Using Winfield

Winfield is a software to compute and analyse fields from their Fourier-Bessel expansions, using a dialog based user interface for Microsoft Windows.

Main dialog controls

open file button: Click here to open the standard Windows file open dialog and select a .bcf or .fbb file to open.

refresh button: updates the field representation (and runs the field computation when needed)

resolution text edit field: number of points along each axis on which the field is computed.

local expansion: When checked (default) a much faster, but also somewhat erroneous method of calculating fields is used. When checked, fields are accurate near cylinders, but inaccurate further away from cylinders, and in particular in a typical PCF's core. Always uncheck this option if you will use the fields to calculate loss, effective areas or overlap integrals.

view pos file button: Click here to open the standard Windows file open dialog and select a structure (or cylinder position) file (.txt extension) for visualization.

More options button: Opens the advanced tools dialog, including controls to compute the Bloch transform, the Wijngaard test, the alternate method to compute losses, and controls for exporting field data in various formats (various formats of raw data or bitmap)

field selector: The three central drop down lists select the field (Poynting vector S, fields H or E), the component (Cartesian x, y or z, cylindrical r or θ, norm, Bloch transform, or structure), and the part of the component (real part, imaginary part, magnitude, phase or magnitude in log scale) to visualize.

zoom group: Enter a zooming coefficient and click the zoom now button to zoom on the current coordinate. Zoom factor>1 zooms in, zoom factor<1 zooms out.

current coordinates group: sets the center for zooming. You can enter the coordinates by clicking on the field map. Clicking on the field map will also give you the z-coordinate, that is the value of the selected part / component / field at the point clicked, and show you which part of the structure you clicked on (in the status bar on the bottom).

color range group: lets you chose whether you want to use the extremal values of the current part / component / field as the limits of the color scale, or if you prefer to set the limits of the color range manually (uncheck use extremal values and enter the minimum and maximum values). You can also inverse the color scale, or use grey scale representation. If you check the Flux norm box, Winfield will use a consistent flux based normalization, useful to compare field densities.

interpolate: When checked, uses bi-cubic interpolation to give a smoother representation of fields, and enables you, with the contour check box next to it, to draw filled contour plots.

no cladding and no jacket check boxes: hide the field in the cladding and jacket, and adjust the colour ranges accordingly.

ignore cladding: performs all field computations as if the cladding and jacket didn’t exist (useful - and automatically set- when the cladding and jacket index are the same as the matrix index).

draw cylinders and fill cylinders check box

enables you to draw the contour of the cylinders and optionally fill them.

The ’Advanced Tools’ dialog appears when clicking on the ’more options...’ button in the main dialog.

Write file group: Controls in this group enable you to write the computed fields to files in

various formats. See Export fields.

Wijngaard test group: Used to perform Wijngaard tests (see Eq. (4), Ref. [2]) around inclusions or at the cladding boundary. It can also check the continuity of fields at the cladding and jacket boundaries. To compute the Wijngaard integral W around a given inclusion, enter the number of points used to compute the integral (number of points edit box) click on the desired inclusion (in the field plot window), select the field (E_z or H_z ) then click the Check it! button. If you check the Write File check box, you can also write the local and Wijngaard fields as a function of angle at the boundary of the inclusion to a file. The resulting file contains 4 columns of numbers, the first is the angle (radians), the second the local field, the third the value of the field resulting from the Wijngaard expansion, and the fourth is the magnitude of the difference between the second and third column. When selecting the Jacket radio button, the local and Wijngaard fields are replaced by the fields just inside and just outside the jacket boundary respectively. When selecting the Cladding continuity radio button, the Wijngaard field is the Wijngaard field expansion at the matrix/cladding boundary, and the local field results from the field expansion in the cladding at the matrix/cladding boundary. The check all button will calculate all W values and color the cylinders from green (good Wijngaard test result) to red (poor result).

Loss group: Used to compute the losses and imaginary part of the effective index using the energy flux method from Eq. (10) in Ref.[2]. To compute the surface integral in that equation, Winfield uses the fields computed for the field representation. For accurate results, resolution should hence be at least 150, and the current view should include all inclusions. Note that even with a perfect numerical integration, the relative error obtained through this method is of the order of the largest W Wijngaard integral of all inclusions. The contour integral is computed using Number of points points on the circle centred on the origin and with radius specified by the user. If the radius if left to zero, 0.99× the cladding radius is used.

Effective Core Areagroup: used to compute effective areas. The conventional effective area formula is used, but the user can select which field and component to use in the integrals. Checking the normalize to pitch check box displays the result divided by the pitch squared. (Note that the algorithm extracting the pitch works properly only with C_6v structures). Again, numerical integration relies on the fields previously computed for displaying fields, and hence the accuracy of the effective area will depend on resolution and the current viewport.

Bloch Transform group: is used to compute the Bloch transform as defined in Ref [5]. The field used for the Bloch transform can be selected either in this group or with the field drop-down list in the main dialog. The resolution to be computed and displayed for the Bloch transform can be defined separately from the resolution for the fields. The Order edit box lets you select the order of the Bloch transform. If you enter a value greater than the truncation order of the Fourier-Bessel series, the total Bloch transform will be displayed.