This paper is the first in a series of publications to investigate the use of commercial-off-the-shelf (COTS) components for space flight fiber laser transmitter systems and LIDAR (laser imaging detection and ranging) detection systems. In the current study, a hermetically sealed COTS LiNbO3 optical modulator is characterized for space flight applications. The modulator investigated was part of the family of “High-Extinction Ratio Modulators” with part number MXPE-LN from Photline Technologies in Besancon, France. Device performance was monitored during exposure to a Cobalt60 gamma-ray source. Results from the testing show little change in device operation for a total accumulated dose of 52 krad.