Hi. You can use Lumerical software. Recent versions support ports which you could use for determining the desired output mode. You can also export the modes from input and output monitors and compare them in Matlab with overlap integral calculation.

@Seyed Hadi Badri , thanks for your helpful answer, but I want to simulate 1 meter length 20/400 bent fiber with 8 cm bending radius, is lumerical useful for this?

Such a large structure would require a very large RAM so you should tweak the mesh setting manually and you should minimize the simulation domain.

You should read " Mode scalability in bent optical fibers" Ross T. Schermer, Optics Express, 2007

@Dirk Nodop , thanks for your very helpful answer.