title: Low-loss coupling between two single-mode optical fibers with different mode-field diameters using a graded-index multimode optical fiber.
abstract: We present a method for ultra-low-loss coupling between two single-mode optical fibers with different mode-field diameters using multimode interference in a graded-index multimode optical fiber. We perform a detailed analysis of the interference effects and show that the graded-index fiber can also be used as a beam expander or condenser. The results are important for devices in which optical fibers with different mode-field diameters are coupled in series, such as in ultra-short-pulse fiber ring lasers, or in optical fiber communication links.
authors.affiliation: Department of Electrical Engineering & Computer Science, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin 53211, USA. mafi@uwm.edu
authors.forename: Arash
authors.initials: A
authors.lastname: Mafi
authors.forename: Peter
authors.initials: P
authors.lastname: Hofmann
authors.forename: Clémence Jollivet
authors.initials: CJ
authors.lastname: Salvin
authors.forename: Axel
authors.initials: A
authors.lastname: Schülzgen