what is your idea about fundamental mode frequency and my simulation result?

Hi.
I have simulated a photonic crystal fiber and get following diagram for electric field on the axis fiber in frequency domain.
what is your idea about:
1. frequency resolution and noise in my FFT ?
2. fundamental mode frequency (and it's value)?
3 Each peak in this figure is corresponding to one mode in my result?
I have attached my input spectrum and electric field in frequency domain (input pulse is a modulated gaussian).

hello, i worke on photonic crystal cavities, and i wrote my fdtd code matlap .i compute the field distribution on the cavity, I find difficulty to calculate the transmision by the fast Fourier transformed (fft)
help me please