An experiment of two-stages four degrees high-order PMD compensation in 40Gb/s RZ optical communication system with a large PMD is achieved.The former stage adopts polarization controller and fixed time-delayed line of PMF.The second stage consists of a polarization rotator and a magneto optical crystal of tunable DGDs that are used to compensate remnant first-order PMD.The PMD monitoring technique is based on DOP as error signal.A novel practical adaptive optimization algorithm was introduced in dynamic adaptive PMD compensation.The experimental results show the improvement in PMD.With this compensator

a significant improvement of system performance can be achieved in the eye pattern of a received signal.Most first-order compensating ability of the compensator is 35 ps.Second order compensating ability of the compensator is 200ps

2

.The optimum compensating time is within several mi

lliseconds.