title: Differential Rayleigh scattering method for measurement of polarization and intermodal beat length in optical waveguides and fibers.
abstract: We propose a modification of the Rayleigh scattering method, which allows for measurement of polarization and intermodal beat length in single-mode and few-mode channel waveguides and optical fibers. A significant sensitivity increase is achieved by taking two high-resolution photographs in oblique scattered light of π-shifted intensity distributions produced by interference of polarization or spatial modes and applying Fourier analysis to the differential image. In the case of polarization beat length measurements, the π-phase shift is obtained by switching the polarization state at the fiber input, while in intermodal measurements, the π-phase shifting is realized by changing the excitation conditions. The usefulness of the method for characterization of channel waveguides and optical fibers is demonstrated in several examples. Moreover, we show that the combination of the spectral interferometry method with the proposed method allows for broadband measurements of differential phase and group effective indices.
authors.affiliation: Institute of Physics, Wroclaw University of Technology, Wybrzeze Wyspianskiego 27, 50370 Wroclaw, Poland. marcin.szczurowski@pwr.wroc.pl
authors.forename: Marcin
authors.initials: M
authors.lastname: Szczurowski
authors.forename: Waclaw
authors.initials: W
authors.lastname: Urbanczyk
authors.forename: Maciej
authors.initials: M
authors.lastname: Napiorkowski
authors.forename: Petr
authors.initials: P
authors.lastname: Hlubina
authors.forename: Uwe
authors.initials: U
authors.lastname: Hollenbach
authors.forename: Heinrich
authors.initials: H
authors.lastname: Sieber
authors.forename: Juergen
authors.initials: J
authors.lastname: Mohr