Using the latest version of the software

If you have obtained and installed the new version of the software, here are few things to get you started, and a few things you need to know.

Important Differences with the public version

The generic way of using the software, the syntax of the parameter file, and the input and output files are very similar to the public version. However structures are no longer defined within the parameter file - instead a graphical user interface in Winfield is used to create structures. The new software uses new file formats; Winfield and Bfld are largely backwards compatible with all versions, including the public version, however Fibre itself requires new file formats, so old position files needs to be converted to the new format, by opening them in Winfield, them saving them using the export button in the structure editor, see below.

Notable changes are:

• the keyword accuracy goal which allows a much better control of accuracy than the now almost obsolete eigenvalue threshold see below;
• the possibility to use different orders of truncation for different cylinders. This can increase calculation speed by an order of magnitude while improving accuracy when simulating structure with a large hollow core;
• the batch processing utility bfld.exe- allowing for example to compute field plots, effective areas and alike for a list of bcf files at once;
• ability to deal with coated inclusions, elliptic inclusions, and circular inclsuions iwth arbitrary radial index profile;
• simple macro capabilities;
• graphic structure designer in winfield;
• high resolution native encapsulated postscript (eps) output in Winfield;
• new file formats;
• tracking of modes with changes in geometry.

The Release notes contain a detailed list of all changes and new features.

Creating structures

Creating structures from the parameter file is no longer recommended, and in some cases no longer supported. Instead, use the structure editor in Winfield, save ('export') the structure to a structure file (.mof) and then load the structure in the parameter file using:

structure=structurefilename.mof

• redefining

order
gorder

in the parameter file should also be avoided. All cylinders can now have their own order parameter, defined in the structure file using the structure editor.

• The default extension for structure files is now .mof rather than .txt (but either can be used).
• User defined new materials with material dispersion can be used.

Threshold keywords

The mode finding algorithm is vastly optimized compared to the public version, and uses slightly different threshold parameters. The parameters eigenvalue threshold and determinant threshold are now far less important, and can in general be set to 0.1. Instead, there is a keyword determining the precision to be reached on the effective index of modes accuracy goal. This parameter should be set to a number close to machine precision, from 3e-14 (smallest acceptable value, for structures with 1--6 inclusions or so) to 1d-11 (for very large structures, such a high value is not recommended when calculating dispersion curves). A value that works in most cases (except for single rod simulations, where 3d-14 should be used) is 1d-13. In summary, for most simulations, use

accuracy goal=1d-13
eigenvalue threshold=1d-1

There is also an additional keyword acceptable accuracy that allows the software to accept values of lesser accuracy if no mode can be found with the accuracy required in 'accuracy goal'. This can be useful in some cases to avoid long simulations stalling, but if accuracy is paramount this should be set to the same value as accuracy goal. A warning is issued in the error file if accuracy goal is not reached, but acceptable accuracy is. See Accuracy goal

File compatibility

Winfield, Fibre and Batchfield are backwards compatible, and files produced with the public version (or other older versions) can be loaded with the new version. However the converse is not true. The new format of structure files is documented in the article on Structure files.