Fueled by rapid growth in demand for optical network capacity, combined with the sudden maturation of wavelength-division-multiplexing (WDM) technologies, the globe's long-haul optical networks are transforming themselves into systems that transport tens to hundreds of wavelengths per fiber, with each wavelength modulated at 10 Gb/s or more. As this happens, it becomes critical to seek new ways of not only surmounting the transmission obstacles associated with hundreds of closely spaced wavelength channels; it becomes imperative to find new ways of provisioning and restoring network traffic in units at roughly the wavelength level. These needs have stimulated a storm of evolution in optical-layer networking, as well as technological advancement on various fronts. Micro-electro-mechanical-systems (MEMS), being studied since 1980's, have recently emerged as a powerful means of implementing various key optical-network elements in compact and low-cost form, owing to the unique capability of this technology to integrate optical, mechanical, and electrical components on a single wafer. Various MEMS components and subsystems for optical-fiber communications, such as tunable lasers and filters, high-speed optical modulators, reconfigurable wavelength-add/drop multiplexers, dynamically adjustable gain-equalizers, tunable chromatic dispersion-compensators, polarization-controllers, polarization-mode-dispersion compensators, and optical crossconnects have been demonstrated. Some of the early resulting devices have already been moved, on exceptionally short timescales, to the brink of commercial realization. This course focuses on the applications of MEMS in various optical-fiber communication components and sub-systems. The aim is to provide a broad understanding of MEMS technology, and detailed principles of optical-network elements implemented by MEMS.