Mellanox's LinkX UltraVOA uses silicon photonics to deliver reliable solid-state current controlled optical attenuation enabling ultra-fast control of signal levels in optical networks. The Variable Optical waveguide. As current is applied through the diodes, the free carriers in the waveguide absorb photons, creating a current-controlled variable attenuation.Because the physical effect is based on electronic control, the response time of the VOA is fast-less than 1 µs in typical situations. This VOA is well suited to the most demanding applications in metro and long-haul transmission applications. The high speed of these VOAs makes them particularly useful for optical transient suppression and analog signal modulation applications.