It is worth taking a second look at fig 14 of the most recently published patent.

https://image-ppubs.uspto.gov/dirsearch-public/print/downloadPdf/20230384516 

2 quad laser arrays (8 lasers) connected to 8 modulators. Those 8 channels are then combined in an 8 channel mux which connect to the single loopback waveguide. Those 8 channels are looped back into the 8 channel de-mux then to the receiving devices. Very compact engine with both fully integrated transmit and receive in a single engine…800G  or 1.6T.