Modal propagation and imaging characteristics of a custom designed coherent fiberbundle for endomicroscopy

In recent years, several groups have investigated the use of Proximal Spatial Light modulation (PSML) as an alternative fiber optic imaging technique. In PSLM, the light exiting the distal end of the fiber optic endoscope can be focused, without any distal micro-optics or micro-mechanics, on any point within the Field Of View (FOV) via spatial modulation of the light before it is coupled in at the endoscope's proximal end. In previous work, we reported on the custom design of a Coherent Fiber Bundle made with soft glasses (as opposed to the commercially available optical fibers used by other groups) to be used with PSLM. In this paper we present the results of the numerical characterization of the Coherent Fiber Bundle fabricated according to our design. We investigate the CFB's modal propagation characteristics as well as its imaging properties (FOV and point spread function). Our numerical characterization also takes into account fabrication induced defects such as variations in core size, core shape (ellipticity) and lattice constant. Realistic values for the defects were obtained via SEM images of the fabricated CFB's cross section. We find that noise on the wave front of the field exiting the distal end of the CFB causes a much larger deterioration of the point spread function than amplitude noise. And while we find that variations in core shape have the largest impact on the CFB's propagation characteristics, our results indicate that this negative impact could be negated if the elliptical cores were aligned along a common axis.