parameters.txt

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	!       CUDOS Fibre Software sample parameter file
! This parameter file is for finding the fundamental mode of 
! a simple fibre with 3 layers of holes, and to compute 
! its effective index as a function of wavelength.
! The fibre is made out of silica, and the software takes
! into account material dispersion of silica.
! The structure is defined in the parameter file, and
! symmetries are used to reduce the problem.
! all internal parameters are adjusted automatically.
!
! First define the structure :

pitch=2.3d0			! center to center distance of the air 
				! cylinders
cylinder index=(1.d0,0d0)	! air cylinders
d/pitch=0.5d0			! diameter on pitch ratio
matrix index=silica		! background is silica
Nr=3				! Number of rings
MNr=1				! The core consists of only one missing
				!  cylinder 
no cladding			! The air cylinders are not surrounded by
				!  a jacket or a cladding
no jacket


! set the truncation order for Fourier Bessel functions to 5, 
! which should ensure sufficient accuracy on the whole wavelength range
order=5

cladding order=1			! there is no cladding or jacket, so the
				! cladding Fourier Bessel expansion is 
				! not used: we set its truncation order to the
				! smallest admissible value

build fibre			! compiles the above parameter into a structure


! save the structure to symhex.txt

save fibre=3layers.txt

! *** Parameters to find initial mode

! define physical parameters
start_lambda=1.			! sets initial wavelength

! ask the software to find the effective index range

suggest n_eff range=fundamental		! finds the range of effective indices where the 
					! fundamental mode should be
! *** Parameters for computing the dispersion curve

stop_lambda=2				! final wavelength
number of points=200			! compute for 200 wavelengths between
					! start_lambda and stop_lambda
number of points between log=20		! log a mode to a Fourier Bessel 
					! coefficient file every 20 
					! wavelength steps


! Now compute the dispersion

compute dispersion curve


! end of parameter file
end