Miniaturized ferrofluid actuated single mode fiber variable optical attenuator (VOA)

We report a miniature variable optical attenuator employing a ferrofluid actuator/shutter combination located between lensed optical fibers. The VOA consists of an opaque, undiluted ferrofluid plug actuator inside a microfluidic channel. The ferrofluid plug position is translated by a variable magnetic field generated from a miniature electromagnet. The ferrofluid plug actuator in turn displaces a second oil-diluted ferrofluid plug acting as an optical shutter. The position of the shutter controls the optical power coupled between the input and output fibers.