33 results on '"Webb, D.J."'
Search Results
2. Thermal and chemical treatment of polymer optical fiber Bragg grating sensors for enhanced mechanical sensitivity
- Author
-
Pospori, A., Marques, C.A.F., Sáez-Rodríguez, D., Nielsen, K., Bang, O., and Webb, D.J.
- Published
- 2017
- Full Text
- View/download PDF
Catalog
3. Polymer optical fiber sensors in human life safety
- Author
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Marques, C.A.F., Webb, D.J., and Andre, P.
- Published
- 2017
- Full Text
- View/download PDF
4. Long-Term Effect of Endothelin Receptor Antagonism With Bosentan on the Morbidity and Mortality of Patients With Severe Chronic Heart Failure: Primary Results of the ENABLE Trials
- Author
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Packer, Milton, Caspi, Avi, Kiowski, Wolfgang, Krum, Henry, Pratt, Craig, Swedberg, Karl, Massie, Barry, McMurray, John, Connally, Eugene, Petrie, Mark, DeMets, David, Anderson, Susan, Barnet, Jody, Cody, Robert, Dargie, Henry, Francis, Gary, Greenberg, Barry, Reichen, Juerg, Karrasch, J., Krum, H., Horowitz, J., Amerena, J., Sindone, A., MacDonald, P., Jeffrey, I., Button, I., DeAngelis, E., Pacher, R., Davies, R., McAlister, F., Tanser, P., Sussex, B., Baumann, G., Fleck, E., Olbrich, H.-G., Werdan, K., Klein, H., Staffeld, F., Zeiher, A.M., Roediger, C., Caspi, A., Marmor, A., Reisin, L., Vered, Z., Klainman, E., Roguin, N., Tzivoni, D., David, D., Lewis, B., Abinader, E., Omary, M., Rosenman, Y., Kaluski, E., Breedveld, R.W., van der Burgh, P.H., Dunselman, P.H.J.M., Schaafsma, H.J., Hertzberger, D.P., Holwerda, N.J., Kragten, J.A., van Wijngaarden, J., Posma, J.L., Said, S.A.M., Slegers, L.C., Tjon Joe Gin, R.M., Wempe, F.N., Wesdorp, J.C.L., Willems, A.R., Withagen, A.J.A.M., Cornel, J.M., van Kempen, L.H.J., Kiowski, W., Bertel, O., Moccetti, T., McMurray, J.J.V., Greenbaum, R.A., Bennett, P., Swan, J., Davies, G., Findlay, I., Gould, B., Ball, S., Hubner, P., Lahiri, A., McLay, J., Northcote, R., Saltissi, S., Squire, I., Stephens, J., Stewart, M., Bridgen, G., Walsh, J., Webb, D.J., Ansari, Z., Baron, S., Bellinger, R., Bennet, W., Benvenuti, D., Dawley, D., Egbujiobi, L.C., Eisenstein, I., Little, T., Hertsberg, A., Greenspan, M., Grossman, R.J., Hanley, P., Jesrani, M., Kashou, H., Levites, R., Malik, R., Marmorstein, B., Schwartz, M., Nisar, A., Perelman, R., Schwarz, M.L., Sedlis, S., Srebro, J., Taveras, M., Weiss, R., Weitzman, P., Wetherley, G.K., El Shahawy, M., Kereiakes, D., Campos, L., Peterson, G., Small, R.S., Davis, W.R., Olivari, M.-T., Meengs, W., Koren, M., Slagona, P., Jennison, S., Hershberger, R., Browne, K.F., Farnham, D.J., Zelenkofske, S., Lawless, C., Nathan, M., Meyer, T., Kukin, M., Parekh, H., Berkowitz, R., Boehmer, J., Brozena, S., Dandona, P., Dec, G.W., DeQuattro, V., Fenster, P., Fowler, M., Ellaham, S., Geller, M., Gheorgiade, M., Ghali, J., Murali, S., Katz, S., Bott-Silverman, C., Singh, B., Thadani, U., Torre, G., Teerlink, J., Chandraratna, T., Kesselbrenner, M., Mukherjee, A., Che-Pin Tsai, C., Abbo, K., Goldberg, M., Smith, T., Martin, R.T., McMurray, John J.V., Massie, Barry M., Pratt, Craig M., Petrie, Mark C., Kobrin, Isaac, and Roux, Sebastien more...
- Published
- 2017
- Full Text
- View/download PDF
5. Imaging of cardiovascular risk in patients with Turner's syndrome
- Author
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Marin, A., Weir-McCall, J.R., Webb, D.J., van Beek, E.J.R., and Mirsadraee, S.
