The transmission system may include: an optical path adjustment device configured to substantially unify optical paths of a first pre-pulse laser beam and a second pre-pulse laser beam; an optical path separation device configured to separate the optical paths of the substantially unified first pre-pulse laser beam and the second pre-pulse laser beam to an optical path for the first pre-pulse laser beam and an optical path for the second pre-pulse laser beam; a first beam adjustment device disposed on the optical path for the first pre-pulse laser beam separated by the optical path separation device and configured to adjust a beam parameter of the first pre-pulse laser beam; and a second beam adjustment device disposed on the optical path for the second pre-pulse laser beam separated by the optical path separation device and configured to adjust a beam parameter of the second pre-pulse laser beam.