  Using the splitting of a $Q$-deformed boson, in the $Q \to q= e^{\frac{\rm
2\pi i}{\rm k}}$ limit, the fractional decomposition of the quantum affine
algebra $\hat A(n)$ and the quantum affine superalgebra $\hat A(n,m)$ are
found. This decomposition is based on the oscillator representation and can be
related to the fractional supersymmetry and k-fermionic spin. We establish also
the equivalence between the quantum affine algebra $\hat A(n)$ and the
classical one in the fermionic realization.
