Browsing by Author "Tatam, Ralph P."

Browsing by Author "Tatam, Ralph P."

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  • Optical gas sensing: a review 
    Hodgkinson, Jane; Tatam, Ralph P. (Iop Publishing Ltd, 2013-01-31)
    The detection and measurement of gas concentrations using the characteristic optical absorption of the gas species is important for both understanding and monitoring a variety of phenomena from industrial processes to ...
  • Optical Gas Sensor Fabrication Based on Porphyrin-Anchored Electrostatic Self-Assembly onto Tapered Optical Fibers 
    Jarzebinska, Renata; Korposh, Sergiy; James, Stephen W.; Batty, William J.; Tatam, Ralph P.; Lee, Seung-Woo (Taylor & Francis, 2012-07-31)
    Tapered optical fibers with nano-assembled coatings of thicknesses of order tens of nanometres were used for the detection of ammonia gas. The film coating was composed of alternate layers of tetrakis-(4-sulfophenyl) ...
  • Optimised process for fabricating tapered long period gratings 
    Mullaney, Kevin; Staines, Stephen; James, Stephen; Tatam, Ralph P. (SPIE, 2017-04-23)
    The process of fabricating tapered long period gratings (TLPGs) using a CO2 laser is described. TLPGs with a period spacing of 378 μm, were fabricated by optimization of the taper waist diameter and careful control of the ...
  • Optoelectronic speckle shearing interferometry 
    Huang, Jen-Rong (1996-04)
    This thesis describes the implementation of enhanced signal processing techniques in electronic speckle shearing interferometry, including two-wavelength slope measurement, phase stepping, and heterodyning and stroboscopic ...
  • Overwrite fabrication and tuning of long period gratings 
    Partridge, Matthew; James, Stephen W.; Barrington, James; Tatam, Ralph P. (Optical Society of America: Open Access Journals / Optical Society of America (OSA), 2016-09-19)
    The central wavelengths of the resonance bands are critical aspect of the performance of long period gratings (LPGs) as sensors, particularly for devices designed to operate near the phase matching turning point (PMTP), ...
  • Passive OCT probe head for 3D duct inspection 
    Ford, Helen D.; Tatam, Ralph P. (Iop Publishing Ltd, 2013-07-24)
    A passive, endoscopic optical coherence tomography (OCT) probe has been demonstrated, incorporating an imaging fibre bundle and 45° conical mirror, and with no electromechanical components at the probe tip. Circular scanning, ...
  • Passive signal processing techniques for miniature fibre fabry-perot interferometric sensors 
    Ezbiri, A (Cranfield University, 1996-03)
    This thesis describes new signal processing techniques applicable to miniature low finesse Fabry-Perot interferometric sensors. The principle of operation behind the techniques presented resides in the use of the axial ...
  • Passively-coupled, low-coherence interferometric duct profiling with an astigmatism-corrected conical mirror 
    Ford, Helen D.; Tatam, Ralph P. (Optical Society of America, 2017-04-06)
    Duct-profiling in test samples up to 25 mm in diameter has been demonstrated using a passive, low-coherence probe head with a depth resolution of 7.8 μm, incorporating an optical-fibre-linked conical mirror addressed by ...
  • Pathlength calibration of integrating sphere based gas cells 
    Bergin, Sarah (Cranfield University, 2016)
    Integrating sphere based multipass cells, unlike typical multipass cells, have an optically rough reflective surface, which produces multiple diffuse reflections of varying lengths. This has significant advantages, including ...
  • Performance and analysis of feature tracking approaches in laser speckle instrumentation 
    Charrett, Thomas O. H.; Tatam, Ralph P. (MDPI, 2019-05-24)
    This paper investigates the application of feature tracking algorithms as an alternative data processing method for laser speckle instrumentation. The approach is capable of determining both the speckle pattern translation ...
  • pH sensor using Langmuir-Blodgett overlays on polished optical fibers 
    Flannery, D.; James, Stephen W.; Tatam, Ralph P.; Ashwell, Geoffrey J. (Optical Society of America, 1997-04-15)
    Evanescent coupling between a side-polished single-mode optical fiber and a single-mode, pH-sensitive Langmuir-Blodgett overlay is used to demonstrate an intrinsic fiber-optic pH sensor. The sensor shows a wavelength ...
