Free-space optical communication systems using laser diode transmitters exhibit data rate limitations imposed by the diode's relatively low average output power. Incoherent power combiners represent a viable method for circumventing this limitation. A polarization beam combiner is described, and overall performance is analyzed in terms of signal extinction ratio and total transmitted power. It is shown that in such a combiner it is possible to increase the total transmitted on-axis far-field intensity, but the signal extinction ratio remains constant. The combiner system's true performance is calculated using polarization and power data for different types of laser diodes.