Spiders and silkworms both make silk. The fibers are a fraction of the thickness of human hair, only about 5 micrometers across. Huby's experiment involved taking spider silk fibers and attaching them to disc-shaped "reservoirs" which guide long-wavelength light (in the near-infrared) to the fiber. They found the light transmitted well enough that it could be used to send data. "Spiders can generate seven kinds of silk," Huby told Discovery News. "We use the kind used in making the web." (Other kinds of silk are used for wrapping up prey when caught or to trap it in the web).
More to the point, both silkworms and spiders make silk that is the same diameter through its whole length. Optical fibers have to be manufactured precisely, and making them that small is difficult and expensive. Silk would be cheaper, and can be made as long as the spiders are able to produce it. Silkworms can also be genetically engineered t produce spider silks.
Meanwhile, Omenetto's work focused on making silk-based polymers, taking advantage of the fact that silk is made up of proteins that can be absorbed back into the body over time. Since silk transmits light in a way similar to expensive plastics, it could be used to build sensors that could be implanted, and then allowed to dissolve.