Wavelength-Insensitive Weakly Coupled FMFs and Components for the MDM-GPON

Mode division multiplexing (MDM) has been widely investigated to enhance the capacities of passive optical networks (PONs), and weakly coupled transmission schemes are highly preferred to reduce the cost and complexity. However, wavelength insensitivities are scarcely studied for such applications. In this letter, an evolution scheme of the cascaded mode division multiplexing PON (MDM-PON) and conventional Gigabit PON (GPON), which supports bidirectional 1310/1490-nm transmission, is proposed. This scheme is enabled by wavelength-insensitive weakly coupled (WIWC) few-mode fiber (FMF) and optical components. Then, the realization of both WIWC few-mode wavelength division multiplexers (FM-WMUXs) and mode-selective couplers (MSCs) is analyzed. Based on the analysis, WIWC FM-WMUXs and MSCs that support two linear polarization modes and 1310/1490-nm transmission with low modal crosstalk are designed and fabricated. Finally, the bidirectional MDM-GPON transmission scheme with 2.5 Gb/s on-off-keying modulation and simple direct detection over 10-km FMF and 10-km single-mode fiber are experimentally demonstrated. The proposed MDM-GPON evolution scheme can achieve maximum compatibility by maintaining both the optical distribution network and the optical network units.