The 1784 Fiber-coupled VCSEL Laser Source is designed for use in laboratory applications or for test and measurement of 25-Gbit/s Datacom devices. The1784 is an 850 nm, 25 Gbit/s, directly modulated, multimode vertical-cavity surface-emitting laser (VCSEL). It uses high-performance microwave circuitry to ensure clean delivery of the electrical input to the VCSEL chip, and the VCSEL's 50-μm output fiber enables the use of either 50 μm or 62.5 μm FC/PC connectorized fiber. The AC-coupled input and internal bias circuitry allows connection to any high-speed 50-Ω SMA-compatible signal source without the need for additional bias circuitry. A 10-position switch allows for optimization of the VCSEL bias for different Datacom applications.