Raman amplification of OAM modes

The set of fibre modes carrying orbital angular momentum (OAM) is a possible basis for mode division multiplexing. In this regard, fibres supporting OAM modes have been fabricated [1], and optical communication using these fibres, has been demonstrated [2]. A vital part of any long range communication system is an optical amplifier. Here we demonstrate, for the first time, Raman amplification of OAM modes.