An optical interconnect circuit for transmitting data between two or more electronic chips. In an example embodiment, the optical interconnect circuit comprises two or more photonic chips, each of which is vertically stacked with the corresponding electronic chip such that compact optical modulators and/or photodetectors of the photonic chip are in close proximity to the data sources/sinks of the corresponding electronic chip. Multi-core optical fibers and vertical coupling structures are used to provide multiple optical connections between different photonic chips. Advantageously, the provided capability to place optical modulators close to the data sources and to place photodetectors close to the data sinks can be used to reduce the amount of required electrical wiring. Optical-waveguide connections to the multi-core fibers can be used to allow for high density of optical conduits without spatially constraining the placement of data sources and/or data sinks on the electronic chips.