Optical Sensors Fiber Optics

Sometimes it is desirable to obtain absolute spectra of a fluorescing compound to calculate quantum efficiencies for different transitions. This would require point-by-point correction for variations in the recorded signal due to variations in the instrumental parameters. Commercial instruments are available that will provide corrected spectra. These adjust for variation in the source intensity with wavelength, so the sample is irradiated with constant energy, and they also correct for variations of the detector response. The recorded emission spectrum is presented directly in quanta of photons emitted per unit bandwidth. 

In a spectrofluorometer, the filters are replaced with scanning monochromators. Either the excitation spectrum (similar to the absorbance spectram) or the emission spectrum may be recorded. 

Fiber-optic cables allow the sample to be far removed from the spectrometer. 

Manufacturers typically provide numerical aperture data for different fibers. Another property usually provided is the hght loss per unit length for different wavelengths. A spectral curve is given that shows attenuation versus wavelength. Attenuation is usually expressed in decibels per kilometer (dB/km), and is given by 

With bifurcated cables, one is used to transmit the source radiation and the other is used to receive the absorbed or fluorescent radiation. 

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Photodiode (LED) Pin photodiode Cameras, strobes, illuminators, remote controls, IR sensors Fiber-optic communications, liber links... 

Embedded sensors Fiber optic sensors H2O, H2, 02, Signal is unaffected by electric fields, should minimally affect cell performance Currently an immature technology... 

Acetylcholineesterase A 350 pM diameter coherent imaging fiber coated on the distal surface with a planar layer of analyte-sensitive polymer that was thin enough not to affect the fiber s imaging capabilities. It was applied to a pH sensor array and an ACh biosensor array (each contain 6000 optical sensor). Fibers were coated with an immobilized layer of poly (hydroxyethylmethacrylate)-N-flurosceinylacrylamide and AChE-fluorescein isothiocyanate isomer poly (acryloamide-co-N-acryl oxysuccinimide), respectively. The response time of the pH sensor was 2 s for a 0.5 unit increase in pH. The biosensor had a detection limit of 35 pM ACh and a linear response in the range 0.1 mM. [90]... 

As a means of incorporating the fiber sensors into systems, incorporation of in-line fiber sensors into non-woven fabrics was explored. In order to incorporate an in-line sensor into a textile fabric, a spun-bonded base fabric was taken and an in-line fiber sensor was placed on top of it. Subsequently, non-woven fibers of polyurethane were electrospun on top of the optical fiber sensor to hold the sensor fiber in its position, thereby incorporating it in a non-woven fabric matrix. The electro-spinning was carried out at a voltage of 18 KV using a solution of polyurethane in the solvent DMP. 

Macedo PB, Barkatt A, Feng X, Finger SM, Hojaji H, Laberge N, Mohr R, Penafiel M, Saad E (1989) Development of porous glass fiber sensors, Fiber optic structures and smart skins. Proc SPIE 986 200-205... 

Leiner M J P and Wolfbeis O S 1991 Fiber optic pH sensors Fiber Optic Chemical Sensors and Biosensors vol 1, ed O S Wolfbeis (Boca Raton, FL Chemical Rubber Company) pp 359-84 Jackson J T and Hui H K 1993 US Patent 5 212092... 

Nelson A, Hui H K, Bennett M, Hahn S and Bankert C S 1993 US Patent 5 204 265 Wolfbeis O S 1991 Oxygen sensors Fiber Optic Chemical Sensors and Biosensors vol 2, ed O S Wolfbeis (Boca Raton, FL Chemical Rubber Company) pp 19-53 Hauenstein B L, Picemo R, Brittain H J and Nestor J A 1993 US Patent 5 190729 Modlin D N and Milanovitch F P 1991 Instrumentation for fiber optic chemical sensors Fiber Optic Chemical Sensors and Biosensors vol 1, ed O S Wolfbeis (Boca Raton, FL Chemical Rubber Company) pp 237-302 Wolthuis R, McCrae D and Hartl I C et al 1992 Development of a medical fiber optic oxygen sensor based on optical absorption change Trans. IEEE Eng. Biol. Med. EBM-39 185-93... 

Photoelectric sensors commonly used in die protection include opposedmode sensors, fiber-optic sensors, convergent photosensors, diffuse reflective sensors, and minilight curtains. Diffuse reflective sensors and minilight curtains are typically used only for part ejection detection and are covered in a later section. 

Pyruvate Corn kernei Pyruvate decarboxyiase CO2 gas sensor, fiber-optic CO2 sensor... 

Parameters to be varied by the measurand are the intensity, the wavelength or phase, and the polarization state of light. Additionally used is, by means of optical time-domain reflectometry (OTDR) technique, the measurement of the travel-time of a light pulse launched at one fiber end and backre-flected at markers. From measurement of the time of transit, the shortening or extension of the optical path length (contraction or extension of the sensor fiber) can be assessed. However, any effects influencing the fiber can be located. It should be noted that a considerable number of fiber optic sensor types has been created in the past decades for measurement of almost all physical, and a lot of chemical, quantities. 

Fiber-Optic Fluorescence Sensors Fiber-optic probes have been used to demonstrate that several fluorescence determinations can be carried out at various locations well awav from a source and a... 

Compared to the conventional mechanical and electrical/electronic humidity sensors, fiber-optic based humidity sensors [6, 14], including silica glass fiber and polymer optical fiber (POP) based sensors [28, 46], demonstrate many unique advantages, such as small size and low weight, immunity to electromagnetic interference, corrosion resistance, potentials for remote operation and distributed sensing. In fiber-optic sensor family, the fiber grating... 

The fitud category to be rfiscuased n a general one which will be denoted measurement instrumentation. Included within this is accelerometers, strain and stress gauges, acoustic emission sensors, fiber optic phase nwdulators. gas emission detectors, and external pressure field flow detection by use of surfsce acoustic wave (SAW) ferroelectric polymer transducer configurations. 

PVDF is useful for a variety of measurement instruments iitcluding acceletometers, stress gauges, strain gauges, shock gauges, turbulence sensors, fiber optic phase modulators. 

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