Facebook and Google aren't leasing wavelengths and haven't for years. Sometimes they lease strands, sometimes they own the fiber in the ground and lease excess

Facebook and Google aren't leasing wavelengths and haven't for years. Sometimes they lease strands, sometimes they own the fiber in the ground and lease excess to traditional carriers. They own the longhaul equipment that puts waves on the strands. They own the transponders that takes normal 100GigE and converts it to waves. Random ISP may not be running MACSec, but a significant portion of subsea cable traffic does run over MACSec as it goes between datacenters and from datacenters to POPs where those cat videos get handed off to ISPs in the same region.