We report a coherent driver modulator sub-assembly for 100-Gbaud class transmitter. The sub-assembly employs a codesigned high-speed driver IC and optical modulator, where the designs for the characteristic impedance between the driver IC and IQ modulator and for the RF pads are optimized. The EO bandwidth is over 67 GHz. This response is sufficient for 100-Gbaud-class operation even if we consider RF losses caused by a package, PCB, and DAC. We also demonstrated QPSK and 16-QAM at the speed of 128 and 112 Gbaud, respectively.