Glass optical fibers silica

The supports employed for covalent attachment of enzymes can be classified into two groups a) natural (agarose, dextran, cellulose, porous glass, silica, the optical fiber itself or alumina) and b) synthetic (acrylamide-... 

Silicon is the most important constituent of igneous and many sedimentary rocks, occurring in combination with oxygen in feldspars, micas, quartz, sands and shales. The element is used in electronic devices, while silicon in combination with oxygen as silica and silicates finds application in concrete, bricks, pottery, enamels, glasses, optical fibers for telecommunications, and refractory (high-temperature resistant) materials. 

Natural supports (agarose, dextran, cellulose, porous glass, silica, the optical fiber itself or alumina) and synthetic resins (acrylamide-based polymers, methacrylic acid-based polymers, maleic anhydride-based polymers, styrene-based polymers or nylon, to name a few) have been applied for covalent attachment of enzymes. These materials must display a high biocatalyst binding capacity (as the linearity and the limit of detection of the sensing layers will be influenced by this value), good mechanical and chemical stability, low cost, and ease of preparation. 

These challenges in fabrication have driven the development of sol-gel processing in pure silica. Several new methods that combine the low temperature processing afforded by working with nanometer sized particles with flexible silica chemistry (MacChesney, 1997 Wang, 2003 Yoon, 2003) have recently come to commercial fruition. This chapter describes the OFS Sol-Gel process used to make over 1(X) tons (MacChesney, 1998 Trevor, 2001) of dimensionally precise high piuity silica glass for fiber optic preform jackets. 

FIGURE 6.7 Vapor axial deposition (VAD) process for synthetic fused silica. (From Optical Fiber Waveguides by R. M. Klein in Glass Science and Technology, Vol. 2, Processing, edited by D. R. Uhlmann and N. J. Kreidl, copyright 1983 by Academic Press, reproduced by permission of the publisher.)... 

There are four principal processes that may be used to manufacture the glass body that is drawn into today s optical fiber. "Outside" processes—outside vapor-phase oxidation and vertical axial deposition— produce layered deposits, of doped silica by varying the concentration of SiCl4 and dopants passing through a torch. The resulting "soot" of doped silica is deposited and partially sintered to form a porous silica boule. Next, the boule is sintered to a pore-free glass rod of exquisite purity and transparency. 

Kirkbir F., Chaudhuri R., Optical fibers from sol-gel-derived germania-silica glasses, SPIE Proc. 1758, 160-172, (1992). 

Figure 12.8. Transmission characteristics of some commonly used optical fibers, (a) glass fiber (b) gradient-index fiber (c) plastic-clad silica fiber (d) plastic fiber. (Reproduced with permission from the Ealing Corporation.)...

The entire spectrum of inorganic fibers can be divided into two classes, based on differences in the crystallinity of the solids (Ray, 1978). Synthetic fibers have been known as man-made mineral fibers (MMMF) and manmade vitreous fibers (MMVF). But fibrous materials can be approached or divided in other ways. For example, in the Concise Encyclopedia of Chemical Technology (1985) the entry for chemical fibers includes both manmade and natural polymers, with the discussion centering on carbon-based compounds such as acetates, acrylics, and cellulose. Fibers of other inorganic compounds were not mentioned in the encyclopedia under this entry, but silica glass fibers were described under the heading Optical Fibers. ... 

Optical fibers are widely used in the telecommunication industry for fhe fransmission of digital pulses of voice, video, and dafa. In order to keep losses in signal strength at a minimum, the fiber (usually a doped silica glass) has to be coated with a material of lower refractive index than its own refractive index. This layer is protected by a "buffer," which acts as a cushion. The buffer is encased in one or more protective layers (see Figure 7.18). Both the primary and protective coatings are very often UV radiation curable. 

In January 1992. E. Desurvire (Columbia University Center for Telecommunications Research) reported that optical fibers made from silica glass and traces of erbium can amplify light signals when they are energized by infrared radiation. Desurvire developed an efficient radiation source (referred (o as a laser diode chip) that, when integrated into a fiber optic communication system, can increase transmission capacity by a factor of 10(1. 

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