- Published
- 2015
- Full Text
- View/download PDF
6. Ultraviolet A radiation and COVID‐19 deaths in the USA with replication studies in England and Italy*
- Author
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Cherrie, M., primary, Clemens, T., additional, Colandrea, C., additional, Feng, Z., additional, Webb, D.J., additional, Weller, R.B., additional, and Dibben, C., additional
- Published
- 2021
- Full Text
- View/download PDF
7. Chirped polymer optical fiber Bragg grating sensors
- Author
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Marques, Carlos A.F., Pereira, L., Antunes, P., Mergo, P., Webb, D.J., Pinto, J.L., André, P., Kalli, Kyriacos, and et al
- Abstract
We report chirped fiber Bragg gratings (CFBGs) photo-inscribed in undoped PMMA polymer optical fibre (POF) for the first time. The chirped polymer optical fiber Bragg gratings (CPOFBGs) were inscribed using an UV KrF excimer laser operating at 248 nm. The rectangular gauss laser beam was expanded to 25 mm in horizontal direction along the fiber core by a cylindrical lens, giving a total of 25 mm grating length. A 25 mm long chirped phase mask chosen for 1550 nm grating inscription was used. The laser frequency was 1 Hz with an energy of 5 mJ per exposure, exposing few pulses for each grating inscription. The reflection amplitude spectrum evolution of a CPOFBG is investigated as a function of the applied strain and temperature. Also, some results regarding to group delay are collected and discussed. These results pave the way to further developments in different fields, where POFs could present some advantages preferably replacing their silica counterparts. more...
- Published
- 2017
8. PMMA based optical fiber Bragg grating for measuring moisture in transformer oil
- Author
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Zhang, W. and Webb, D.J.
- Subjects
genetic structures ,sense organs - Abstract
Water contamination can cause serious problems that compromise in transformer's safe operation and reduce its lifetime. Online monitoring of moisture concentration in transformer oil would permit the control of moisture buildup. This letter presents a direct optical measurement of moisture concentration in transformer oil using a poly(methyl methacrylate) (PMMA)-based optical fiber Bragg grating (POFBG). The refractive index and volume of PMMA-based optical fiber vary with the moisture in the surrounding transformer oil, changing the reflecting wavelength of the grating. A sensitivity of POFBG wavelength change to moisture content of 29 pm/ppm is demonstrated in this letter, indicating detectable water content better than 0.05 ppm. more...
- Published
- 2016
9. Sensitivity enhancement using annealed polymer optical fibre based sensors for pressure sensing applications
- Author
-
Pospori, A., Marques, C.A.F., Sáez-Rodríguez, D., Nielsen, K., Bang, O., Webb, D.J., and Lewis, Elfed
- Abstract
Thermal annealing can be used to induce a permanent negative Bragg wavelength shift for polymer fibre grating sensors and it was originally used for multiplexing purposes. Recently, researchers showed that annealing can also provide additional benefits, such as strain and humidity sensitivity enhancement and augmented temperature operational range. The annealing process can change both the optical and mechanical properties of the fibre. In this paper, the annealing effects on the stress and force sensitivities of PMMA fibre Bragg grating sensors are investigated. The incentive for that investigation was an unexpected behaviour observed in an array of sensors which were used for liquid level monitoring. One sensor exhibited much lower pressure sensitivity and that was the only one that was not annealed. To further investigate the phenomenon, additional sensors were photo-inscribed and characterised with regard their stress and force sensitivities. Then, the fibres were annealed by placing them in hot water, controlling with that way the humidity factor. After annealing, stress and force sensitivities were measured again. The results show that the annealing can improve the stress and force sensitivity of the devices. This can provide better performing sensors for use in stress, force and pressure sensing applications. more...
- Published
- 2016
10. Annealing effects on strain and stress sensitivity of polymer optical fibre based sensors
- Author
-
Pospori, A., Marques, C.A.F., Zubel, M.G., Sáez-Rodríguez, D., Nielsen, K., Bang, O., Webb, D.J., Kalli, Kyriacos, and Mendez, Alexis
- Subjects
Condensed Matter::Materials Science ,Physics::Optics - Abstract
The annealing effects on strain and stress sensitivity of polymer optical fibre Bragg grating sensors after their photo-inscription are investigated. PMMA optical fibre based Bragg grating sensors are first photo-inscribed and then they were placed into hot water for annealing. Strain, stress and force sensitivity measurements are taken before and after annealing. Parameters such as annealing time and annealing temperature are investigated. The change of the fibre diameter due to water absorption and the annealing process is also considered. The results show that annealing the polymer optical fibre tends to increase the strain, stress and force sensitivity of the photo-inscribed sensor. more...
