In this paper we review field data from failures related to materials and devices that are the building blocks of optically amplified dense-wavelength division multiplexed (DWDM) transmission systems. A DWDM transmission system consists of at least three distinct components: an optical multiplexer, one or more optical fiber amplifiers (OFAs), and an optical demultiplexer. A tandem arrangement of these components performs the function currently up to 40 independent high speed optical communications channels (about 2 million phone calls) over a single fiber link. Of these components, OFAs are considered the workhorse of this new technology, and, as with any new technology, their reliability is the focus of considerable attention. Commercially available OFAs are erbium-doped silica or fluoride fibers that operate in the 1550 nm optical communication window. Such OFAs consist of an active Er-doped fiber and pump laser(s) that collectively are referred to as the gain module, passive optical components used for routing, and electronic components for monitoring and operational support. We present the result of the failure analysis for each part as well as their role in the failure of the OFA. Using the data from systems deployed in the field, we summarize the history of failures of OFAs and other components and discuss their impact on the reliability of the DWDM system as a whole. From a material, packaging and system integration point of view, we address the reliability merits of different designs that, by and large, perform the same overall function. Finally, we shall outline how network providers that deploy such DWDM systems would benefit from a manufacturing strategy that incorporates reliability in its initial steps starting with the materials and packaging needs.