Unique multi-
diffraction structures using electronically controlled Bragg
diffraction devices such as acousto-optic (AO) devices to accomplish
optical beam attenuation control functions. These variable
optical attenuator (VOA) modules can be fully inertialess as they can use electronically programmable sub-
microsecond speed AO devices to implement optical
gain controls. These VOAs deliver desirable capabilities in one optically reversible unit, making
high dynamic range, low loss, high
power handling, ultra-fast, high optical isolation,
broadband operation, self-aligning robust modules. These VOAs can be made essentially independent of the
optical polarization of the incident light by the use of a unique fixed
waveplate compensation technique within the VOA configuration that suppresses
polarization dependent loss.
Broadband gain control operation over several wavelengths can be achieved by controlling the frequency and
electrical drive power of the chosen frequencies feeding the acousto-optic devices. Interleaver devices can be cascaded with the acousto-optic modules to improve
wavelength selectivity of the overall VOA modules. Alternative embodiments can use electrically programmable Bragg gratings in
polymer dispersed
liquid crystal and acousto-optic tunable filter devices as Bragg
grating devices. Embodiments are proposed using independently controlled Bragg diffractions using multiple drive signals connected to
multiple device transducers. Drive
signal formats can be digital, analog, or a combination for simultaneously driving the VOA modules. Dual-mode VOA module designs are also described using mirror positioning.