The 29-year-old Cameroon forward joins the Imps for a month, after failing to make an impact on Doncaster's first-team.
Lincoln boss Keith Alexander said: "Guy has got plenty of experience and knows what is required at this level."
Ipoua, who formed a formidable strike partnership alongside Steve Torpey in his time at Glanford Park, is included in their squad to face Rochdale on Saturday.