Authors - Shakeeb Abdullah, Jim Hjartarson, Rony E. Amaya Abstract - Currently the fastest tried, tested, and reliable electro-optical transceivers operate at 56 Gbaud (56 Gbit/s NRZ or 112 Gbit/s PAM-4) communication speeds per lane, and while some companies have finally started rolling out their 112 Gbaud (224 Gbit/s PAM-4) line of products for commercial use, not all companies have caught up; nor is their much research presented on 112 Gbaud TIAs. Higher speeds such as 400 Gbit/s are usually obtained by transmitting data through multiple parallel lanes of 100 Gbit/s PAM-4. The optical industry has been pushing for the next generation of 112 Gbaud (112 Gbit/s NRZ or 224 Gbit/s PAM4) rates for devices, however, it had stalled (hitting many roadblocks) in the past six years or so. Currently, the popularized TIA architectures are producing diminishing returns in terms of their bandwidth performance for every incremental improvement in its designs (or heavily relying on DSP); for this reason, a new paradigm construct is required to overcome such obstacles and meet the new standards of the next generations of TIAs. This brief proposes a different approach in designing TIAs for 112 Gbaud speeds or higher. Estimated criterion dictates a 3-dB BW of 78.4 GHz to process clean eyes at 112 Gbaud. Proposed TIA architecture in this paper utilizes distributed approach instead of usual common gate or feedback mode to convert the incoming photodiode current into an electrical voltage. Post-layout electromagnetic simulations show that these amplifiers can process PAM-4 eyes with 40 mV pk-pk outputs at -3 dBm of input optical power.
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