- Published
- 2016
11. Performance analysis of polymer optical fibre based Fabry-Perot sensor formed by two uniform Bragg gratings
- Author
-
Pospori, A., Webb, D.J., Kalli, Kyriacos, and Mendez, Alexis
- Subjects
Physics::Optics - Abstract
The stress sensitivity of polymer optical fibre (POF) based Fabry-Perot sensors formed by two uniform Bragg gratings with finite dimensions is investigated. POF has received high interest in recent years due to its different material properties compared to its silica counterpart. Biocompatibility, a higher failure strain and the highly elastic nature of POF are some of the main advantages. The much lower Young’s modulus of polymer materials compared to silica offers enhanced stress sensitivity to POF based sensors which renders them great candidates for acoustic wave receivers and any kind of force detection. The main drawback in POF technology is perhaps the high fibre loss. In a lossless fibre the sensitivity of an interferometer is proportional to its cavity length. However, the presence of the attenuation along the optical path can significantly reduce the finesse of the Fabry-Perot interferometer and it can negatively affect its sensitivity at some point. The reflectivity of the two gratings used to form the interferometer can be also reduced as the fibre loss increases. In this work, a numerical model is developed to study the performance of POF based Fabry-Perot sensors formed by two uniform Bragg gratings with finite dimensions. Various optical and physical properties are considered such as grating physical length, grating effective length which indicates the point where the light is effectively reflected, refractive index modulation of the grating, cavity length of the interferometer, attenuation and operating wavelength. Using this model, we are able to identify the regimes in which the PMMA based sensor offer enhanced stress sensitivity compared to silica based one. more...
- Published
- 2016
12. A comparison of sea surface temperatures in the Equatorial Pacific Nino regions with results from two early runs of the NEMO 1/12° Ocean Model
- Author
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Webb, D.J.
- Subjects
Physics::Atmospheric and Oceanic Physics ,Physics::Geophysics - Abstract
Sea surface temperature observations from the Nino regions of the Tropical Pacific are compared with results from two 1/12° runs of the NEMO global ocean model. The results show good agreement between the model and observations.There was some concern that the model surface temperatures were being strongly coupled to the actual temperatures via the surface boundary conditions. The near surface structure of the ocean was investigated, as were the individual surface flux terms, but no evidence of strong coupling was found. In fact during the strongest warming periods the surface boundary conditions cooled the ocean more than normal. more...
- Published
- 2016
13. Hand eczema and steroid-refractory chronic hand eczema in general practice: prevalence and initial treatment
- Author
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Crane, M.M., primary, Webb, D.J., additional, Watson, E., additional, Cunliffe, T., additional, and English, J., additional
- Published
- 2017
- Full Text
- View/download PDF
14. Fiber-optic liquid level monitoring system using microstructured polymer fiber Bragg grating array sensors:performance analysis
- Author
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Marques, C.A.F., Pospori, A., Sáez-Rodríguez, D., Nielsen, K., Bang, O., and Webb, D.J.
- Abstract
A highly sensitive liquid level monitoring system based on microstructured polymer optical fiber Bragg grating (mPOFBG) array sensors is reported for the first time. The configuration is based on five mPOFBGs inscribed in the same fiber in the 850 nm spectral region, showing the potential to interrogate liquid level by measuring the strain induced in each mPOFBG embedded in a silicone rubber (SR) diaphragm, which deforms due to hydrostatic pressure variations. The sensor exhibits a highly linear response over the sensing range, a good repeatability, and a high resolution. The sensitivity of the sensor is found to be 98 pm/cm of water, enhanced by more than a factor of 9 when compared to an equivalent sensor based on a silica fiber around 1550 nm. The temperature sensitivity is studied and a multi-sensor arrangement proposed, which has the potential to provide level readings independent of temperature and the liquid density. more...
- Published
- 2015
15. Chirped polymer optical fiber Bragg grating sensors
- Author
-
Kalli, Kyriacos, et al, Marques, Carlos A.F., Pereira, L., Antunes, P., Mergo, P., Webb, D.J., Pinto, J.L., André, P., Kalli, Kyriacos, et al, Marques, Carlos A.F., Pereira, L., Antunes, P., Mergo, P., Webb, D.J., Pinto, J.L., and André, P. more...
