# Can you pass 400mJ laser light through a fiber?

What is the energy limit for fibre optics? For a dual-pulsed nd:yag laser firing at 10Hz with energy roughly 2x 400mJ, and pulse width ~5-10ns. My gut says that this is far too high to pass through fiber optics, but I have no experience in this matter.

Back of envelope - .4 J in 10 ns is 40 MW peak power. Put that into a 10 µm fiber, and the peak flux is $5\cdot 10^{17} W/m^2$. Nonlinearity sets in at field strengths above 10$^8$ V/m. Relationship between power and field is $$E = \sqrt{\frac{P}{\epsilon_0 c}} = 1.4\cdot 10^{10}V/m$$ - so your power density is two orders of magnitude above where nonlinearity sets in. It's likely that you will have trouble transmitting the power - in the nonlinear regime, fibers can get pretty weird (although exactly how they respond depends on the type of fiber).