Fiber-optic sensor

Optical biosensors typically consist of an optical fiber which is coated with the indicator chemistry for the material of interest at the distal tip (Fig. 22). The quantity or concentration is derived from the intensity of absorbed, reflected, scattered, or re-emitted electromagnetic radiation (e.g. fluorescence, bio- and chemiluminescence). Usually, enzymatic reactions are exploited, e.g. [463]. 

The best sensor option is an intrinsically safe fiber-optic photonic sensor system, either infrared or visible spectrum. 

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Elosua, C., Bariain, C., Matias, I.R., Arregui, F.J., Luquin, A., Vergara, E. and Laguna, M. (2008) Indicator immobilization on Fahry-Perot nanocavities towards development of fiber optic sensors. Sensor and actuators B, 130, 158-163. 

Capacitance or conductance measurement This method is applied where the working fluid acts as a capacitive or conductive element in a circuit (Jones et al., 1981). Use of fiber optics sensors has been developed recently (Moujaes and Dougall, 1987, 1990). These methods are used to measure film thickness in annular flow. Further discussion appears in Section 3.3.4.4. For other regimes, the use of the electrical impedience imaging method has also been introduced (Lin et al., 1991). 

Resonant photoacoustic gas spectrometry was adapted to fiber optic sensor technology32 as early as in 1984. A Mach-Zehnder arrangement was combined with a resonant photoacoustic cell for gap analysis. The pollutant gas NO2 was detectable in a concentration of 0.5 ppm. In a smart optical fiber hydrogen sensor, the fiber is coated with palladium metal which expands on exposure to hydrogen. This changes the effective optical path length of the fiber, which is detected by interferometry33. 

Hesse 1974 first fiber optic sensor also measures decay time... 

Kopelman et al.73 have prepared fiber optic sensors that are selective for nitric oxide and do not respond to most potential interferents. Both micro-and nanosensors have been prepared, and their response is fast (<1 s), reversible, and linear up to 1 mM concentrations of nitric oxide. The respective "chemistry" at the fiber tip was contacted with the sample, light was guided to the sample through the microfiber, and emitted light was collected by a microscope (without the use of fibers, however). 

Petersons pH probe also was modified in order to give a miniature fiber optic sensor potentially suitable for glucose measurements90. Kopelman et al.91 developed a fiber-optic pH nanosensor for physiological measurements using a dual-emission sensitive dye. The performance of a pH sensor was reported92. An unclad fiber was dip-coated with a thin layer of porous cladding within which a pH-sensitive dye was entrapped. The fundamental... 

A novel fiber optic sensor concept using antibody-antigen reactions at a glass-liquid interface was reported by Daehne146. The reaction of antibodies immobilized onto the surface of fused silica fiber optic or planar waveguides with antigens in solution was detected by interaction with the evanescent wave. By detecting in-line fluorescence, the measurement of human IgG is described. 

Table 4 below summarizes the commercial fiber optical sensors that have come to our attention. 

Ivanov V.N., Ivanov S.V., Kel baHkhanov B.F., Klimova L.G., Trubnikov B.N., Chemyi V.V., Elisashvili D.T., Measurement of temperature and salinity variations of water with a fiber-optical sensor, Fizika Atmosfery i Okeana 1985 21 555. 

Munkholm C., Walt D.R., Milanovich F.P., A fiber-optic sensor for carbon dioxide... 

Kawabata Y., Kamichika T., Imasaka T., Ishibashi N., Fiber-optic sensor for carbon dioxide with a pH indicator dispersed in a poly(ethylene glycol) membrane, Anal. Chim. Acta 1989 219 223. 

Arnold M.A., Enzyme-based fiber optic sensor, Anal. Chem. 1985 57 (2) 565. 

Daehne C., Sutherland R.M., Place J.F., Ringrose A.S., Detection of antibody-antigen reactions at a glass-liquid interface a novel fiber-optic sensor concept, Proc. SPIE-Int. Soc.Opt. Eng. 1984 514 75. 

Gautier S., Blum L.J., Coulet P.R., Alternate determination of ATP and NADH with a single bioluminescence-based fiber-optic sensor, Sensor Actuat B-Chem 1990 1 580. 

Peterson J.I., Vurek G.G., Fiber-optic sensors for biomedical applications, Science 1984 224 123. 

There are several works published on pH sensors based on energy transfer. Jordan and Walt developed a single-fiber optic sensor based on... 

Figure 4. Luminescence decay profile of an oxygen indicator dye excited by a short flash of light, in (a) solution and (b) embedded into a gas-permeable film used to fabricate fiber-optic sensors for such species. The logarithmic scale of the Y-axis allows to compare the exponential emission decay in homogeneous solution and the strongly non-exponential profile of the photoexcited dye after immobilization in a polymer matrix.

Krska R., Kellner R., Schiessl U., Tacke M. and Katzir, Fiber optic sensor for chlorinated hydrocarbons in water based on infrared fibers and tunable diode lasers, Appl. Phys. Lett., 1993 63 (14), 1868-1871 A. 

Slavik R., Homola J., Ctyroky J., Novel spectral fiber optic sensor based on surface plasmon resonance, Sensors and Actuators B 2001 74 106 - 111. 

Optical transduction modes applied in combination with enzyme based fiber-optic sensors include absorbance, reflectance, fluorescence,... 

Figure 8. Examples of enzyme-based fiber-optic sensor designs. Adapted from refs, a) 43 b) 44 c) 45 d) 46 e) 47 f) 48.

To monitor the brain tissue, the fiber optic sensor based on the immobilization of a pH-sensitive dye, seminaphthorhodamine-1 carboxylate (SNARF-1C), was designed66. The dye-doped sol-gel was deposited onto the end of a 12 pm-diameter silica optical fiber and in vivo studies were performed. 

Identical olfactory neurons are located in different places in the cavity, and therefore occupy different positions in the flow path. By using a nasal cavity model, we investigated the influence of the dynamic flow on the sensors response14. The responses from identical fiber optic sensors located... 

Grant S.A., Glass S.R., A sol-gel based fiber optic sensor for local blood pH measurements, Sensors andActuat. B 1997 45 35. 

Stefansson E., Peterson J.I., Wang Y.H., Intraocular oxygen tension measured with a fiber optic sensor in normal and diabetic dogs, Am. J. Phys. 1989 256 HI 127. 

For leak detection, the sensor must be sensitive and fast enough to provide early leak detection so that action can be taken before the explosive limit in air is reached. Utilizing a fiber-optic sensor configuration could provide the best chance of meeting fast response and inexpensive and reliable goals. 

Figure 10.19 is an example that illustrates the Brillouin fiber-optic sensor system that could be applied to pipelines for integrity monitoring [39]. 

Tennyson, R.C., Morison, D., Colpitts, B., and Brownn, A. Application of Brillouin fiber optic sensors to monitor pipeline integrity IPC2004, Paper 0711, Calgary, October 2004. 

Butler, M.A., Fiber optic sensor for hydrogen concentrations near the explosive limit, Journal of Electrochemical Society, 46(138), L46,1991. 

Fig. 1.98. Schema of the fiber-optic sensor to measure the residual moisture content (RM) through the bottom of the container with the product.

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