Transmission of 35-Gb/s all-optical OFDM signals over 1650-km fibers without using tunable dispersion compensation

We demonstrate long-haul transmission of 35-Gb/s (7x5 Gb/s NRZ-OOK) all-optical OFDM signals. We -3 achieve bit error ratio of 3x10 for transmission over 1650-km span consisting of SSMF and DCF with all-EDFA amplification. Introduction Coherent optical orthogonal frequency division multiplexing (CO-OFDM) has received much attention as a promising technique in supporting transport capacity beyond 100Gb/s [1]. As is the case with single-carrier coherent modulation formats, the excellent transmission performance of CO-OFDM is in large part due to the advancement of high-speed digital signal processing for computationally compensating various transmission penalties. The high-speed electronic processing, however, has the drawback of high power consumption, which increases with increasing processing speed. Thus, it is desirable to perform some of the signal processing all-optically, preferably using passive devices, so that the burden on the electronic signal processing and power consumption can be minimized. Discrete Fourier transform (DFT) is a key operation for channelizing orthogonally multiplexed sub-carriers and it can be implemented all-optically [24]. Recently, we have implemented an all-optical (AO) OFDM system supporting reception of 35-Gb/s (7 x 5 Gb/s NRZ-OOK) data having near-unity spectral efficiency with 1-dB dispersion margin of ~1000 ps/nm [4]. The AO-OFDM was enabled by passive-optical DFT circuit implemented using multimode interference (MMI) couplers on a high indexcontrast silica integrated-optic platform.