Optical microelectromechanical systems (MEMS) technology or micro-optoelectromechanical systems (MOEMS) technology has proven to be an enabling technology for many components of optical networking applications. Due to their widespread applications, MEMS variable optical attenuators (VOA) have been one of the most attractive MEMS-based key devices in the optical communication market. Micromachined shutters and refractive mirrors assembled with 2D and 3D optics are the subjects of tremendous research activity. We conduct a comprehensive literature survey with respect to technologies such as fabrication processes, optical designs, actuators, and systems. Apparently, MEMS VOA technology is still evolving into a mature technology step by step. MEMS VOA technology is not only the cornerstone to support future optical communication technology, but also the best example for understanding the evolution of MOEMS technology and the commercialization of MOEMS devices.