1.5 terabit/s submarine 4000 km system validation over a deployed line with industrial margins using 25 GHz channel spacing and NRZ format over NZDSF

We have transmitted 1.5 Tbit/s over a deployed line of 4000 km of NZDSF using only C-band EDFAs with 25 GHz spacing and NRZ modulation format. The average performance obtained correspond to a 4.8 dB margin for a system designed with Enhanced 7% redundancy FEC scheme based on concatenated Reed-Solomon code. This experiment demonstrates for the first time the industrial feasibility of a 1.5 Tbit/s regional network transmission which is compatible with 0.4 (bit/s)/Hz. The use of NRZ format has two advantages. The first one is a low cost and compact terminal equipment due to less modulation stages compared to RZ or CRZ. The second one is a better compatibility with high channel density allowing simpler and lower cost repeaters for a given capacity. Furthermore, the demonstration of the excellent robustness of NRZ format over NZDSF allow direct field deployment or upgrades.