- Abstract
We report chirped fiber Bragg gratings (CFBGs) photo-inscribed in undoped PMMA polymer optical fibre (POF) for the first time. The chirped polymer optical fiber Bragg gratings (CPOFBGs) were inscribed using an UV KrF excimer laser operating at 248 nm. The rectangular gauss laser beam was expanded to 25 mm in horizontal direction along the fiber core by a cylindrical lens, giving a total of 25 mm grating length. A 25 mm long chirped phase mask chosen for 1550 nm grating inscription was used. The laser frequency was 1 Hz with an energy of 5 mJ per exposure, exposing few pulses for each grating inscription. The reflection amplitude spectrum evolution of a CPOFBG is investigated as a function of the applied strain and temperature. Also, some results regarding to group delay are collected and discussed. These results pave the way to further developments in different fields, where POFs could present some advantages preferably replacing their silica counterparts. more...
- Published
- 2017
16. Polymer optical fiber Bragg grating inscription with a single UV laser pulse
- Author
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Pospori, A., Marques, Carlos A.F., Bang, O., Webb, D.J., André, P., Pospori, A., Marques, Carlos A.F., Bang, O., Webb, D.J., and André, P.
- Abstract
We experimentally demonstrate the first polymer optical fiber Bragg grating inscribed with only one krypton fluoride laser pulse. The device has been recorded in a single-mode poly(methyl methacrylate) optical fiber, with a core doped with benzyl dimethyl ketal for photosensitivity enhancement. One laser pulse with a duration of 15 ns, which provide energy density of 974 mJ/cm2, is adequate to introduce a refractive index change of 0.74×10-4 in the fiber core. After the exposure, the reflectivity of the grating increases for a few minutes following a second order exponential saturation. The produced Bragg grating structure rejects 17.9 dB transmitted power, thus providing 98.4% reflectivity, which is well suited for sensing applications. In addition, we report the importance of the fiber thermal treatment before or after the inscription, showing its effects on the lifetime and quality of the grating structures. Optimizing the irradiation conditions and the material chemical composition, a higher refractive index change in the fiber core is feasible. This demonstration significantly improves the potential for commercial exploitation of the technology. more...
- Published
- 2017
17. Annealing and etching effects on strain and stress sensitivity of polymer optical fibre Bragg grating sensors
- Author
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Webb, D.J., Webb, David J., Scully, Patricia, Sugden, Kate, Pospori, A., Marques, C.A.F., Sáez-Rodríguez, D., Nielsen, K., Bang, O., Webb, D.J., Webb, David J., Scully, Patricia, Sugden, Kate, Pospori, A., Marques, C.A.F., Sáez-Rodríguez, D., Nielsen, K., and Bang, O. more...
- Abstract
Thermal annealing and chemical etching effects on the strain and stress sensitivity of polymer optical fibre based sensors are investigated. Bragg grating sensors have been photo-inscribed in PMMA optical fibre and their strain and stress sensitivity has been characterised before and after any annealing or etching process. The annealing and etching processes have been tried in different sequence in order to investigate their impact on the sensor’s performance. Results show with high confidence that fibre annealing can improve both strain and stress sensitivities. The fibre etching can also provide stress sensitivity enhancement, however the strain sensitivity changes seems to be random. more...
- Published
- 2016
18. Passive and portable polymer optical fiber cleaver
- Author
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Sáez-Rodríguez, D., Min, R., Ortega, B., Nielsen, K., Webb, D.J., Sáez-Rodríguez, D., Min, R., Ortega, B., Nielsen, K., and Webb, D.J.
- Abstract
Polymer optical fiber (POF) is a growing technology in short distance telecommunication due to its flexibility, easy connectorization, and lower cost than the mostly deployed silica optical fiber technology. Microstructured POFs (mPOFs) have particular promising potential applications in the sensors and telecommunications field, and they could specially help to reduce losses in polymer fibers by using hollow-core fibers or reduce the modal dispersion by providing a large mode area endlessly single-mode. However, mPOFs are intrinsically more difficult to cut due to the cladding hole structure and it becomes necessary to have a high quality POF cleaver. In the well-known hot-blade cutting process, fiber and blade are heated, which requires electrical components and increases cost. A new method has recently been identified, allowing POF to be cut without the need for heating the blade and fiber, thus opening up the possibility of an electrically passive cleaver. In this letter, we describe the implementation and testing of a high quality cleaver based on a mechanical system formed by a constant force spring and a damper, which leads to the first reported electrical passive and portable cleaver. more...
- Published
- 2016
19. Portable polymer optical fibre cleaver
- Author
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Webb, D.J., Webb, David J., Scully, Patricia, Sugden, Kate, Sáez-Rodríguez, David, Min, R., Ortega, B., Nielsen, K., Bang, O., Webb, D.J., Webb, David J., Scully, Patricia, Sugden, Kate, Sáez-Rodríguez, David, Min, R., Ortega, B., Nielsen, K., and Bang, O. more...
