A novel technique to measure the full 4 × 4 Mueller matrix of a sample through an optical fiber is proposed, opening the way for endoscopic applications of Mueller polarimetry for biomedical diagnosis. The technique is based on two subsequent Mueller matrices measurements: one for characterizing the fiber only, and another for the assembly of fiber and sample. From this differential measurement, we proved theoretically that the polarimetric properties of the sample can be deduced. The proof of principle was experimentally validated by measuring various polarimetric parameters of known optical components. Images of manufactured and biological samples acquired by using this approach are also presented.

We report on a novel endomicroscope, to the best of our knowledge, designed for achieving full 4×4 Mueller polarimetric images of biological tissues through a fiber endoscope for medical diagnosis. The polarimetric technique is based on a previously published two-wavelength differential method (TWDM). A key component of the endomicroscope is a resonant fiber-based microprobe including a highly-selective fiber Bragg grating (FBG), free of detrimental polarimetric effects, photo written in the core of the fiber, near the output face. By means of the TWDM, and using the specially designed microprobe (diameter 2.9 mm, length 30 mm), full Mueller images of 250×250 pixels were produced at the rate of 1 image/2 s through a 2 m single mode fiber, paving the way to in vivo applications in polarimetric endomicroscopy.

We report a novel technique for polarimetric characterization of samples through a flexible fiber endoscope, with a single shot measurement per pixel. The sample is simultaneously probed with a large diversity of polarization states, and both degree of polarization and linear retardance are determined thanks to specific processing of data. The probe polarization states are spectrally encoded on the 10 nm bandwidth of the source. The key component of the endoscope is a 3 m long specially designed optical fiber which consists of the optimized concatenation of highly birefringent fiber pieces. For a proof of principle, different calibrated or manufactured samples were successfully characterized. The proposed technique is attractive in view of reducing the measurement time of polarimetric images, in endoscopic applications.

Coupled to endoscopic techniques, Mueller polarimetry has been proven to be promising for early detection of certain diseases which affect biological tissues of inner organs. However, the depolarization power which is one of the most informative polarimetric characteristics cannot be directly measured through a fiber endoscope. For evaluating this quantity, we propose a method based on the Lu–Chipman decomposition of the averaged sum of the Mueller matrices of neighboring pixels. The principle is well supported by numerical simulations. Depolarization powers of Spectralon and of different areas of a biological sample are also successfully evaluated.