A 1580-nm band WDM transmission technology employing optical duobinary coding

This paper reports 1580-nm band wavelength division multiplexed (WDM) trans mission employing optical duobinary coding over dispersion-shifted fibers. By using the 1580 nm band, the generation of four-wave mixing (FWM) over di spersion-shifted fibers (DSF's) can be suppressed. Optical duobinary coding is dispersion-tolerant because of its narrow bandwidth, and enables the us e of the conventional binary intensity modulated direct detection (IM-DD) r eceiver. First, comparisons are made for WDM transmission performance in th e 1580-nm band between conventional binary nonreturn-to-zero (NRZ) coding w ith and without postdispersion compensation, and optical duobinary coding b y computer simulation is described. From the numerical simulations, it is f ound that the optical duobinary coding has superior transmission performanc e to the conventional binary coding without any dispersion compensation, an d that the difference in the transmission performance between two coding me thods is very small even if postdispersion compensation at the optical rece iver is applied to the NRZ coding method. Second, transmission performance between the conventional binary NRZ and the optical duobinary signals witho ut any dispersion compensation is compared with the straight-line experimen t over 500-km dispersion-shifted fiber. The experimental results reveal tha t the transmission distance with optical duobinary coding is doubled in com parison with that of the conventional binary NRZ signals. Finally, 16-chann el, 10-Gb/s optical duobinary WDM signals in the 1580-nm band are successfu lly transmitted over 640 km (80 km x 8) of DSF without any dispersion compe nsation or management.