Phase reconstruction and chromatic dispersion characteristic of thin film filters

Thin Film Filters (TFFs) are minimum phase filters, and the Hilbert Transform law is related to the relationship between a TFF's amplitude and phase response. It should be possible to obtain the phase response from the amplitude response by this law, but the Cauchy Integral is too complex to calculate the phase response directly. In this paper, a method to reconstruct the phase response from the amplitude response was proposed, and then the group velocity delay and the chromatic dispersion of a TFF could also be obtained just by simple calculations. An experimental setup based on the RF modulation was designed. The test results were in good agreement with the theoretical value within passband, as determined by contrast analysis, and the validity of the method was proven. In addition, the dispersion characteristic of TFFs was also analyzed.

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