I am still confused about extracting phase information using FDTD::port. I have tested this method with the simplest model that TE0 mode whose wavelength is 1.55 ╬╝m travels through one strip waveguide. The distance between input port and output port is 10 ╬╝m, and neff = 2.27146. In this case, phase change = neff*2*pai*10/1.55 = 92.077. However, I extracted phase information using command unwrap(angle(S21))*180/pi and the result is -109.562.
The input port is set forward and the output port is set backward. The simulation is autoshutoff. Override mesh size is set 0.03 ╬╝m for x,y and z directions.
There may be something important that I missed. Besides, are there any other methods to extract phase information from waveguide?
Many thanks Haoyang