- Abstract
Polymer optical fibre (POF) is a growing technology in short distance telecommunication due to its flexibility, easy connectorization, and lower cost than the mostly deployed silica optical fibre (SOF) technology. Microstructured POFs (mPOFs) have particular promising potential applica-tions in the sensors and telecommunications field, they could specially help to reduce losses in poly-mer fibres by using hollow-core fibres. However, mPOFs are intrinsically more difficult to cut due to the cladding hole structure and it becomes necessary to have a high quality polymer optical cleaver. In the well-known hot-blade cutting process, fibre and blade are heated, which requires electrical compo-nents and increases cost. A new method has recently been published to cut POF without the need for heating the blade/fibre, therefore electronically devices are not required if it is used a proper mechani-cal system. In this paper, we present a passive and portable polymer optical cleaver implemented with a mechanical system formed by a constant force spring and a damper. more...
- Published
- 2016
20. Determination of the radial profile of the photoelastic coefficient of plastic optical fibers
- Author
-
Webb, D.J., Webb, David J., Scully, Patricia, Sugden, Kate, Acheroy, S., Geernaert, T., Ottevaere, H., Thienpont, H., Marques, C.A.F., Peng, G., Pawel, M., Berghmans, F., Webb, D.J., Webb, David J., Scully, Patricia, Sugden, Kate, Acheroy, S., Geernaert, T., Ottevaere, H., Thienpont, H., Marques, C.A.F., Peng, G., Pawel, M., and Berghmans, F. more...
- Abstract
We developed a measurement method to determine the radial distribution of the photoelastic coefficient C(r) in step-index polymer optical fibers (POFs). The method is based on the measurement of the retardance profile of a transversally illuminated fiber for increasing tensile load. The radial profile C(r) is obtained from the inverse Abel transform of this retardance profile. We measured polymer fibers from different manufacturers. The radial profile of the photoelastic constant can considerable vary depending on the type and treatment of POFs, even when made from similar materials, which leads to the conclusion that the photoelastic constant should be characterized for each different type of POF. The impact of annealing the fiber samples on C(r) is also addressed. more...
- Published
- 2016
21. Fuel level sensor based on polymer optical fiber Bragg gratings for aircraft applications
- Author
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Kalli, Kyriacos, Mendez, Alexis, Marques, C.A.F., Pospori, A., Sáez-Rodríguez, D., Nielsen, K., Bang, O., Webb, D.J., Kalli, Kyriacos, Mendez, Alexis, Marques, C.A.F., Pospori, A., Sáez-Rodríguez, D., Nielsen, K., Bang, O., and Webb, D.J. more...
- Abstract
Safety in civil aviation is increasingly important due to the increase in flight routes and their more challenging nature. Like other important systems in aircraft, fuel level monitoring is always a technical challenge. The most frequently used level sensors in aircraft fuel systems are based on capacitive, ultrasonic and electric techniques, however they suffer from intrinsic safety concerns in explosive environments combined with issues relating to reliability and maintainability. In the last few years, optical fiber liquid level sensors (OFLLSs) have been reported to be safe and reliable and present many advantages for aircraft fuel measurement. Different OFLLSs have been developed, such as the pressure type, float type, optical radar type, TIR type and side-leaking type. Amongst these, many types of OFLLSs based on fiber gratings have been demonstrated. However, these sensors have not been commercialized because they exhibit some drawbacks: low sensitivity, limited range, long-term instability, or limited resolution. In addition, any sensors that involve direct interaction of the optical field with the fuel (either by launching light into the fuel tank or via the evanescent field of a fiber-guided mode) must be able to cope with the potential build up of contamination-often bacterial-on the optical surface. In this paper, a fuel level sensor based on microstructured polymer optical fiber Bragg gratings (mPOFBGs), including poly (methyl methacrylate) (PMMA) and TOPAS fibers, embedded in diaphragms is investigated in detail. The mPOFBGs are embedded in two different types of diaphragms and their performance is investigated with aviation fuel for the first time, in contrast to our previous works, where water was used. Our new system exhibits a high performance when compared with other previously published in the literature, making it a potentially useful tool for aircraft fuel monitoring. more...
- Published
- 2016
22. Sensitivity enhancement using annealed polymer optical fibre based sensors for pressure sensing applications
- Author
-
Lewis, Elfed, Pospori, A., Marques, C.A.F., Sáez-Rodríguez, D., Nielsen, K., Bang, O., Webb, D.J., Lewis, Elfed, Pospori, A., Marques, C.A.F., Sáez-Rodríguez, D., Nielsen, K., Bang, O., and Webb, D.J. more...
