I think you're confused about some of how this works.
It sounds like you're saying the wifi is also light signals. Fibre optic cables do transmit light signals, but that only goes up to the Bell modem at best (and possibly not even that far). Everything after that is either copper wire in the case of Ethernet, or radio frequency in the case of WiFi. Installing a router will not effect light signals in any way as your router would be using standard copper wire.
It sound like you had wifi issues in part of your home the was located far from the Bell modem/router, so you ran a copper Ethernet cable and set up a modem in a different area to improve the signal. But all of that is conventional, not light signals.
One of the big advantages of fiber optic light signals is that they are unaffected by all the things that cause interference for traditional electromagnetic signals in copper wire and wireless radio frequency signals. EMI and RF interference is everywhere and is the cause of many problems with electronics, but fibre optic is completely immune to it. So you should not experience any issues at all with the "light signal being interrupted by several factors". Fibre optic can only get interference from itself, and it should be non-existent within this context.