Well, there are at least two options that I can suggest: (1) use the function BDD2FDD on page 157 of VRS-03-BinaryDecisionDiagrams or (2) use the following steps:

- convert the BDD to a DNF : !d | d&b | d&!b&!a = a&b&d | a&b&!d | a&!b&!d | !a&b&d | !a&b&!d | !a&!b&d | !a&!b&!d
- convert the DNF to a RMF : a&b&d ⊕ a&d ⊕ true
- convert the RMF to a FDD : true ⊕ d&(a&b ⊕ a) = true ⊕ d&(a ⊕ b&(a))