Real-Time LR-DDO-OFDM Transmission System Using EML With 1024-Point FFT

In this letter, we experimentally demonstrate a complete Field Programmable Gate Array (FPGA)-based real-time point-to-point long-reach (LR) direct-detection optical orthogonal frequency division multiplexing (DDO-OFDM) transmission system using a cost-effective electroabsorption modulated laser with 1024-point fast Fourier transform (FFT). To the best of our knowledge, it is the so-far reported largest FFT size used in real-time DDO-OFDM system. Based on the system, in an asynchronous way, an adaptively 16-quadratic-amplitude modulation/quadrature phase shift keying/binary phase shift keying modulated real-time optical OFDM LR transmission has been experimentally demonstrated without sampling frequency offset compensation, which is achieved by utilizing the effective symbol timing synchronization and the pilot-aided and linear-interpolated channel estimation scheme. Moreover, the bit-error rate of below than 1e-3 can be successfully achieved after 150-km standard single mode fiber transmission.