The Calculation menu allows you to do your calculations quickly and efficiently.

**Run**

To perform your Calculation, Spectrum, and Pulse Response calculations, just click

either Run from the Calculation menu or the Run button on the Toolbar.

In the dialog box that opens, you can see when the calculation is completed.

**Scan**

To perform your parameter scan calculation.

**Inverse Scattering Solver**

To solve the inverse scattering problem of Bragg gratings. The method is based on a layerpeeling algorithm. See the Technical Background chapter of the OptiGrating manual for details.

## The Scan dialog box

**Select Grating/Phase Shift**

Select either Grating or Phase Shift from the list

**Select Scan Parameter**

Select a scan parameter from the grating list in this section

**Scan the Parameter**

From – Initial value of the scan parameter

To – final value of the scan parameter

Steps – Number of the calculation steps in the Scan calculation

## The Inverse Scattering Solver

For detailed information on how to use the Inverse Scattering Solver to solve the

inverse scattering problem, please refer to Lessons 5 -8 in the Tutorial section of the

OptiGrating manual.

**From**

The starting wavelength.

**To**

The ending wavelength.

**Steps**

The Steps field indicates the number of divisions used in the specified wavelength

range.

**Ref/Tran Define**

Brings up a dialog box for defining the target reflectivity spectrum as seen below:

- Click on Display to plot the curve shown. The desired impulse response will be

calculated from the Fourier transform of the reflection coefficient.

Dispersion profile Define

Located beside the Phase, Delay, and Disp radio buttons. Defines the target spectrum for the quantity indicated by the radio buttons.

**Length**

This is the length of the grating.

**From File**

Enable this checkbox and define a path to a file which contains a complex reflection

spectrum. The algorithm will try to find a grating that has this spectrum.

**Segments**

The grating length is divided into this number of segments. Each segment has a

constant coupling coeffiecient

**Over Sample**

Over Sample is used in the reconstruction ofthe truncated impulse response.

Accuracy is sometimes improved by using finer steps in the spectrum.

**Causality**

Clicking on this button will display the impulse response calculated from the spectrum

the user has defined.

Clicking on Causality will show the following screen:

- Because of causality, any real impulse response must be zero for negative

arguements.

**Note**: You can experiment with various delays by entering other numbers in the

Linear Phase Shift field, and clicking the Impulse Response to see the result.

**Start**

Clicking on start begins the reconstruction. A progress bar indicates the progress of

the layer peeling algorithm. When this process finishes, the reconstructed grating

profile is used to generate the spectrum of the new grating. A second progress bar

displays the progress of the calculation of the spectrum