Short optical fibers

Chen, YC. (1980) Noise characteristics of semiconductor laser diode coupled to short optical fibers. Appl. Phys. Lett, 37 (7), 587 - 589. 

However, optical fiber communications are not useful only for long-distance communication links. Fiber-optic data links are also used in a variety of short-distance systems, for example in computer—computer links and for internal communications on ships and aircraft. Figure 16 shows some possible appHcations for fiber-optic communications, with respect to length and bit rate. The common carrier appHcations, like telephone links. He to the upper right of the dashed line labeled 100 MHzkm. However, a wide variety of other lower performance appHcations, illustrated to the lower left of the dashed line, are in use or under development. 

The direct melt process economically produces thick optical fibers (250-400 pm in diam.), which is advantageous, but their relatively high attenuation (3-20 dB/km) due to impurities is not. As a result, they are limited to short distance multimode applications. 

In LIBS analysis, a pulsed laser is focused on the gem surface. The laser energy ablates a small amount of gem material which burns in a short-lived plasma. As the plasma cools, excited electrons decay into lower-energy orbitals, releasing energy in the form of photons in the ultraviolet-visible-infrared range. This light is collected by optic fiber, diffracted, and recorded as a spectrum, generally between 200 and 1000 nm. 

The second possibility is to make use of the continuous evanescent field that exists at the surface of an optical fiber. The cladding layer is replaced by a layer containing the fluorescent molecular sensor in a short portion of the optical fiber (Figure 10.45). At each reflection at the surface of the fiber core, the eva-... 

A phenytoin energy transfer immunosensor has been reported that is reversible and direct, in which macromolecular reagents are retained within a short length of 200-/dialysis tubing cemented to the end of an optical fiber (Figure 14.18).018 119)A... 

By inserting either an interference filter or a colored filter, it is possible to select a more or less extended region of the spectrum likewise, by adding an optical fiber it is possible to direct the beam where desired. This set-up best exploits the characteristics of these powerful lamps, and offers an excellent choice for the irradiation of small surfaces. Consequently, spectrophotometric cuvettes or cylindrical cuvettes are used for the irradiation, which involves small volumes. Such restrictions, as well as the high price and short lifetime of the lamp and its accessories, favors the use of these arcs for kinetics studies and quantum yield measurements, rather than for preparative photochemistry. 

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