Variable optical attenuators with ability to independently contr...

New techniques for controlling the amplitudes of two orthogonal linearly polarized light are presented. One is based on adjusting the DC voltage into a Mach–Zehnder modulator (MZM) to alter the amplitude of the light traveling on the slow axis of a fiber into the modulator with little changes in the fast-axis light amplitude. Another is based on adjusting the input DC voltages of a dual-polarization MZM operating in the reverse direction, which enables independent control of the two input orthog