SAN JOSE, Calif. — Stanford University's unique diffraction microelectromechanical systems technology moves into the mainstream for long-haul communications this week with offerings from two companies.
Both Silicon Light Machines Inc., a subsidiary of Cypress Semiconductor, and startup LightConnect Inc. will debut samples of gain equalizers using the unusual MEMS methodology, which positions thousands of tiny silicon-nitride ribbons above a silicon substrate.
The ribbons — 500 to 600 microns long, 10 to 30 microns wide — are spaced according to CMOS design rules, currently about 0.35 micron between ribbons. A cluster of six ribbons forms a pixel. By controlling the ribbons' voltages, designers can control how light is diffracted from the grating created by the ribbons.
Cypress has taken the SLM technology into production at its CMOS fab, using the MEMS in printing and display applications. While long-haul fiber telecom markets remain flat, these consumer markets represent an important learning-curve area for diffraction MEMS. Now, however, the technology is being aimed at a natural application in dense wavelength-division multiplexing.
SLM has used its grated light-valve technology to create its first telecom subsystem product, the Model 2200 Dynamic Gain Equalizer (DGE). Tom Werner, president of SLM, said that post-EDFA (erbium-doped fiber amp) amplified optical signals have such a tough time maintaining equalization across channels, the equalizer could be applied to a range of areas in L-band DWDM, metropolitan networks and other applications. But for starters SLM is introducing a C-band subsystem for long-haul applications.
The resulting equalizer subsystem, which includes control electronics and an optical circulator, can keep power differences within a plus or minus single-decibel range over a dynamic range of 15 dB. The power is attenuated independently over multiple spectral regions, allowing carriers to dynamically add or drop wavelengths in DWDM transport without impacting adjacent channels.
Meanwhile, MEMS startup LightConnect (Newark, Calif.), founded by executives from E-Tek, New Focus and Hitachi Semiconductor, has taken an existing equalizer to a module package. LightConnect, the only other licensee of the Stanford technology, had introduced a C-band DGE in July 2001, following it up with L-band devices at the end of last year. LightConnect is putting most of its efforts into using diffraction MEMS in DGE and variable optical attenuator applications.
SLM's Werner said a handful of other vendors had tried to develop similar diffraction technology outside the Stanford design principles, but none appears ready to move to market. SLM and LightConnect are developing similar marketing strategies for using the equalizers in both long-haul and metro applications, so Werner said he expects the two of them to compete head-to-head soon.
