Hi Taiwo,Basically it depends upon manufactrur as Ravil said.In most of the papers that i have seen value of dispersion taken is -85ps/nm/km and attenuation 0.5 db/km for dcf.Roughly ,dcf dispersion is negtive 5 times the dispersion of your SMF.If it is 16 ps/nm/km then dcf of -80ps/nm/km would be best and if you are using SMF of dispersion 17 then -85 would be best choice.Rest attenuation may vary 0.5-0.6 dB/km