I am trying to simulate an optic-fiber sensor (in-fiber interferometer) to study its respond to temperature. The method I am using is finite-difference time-domain (FDTD), and I come out with a large memory usage problem. The wavelength of the light source centered at 1.55μm while the optical fiber has diameter of 125μm and the length of it is set to order of 10-3m. This make the number of cells become very large.
After that I had tried to reduce the length by 1/62.5 which the memory usage drop to a more reasonable value (7.8Gb) but the result become weird, in which the amplitude of the signal at point of interest is higher than the source (I don't know why).
I found that many people are using beam propagation method (BPM) instead of FDTD. Is FDTD suitable for this case (with some modification on the model) which the wavelength is much much smaller than the geometry, or is there another method which is more suitable to compute?