The Model 2200 dynamic-gain equalizer from Cypress Semiconductor subsidiary Silicon Light Machines is a subsystem that balances channels for dense wave-division multiplexing (DWDM), within a plus-or-minus single-decibel range over a dynamic range of 15 dB. By attenuating power independently over multiple spectral regions, it lets service providers add or drop wavelength channels with no impact on adjacent-channel power.
The company uses licensed diffraction MEMS technology from Stanford University in which thousands of tiny "ribbons" of silicon nitride are positioned above a silicon substrate. Silicon Light Machines has been awarded 20 patents on control of the ribbons, whose position determines light diffraction. The underlying technology, fabricated at Cypress, has been used in printer and display products in the past, but the debut of the Model 2200 represents its first use in optical telecom applications.
In post-erbium-doped fiber amplification in long-haul networks, gain equalization of WDM channels is needed to improve channel count, tighten optical signal-to-noise ratios and speed the ability to add and drop wavelengths. The "grating light valve" ribbon device used with a static grating provides the benefits of both traditional spectral shaping and channel-by-channel WDM equalization. The result is control of C-band (and future L-band) channel "ripple" to less than 0.1dB, with an equalization time of less than 1 ms.
The full subsystem, comprising a one-dimensional array of variable optical attenuators along with control electronics and optical circulator, dissipates less than 5 watts. It is sampling now.
Silicon Light Machines, www.siliconlight.com
