ZrW2O8 Could Help Fiber Optics
Laurel M. Sheppard
MURRAY HILL, N.J. — More than three decades have passed since the unique properties of zirconium tungstate were first observed by Penn State University researchers. This material exhibits negative thermal expansion -- expansion occurs on cooling rather than heating -- equally in all directions. The material also has the largest known negative linear expansion over a broad temperature range: 210 ppm/°C from nearly absolute zero to 150°C.
Although the Penn State researchers ignored zirconium tungstate because its properties were not what they were looking for, it has piqued the interest of scientists at Lucent Technologies' Bell Laboratories. Potential applications, they note, include packaging materials for Bragg reflection gratings or filters used in optical fiber.
NIST will experiment with laser scanning and 3-D computer modeling to help streamline work site management in the construction industry. As its laboratory, NIST will use an actual building project slated to start next year at its Maryland campus. Courtesy of NIST.
These gratings are temperature-sensitive; when the temperature changes, so does the wavelength. To avoid these changes without being limited to constant-temperature environments, the fiber could be bonded to a negative-expansion material that could compensate for any temperature change. Zirconium tungstate packages offer a simple solution, while other options -- such as using two dissimilar metals -- are much more complex to make.
Another advantage of zirconium tungstate is that it can be easily doped with other oxides, such as zirconia or tungsten oxide, to tailor its thermal expansion. Lucent is evaluating composites based on these compositions for any potential shortcomings, as well as testing them for environmental stability. "We are currently in the preliminary research stages and are looking at other potential applications," said Dave W. Johnson Jr., head of the lab's metallurgy and ceramics research department.
If the material lives up to its potential, it could help reach the vision for dense wavelength division multiplexing of 1000 multiple transmission channels in a single fiber, as long as other technical challenges are solved. Optical fiber currently handles up to 80 multiple channels or wavelengths of light.
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