title: Measurement of effective refractive index differences in multimode optical fibers based on modal decomposition.
abstract: We demonstrate the nondestructive measurement of the effective refractive index difference of two arbitrary modes within a multimode optical fiber by utilizing a tunable fiber grating. We use a mechanical grating of variable period to couple the respective modes and measure the mode content at the fiber output based on the correlation filter technique. From the dependence of the coupling efficiency on the grating period, the effective index difference of the modes can be extracted with high accuracy.
authors.forename: Christian
authors.initials: C
authors.lastname: Schulze
authors.forename: Johannes
authors.initials: J
authors.lastname: Wilde
authors.forename: Robert
authors.initials: R
authors.lastname: Brüning
authors.forename: Siegmund
authors.initials: S
authors.lastname: Schröter
authors.forename: Michael
authors.initials: M
authors.lastname: Duparré