Polarization-insensitive variable optical attenuator

摘要

A polarization-insensitive broad-band variable optical attenuator (10) includes a first thermally tuned Mach-Zehnder interferometer (MZI) stage (12) having a polarization dependence loss mainly in a first polarization direction and a second thermally tuned Mach-Zehnder interferometer (MZI) stage (14) coupled in series, or cascaded, to the first Mach-Zehnder stage (12) and having a polarization dependence loss mainly in a second polarization direction perpendicular to the first polarization direction and arranged such that the polarization dependent loss of the second stage compensates that of the first stage to achieve polarization insensitivity. <IMAGE>