page_title: Optical fiber
section_title: Phosphate glass
hierarchical_section_title: Optical fiber / Manufacturing / Materials / Phosphate glass
context_page_description: An optical fiber is a flexible, transparent fiber made by drawing glass or plastic to a diameter slightly thicker than that of a human hair. Optical fibers are used most often as a means to transmit light between the two ends of the fiber and find wide usage in fiber-optic communications, where they permit transmission over longer distances and at higher bandwidths than electrical cables. Fibers are used instead of metal wires because signals travel along them with less loss; in addition, fibers are immune to electromagnetic interference, a problem from which metal wires suffer. Fibers are also used for illumination and imaging, and are often wrapped in bundles so they may be used to carry light into, or images out of confined spaces, as in the case of a fiberscope. Specially designed fibers are also used for a variety of other applications, some of them being fiber optic sensors and fiber lasers.
  Optical fibers typically include a core surrounded by a transparent cladding material with a lower index of refraction. Light is kept in the core by the phenomenon of total internal reflection which causes the fiber to act as a waveguide.
context_section_description: Phosphate glass constitutes a class of optical glasses composed of metaphosphates of various metals. Instead of the SiO₄  tetrahedra observed in silicate glasses, the building block for this glass former is phosphorus pentoxide (P₂O₅), which crystallizes in at least four different forms. The most familiar polymorph (see figure) comprises molecules of P₄O₁₀.
  Phosphate glasses can be advantageous over silica glasses for optical fibers with a high concentration of doping rare-earth ions. A mix of fluoride glass and phosphate glass is fluorophosphate glass.
caption: The P4O10 cagelike structure—the basic building block for phosphate glass
exif: {}