Fiber Optic Multiplexing Solution?

Before I begin, let me detail my setup. I have a house, wired with a phone and intercom, and connected to the internet. I have a very large storage shed, down a hill connected with about 2000 ft. of fiber optic cable for the intercom. I am trying to multiplex my ethernet connection down that cable and demultiplex it down at the end of the cable where it comes into the building. That way I can use the current cable to transfer an internet connection instead of laying another ethernet cable. It would be cheaper, and most importantly, have minimal labor costs. How would I do this? Where would I buy a fiber multiplexing system that fits my needs? Please help.