The world’s fiber-optic network spans more than 550,000 miles of undersea cable that transmits e-mail, websites, and other packets of data between continents, all at the speed of light. A rip or tangle in any part of this network can significantly slow telecommunications around the world.

Now engineers at MIT, along with computer scientists at Columbia University, have developed a method that predicts the pattern of coils and tangles that a cable may form when deployed onto a rigid surface. The research combined laboratory experiments with custom-designed cables, computer-graphics technology used to animate hair in movies, and theoretical analyses.

In the lab, MIT engineers set up a desktop system to spool spaghetti-like cables onto a conveyor belt. They adjusted parameters such as speed of deployment and the speed of the belt, and observed how the cable coiled as it hit the surface.

At Columbia, computer scientists adapted a source code used for simulating animated hair and, incorporating the parameters of the MIT experiment, found that the simulation accurately predicted the coiling patterns seen in the lab.

The researchers say the coil-predicting method may help design better deployment strategies for fiber-optic cables to avoid the twisting and tangling that can lead to transmission glitches and data loss.

“We now have a set of design guidelines that allow you to tune certain parameters to achieve a particular pattern,” says Pedro Reis, an associate professor of mechanical engineering and civil and environmental engineering at MIT. “We have a description that applies to many systems.”

Reis and his colleagues publish their results this week in the Proceedings of the National Academy of Sciences. His co-authors are Khalid Jawed of MIT and Fang Da, Jungseock Joo, and Eitan Grinspun of Columbia University.

Shipping up to Boston

Fiber-optic cables are typically deployed from a sailing vessel, which unfurls lengths of cable from a large spool. Depending on how the sailing speed of the boat relates to the speed of the spool, cable can be deposited on the seafloor in straight lines, or in meandering, coiling patterns.

“If the boat is sailing slower than the rate of the cable, then you’re putting more cable down, which generates loops, coils, and tangles,” Reis says. “That can lead to signal attenuation. But if the boat is traveling faster, then the cable can get taut and fracture, which is really bad news. So we wanted to understand what was underlying those patterns.”

To do this, Reis set up a small-scale version of a cable-deploying system in his lab. He and his students fabricated filaments from silicone-based rubber, and rigged a spool to automatically reel out the wire onto a conveyor belt. They altered various parameters of the setup, including the speed of the belt and the spool.

The team used a digital video camera to record the filaments’ motion as they hit the belt, and observed three main patterns: meandering waves, alternating loops, and repeated coils.