That is not an easy question to answer. What we do know is that monolithic integration of all optical functions and electronic functions on a single die in silicon CMOS is never going to happen. The processing requirements are too different with different annealing temperatures which are not compatible for the materials associated with the active optical elements and electronic elements at the same time. However I think what POET has succeeded in doing is a backend process where the InP PICs are placed on a processed silicon wafer through automated pick and place and then the dielectric is deposited between the two dies, metalized for electrical connections and waveguides etched to form the mux/demux.

Poet's optical interposer provides the ability to run electrical and optical interconnections side by side on the same interposer chip at a micrometre scale. The optical interposer represents an integral part of Poet's hybrid integrated optical engines and leverages the manufacturing processes and unique capabilities of its dielectric waveguides.

It is easy to recognize how this provides for a transceiver with a compact foot print which could provide chip to chip optical capability. But you can also begin to understand that it also provides a means to pass both optical and electrical data into and out of the silicon chip whether that is memory, processor, sensor or other.