40-Gb/s RZ signal transmission in a transparent network based on wavelength-selective optical cross connect

We investigate 40-Gb/s return-to-zero signal transmission in a transparent optical network equipped with wavelength-selective optical cross connects (WSOXCs). The investigation is performed in a recirculating loop setup consisting of 4100-km spans of transmission fiber. A WSOXC is placed inside the loop to mimic cascaded WSOXCs with a spacing of 400 km. We study various degradation effects in the system, particularly those of node loss and optical filtering. Q value measurements of the received signal were carried out at different transmission distances and WSOXC loss conditions. A Q value of 15.5 dB was measured at 1200-km distance with two cascaded WSOXCs of which the node loss is 17 dB.