Hydrogen darkening

Hydrogen darkening is a physical degradation of the optical properties of glass. Free hydrogen atoms are able to bind to the SiO₂ silica glass compound forming hydroxyl (OH) - a chemical compound that interferes with the passage of light through the glass.

The problem is particularly relevant to fiber optic cables — particularly in oil and gas wells where fiber optic cables are used for distributed temperature sensing. Hydrogen can be present due to the cracking of hydrocarbons in the well. The darkening of the fiber can distort the DTS reading and possibly render the DTS system inoperable due to the optical loss budget being exceeded.

To prevent this, coatings such as carbon are applied to the fiber, and hydrogen capturing gels are used to buffer the fiber, and other proprietary techniques may be used to prevent hydrogen atoms from reaching the glass fiber via the cable sheath.

A recent reference is found here: https://theses.lib.vt.edu/theses/available/etd-05202015-113311/unrestricted/Bonnell_EA_T_2015_3.pdf

Glass science topics

Basics	Glass Glass transition Supercooling

Formulation	AgInSbTe Bioglass Borophosphosilicate glass Borosilicate glass Ceramic glaze Chalcogenide glass Cobalt glass Cranberry glass Crown glass Flint glass Fluorosilicate glass Fused quartz GeSbTe Gold ruby glass Lead glass Milk glass Phosphosilicate glass Photochromic lens glass Silicate glass Soda-lime glass Sodium hexametaphosphate Soluble glass Tellurite glass Ultra low expansion glass Uranium glass Vitreous enamel Wood's glass ZBLAN

Glass-ceramics	Bioactive glass CorningWare Glass-ceramic-to-metal seals Macor Zerodur

Preparation	Annealing Chemical vapor deposition Glass batch calculation Glass forming Glass melting Glass modeling Ion implantation Liquidus temperature Sol-gel technique Viscosity Vitrification

Optics	Achromat Dispersion Gradient-index optics Hydrogen darkening Optical amplifier Optical fiber Optical lens design Photochromic lens Photosensitive glass Refraction Transparent materials

Surface modification	Anti-reflective coating Chemically strengthened glass Corrosion Dealkalization DNA microarray Hydrogen darkening Insulated glazing Porous glass Self-cleaning glass Sol-gel technique Toughened glass

Diverse topics	Glass-coated wire Safety glass Glass databases Glass electrode Glass fiber reinforced concrete Glass ionomer cement Glass microspheres Glass-reinforced plastic Glass-to-metal seal Porous glass Prince Rupert's Drops Radioactive waste vitrification Windshield

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