We have studied the pulse transmission properties in a nonlinear optical loop mi rror (NOLM) with abnormal despersion and obtained the firs t maximum of transmission, the compression ratio and related soliton order at th e first maximum as functions of nomarlized loop length. With the comparison of t ransmission and compression properties of both transmission limited and chirped pulses in long and short loop loop length NOLMs, we conclude that long NLOM is f it for pulse shaping, while short NOLM is fit for pulse compression.