Evolution of optical subassemblies in IBM data communication transceivers

Optical subassemblies (OSAs) are the highest-cost component of datacom transceivers, and therefore the component that is most constrained by production cost concerns. While transceiver costs have declined, operating rates have increased from 266 Mb/s to 10.3 Gb/s. Corresponding OSA designs, based on multimode fiber, have evolved incrementally through several generations, to 2.4 Gb/s. Costs have been lowered in successive generations by reducing the number of parts, material costs, and complexity of assembly, and by using lower-cost optoelectronic devices—vertical-cavity surface-emitting lasers (VCSELs). This paper traces the mechanical aspects of OSAs that have been developed and introduced into products or developed as demonstration projects.