Based on the two-orbital double-exchange model, we discuss the affect of the on- site Coulomb interaction on the orbital ordering in hafl-doped manganites and de rive a formula of the optical conductivity for various phases of half-doped mang anites. The results show that there exists a correlation between the orbital ord ering and the optical absorption. For the magnetic phase (FM), with the transiti on from orbital-disordered to orbital-ordered states induced by the on-site Coul omb interaction(U),the incoherent optical absorption we calculate is substantial ly different. For the layered antiferromagnetic phase (A), the increase of the o n-site Coulomb interaction enlarges the orbital ordering. As a result, the energ y gap in the incoherent absorption is also widened.