Channeling light in the deep sea

A genus of sea sponges grows its own light-conducting fibers that are remarkably similar to commercial-grade optical fibers–and in some ways better. A team of U.S. and Israeli researchers that recently studied several Euplectella species says the primitive creatures’ fibers might serve as a model for improved telecommunications fiber optics.

LIGHT HOUSE. A deep-sea Euplectella sponge grows light-transmitting glass fibers (arrow) that are in some ways superior to commercial optical fibers. V. Sundar et al./Nature

In the Aug. 21 Nature, Joanna Aizenberg of Lucent Technologies’ Bell Labs in Murray Hill, N.J., and her colleagues report that the sponges’ fibers, called spicules, have glass cores infused with sodium ions that enhance the fibers’ optical properties.

Made at high temperatures, commercial fibers can’t exploit such impurities because those additives tend to clump as the glass cools. Moreover, these heated-then-cooled fibers develop undesirable internal stresses. On both counts, Aizenberg says, human-made fibers might benefit if manufacturers could assemble them bit by bit at low temperatures, as the sponges do.

Other sponges previously found to sprout light-conducting spicules (SN: 8/4/01, p. 77: Available to subscribers at Soaking Up Rays) inhabit shallower water than does Euplectella and may harvest sunlight with their fibers. At the inky depths of 500 to 1,000 meters, says Aizenberg, Euplectella‘s fibers are more likely to transmit photons from bioluminescent organisms to help the sponges find their meals.


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