The toughest part (as I see it) is the business/economic part, getting multiple ISPs to cooperate and enable end-to-end optical paths. Having a control plane th

The toughest part (as I see it) is the business/economic part, getting multiple ISPs to cooperate and enable end-to-end optical paths. Having a control plane that works across multiple ISPs also requires solving technical and business problems. Optical paths, especially long-range optical paths, also have to deal with all sorts of signal loss and impairments, including effects from optical amplification, switching, coupling, and fiber itself.