A modular optical device having a set of optoelectronic modules that enables the device to operate, e.g., as a WDM or multichannel transceiver. In an example embodiment, the set of optoelectronic modules includes a laser module, a modulator module, and an optical-to-electrical converter module, all mounted on the same circuit board and optically and electrically connected for the intended application. Each of the optoelectronic modules comprises a respective stack of integrated circuits, at least one of which is a photonic integrated circuit (PIC). Some of the PICs may be configurable for different applications, with the configuration setup being carried out using electrical control signals and/or optical connections of the PICs. The modular structure of the device enables the manufacturer to provide customized solutions to different customers according to their respective specifications while using the same device architecture and/or to interchangeably use parts obtained from different suppliers to engineer those solutions.