Exotic fiber optics, such as a type that goes by the initials ZBLAN, can be made on Earth, but it's not easy. The normal process of making ZBLAN involves heating a blob, or "preform," of this special glass to hotter than 300 degrees Celsius, and then pulling it down, like a long string of chewing gum, from a drop tower typically between 10 and 20 meters tall. But the size of the white-hot blob limits how long the resulting cable can be—fibers max out at about 700 meters in length. Ideally, companies want longer segments, because connection points lead to signal loss. Plus, gravity causes sedimentation in the crystal structure of the ZBLAN, creating defects that result in a weaker signal.