Polarization measurements through a standard single mode fiber for imaging and remote characterization

We report on a polarization imaging device which probes a remote sample through a flexible standard single-mode fiber. Both polarized laser source and polarization analysis system are set on one side of the fiber, the object of interest being probed by the beam exiting at the opposite end. Phase retardation and polarization rotation angle due to either pure linear or pure circular birefringent targets can be measured. In addition, the degree of polarization of partially depolarizing targets is evaluated. The measurement method is based on two key points: (i) the compensation of the fiber birefringence effects over a round trip of the light by means of a miniaturized Faraday rotator set between the output fiber end and the target, (ii) the recording of a set of data operated when the polarization states of the light at the fiber input are varied, followed by a specific processing of these data. An experimental setup based on this process has been implemented. The method was assessed using calibrated birefringent targets, and polarization images of a large variety of targets were obtained.