One directional relationship in Sankey Chart

Hi, 

I want to create a Sankey Chart that has one directional relationship from source to destination. Whenver I attempt build the visual, the result comes with multiple branches assuming a multiple flow when the data has just one flow; source to desttination.What I wantWhat I get

See sample visual of what I want to achieve. The left visual explains the exact flow of information in my data but when I use Sankey, it gives the result on the right, assuming a flow accross multiple sources and destination. How I can achive the visual on the left?