Light-wave timekeeper for faster networks.
Oscillators are at the heart of every communications device, from FM radio receivers to cell phones to sophisticated optical networking equipment. By beating out a reference signal like the ticking of a clock, they allow such gadgets to interpret and process incoming signals. But in today’s oscillators the frequency of the signal is set by a vibrating quartz crystal, and quartz just isn’t fast enough for the transmitters and other machines that drive optical networks. Enter OEwaves, a Pasadena, CA, startup that’s using technology from Caltech to build a better, faster oscillator-one that keeps time, not with vibration, but with light.
In a conventional oscillator, an electric current causes the quartz to vibrate at a natural frequency of about five million cycles per second, or five megahertz. But optical networks currently operate at frequencies of up to 10 gigahertz-2,000 times as fast-and could eventually reach 40 gigahertz. Special equipment can multiply the natural frequency of quartz up to the rate of the network, but the process adds both cost to the system and noise to the signal. OEwaves’ “opto-electronic oscillator” would solve both problems by using light to create a reference signal-tuned to any frequency required. To accomplish this, the device uses a tiny sphere of glass. Laser light beamed into the sphere is trapped, perpetually glancing off the walls; the frequency of this trapped light wave-which can be altered by adjusting the laser beam or the size of the microsphere-becomes the reference oscillation. “It’s the first new approach to oscillator technology for 30 years,” says OEwaves cofounder Lute Maleki. “It will reduce the cost and the complexity of the system, and it also lets the network carry more information.”
Maleki, a physicist at Caltech’s Jet Propulsion Laboratory, and OEwaves cofounder Steve Yao first tried to build the optical oscillator using a length of fiber-optic cable to trap the light. The idea of using microspheres came from Vladimir Ilchenko, then at Moscow’s Lebedev Institute and soon to be OEwaves’ chief scientist. With CEO Julie Schoenfeld, Maleki and Yao founded OEwaves last year, raising an initial $4.4 million. The company plans to have a working oscillator the size of a small circuit board by the first quarter of 2002. This device will be small enough to use in optical network transmitters, OEwaves’ first target application.
As in most new ventures, there are still many technological hurdles to overcome. A nearly identical project at the National Institute of Standards and Technology, for example, was tabled in 1999 when researchers found that minor variations in temperature would distort the signal. “As the temperature changes, it will actually change the shape of the material,” says John Kitching, who worked on the oscillator project. “Then the frequency will drift around. Because of that instability, it didn’t seem like it was worth pursuing.”
Maleki points out that, like his own early efforts, the national lab’s project used fiber-optic cable. He argues that the move to microspheres will solve the temperature problem. If OEwaves succeeds in meeting these and the other challenges it will undoubtedly face, its persistence could pay off handsomely. CEO Schoenfeld claims that a high-performance, high-frequency oscillator will have applications in markets ranging from optical networks to high-bandwidth fixed wireless networks and beyond. If she’s right, OEwaves’ timing may be just about perfect.