Characterization of single-mode fibers from wavelength dependence of modal field and far field

We present direct methods for determination of equivalent-step-index (ESI) parameters and file modal field by measurement of the wavelength dependence of the far-field intensity in single-mode fibers. A comparison is made with the spot-size method commonly used for characterization of such fibers. A new technique for measuring the LP
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mode cutoff wavelength is also presented.