Fibre-coated sensors

So the function of special optical fibres for sensing is to produce a sensitive response to changes in the fibre surroundings. Such requirements on optical hardware as durability to the analyte, transparency (i.e. minimum optical losses) in a wide spectral range and common availability should be pointed out. Related to the these requirements, the choice of the fibre material as well as of the fibre coating and fibre structure belong to fundamental tasks in the design of fibre-optic sensors. 

James, S. W. Tatarn, R. P., Fibre optic sensors with nano structured coatings, J. Opt. A 2006, 8, S430 S444... 

Butler MA (1994) Micromirror optical-fibre hydrogen sensor. Sens Actuators B 22 142-145 Butler MA, Ginley DS (1988) Hydrogen sensing with palladium coated optical fibers. J Appl Phys 64(7) 3706-3712 Butler MA, Sanchez R, DulleckGR (1996) Fiberoptic hydrogen sensor. Sandia report SAND-96-1133. Sandia National Labs, Albuquerque, NM... 

Temperature assessment performed by fibre-based sensors can be implemented also by optical technology. One of the promising approaches is coating of FBG fibres with thermo-sensitive substances such as a mixture of methyl ethyl ketone peroxide and cobalt naphthenate. Optical estimation of temperature measurements ensures high accuracy of the results, but the functional coating enhances the performance of the sensor (Li et al., 2012). 

The development of new and novel sensors, including fibre optic sensors, piezoelectric sensors, chemical sensors, and sensitive textile fibres (coatings) ... 

Optical enzyme sensors are designed preferably as extrinsic sensors, i.e. as op-todes. There are, however, some examples of intrinsic sensors. As an example, an optical fibre has been described which was manufactured on the basis of a polystyrene fibre coated with adsorbed enzyme and indicator molecules. The colour changes brought about by the enzymatic reaction was detected using the evanescent field. 

The preparation of a coated special fibre from a suitable material in a proper structure and the source and detector choice are not the final list of problems to be solved in the framework of sensor design. From Figure 3 it... 

Consequently, mirror optics are more common, in particular in the mid-IR. The mirrors used are usually aluminium- or gold-coated flat or curved substrates. While near-IR mirrors are usually protected by thin SiO-layers, in the mid-IR unprotected mirrors have to be used. Disadvantages of mirror optics are the elevated space consumption and the higher prices in comparison to refractive optics, especially comparing non-standard mirrors against non-standard lens. In total, mirror optics are so preferable to fibres and refractive optics, at least in the mid-IR, that in some technical applications they are used to replace waveguides to transport IR radiation between source, sensor head and spectrometer. 

The fabrication and characterization of a fiber optic pH sensor based on evanescent wave absorption was presented by Lee63. The unclad portion of a multi-mode optical fibre was coated with the sol-gel doped with pH sensitive dye. The sensitivity of the device increased when the multiple sol-gel coatings were used in the sensing region. The dynamic range and the temporal response of the sensor were investigated for two different dyes -bromocresol purple and bromocresol green. 

Lee S., Gin J., Nampoori V., Vallabhan C., Unnikrishnan N., Radhakrishnan P., A sensitive fibre optic pH sensor using multiple sol-gel coatings, Journal of Optics A Pure and Applied Optics 2003 3 355-359. 

Villatoro, J., Diez, A., Cruz, J.L. and Andres, M.V., Highly sensitive optical hydrogen sensor using circular Pd-coated single mode tapered fibre, Electron, 37,1011, 2001. 

The nonlinear optical and dielectric properties of polymers find increasing use in devices, such as cladding and coatings for optical fibres, piezoelectric and optical fibre sensors, frequency doublers, and thin films for integrated optics applications. It is therefore important to understand the dielectric, optical and mechanical response of polymeric materials to optimize their usage. The parameters that are important to evaluate these properties of polymers are their dipole moment polarizability a, hyperpolarizabilities 0... 

PS2 activity measurements were done with an oxygen sensor consisting of a polymer optical fibre (POF) coated with an oxygen-sensitive foil (Presens, Regensburg, Germany) as specified in [Nowaczyk et al., in this book]. 

Optics und hence guided wave velocity can be controlled with great precision acceptable attenuation loss. Possible uses in conventional optics and optical data storage, pboiochromic and ablative systems. Optical sensors e g. based on coated fibres. 

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