Patent ID: 7050694

Claim:
A variable optical attenuation device, the device comprising: an optical signal source generating an optical signal that is polarized in an original polarization direction D; an optical isolator located to receive the optical signal, wherein the optical isolator includes: a first polarizer that transmits only light that is substantially polarized in a first polarizer direction T 1 ; a polarization rotator optically coupled to the first polarizer for rotating the optical signal by a predetermined angle; and a second polarizer optically coupled to the polarization rotator, the second polarizer transmitting only light that is polarized in a second polarizer direction T 2 that is different from the first polarization direction T 1 ; means for rotating at least one of the optical isolator and the optical signal source to adjust an angle θ, wherein the angle θ is the angle between the original polarization direction D and the polarizer direction T 1 ; and wherein the predetermined angle is equal to the difference between the first polarizer direction T 1 and the second polarizer direction T 2 .