Insert a multimode optical fiber bundle with a nummerical aperture of 0. 07into the duoble-pass SBS-phase conjugate master oscillator-power amplifier arrangement,we have got the typical far field diffraction pattern of the two-dementional matrixaperture. The output laser energy was concentrated into a angular aperture of 26 mrad.which correponds to the diffraction limit of the singel fiber diameter and is much smallerthan the beam divergence of the high order mode according to the numerical aperture of the optical fiber.Also the compensaiton of the optical inhomogeneity of the fiber bundle has been observed.