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 a cladding that includes 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 VOA also includes a layer that is
parallel to the core of the waveguide and that optically couples to the core to
receive light from the attenuated signal. A power meter receives light from the
layer as an indication of the amount of light attenuated from the signal and for
controlling the voltage to the electrodes.