The use of fiber lasers to engrave wood should be avoided. There are two main reasons not to use a fiber laser to engrave wood:

Fire Hazard: Applying heat to wood results in the obvious - a fire. Doing this with laser engraving can ignite your wood, which is a very serious safety risk. The danger arises when the beam goes to the wood where there is no controlled absorption due to the shorter wavelength.

Lack of control: Due to the uncontrolled absorption that wood has on fiber lasers, it is almost impossible to make smooth or clean marks. As a result, they are often charred and sometimes unidentifiable, making it impossible to make clear designs.

While fiber lasers can successfully engrave other materials, you should not use them to engrave wood and other organic materials.

Atomstack M4 Fiber Laser Marking Machine