The present invention relates to an optical amplifier arrangement and a method of amplifying an optical signal. The optical amplifier arrangement (20) comprises an optical dividing device (21) arranged to divide an optical input pulse into a plurality of non-overlapping pulses forming a pulse train, an optical amplifier (22) arranged to amplify the pulse train, and an optical aligning display (23) arranged to temporally align the plurality of amplified pulses in the amplified pulse train into a single output pulse having the same temporal width as the input pulse.