Seesaw' Switch is First Practical

Micro-Electro-Mechanical Optical Switch

                       
                  A photo of an experimental optical switch.
 

MURRAY HILL, N.J. (Feb. 23, 1999) -- Scientists at Bell Labs have built a microscopic optical switch that works like a child's seesaw and demonstrates the world's first practical optical-switching technology using micro-electro-mechanical systems (MEMS). "Our optical switch shows the potential for MEMS to be a disruptive technology -- one that changes the paradigm for an entire industry," said David Bishop, head of the Microstructure Physics Research Department at Bell Labs.

"We believe these advances will form the basis for switching technology that will be used in future optical networking systems," he said. The "seesaw" of the experimental switch is a tiny, pivoting bar with a gold-plated mirror on one end. The mirrored end fits in a space, about one-tenth as wide as a human hair, between two hair-thin optical fibers lined up end to end. When the switch is off, the mirror rests below the cores of the two fibers, allowing lightwave signals to travel from the core of one to the other.

To turn the switch on, a voltage is applied at the other end of the bar, beneath an attached plate; the electrostatic forces pull the plate down, lifting the bar so the mirror reflects the light instead of letting it move from one fiber to the other.

The technology promises to allow a wide variety of devices and systems to be built, such as wavelength add/drop multiplexers, devices that add or drop signals carried on specific wavelengths, or colors, of light; provisioning switches; optically reconfigurable communications networks; power limiters; variable attenuators and wavelength-division multiplexed (WDM) signal equalizers.

Bishop described the experimental optical switch in a talk, "Silicon Micromechanics for Lightwave Networks," presented today at the international Optical Fiber Communications (OFC) Conference in San Diego, California.

                The bar, when lowered (as shown), deflects the signal to its left toward the
                rear fiber. When raised, the signal continues in a straight line to the fiber on
                the right.
 

MEMS devices are built in much the same way as are silicon integrated circuits. Various films, such as polysilicon, silicon nitride, silicon dioxide, and gold, are deposited and patterned to produce complicated, multilayer three-dimensional structures. The major difference is a release step at the end of fabrication:
In a MEMS device, some of the materials are removed using a selective etching technique that leaves the device with moveable elements.

Bishop's talk was one of more than 40 Bell Labs technical presentations scheduled for OFC this week.

This information is based on a press release written by Donna Cunningham of Bell Labs Media Relations.