Patent ID: 7027135

Claim:
A method of providing dispersion compensation to an optical signal having a direction of propagation, the method comprising in order: passing the optical signal through a first birefringent element having a fast axis and a slow axis in a normal plane oriented normal to the direction of propagation, the fast axis oriented in a first direction in the normal plane; passing the optical signal through a second birefringent element having a second fast axis oriented in a second direction in the normal plane, the second direction being at a nonzero angle from θ the first direction; passing the optical signal through a third birefringent element having a third fast axis oriented in a third direction in the normal plane, the third direction being orthogonal to the first direction; and passing the optical signal through a fourth birefringent element having a fourth fast axis oriented in a fourth direction in the normal plane, the fourth direction being orthogonal to the second direction wherein passing the optical signal though the first, second, third and fourth birefringent elements results in compensation of second order polarization mode dispersion but leaves first order polarization mode dispersion substantially uncompensated.