USB to Optical Signal Conversion
10 megabit ethernet is a simple digital signal, so convert your video into
a UDP stream, and wire the sending ethernet pair to a LED

at the other end you'll need to amplify the signal such that it can be fed into an etherent socket,

10MBit ethernet has a frequency range of 10-20 Mhz so LEDs should bet fast enough 

A raspberry Pi might work well at both ends, it has ethernet, USB, and analogue video out.

10Mbit/s is fast enough for compressed video, but not for raw digitised video, fortunately the raspberry pi has a built-in H.264 codec.

Netcat might be all that's needed to send and receive the UDP stream, 
but you may need to tweak the ARP tables to get the ethernet layer 
lined up to work with a simplex (monodirectional) link.

this might be a plan of action:


make it work with easycap and one raspberry pi between the camera and the display
replace the single raspberry pi with two connected by a LAN
replace the LAN with a cross-over cable
override autonegotiation the get the cable running at 10Mbit speed
replace the cross-over cable with a single pair cable
replace the single pair with an optical link.