Long-haul coherent QPSK transmission of 40G channels with 120% spectral efficiency using increased linearity dispersion map with 100km spans and EDFAs

We study transmission of 40 Gb/s signals using coherent RZ-QPSK with and without polarization multiplexing using 100 km large effective area fiber-spans and dual-stage EDFAs with mid-stage dispersion compensation. We show advantage and disadvantage of coherent detection schemes.