If you want speed and these fibre lines are from the same ISP, then you just ask them to bond the connections. They'll send you their modem that can do it. However if they're different ISP's or your ISP refuses. There are third party services that can set it up for. This guide walks you through everything you need to know about fiber ring networks—from basic concepts to topology diagrams and essential protocols. SD-WAN is one of the most robust and cutting-edge solutions that cater to small, medium, and large business locations and data center sites. Bridging two routers on one network isn't as common as it used to be (thanks to mesh Wi-Fi systems), but it can still be an effective way to improve network access in larger. Any possible way to convince ATT to just set up a second line if earthlink is basically going to do that and charge more? Yes, it's possible to have multiple providers at one building.
[PDF Version]