- Abstract
Thermal annealing can be used to induce a permanent negative Bragg wavelength shift for polymer fibre grating sensors and it was originally used for multiplexing purposes. Recently, researchers showed that annealing can also provide additional benefits, such as strain and humidity sensitivity enhancement and augmented temperature operational range. The annealing process can change both the optical and mechanical properties of the fibre. In this paper, the annealing effects on the stress and force sensitivities of PMMA fibre Bragg grating sensors are investigated. The incentive for that investigation was an unexpected behaviour observed in an array of sensors which were used for liquid level monitoring. One sensor exhibited much lower pressure sensitivity and that was the only one that was not annealed. To further investigate the phenomenon, additional sensors were photo-inscribed and characterised with regard their stress and force sensitivities. Then, the fibres were annealed by placing them in hot water, controlling with that way the humidity factor. After annealing, stress and force sensitivities were measured again. The results show that the annealing can improve the stress and force sensitivity of the devices. This can provide better performing sensors for use in stress, force and pressure sensing applications. more...
- Published
- 2016
23. Aviation fuel gauging sensor utilizing multiple diaphragm sensors incorporating polymer optical fiber Bragg gratings
- Author
-
Marques, C.A.F., Pospori, A., Sáez-Rodríguez, D., Nielsen, K., Bang, O., Webb, D.J., Marques, C.A.F., Pospori, A., Sáez-Rodríguez, D., Nielsen, K., Bang, O., and Webb, D.J.
- Abstract
A high-performance fuel gauging sensor is described that uses five diaphragm-based pressure sensors, which are monitored using a linear array of polymer optical fiber Bragg gratings. The sensors were initially characterized using water, revealing a sensitivity of 98 pm/cm for four of the sensors and 86 pm/cm for the fifth. The discrepancy in the sensitivity of the fifth sensor has been explained as being a result of the annealing of the other four sensors. Initial testing in JET A-1 aviation fuel revealed the unsuitability of silicone rubber diaphragms for prolonged usage in fuel. A second set of sensors manufactured with a polyurethane-based diaphragm showed no measurable deterioration over a three month period immersed in fuel. These sensors exhibited a sensitivity of 39 pm/cm, which is less than the silicone rubber devices due to the stiffer nature of the polyurethane material used. more...
- Published
- 2016
24. Performance analysis of polymer optical fibre based Fabry-Perot sensor formed by two uniform Bragg gratings
- Author
-
Kalli, Kyriacos, Mendez, Alexis, Pospori, A., Webb, D.J., Kalli, Kyriacos, Mendez, Alexis, Pospori, A., and Webb, D.J.
- Abstract
The stress sensitivity of polymer optical fibre (POF) based Fabry-Perot sensors formed by two uniform Bragg gratings with finite dimensions is investigated. POF has received high interest in recent years due to its different material properties compared to its silica counterpart. Biocompatibility, a higher failure strain and the highly elastic nature of POF are some of the main advantages. The much lower Young’s modulus of polymer materials compared to silica offers enhanced stress sensitivity to POF based sensors which renders them great candidates for acoustic wave receivers and any kind of force detection. The main drawback in POF technology is perhaps the high fibre loss. In a lossless fibre the sensitivity of an interferometer is proportional to its cavity length. However, the presence of the attenuation along the optical path can significantly reduce the finesse of the Fabry-Perot interferometer and it can negatively affect its sensitivity at some point. The reflectivity of the two gratings used to form the interferometer can be also reduced as the fibre loss increases. In this work, a numerical model is developed to study the performance of POF based Fabry-Perot sensors formed by two uniform Bragg gratings with finite dimensions. Various optical and physical properties are considered such as grating physical length, grating effective length which indicates the point where the light is effectively reflected, refractive index modulation of the grating, cavity length of the interferometer, attenuation and operating wavelength. Using this model, we are able to identify the regimes in which the PMMA based sensor offer enhanced stress sensitivity compared to silica based one. more...
- Published
- 2016
25. Annealing effects on strain and stress sensitivity of polymer optical fibre based sensors
- Author
-
Kalli, Kyriacos, Mendez, Alexis, Pospori, A., Marques, C.A.F., Zubel, M.G., Sáez-Rodríguez, D., Nielsen, K., Bang, O., Webb, D.J., Kalli, Kyriacos, Mendez, Alexis, Pospori, A., Marques, C.A.F., Zubel, M.G., Sáez-Rodríguez, D., Nielsen, K., Bang, O., and Webb, D.J. more...
