The intensity of signals in optical networks can be controlled using a variable
optical attenuator (VOA). The present invention is a VOA that is particularly well
suited for optical networks, for example to provide channel-by-channel normalization
of gain control of wavelength division multiplexed signals. The inventive VOA includes
a waveguide having an electro-optical material and electrodes that produce an electric
field within the electro-optical material when a voltage difference is applied
to the electrodes. The electro-optical material can either be a substrate or can
be a layer deposited on a substrate. In an alternative embodiment, a polarization
independent VOA is formed from a waveguide that includes two, end-to-end waveguides.
In one embodiment, a 90 degree polarization rotator is provided between the two
waveguides. In another embodiment, each of the two waveguides has a different electro-optical
material selected to selectively pass one of two 90 degree polarizations.
