re: “Usually, lasers can generate only one wavelength,” Arabzadeh explains.”
This is not accurate, or at best, it's a dated notion. The statement leaves one to wonder if the author actually meant "generate", or through some other filtering means "extracted" multiple wavelengths. In any case, WDM PONs have been using broadband light sources for over a decade, employing various wavelength slicing techniques.
Incidentally, Nortel <R.I.P.>, or one of its surviving components, which is mentioned in the RANOVUS material, was among the first to take this approach, IIRC.
Now, whether quantum dot technology is more recently the enabler of a new approach to multi-wavelength lasers, is something I'd have to look at more closely. Thanks for the homework assignment ;)
As to the basic premise concerning energy savings, while very likely true, my thinking is that this would be consistent with the per-unit energy consumption curve of most newly introduced ICT technologies. And if it's not, it probably wouldn't doesn't pass muster, thus relegating it to non-starter status."