The Models 2510 and 2510-AT TEC SourceMeter SMU instruments enhance Keithley's CW (Continuous Wave) test solution for high speed LIV (lightcurrent- voltage) testing of laser diode modules. These 50W bipolar instruments were developed in close cooperation with leading manufacturers of laser diode modules for fiberoptic telecommunications networks. Designed to ensure tight temperature control for the device under test, the Model 2510 was the first in a line of highly specialized instruments created for telecommunications laser diode testing. It brings together Keithley's expertise in high speed DC sourcing and measurement with the ability to control the operation of a laser diode module's Thermo- Electric Cooler or TEC (sometimes called a Peltier device) accurately. The Model 2510‑AT expands the capability of the Model 2510 by offering autotuning capability. P, I, and D (proportional, integral, and derivative) values for closed loop temperature control are determined by the instrument using a modified Zeigler-Nichos algorithm. This eliminates the need for users to determine the optimal values for these coefficients experimentally. In all other respects, the Model 2510 and Model 2510‑AT provide exactly the same set of features and capabilities.