  We study the existence of Milnor fibration on a big enough sphere at infinity
for a mixed polynomial $f: \bR^{2n} \to \bR^2$. By using strong non-degeneracy
condition, we prove a counterpart of N\'emethi and Zaharia's fibration theorem.
In particular, we obtain a global version of Oka's fibration theorem for
strongly non-degenerate and convenient mixed polynomials.