- Abstract
The annealing effects on strain and stress sensitivity of polymer optical fibre Bragg grating sensors after their photo-inscription are investigated. PMMA optical fibre based Bragg grating sensors are first photo-inscribed and then they were placed into hot water for annealing. Strain, stress and force sensitivity measurements are taken before and after annealing. Parameters such as annealing time and annealing temperature are investigated. The change of the fibre diameter due to water absorption and the annealing process is also considered. The results show that annealing the polymer optical fibre tends to increase the strain, stress and force sensitivity of the photo-inscribed sensor. more...
- Published
- 2016
26. Passive and Portable Polymer Optical Fiber Cleaver
- Author
-
Universitat Politècnica de València. Departamento de Comunicaciones - Departament de Comunicacions, D. Sáez-Rodriguez, Min, Rui, Ortega Tamarit, Beatriz, Nielsen, K., Webb, D.J., Universitat Politècnica de València. Departamento de Comunicaciones - Departament de Comunicacions, D. Sáez-Rodriguez, Min, Rui, Ortega Tamarit, Beatriz, Nielsen, K., and Webb, D.J. more...
- Abstract
"(c) 2016 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works.", Polymer optical fiber (POF) is a growing technology in short distance telecommunication due to its flexibility, easy connectorization, and lower cost than the mostly deployed silica optical fiber technology. Microstructured POFs (mPOFs) have particular promising potential applications in the sensors and telecommunications field, and they could specially help to reduce losses in polymer fibers by using hollow-core fibers or reduce the modal dispersion by providing a large mode area endlessly single-mode. However, mPOFs are intrinsically more difficult to cut due to the cladding hole structure and it becomes necessary to have a high quality POF cleaver. In the well-known hot-blade cutting process, fiber and blade are heated, which requires electrical components and increases cost. A new method has recently been identified, allowing POF to be cut without the need for heating the blade and fiber, thus opening up the possibility of an electrically passive cleaver. In this letter, we describe the implementation and testing of a high quality cleaver based on a mechanical system formed by a constant force spring and a damper, which leads to the first reported electrical passive and portable cleaver. more...
- Published
- 2016
27. High performance liquid-level sensor based on mPOFBG for aircraft applications
- Author
-
Marques, C.A.F., Pospori, A., Sáez-Rodríguez, D., Nielsen, K., Bang, O., Webb, D.J., Marques, C.A.F., Pospori, A., Sáez-Rodríguez, D., Nielsen, K., Bang, O., and Webb, D.J.
- Abstract
A high performance liquid-level sensor based on microstructured polymer optical fiber Bragg grating (mPOFBG) array sensors is reported in detail. The sensor sensitivity is found to be 98pm/cm of liquid, enhanced by more than a factor of 9 compared to a reported silica fiber-based sensor. more...
- Published
- 2015
28. Comprehensive microRNA profiling in acetaminophen toxicity identifies novel circulating biomarkers for human liver and kidney injury
- Author
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Vliegenthart, A.D.B., Shaffer, J.M., Clarke, J.I., Peeters, L.E.J. (Laura), Carporali, A., Bateman, D.N., Wood, D.M., Dargan, P.I. (Paul), Craig, D.G., Moore, J.K., Thompson, A.I., Henderson, N.C., Webb, D.J., Sharkey, J., Antoine, D.J., Park, B.K., Bailey, M.A., Lader, E., Simpson, K.J., Dear, J.W., Vliegenthart, A.D.B., Shaffer, J.M., Clarke, J.I., Peeters, L.E.J. (Laura), Carporali, A., Bateman, D.N., Wood, D.M., Dargan, P.I. (Paul), Craig, D.G., Moore, J.K., Thompson, A.I., Henderson, N.C., Webb, D.J., Sharkey, J., Antoine, D.J., Park, B.K., Bailey, M.A., Lader, E., Simpson, K.J., and Dear, J.W. more...
