Comparison of MEMS variable optical attenuator designs

Two micro electro mechanical systems (MEMS) - based electrical variable optical attenuator (eVOA) designs are discussed and compared with respect to polarization dependent loss (PDL) and wavelength dependent loss (WDL) characteristics. The first design is based on a shutter, whereas the second device works in reflection, where the movement of a mirror creates misalignment losses by steering the beam away from the core of the output fiber. The reflective-based design shows better PDL values typically below 0.1 dB at 10 dB attenuation. PDL values of the shutter-based design are 3.4 times higher, i.e. 0.5 dB around 10 dB. On the other hand the shutter design has less wavelength dependent loss.