The demands of high-capacity optical fiber transmission fuel an ever-increasing level of sophistication in the design of today's semiconductor lasers. The advent of erbium amplifiers has sparked worldwide R&D in integrated laser/electroabsorption modulators as low chirp transmitters. Wavelength division multiplexing, for both increased capacity point-to-point and networking applications, has also stimulated substantial interest in tunable and multi-wavelength array sources. Integration also has the potential to impact the design of low-cost transceivers for widely deployed fiber-to-the-home applications. This tutorial will survey the state of the art, and review the design, fabrication, and performance issues for advanced integrated lasers that will play a critical role in these and other application areas.