We propose a flexible optical transmitter for the short-reach optical interconnects that includes a silicon photonic segmented Mach-Zehnder modulator driven by a distributed six-channel 32-nm silicon on insulator (SOI) complementary metaloxide semiconductor driver integrated circuit. Optical equalization is demonstrated to extend the bandwidth limitation of the transmitter with non-return to zero signaling at 25Gb/s. We also generate four-level pulse amplitude modulation (PAM-4) signaling using the same transmitter architecture. Transmission of 46 Gb/s PAM-4 signal with bit error rate (BER) well below hard-decision forward error correction limit is experimentally demonstrated. Low driver power consumption of 130 mW at 46Gb/s PAM-4, corresponding to 2.8 pJ/bit power efficiency, is also achieved.