The key, and probably the most difficult issue in optical CATV communication technology is how to make the optical unit qualify the requirements on nonlinearity distortion and noise in transport links. The principles of externally modulated transmitter are presented. The key technologies related to the method of using optically linearized modulator to achieve non-linearization compensation of optical CATV transmitter are mainly discussed, including the theoretical principles, system architectures, and factors affecting system performance (modulation index, time delay etc.).