We have the pleasure to see one of the best hybrid integrated implementation made by InnoLight/Google JV in China.
Yole Développement & System-Plus-Consulting is to thank.

InnoLight/Google’s is one of the first 400G optical transceivers on the market, allowing communication up to 2km using PSM4 modulation, wavelength spectrum is 1310nm.
The solution is based on Inphi's (now Marvell Technology Group (US):
- PAM4 DSP (Digital Signal Processor) chipset,
- four GaAs laser driver dies and 
- TIA die (Transimpedance Amplifier)
The transceivers come with two separated lines, each with several dies aligned on the green PCB (printed circuit board).
- Upper part is the transmitter subassembly 
- Lower part is the receiver subassembly
The transceivers came with a transmitter that integrates four InP lasers (gold squares) driven by four GaAs dies (4 dark black rectangle. Other components are added to the system in order to focus or isolate the signals. The data are processed using a PAM4 DSP from Inphi. The DFB lasers are electro-absorption modulated.

InP lasers die and lens - (remarkably the lasers die comes with a *peltier cooler)


The connector assembly is complex. For the four emission fibers, a laser, a lens, an isolator and the fiber are aligned.

The receiver function is performed by four InP photodiode die and a TIA circuit. A fiber optic coupler and focusing lenses are used to connect the photodiode die with the fiber optic.

Again IMO - Overall, this is a far cry from wafer scale integration.

- For additional pics please download the report sample and flyer sample here
https://www.i-micronews.com/products/innolights-400g-qsfp-dd-optical-transceiver/

- 400G transceivers are expected to have the highest Compound Annual Growth Rate (CAGR) over the next five years, at 65%. 400G adoption started in 2019 with InnoLight being one of the top five suppliers.

*Peltier cooler
 https://en.wikipedia.org/wiki/Thermoelectric_cooling


Cheers

PS. Hey Leb -  I expected more from you too!