Briefly, fiber laser light is created by banks of diodes. The light is channeled and amplified through fiber optic cable similar to that used for data transfer. The amplified light, on exiting the fiber cable, is collimated or straightened and then focused by a lens onto the material to be cut.
Creation of the light is 200% more efficient than via a traditional CO2 laser, and delivery is far simpler, with no expensive optical mirrors. The focusing lens, unlike on a conventional CO2 laser machine, is sealed in the cutting head and thus not a consumable item.
Fiber-Coupled Diodes - Disambiguation
Is a fiber laser the same as fiber-coupled laser? No - in a fiber-coupled laser, the fiber is just a means of transmitting power, not generating the amplification - 
- 120W - LIMO - 
- Multiple bars can be combined readily - 105W here - 
- LIMO 500W for plastics welding - 
- 40W Laser diode for coupling to a fiber - $325 -