Dancing on the Head of a Pin
From the beginning, the lab’s work on micro-electro-mechanical systems (MEMS) was set up to have both near-term and long-range benefits for Lucent. The goal of this research is to improve communications systems by building miniature machines-microphones, mirrors and more-that are riddled with moving parts but so small that hundreds fit on a pinhead.
The field has exploded in recent years. Because MEMS devices can be fabricated like an integrated circuit on “last generation” equipment, they can conceivably be made for pennies-and thereby become ubiquitous. MEMS sensors already control automotive air bags, and futurists picture these micromachines driving button-sized cell phones that fit on a lapel, or buildings that sense stress changes caused by an earthquake and adjust their structure accordingly. Lucent won’t be making air bag sensors or smart steel. However, explains David J. Bishop, who heads the Microstructure Physics Research Department, “silicon micromechanics has a huge possibility for impacting lots of technologies we care about- particularly optics, acoustics and wireless.”
An early payoff could lie in MEMS-based residential communications systems. The volume of data that can be quickly passed in and out of homes keeps running up against the severe limitations of traditional twisted copper telephone lines. Several schemes have surfaced to ease this problem. Some cable companies, for instance, offer Internet connections over the broadband lines that bring in television pictures. But such alternatives have capacity and reliability limitations, says Bishop. So the ultimate goal is fiber optics, “future-proof” because it offers near-infinite bandwidth with a minimum of maintenance.
Due to copper wire’s limited capacity, separate telephone lines now have to be run from the central phone company office to each home. The same strategy with fiber optics would be prohibitively expensive.
However, since one fiber optic line can handle thousands of phone and data transmissions simultaneously, it might be possible to run a single line to a neighborhood node, then string shorter lines to individual houses-making fiber optics an affordable alternative to copper wires.
Yet there’s still a hitch. Signals are transmitted along fiber optics lines by lasers-power-hungry devices too expensive to provide to every household. Bishop likens the problem to that facing hypothetical explorers on adjacent mountain tops. They communicate by flicking flashlights on and off. After all, that’s basically how optical communications works-only using lasers instead of flashlights. But suppose flashlights are so expensive only one explorer can afford his own. Two-way communications could still be maintained if the flashlight owner leaves his light on-allowing his counterpart to wield a mirror and reflect rays back to the other mountain in a recognizable pattern.
That’s where MEMS comes in. Data would stream into homes in the usual way. But micro-mirrors invented by Jim Walker and Keith Goossen would reflect light back to the central station, simulating lasers in every household for a fraction of the price. Bell Labs has already built mechanical mirrors that can handle in excess of 10 megabits of data per second, nearly 200 times the capacity of today’s 56-kilobit-per-second high-speed modems. Says Bishop, “It is our hope that there will be some limited field trials in the next year.”