In this lesson we check that the layer peeling algorithm can reconstruct an unknown
grating with knowledge of only the reflection coefficient. In the first step, we select a
typical grating with chirp and apodization and calculate its reflection coefficient. This
spectrum is then exported to a text file. In the next step, OptiGrating is run again and
the spectrum file imported. The layer peeling algorithm is applied to the imported
spectrum to reconstruct the original grating.
|1||File > Open. Choose file Ex1a.ifo.|
|2||Select the Profile tab to see the details of this grating.
|3||Select the Power tab to see the reflection and transmission spectra.
Note: You can press Calculate to calculate the spectrum again, if desired.
|4||Click on Spectrum in the Single Fiber drop down menu, then click on the graph in the main window to active it.|
|5||Select Tools > Export Complex Spectrum and select the Reflection button as shown below:|
|7||In the Save As dialog box, find a suitable place and name for your data file.|
|1||Now, open a new project with File > New > Single Fiber.|
|2||Choose Calculation > Inverse Scattering Solver to get the Inverse Problem Solver dialog box.|
|3||Select the From File checkbox.|
|4||Navigate to the place where you left the file with the reflection spectrum. Open the file.|
|5||We suppose that the original length of the grating is known, so enter 50000 μm in the Length box. (Feel free to experiment with different lengths.)
|6|| Click on the Causality button to test this spectrum.
|8||Click Start in the Inverse Problem Solver dialog box to begin the
|9||Click on Spectrum to enable all tabs.|
|10|| Select the Profile tab to see the reconstructed profile.
|11||To see the chirp more clearly, right click the mouse in the Profile window and select Chirp Period.
. . . to get the following:
|12||Select the Power tab to compare the reflectivities, one from the imported complex spectrum and the other from the calculated response of the reconstructed grating.|