We have fabricated 2.5-Gb/s/ch long wavelength optical transmitter modules in planar and multichip module structures for chip-to-chip optical printed-circuit board (OPCB) applications. Their performance has been analyzed and compared with two types of short wavelength structures. The long wavelength multichip module showed a 3-dB bandwidth of 2.46 GHz while the planar showed 2.16 GHz. The modules showed clear eye openings at 2.5 Gb/s with a bit-error rate less than 10(-12) and can be used for optical interconnections in OPCBs.