  • Photorefractive Volume Holographic Demodulation of In-Fiber Bragg Grating Sensors 
    James, Stephen W.; Dockney, Michael L.; Tatam, Ralph P. (IEEE Institute of Electrical and Electronics, 1996-05-05)
    A demodulation scheme for an in-fiber Bragg grating sensor using a volume holographic filter formed in photorefractive BaTiO3 is proposed and demonstrated. A strain range of 2500 μstrain, with minimum detectable strain ...
  • Planar Doppler velocimetry measurements of flows using imaging fibre bundles 
    Nobes, David S.; Ford, Helen D.; Tatam, Ralph P. (SPIE - International Society for Optics and Photonics, 2003-08-03)
    The development of a planar Doppler velocimetry is described. The technique is capable of measuring the three, instantaneous components of velocity in two dimensions using a single pair of signal and reference cameras. ...
  • A polarisation maintaining fibre Bragg grating interrogation system for multi- axis strain sensing 
    Ye, Chen-Chun; Staines, Stephen E.; James, Stephen W.; Tatam, Ralph P. (International Society for Optical Engineering; 1999, 2002-12-31)
    Fibre Bragg gratings (FBGs) written into polarisation maintaining (PM) fibres have been employed for multi-axis strain and temperature sensing. In this paper we report the development of a FBG interrogation system that ...
  • Polarization-sensitive transfer matrix modeling for displacement measuring interferometry 
    Bridges, Angus; Yacoot, Andrew; Kissinger, Thomas; Tatam, Ralph P. (Optical Society of America, 2020-09-01)
    The use of polarizing optics for both beam steering and phase measurement applications in displacement measuring interferometer designs is almost universal. Interferometer designs that employ polarizing optics in this ...
  • Production process monitoring and post-production strain measurement on a full-size carbon-fibre composite aircraft tail cone assembly using embedded optical fibre sensors 
    Chehura, Edmon; James, Stephen W.; Staines, Stephen; Groenendijk, Chris; Cartié, Denis; Portet, Stephanie; Hugon, Michael; Tatam, Ralph P. (IOP, 2020-07-13)
    Multiplexed optical fibre sensors were embedded into a carbon-fibre-reinforced-preform during the industrial production of a full-sized, one-piece tail cone assembly for a regional jet aircraft. Optical fibre Fresnel sensors ...
  • Properties of length-apodized phase-shifted lpgs operating at the phase matching turning point 
    James, Stephen W.; Topliss, Stephen M.; Tatam, Ralph P. (IEEE Institute of Electrical and Electronics, 2012-07-01)
    The characteristics of length-apodized phase-shifted fiber optic long period gratings with full and partial nanostructured coatings have been explored theoretically and experimentally. The twin rejection bands that ...
  • Pseudo-heterodyne signal processing scheme for interrogation of fiber Bragg grating sensor arrays 
    Chatterjea, C. K.; James, Stephen W.; Tatam, Ralph P. (International Society for Optical Engineering; 1999, 1998-12-31)
    An intensity-based interrogation technique for arrays of fiber bragg grating (FBG) sensors is reported. The technique is based upon each FBG forming one mirror of a Michelson interferometer. Source wavelength modulation ...
  • Quantitative shearography: error reduction by using more than three measurement channels 
    Charrett, Thomas O. H.; Francis, Daniel; Tatam, Ralph P. (Osa Optical Society of America, 2011-01-05)
    Shearography is a noncontact optical technique used to measure surface displacement derivatives. Full surface strain characterization can be achieved using shearography configurations employing at least three measurement ...
  • Quantum cascade laser light propagation through hollow silica waveguides 
    Francis, D.; Hodgkinson, Jane; Livingstone, B.; Tatam, Ralph P. (Springer Verlag, 2015-04-03)
    In this paper, the transmission characteristics of hollow silica waveguides with bore diameters of 300 and 1000 μm are investigated using a 7.8-μm quantum cascade laser system. We show that the bore diameter, coiling and ...