As you said 400 gigabits/ sec seems to be the magic number, and 200 might not have been that crucial, as some solutions have already shown up
From YL:
“…Since I joined the Board of Directors in August and even more since I took on the CEO role, I've met with CEO, CTO and product leaders of some of the most significant players in the optical communication industry and will continue to do so over the next few months. My key takeaway is that the lack of a scalable modulator of technology reaching to 400 gigabits per second per lane and beyond is a serious problem for the industry. Forcing customers to adopt suboptimal optical solutions or rely on inefficient, power hungry, complex electronic signal processors …”
My interpretation from the quote is that the industry somehow has already covered the 200 gigabits/sec with acceptable solutions, but the real wall starts at 400gb/sec… So, it is time for some partner to be ready to try EOP, otherwise - for the time being - the industry would be stuck (and so would we :) )