- Abstract
Our objective was to identify microRNA (miRNA) biomarkers of drug-induced liver and kidney injury by profiling the circulating miRNome in patients with acetaminophen overdose. Plasma miRNAs were quantified in age- and sex-matched overdose patients with (N=27) and without (N=27) organ injury (APAP-TOX and APAP-no TOX, respectively). Classifier miRNAs were tested in a separate cohort (N=81). miRNA specificity was determined in non-acetaminophen liver injury and murine models. Sensitivity was tested by stratification of patients at hospital presentation (N=67). From 1809 miRNAs, 75 were 3-fold or more increased and 46 were 3-fold or more decreased with APAP-TOX. A 16 miRNA classifier model accurately diagnosed APAP-TOX in the test cohort. In humans, the miRNAs with the largest increase (miR-122-5p, miR-885-5p, miR-151a-3p) and the highest rank in the classifier model (miR-382-5p) accurately reported non-acetaminophen liver injury and were unaffected by kidney injury. miR-122-5p was more sensitive than ALT for reporting liver injury at hospital presentation, especially combined with miR-483-3p. A miRNA panel was associated with human kidney dysfunction. In mice, miR-122-5p, miR-151a-3p and miR-382-5p specifically reported APAP toxicity - being unaffected by drug-induced kidney injury. Profiling of acetaminophen toxicity identified multiple miRNAs that report acute liver injury and potential biomarkers of drug-induced kidney injury. more...
- Published
- 2015
- Full Text
- View/download PDF
29. Clinical Utility Of Optical Coherence Tomography (Oct) In High Cardiovascular Risk Patients
- Author
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Webb, D.J., primary, Balmforth, C., additional, Ruiys, T., additional, Dhaun, N., additional, Cameron, J., additional, Borooah, S., additional, Dhillon, B., additional, and Chandran, S., additional
- Published
- 2015
- Full Text
- View/download PDF
30. Uk Translational Medicine and Therapeutics (Tmat) Phd Training
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Webb, D.J., primary
- Published
- 2015
- Full Text
- View/download PDF
31. Annealing and etching effects on strain and stress sensitivity of polymer optical fibre Bragg grating sensors
- Author
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Pospori, A., Marques, C.A.F., Sáez-Rodríguez, D., Nielsen, K., Bang, O., Webb, D.J., Webb, David J., Scully, Patricia, and Sugden, Kate
- Subjects
genetic structures ,fungi ,technology, industry, and agriculture ,sense organs ,macromolecular substances - Abstract
Thermal annealing and chemical etching effects on the strain and stress sensitivity of polymer optical fibre based sensors are investigated. Bragg grating sensors have been photo-inscribed in PMMA optical fibre and their strain and stress sensitivity has been characterised before and after any annealing or etching process. The annealing and etching processes have been tried in different sequence in order to investigate their impact on the sensor’s performance. Results show with high confidence that fibre annealing can improve both strain and stress sensitivities. The fibre etching can also provide stress sensitivity enhancement, however the strain sensitivity changes seems to be random. more...
- Published
- 2016
32. Determination of the radial profile of the photoelastic coefficient of plastic optical fibers
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Acheroy, S., Geernaert, T., Ottevaere, H., Thienpont, H., Marques, C.A.F., Peng, G., Pawel, M., Berghmans, F., Webb, D.J., Webb, David J., Scully, Patricia, and Sugden, Kate
- Abstract
We developed a measurement method to determine the radial distribution of the photoelastic coefficient C(r) in step-index polymer optical fibers (POFs). The method is based on the measurement of the retardance profile of a transversally illuminated fiber for increasing tensile load. The radial profile C(r) is obtained from the inverse Abel transform of this retardance profile. We measured polymer fibers from different manufacturers. The radial profile of the photoelastic constant can considerable vary depending on the type and treatment of POFs, even when made from similar materials, which leads to the conclusion that the photoelastic constant should be characterized for each different type of POF. The impact of annealing the fiber samples on C(r) is also addressed. more...
- Published
- 2016
33. Portable polymer optical fibre cleaver
- Author
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Sáez-Rodríguez, David, Min, R., Ortega, B., Nielsen, K., Bang, O., Webb, D.J., Webb, David J., Scully, Patricia, and Sugden, Kate
- Abstract
Polymer optical fibre (POF) is a growing technology in short distance telecommunication due to its flexibility, easy connectorization, and lower cost than the mostly deployed silica optical fibre (SOF) technology. Microstructured POFs (mPOFs) have particular promising potential applica-tions in the sensors and telecommunications field, they could specially help to reduce losses in poly-mer fibres by using hollow-core fibres. However, mPOFs are intrinsically more difficult to cut due to the cladding hole structure and it becomes necessary to have a high quality polymer optical cleaver. In the well-known hot-blade cutting process, fibre and blade are heated, which requires electrical compo-nents and increases cost. A new method has recently been published to cut POF without the need for heating the blade/fibre, therefore electronically devices are not required if it is used a proper mechani-cal system. In this paper, we present a passive and portable polymer optical cleaver implemented with a mechanical system formed by a constant force spring and a damper. more...
- Published
- 2016
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