Digital power division multiplexed DD-OFDM using fundamental mode transmission in few-mode fiber.

We experimentally demonstrate fundamental mode transmission of digital power division multiplexed direct detection - orthogonal frequency division multiplexed (DD-OFDM) signal at 25.3 Gbps in 6.5 GHz bandwidth through a 5.3 km few-mode fiber. We compare the performance of a two-channel digital power division multiplexed (DPDM) signal with DD-OFDM of higher modulation format with the same spectral efficiency in both linear and nonlinear regimes of operation. In the linear regime, the mean bit error rate performance of the two-channel DPDM signal performance is comparable to the DD-OFDM signal with higher-order modulation. In the nonlinear regime, both the constituent signals of the DPDM scheme have similar nonlinear thresholds compared to the DD-OFDM signal with higher-order modulation. DPDM transmission with DD-OFDM over few-mode fiber offers doubling of both split ratio and spectral efficiency over single-mode fibers when used for passive optical networks.