Designed for precision optical power control, the Polarization-Maintaining (PM) Variable Optical Attenuator is an essential tool for testing and optimizing optical components and systems. All input and output fibers are polarization maint ining to maintain the polarization state of the light. Our MEMS VOA PM attenuates light signals while. Thorlabs' Fiber-Coupled Electronic Variable Optical Attenuators (VOAs) are microelectromechanical system (MEMS) based devices that provide attenuation up to >30 dB or >25 dB, depending on the model.