740 km transmission of 78-channel 64-QAM signals (2.34 Gb/s) without dispersion compensation by using a recirculating loop

A long distance 1550 nm subcarrier multiplexed lightwave trunk system which transported 78 channels of 64-QAM signal was demonstrated in a recirculating loop experiment. Each channel can achieve a carrier-to-( noise + nonlinear distortion) ratio of 30 dB after 740 km transmission through conventional single-mode fiber without dispersion compensation.