Optical Properties of Fibers

When light encounters a fiber, it is either transmitted, reflected or absorbed, depending on the structure of the fiber and the wavelength of the light. The transmission, reflection and absorption of light determine the visual appearance of an individual fiber. The appearance of fiber assembles then is the result of the combined effects of individual fibers, and also is affected by the arrangements of fibers. In addition, optical properties of fibers provide a conveiuent measure of many strac-tural characteristics, especially the molecular orientation. Theoretical treatment of optical properties of fibers is complex. This chapter discusses the practical aspects of the optical properties of fibers. 

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Optical Properties. When light falls on an object, it is either partially absorbed, reflected, or transmitted. The behavior of the object as it relates to each of these three possibiUties determines visual appearance. Optical properties of fibers give useful information about the fiber stmcture refractive indexes correlate well with fiber crystalline and molecular orientation and birefringence gives a measure of the degree of anisotropy of the fiber. 

Optical properties of fibers are measured by light microscopy methods. ASTM D276 describes the procedure for fiber identification using refractive indexes and birefringence. Other methods for determining fiber optical properties have been discussed (3,38—44). However, different methods of determining optical properties may give different results (42). 

Tones of dyed fabrics, composed of a color development,color brightness, and color depth are related to optical properties of fibers. The larger... 

When the light falls on a fiber, part of the light is reflected. The amount of light reflected and how it is reflected are important optical properties of fibers. The amount of light reflected can be estimated by ... 

Hamza, A. A., A Contribution to the Study of Optical Properties of Fibers with Irregular Transverse Sections , Textile Research Journal, 50,731-734, 1980. 

Optics. Good optical properties and low thermal resistance make poly(methyl methacrylate) polymers well suited for use as plastic optical fibers. The manufacturing methods and optical properties of the fibers have been reviewed (124) (see Fiber optics). Methods for the preparation of Fresnel lenses and a Fresnel lens film have been reported (125,126). Compositions and methods for the industrial production of cast plastic eyeglass lenses are available (127). 

Possible future applications of up-converting phosphors include (i) three-dimensional displays 249-251 (ii) fiber optic amplifiers (referred to above) that operate at 1.55, 1.46, and 1.31 pm,, 2 1-255 (iii) up-conversion lasers 250 and (iv) remote sensing thermometers for high-temperature applications (utilizing the temperature dependence of optical properties of, for example, cubic Y203 Er3+).256-258... 

Shalem S., German A., Barkay N., Moser F., Katzir A., Mechanical and optical properties of silver-halide infrared transmitting fibres, Fiber and integrated optics 1997 16 27-54. 

Optical fiber sensors that use enzymes can operate in the direct or indirect detection mode. In the first case, the optical properties of the reactives, intermediates or products of the biocatalyzed reaction can be monitored using the optical fibers. In the second type, an optochemical transducer generates the optical changes. 

The optical properties of low density, carbon fiber-carbon binder composites have... 

Experiments using the DCC approach aimed at the discovery of improved phosphor materials have also been described. [9] In this case, samples are evaluated optically, an approach well suited to direct comparisons of large numbers of samples, although it is somewhat difficult to compare the results to the optical properties of bulk materials. Further spectroscopic evaluations of individual elements of the sample array are also easily accomplished by a variety of approaches including scanning fiber techniques. One concern in studies of phosphors is the sensitivity of the optical behavior including fluorescence intensity to processing effects such as details of the microstructure or surface preparation. 

Abstract This chapter reviews the development of optical fiber probe Raman systems and their applications in life science and pharmaceutical studies. Especially, it is focused on miniaturized Raman probes which open new era in the spectroscopy of the life forms. The chapter also introduces the important optical properties of conventional optical fibers to use for Raman probes, as well as new types of optical fiber and devices, such as hollow optical fibers and photonic crystai fibers. 

High quality optical fibers obtained using the PCVD method demonstrate that the plasma activated deposition fulfills the extreme requirements for optical fibers almost ideally. This is underlined by the optical properties of a large number of fibers prepared under the same PCVD conditions on a pilot plant scale which show a narrow distribution in their attenuation and pulse broadening values. This in turn is directly correlated with the good process control which is achievable. 

The Kubelka-Munk theory of diffuse reflectance is a good description of the optical properties of paper. The two parameters of the theory, absorption and scattering coefficient, are purely phenomenological, but are closely related to basic properties of paper. The absorption coefficient is approximately a linear function of the chrcmgphore concentration in the paper. The scattering coefficient is related to the nonbonded fiber surface area in the paper, or the area "not in optical contact," and the Fresnel reflectivity of that surface. 

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