Optical fibers have been traditionally produced by making a cylindrical object called a preform — essentially, a scaled-up model of the fiber — and then heating it. Softened material is then drawn or pulled downward under tension and the resulting fiber is collected on a spool.
The key breakthrough for producing these fibers was to add to the preform light-emitting semiconductor diodes the size of a grain of sand, and a pair of copper wires a fraction of a hair's width. When heated in a furnace during the fiber-drawing process, the polymer preform partially liquified, forming a long fiber with the diodes lined up along its center and connected by the copper wires.
High-speed optoelectronic semiconductor devices, including light-emitting diodes (LEDs) and diode photodetectors, have been embedded within fibers that were then woven into soft, washable fabrics and made into communication systems. In this case, the solid components were two types of electrical diodes made using standard microchip technology: LEDs and photosensing diodes. Both the devices and the wires maintain their dimensions while everything shrinks around them in the drawing process. The resulting fibers were then woven into fabrics that were laundered 10 times to demonstrate their practicality as possible material for clothing.
One of the advantages of incorporating function into the fiber material itself is that the resulting fiber is inherently waterproof. To demonstrate this, some of the photodetecting fibers were placed inside a fish tank. A lamp outside the aquarium transmitted music through the water to the fibers in the form of rapid optical signals. The fibers in the tank converted the light pulses — so rapidly that the light appears steady to the naked eye — to electrical signals that were then converted into music. The fibers survived in the water for weeks.
New techniques for weaving these fibers into fabrics use a conventional industrial manufacturing-scale loom. Initial applications for the fabrics will be specialized products involving communications and safety. In addition, the U.S. Department of Defense is exploring applications of these ideas to soldiers’ uniforms. Beyond communications, the fibers could potentially have significant applications in the biomedical field; for example, devices using such fibers might be used to make a wristband that could measure pulse or blood oxygen levels, or be woven into a bandage to continuously monitor the healing process.