In a preferred embodiment, a motorized variable optical attenuator comprises
an
input fiber collimator; an output fiber collimator disposed substantially along
the first collimator; and a right-angle reflector movable relative to the input
collimator and the output collimator along a translation direction forming a non-zero
angle with a direction of a light beam emitted by the input collimator. The reflector
comprises two mutually-perpendicular reflective surfaces for sequentially reflecting
the light beam emitted by the input collimator to the output collimator. A variable
attenuation imparted by the attenuator on the light beam is determined by a position
of the reflector relative to the input collimator and the output collimator, along
the translation direction. The reflector preferably comprises a right-angle prism
adhered to a nut mounted on a threaded axle driven by a stepper motor. The attenuator
can achieve stable, ripple-free attenuation characteristics at insertion losses
beyond -40 dB.
