Faster-than-Nyquist non-orthogonal frequency-division multiplexing based on fractional Hartley transform.

In this Letter, we propose, to the best of our knowledge, the first faster-than-Nyquist non-orthogonal frequency-division multiplexing based on fractional Hartley transform (FrHT). Different from the existing NOFDM signal, the real-valued FrHT-based NOFDM signal can be directly applied to an intensity-modulated/direct-detection optical system without upconversion, and it can achieve a transmission rate faster than the Nyquist rate, which is the up limit of orthogonal frequency-division multiplexing. For example, when bandwidth compression factor α is set to 0.4, the transmission rate is 20 percent faster than the Nyquist rate. Furthermore, we demonstrate simulations and experiments to verify the feasibility of FrHT-based NOFDM. After a 25 km standard single-mode fiber transmission, the bit error rate of FrHT-based DC-offset NOFDM can achieve a 7% and 20% forward error correction limit when α is set to 0.45 and 0.4, respectively.