I think if you read the press release POETMMc you will see the advantages of using the POET O/I for a 100G engine.  My understanding is this product range is not inteneded to be a game changer in the 100G space, merely a chance to show that this technology can be massed produced and save significant costs, since it integrates transmit and receive functionallity into one engine.  4x100G engines can fit into a transceiver, which can then plug into a 400G socket, therefore maintaining legacy equipment, instead of costly upgrades.  Ross Saunders of ADVA sums it up.

The MicroMux Quattro is the latest addition to ADVA’s MicroMux portfolio (see, for example, “ADVA offers MicroMux Edge BiDi pluggable for access networks” and “ADVA expands MicroMux pluggable multiplexer line for edge and core networks”). “ADVA’s MicroMux Quattro brings the industry’s smallest aggregation technology all the way to the network core. Engineered as a standard-compliant plug in a QSFP-DD form factor, it fits into a 400-Gbps socket, enabling it to meet legacy needs,” explained Ross Saunders, general manager of optical engines at ADVA. “This innovative pluggable solution packs the functionality of four independent 100-Gbps interfaces or two independent 200-Gbps interfaces into a single QSFP-DD housing.

“POET’s unique design of its optical engines with hybrid integration of optical chips and monolithically integrated mux and demux enables us to deliver industry-leading products in a small form factor that is scalable to high-volume production as well as to higher data rates, such as 1.6 Tbps and 3.2 Tbps, thereby enabling much higher bandwidth in a pluggable form factor,”