Ultra-broadband OFDM signal generation for 1-Tb/s super-channel coherent optical OFDM transmission

A 320.6-GHz multi-band optical OFDM signal generation scheme consisting of continuous 4,104 subcarriers is demonstrated for 1-Tb/s coherent optical OFDM (CO-OFDM) transmission. The 36 uncorrelated orthogonal bands are generated using a recirculating frequency shifter (RFS) with single laser by adjusting the loop delay of RFS to be an integer multiple of OFDM symbol period. The principle and performance of this generation scheme is studied theoretically and experimentally. The 1-Tb/s CO-OFDM signal is successfully received after 600-km SSMF fiber transmission without any dispersion compensation.

Research Highlights
► A novel approach of multi-tone generation using a recirculating frequency shifter (RFS) architecture is proposed. It generates 36 tones spaced at 8.9 GHz with only one optical I/Q modulator. The RFS is able to generate multi-tone source effectively with superior flatness and tone-to-noise ratio.
► The entire CO-OFDM signal spectrum is generated without frequency guard bands between sub-bands. Furthermore, the orthogonality makes it an orthogonal-band-multiplexed OFDM (OBM-OFDM) signal.
► The 1-Tb/s CO-OFDM transmission with a reach of 600 km over standard single mode fiber (SSMF) is demonstrated.
► A spectral efficiency of 3.3 bit/s/Hz is achieved without either Raman amplification or dispersion compensation.