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Proceedings Paper

Proximal measurement of multimode fiber transmission matrix (Conference Presentation)
Author(s): Szu-Yu Lee; Martin Villiger; Brett Bouma

Paper Abstract

The recent progress of controlling light propagation in complex media has enabled the use of plain multimode fiber (MMF) as compact optical endoscope with sub-micron spatial resolution and sub-millimeter footprint. With the knowledge of the MMF’s transmission matrix (TM), the scrambling of the light propagating through the fiber can be compensated, physically or computationally. Current MMF endoscopes require distal access to calibrate the TM, which furthermore is vulnerable to perturbations and bending of the MMF. This necessitates repeated TM calibration or a rigid geometry that limits the intrinsic advantages of MMF. For practical applications of MMF endoscopy, calibration of the TM should be conducted without direct access to the distal fiber end. Here, we experimentally demonstrate that the forward and backward transmission through the MMF are the transpose of each other, imposed by the laws of optical reciprocity. This results in a transpose-symmetric double-pass TM (TM2x). Although it can be readily measured from the proximal side, the symmetry prevents unambiguous deduction of the single-pass TM from the measurement of TM2x. We then propose a strategy to obtain the single-pass TM in arbitrary fiber geometry by measuring TM2x with distinct pre-calibrated distal fiber elements and discuss the necessary conditions for the pre-calibrated elements to allow recovery of the single-pass TM. This proximal calibration technique may offer a pathway to flexible MMF endoscopy and find use in related applications involving measurement of TMs.

Paper Details

Date Published: 4 March 2019
Proc. SPIE 10886, Adaptive Optics and Wavefront Control for Biological Systems V, 108860L (4 March 2019); doi: 10.1117/12.2509043
Show Author Affiliations
Szu-Yu Lee, Harvard-MIT Health Sciences and Technology (United States)
Martin Villiger, Wellman Ctr. for Photomedicine (United States)
Massachusetts General Hosptal, Harvard Medical School (United States)
Brett Bouma, Institute for Medical Engineering and Science, Massachusetts Institute of Technology (United States)

Published in SPIE Proceedings Vol. 10886:
Adaptive Optics and Wavefront Control for Biological Systems V
Thomas G. Bifano; Sylvain Gigan; Na Ji, Editor(s)

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