8x107 Gbit/s NRZ-VSB DWDM Field Transmission over 500 km SSMF

We present the results of an 8x107 Gbit/s ASK-NRZ-VSB DWDM field transmission trial in the fiber network of Deutsche Telekom. The 8x107 Gbit/s DWDM signal was generated by two Mach-Zehnder modulators each modulating a group of four wavelength on a 200 GHz grid for decorrelation of the neighbouring DWDM channels. Both wavelength channel groups are combined by a 100 GHz interleaver, which additionally converts the NRZ signals by vestigial-side-band (VSB) filtering to NRZ-VSB signals with 1 bit/s/Hz spectral efficiency. The transmission link consisted of 6 spans of standard single-mode fiber with an overall link length of 500 km. Pure EDF-amplification was used to compensate for the fiber loss. The link included two spans with high attenuation (~29 dB) and two spans with high PMD resulting in an overall link PMD of ~8 ps. Within the wavelength band covered by the DWDM channels the DGD was in the range of 3 to 15 ps, which corresponds up to the 1.6-fold of the bitperiode of the 107 Gbit/s OOK signal. Therefore application of a optical PMD compensation was mandatory for the transmission trial. After DWDM demultiplexing and direct detection of the 107 Gbit/s data signal in the ETDM receiver the BER of all tributaries of all DWDM channels was measured. We measured an average BER of 7x10(exp -4) and achieved stable operation .