves proper waypoint path following behavior. This work builds on previous evaluation of the approach in simulation; here, we present results from preliminary field testing.

© OSA 2016. The inscription of fibre Bragg gratings in endlessly single mode photonic crystal fibre using H2 loading and direct-writing sthrough a phase mask with a 193 nm ArF laser is reported.