Simulation about fiber tip with grating

Hi, all,

I am stuck at how to simulate such a structure (see attached), which includes grating is built in end face of the single mode fiber. Main purpose is to get the transmission.

Without grating, I can use boundary mode analysis+frequency domain to get it, among which the light is defined by port boundary condition, but due to the existence of the grating, the scattering will be occured, so the definition of Port will useless.

Is it feasible to simulate it using scattering field method? And are there any tutorial about this?
Anybody can give me some help about this model? Thanks!

Regards,
Marvin