Hi

It is possible because you are supposing Electric and Magnetic field in a cylindrical structure so these fields can be written (excluding the dependence of time) like E(x,y)e-bz and H(x,y)e-bz, where E(x,y) and H(x,y) are the  transverse components of the fields, while the exponential is the propagation component along z (along the fiber length, of course). When you will write the curl-curl equation (on H or on E, you can choose... ) you will obtain a second order differential problem with boundary conditions, which can be discretize using FEM in  an eigen-value problem, where  E(x,y) or H(x,y) (it depends if you choose to solve using electric or magnetic problem) will the the eigen-vectors (modes), while the propagation constants will be the eigen-values.

For a PCF, considering the how much is complex the geometry of the cross-section, using a numerical method to investigate modal content is mandatory. FEM is quite efficient.

If you need more infos, send me an email ([email protected]), I will try to clear your doubts.

Anyway I suggest this book as a reference:

Jian-Ming Jin - "The Finite Element Method in Electromagnetics"

It is really well-written.

Hi, some softwares are efficient tools  to calculate the modal characteristics of a fiber. For example, comsol is very useful in simulation of PCF based on FEM. You can try it.

FEM is a very efficient frequency domain method to calculate modal characteristics of any type of fibers.

You can use Mode analysis module in the COMSOL for modal characteristics. 

Based on Yee Mesh, you can code FEM using solver MATLAB.

Thanks all for giving me the answer