MEMs eye dynamic optical products

MEMs eye dynamic optical products
The current slowdown in telecommunications spending clearly indicates that increased bandwidth capacity will not automatically translate into increased demand for the optical components and subsystems needed to enhance the network infrastructure. Instead, the industry is in debate over what architecture, technology and equipment will ultimately provide the speed, performance and economy required in second-generation optical networks.

While the shift from point-to-point networks to a more meshed architecture is inevitable, it is difficult to predict with any accuracy how the dynamic nature of this new architecture will evolve. Numerous component and subsystem manufacturers are aggressively pursuing the challenge of developing innovative products that control and manipulate light in optically reconfigurable networks. Products based on diffractive microelectromechanical systems (D-MEMS) have emerged as the leading dynamic optical components.

Dynamic components complement the traditional active and passive components by controlling and purifying light for optimum link performance. They can be software-configured and electronically controlled to compensate for changes in performance by enabling switching between optical paths, equalizing channel power, managing link dispersion and optimizing amplifier chain performance. By optimizing link performance, providers can reconfigure optical paths while maintaining maximum network reliability.

The ability to package more powerful and complex functions in smaller packages makes MEMS the ideal technology for building dynamic optical components. D-MEMS technology has proved to be the most flexible platform. The technology is based on D-MEMS actuators, a series of silicon nitride ribbons suspended above a silicon substrate, which utilize the wave properties of light to provide varying levels of attenuation.

Fabricated devices are very reliable since, with those small deflections, the material experiences negligible fatigue. Devices have been actuated more than 100 billion times with no measurable change in performance. An important added advantage is immunity to ambient acoustic noise and vibration. Products based on D-MEMS also have demonstrated extremely fast response times, passing rigorous Telcordia qualification testing.

One integrated dynamic channel equalizer (DCE) component can manage 100-plus wavelengths, selectively block any channel by software command and selectively control output power for any pass-through channel. Source: Lightconnect Inc.

This platform can be used for dynamic gain and dynamic channel equalization applications in metro core and long-haul dense wave-division multiplexing (DWDM) optical networks. Dynamic gain equalizers (DGEs) are powerful components that reduce the attenuation of the individual wavelengths within the light band. They can be used for power control in dynamic erbium-doped fiber amplifiers (EDFAs) and power equalization in metro, long-haul and ultralong-haul transmission. They flatten EDFA gain profiles or control gain shape changes caused by add/drops, minimizing the need for OEO (optical-electrical-optical) regeneration. The device is invaluable in its ability to compensate for the nonlinearity of EDFA optical amplifiers.

Amp range
The device compensates amplifier gain profiles, enabling high signal-to-noise ratio for all channels in an optical amplifier system. Dynamic gain compensation improves system performance, flexibility and increases the distance between amplifiers in long-haul and ultralong-haul transmission systems. DGE devices can be used with EDFAs and Raman amplifiers in the C, L or extended bands.

Dynamic channel equalizers (DCEs) can equalize or block individual channels across the C, L or extended bands. Applications include long-haul and ultralong-haul transport, DWDM optical add/drop multiplexers and wavelength-selective switching. When used in a feedback loop, the DCE can compensate for variation in transmission losses on individual channels and can also be used to block or attenuate a channel completely.

DCEs are electronically controlled and software-configured, offering agility in responding to changing network or system conditions, as well as simplicity in control and configuration. The DCE's ability to control the power of more than 100 wavelengths in one compact module eliminates the need for multiple discrete components to control each individual channel.

The high-channel-count device provides attenuation control, a wide dynamic range for blocking, as well as 4x reduction in size and power compared with existing discrete architectures. DCEs can also selectively control output power for any pass-through channel.

The success of second-generation optical networks will be driven by the ability of component vendors to provide highly flexible, scalable, integrated solutions for managing complex optically reconfigured networks. D-MEMS technology has emerged as the optimal platform for achieving enhanced DWDM operational efficiency and economy, as well as the best platform for low-cost, high-volume manufacturing. D-MEMS will enable the network evolution to dynamic architecture.

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