So I am slightly unclear on what you are attempting to plug the the routers into. The OLT cable may look like a CAT5,5a,6,7 cable but it is not compatible with Ethernet. I believe that OLT connections are colored green and Ethernet should be yellow, blue or silver. A picture of the ports of the device might help. You could also have a bad or unsupported Ethernet cable. You want a Cat 5a at the very least.

ONT stands for Optical Network Terminal​. It is an outlet to the Internet for fiber technology just like how a cable modem is the outlet for a coaxial cable Internet connection. It is a device that communicates directly with an Internet service provider (ISP) to get a fiber-optic Internet connection in your home or office. However, an ONT is specific to fiber-optic Internet so you cannot use an ONT with an Ethernet over coax or MoCA device like a cable modem, router or cable modem router, for example.

This page focuses on ONT, but there are other fiber technology abbreviations to know. The other abbreviations are:

  • PON​, which stands for ​Passive Optical Network.​ A PON is the “last stop” between you and your ISP. More specifically, the PON is the last part of the communication chain that reaches your home.
  • OLT​, which stands for ​Optical Line Terminal. ​An OLT is the device that serves as your ISPs endpoint of the PON. ​An OLT provides the interface between a PON and a service provider’s core network.​ ​For more, c​heck out our OLT page.
  • ONU​, which stands for ​Optical Network Unit. ​This is a combo device that functions as both an ONT and OLT. That means an ONU acts as both the endpoint of the PON and as the interface for the user. ​For more, ​check out our ONU page.

Overall, a PON consists of an OLT at the service provider’s central office and a number of ONUs or ONTs near end users.