MEMS variable optical attenuator with linear attenuation using normal fibers

The paper described a new micromachined reflection-type variable attenuator (VOA), which uses an elliptical mirror as the moveable reflector. It has superior performance as compared with the conventional flat-mirror reflection-type VOAs and shutter-type VOAs. This design assembles the input and output fibers at the two foci of the reflective elliptical mirror. As the input light will be automatically focused to the output point, the VOA has low insertion loss at normal single mode fibers without any further collimating equipment. Once the mirror is displaced, the input beam is rapidly defocused, and a large attenuation can be achieved therefore. The VOA also has low polarization dependence loss (PDL), low wavelength dependence loss (WDL) and low back reflection. Moreover, this VOA presents the relationship between the mirror displacement and the optical attenuation is almost linear.