I am using FDTD v2017a to run simulations over a wide bandwidth from 1200nm to 1700nm. I simulated a regular waveguide tapers using the EME monitor to extract the fundamental TE mode transmission efficiency. I first ran the FDTD simulation over the entire 500nm wavelength range with the linear wavelength spacing and 501 data points. I then ran the simulation on the same structure with 5 sweeps of 100nm wavelength ranges. Each sweep covers 100nm wavelength range and have 101 data points. Both simulations have the same mesh setting and conformal mesh accuracy.
I suppose that the two simulations should give me similar results. However, the results are very different. I wonder if there is an efficient and accurate way to simulate a structure over such a wide bandwidth.
I attached with the FDTD file and the results of the two simulations.
WG_StripTaper_WG350650L3_Model.fsp (3.7 MB)