Ch5Sec3 - THE FIBER FORUM Fiber Optic Communications...

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THE FIBER FORUM Fiber Optic Communications JOSEPH C. PALAIS PRESENTED BY
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Joseph C. Palais 5.3 2 Section 5.3 Attenuation If a signal reaches the receiver with very low power, it cannot be detected, the information may not be clear, or transmission errors will occur. Therefore, it is essential that the loss in the fiber be as low as possible.
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Joseph C. Palais 5.3 3 ATTENUATION 5.3.1 Glass Fused silica (SiO 2 ) powder, or fused vapors containing Si and O. Silica glass consist of molecules of SiO 2 located randomly in the material. To vary the refractive index, the glass is doped with other atoms. For example: germanium (raises the index), boron, and others. Low loss requires high chemical purity.
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Joseph C. Palais 5.3 4 Glass Losses may be classified as: Absorption Scattering Geometric effects
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Joseph C. Palais 5.3 5 5.3.2 Absorption 1. Intrinsic Absorption All materials absorb certain bands of frequencies. This is due to resonant vibrations of atoms and molecules. For silica glass, these losses occur in the UV and have peaks also in the IR in the 7 to 12 μ m region.
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Joseph C. Palais 5.3 6 100 10 1 0.1 0.01 ATTENUATION (dB/km) WAVELENGTH ( μ m) 0.5 0.6 0.7 1 1.2 1.5 2 3 5 10 Absorption for a Silica Glass Fiber Glass Absorption in UV Glass Absorption in IR Absorption
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Joseph C. Palais 5.3 7 2. Impurities (a) Metal ions Fe, Cu, and Ni, absorb light in the 0.6 - 1.6 μ m range. The fiber must be free of
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Ch5Sec3 - THE FIBER FORUM Fiber Optic Communications...

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