Multi channel signals

Sub carrier multiplexing was/is used for analog CATV distribution and is essentially the same as RF multiplexing but there are a lot of parameters which need very careful control for this to work successfully.

For digital signals the first stage is /time division multiplexing/ of various channels into one continuous digital stream. Of course this is common to all digital transmission not just optical.

On the optical side you can take different wavelengths and then combine them using /wavelength division multiplexing/ so you transmit several seperate optical channels down one fibre

A quick search for any one of these key phrases should get you on the road.

Depending on what level you are at and what level of understanding you want to get to then the best option is to get hold of a decent book.

For a low level math free start Jeff Hecht's Understanding Fiber Optics is pretty good.

For a technical perspective, there are probably a dozen books with the title rough title Optical Fiber Communications that all do a similar job. For example Agrawal, Keiser or Senior are all pretty good

cheers

David