Research into a material with the potential to become the optical fiber cable of the 21st century has taken a step forward with the acceptance of space-based research for publication in the peer-reviewed Journal of Materials Research. Dr. Dennis Tucker of NASA/Marshall Space Flight Center, along with co-investigators from the University of Alabama in Huntsville and Boeing have found that ZBLAN manufactured in a nearly gravity-free environment has properties that far exceed current state-of-the-art optical fiber materials or even ZBLAN made on Earth.
Discovered by a team of French researchers in 1974, ZBLAN is named after the heavy metals found in the chemical composition of the material: zirconium, barium, lanthanum, aluminum, and sodium (chemical symbol "Na"). ZBLAN is a member of the heavy metal fluoride family of glasses, and has promising applications in fiber optics. It is highly transparent in the infrared region of the electromagnetic spectrum, thus opening an entirely new energy range for optical fiber communications, sensing, and technology development. But to develop this new material fully will require some more hard science be done.
>In theory, one should be able to make a ZBLAN optical fiber cable that has the capability to carry more than 100 times the amount of data carried by today's traditional silica-based optical fiber cables. In practice, however, the best that has been achieved has only been about 1/5 of current cables. "This is primarily because of the fact that when you make ZBLAN on the ground, it has this nasty tendency to crystallize - to come out of its glass-like state - which severely degrades its optical properties," commented Tucker.
The two pictures above demonstrate this. The ZBLAN on the left, made on Earth in a one-gravity environment, shows a great deal of non-uniformity and inhomogeneities due to its crystalline state. By contrast, the ZBLAN on the right was made aboard a Conquest-1 suborbital rocket flight. Its glassy nature is readily visible, as are some bubbles that formed when the sample inadvertently came in contact with the container.
"It's really fascinating stuff," remarked Tucker. "Most of my colleagues perform experiments in space in order to make very high-quality crystals, but ZBLAN doesn't crystallize."
Potential areas of application for this material include medical surgery and cauterization, temperature monitoring, infrared imaging, fiber-optic lasers, optical power transmission, and a host of other areas. A recent marketing survey indicated that the annual impact of ZBLAN on the economy might total as much as nearly $8 billion.
"But before we get there, we've got a lot of hard science to do first," said Tucker. "We really have to get to the physical understanding of why ZBLAN behaves the way it does, and what makes it stay in the glass state in microgravity, as opposed to crystallize like it does on the ground."