Experimental investigation on transmission system of dual-polarization mode-division-multiplexing signals with few-mode erbium-doped fiber amplifiers

The transmission capacity of optical fiber communication can be effectively improved by the combination of dual-polarization (DP) high-order modulation format with mode division multiplexing (MDM) technology. We build up an experimental system for amplification and transmission of DP-MDM signals with orthogonal mode combination (OMC) and identical mode combination (IMC). The MDM transceiver units are composed of mode-selective photonic lanterns (MSPLs) and few-mode polarization controllers (FMPCs). The few-mode erbium-doped fiber amplifier (FM-EDFA) used here is constructed by homemade isolation and wavelength division multiplexers (IWDMs). The amplification and transmission experiments for 100 Gb/s dual-polarization quadrature phase shift keying (DP-QPSK) MDM signals are carried out by the commercial optical transport network (OTN) platform. An effective method of optimally receiving DP-MDM signals are presented by appropriately controlling the FMPC in the MDM receiver unit. The experimental results show that, (1) OMC DP-MDM signals have a better performance than IMC cases in differential modal gain (DMG), which provides a new means to reduce the DMG; and (2) under the optimization conditions, OMC and IMC DP-MDM systems possess a close receiver sensitivity, but the former has a larger optical power margin than the latter by 2.2 dB. •To the best of our knowledge, the combination scheme of dual-polarization (DP) with spatial modes has not been investigated deeply until now.•Firstly, a simple and feasible experimental device for generating two types of mode combinations including orthogonal mode combination (OMC) and identical mode combination (IMC) are proposed and verified.•Next, the modal gain and differential modal gain (DMG) of DP-MDM signals under the two mode combinations are compared. It is shown that OMC DP-MDM signals can offer a new approach to modal gain equalization.•Finally, an effective method of optimally receiving DP-MDM signals is presented to improve the transmission performance.