A 10-Gb/s optical transceiver using the Yuen 2000 (Y-00) encryption protocol was developed. The key device in the transceiver, a 10-GS/s, 10-bit digital-to-analog converter (DAC) LSI, was fabricated using 0.25-μm SiGe BiCMOS technology. Circuit techniques such as segmented architecture, parasitic capacitance separation using the base-common transistor, and the usage of a common mode logic (CML) driver were employed to minimize glitches. The Y-00 transceiver equipped with the DAC LSI operated at 10 Gb/s. Moreover, a 300-km transmission experiment performed at a data rate of 10 Gb/s proved that the developed transceiver can be used in a practical application when forward error correction is applied.