In-line light-saving photopolarimeter and its fiber-optic analog.

An in-line light-saving photopolarimeter (ILLSP) is described that employs four highly reflecting detectors, each of which absorbs only a small polarization-dependent fraction of the light that falls upon it. The polarimeter conserves most of the power and direction and possibly the polarization of the incident beam whose Stokes parameters it measures. The principle of operation of the ILLSP can be extended to apply to light guided by an optical fiber using polarization-dependent evanescent-field coupling at four successive locations on the fiber that are separated by rotations induced by twists or the Faraday effect.