Optical filters are crucial devices for wavelength channel selecting in wavelength-division-multiplexed fiber-optic communication networks. Measuring the inner physical parameters of optical filters is significant for analyzing emerging new and more complex structures. This paper proposed a general and easy-to-operate method to extract physical parameters for complex filter structures with optical low-coherence measurement. By treating optical filters with digital filter concepts and z-transform analysis, we can build the relation between interferogram peak values and transfer function coefficients with brief linear equations. These equations can be used to derive the exact expression of transfer functions, which can manipulate the physical parameters. For a given filter structure, according to relations between transfer functions and physical parameters, the physical parameters could be extracted. This is especially meaningful in the postfabrication process.
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