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Silica Fibers

Definition: optical fibers based on fused silica or related materials

German: Quarzglasfasern

Categories: fiber optics and waveguides, optical materials

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Optical fibers are long and flexible kinds of optical waveguides. They are essentially always based either on some glass or on polymers (plastic optical fibers). Among the glasses, fused silica (amorphous silicon dioxide, SiO2) is the strongly dominating material in fiber optics (particularly for optical fiber communications, → telecom fibers), because it has a number of very favorable properties:

intrinsic losses of silica
Figure 1: Intrinsic losses of silica. At long wavelengths, infrared absorption related to multiphonon absorption (vibrational resonances) is dominating. At shorter wavelengths, Rayleigh scattering at the unavoidable density fluctuations of the glass is more important. There is a loss minimum of ≈ 0.2 dB/km around 1.55 μm. Some telecom fibers nearly reach that level. If the fiber contains hydroxyl (OH) ions, additional peaks at 1.39 μm and 1.24 μm can be seen in the loss spectrum.

Silica fibers dominate many applications, such as optical fiber communications (except for very short distances with plastic optical fiber), most fiber lasers and amplifiers, and fiber-optic sensors. The large efforts which have been invested in the development of various kinds of silica fibers have further increased the performance advantages of such fibers over fibers based on other materials (see below).

There are also pure silica fibers in the form of photonic crystal fibers, containing tiny air holes. Here, the guidance (waveguide function) is achieved either by a reduced effective index of the cladding (caused by a larger fraction of air) or by a photonic bandgap effect.

For special applications, certain non-silica fibers are required:

Bibliography

[1]W. A. Gambling, “The rise and rise of optical fibers”, IEEE J. Sel. Top. Quantum Electron. 6 (6), 1084 (2000)

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See also: fibers, telecom fibers, rare-earth-doped fibers, fiber optics, photodarkening, photonic crystal fibers, optical fiber communications, fluoride fibers
and other articles in the categories fiber optics and waveguides, optical materials

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