title: Experimental characterization of Raman overlaps between mode-groups.
abstract: Mode-division multiplexing has the potential to further increase data transmission capacity through optical fibers. In addition, distributed Raman amplification is a promising candidate for multi-mode signal amplification due to its desirable noise properties and the possibility of mode-equalized gain. In this paper, we present an experimental characterization of the intermodal Raman intensity overlaps of a few-mode fiber using backward-pumped Raman amplification. By varying the input pump power and the degree of higher order mode-excitation for the pump and the signal in a 10 km long two-mode fiber, we are able to characterize all intermodal Raman intensity overlaps. Using these results, we perform a Raman amplification measurement and demonstrate a mode-differential gain of only 0.25 dB per 10 dB overall gain. This is, to the best of our knowledge, the lowest mode differential gain achieved for amplification of mode division multiplexed signals in a single fiber.
authors.affiliation: Department of Photonics Engineering, Technical University of Denmark, 2800 Kongens Lyngby, Denmark.
authors.forename: Erik N
authors.initials: EN
authors.lastname: Christensen
authors.affiliation: Department of Photonics Engineering, Technical University of Denmark, 2800 Kongens Lyngby, Denmark.
authors.forename: Jacob G
authors.initials: JG
authors.lastname: Koefoed
authors.affiliation: Department of Photonics Engineering, Technical University of Denmark, 2800 Kongens Lyngby, Denmark.
authors.forename: Søren M M
authors.initials: SM
authors.lastname: Friis
authors.affiliation: Department of Photonics Engineering, Technical University of Denmark, 2800 Kongens Lyngby, Denmark.
authors.forename: Mario A Usuga
authors.initials: MA
authors.lastname: Castaneda
authors.affiliation: Department of Photonics Engineering, Technical University of Denmark, 2800 Kongens Lyngby, Denmark.
authors.forename: Karsten
authors.initials: K
authors.lastname: Rottwitt