Abstract
We present a double-clad fiber coupler (DCFC) for use in confocal endomicroscopy to reduce speckle contrast, increase signal collection while preserving optical sectioning. The DCFC is made by incorporating a double-clad tapered fiber (DCTF) to a fused-tapered DCFC for achromatic transmission (from 1265 nm to 1325 nm) of > 95% illumination light trough the single mode (SM) core and collection of > 40% diffuse light through inner cladding modes. Its potential for confocal endomicroscopy is demonstrated in a spectrally-encoded imaging setup which shows a 3 times reduction in speckle contrast as well as 5.5 × increase in signal collection compared to imaging with a SM fiber.
Highlights
Endomicroscopy is an emerging medical imaging technique combining the flexibility of endoscopy with the advantages of confocal microscopy, namely micrometric resolution and optical sectioning
We showed in a previous article [13] that double-clad fiber coupler (DCFC) allowed quasi-lossless integration of double-clad fibers (DCFs) in a wide field endoscopy setup
We propose to use a DCFC previously designed for endoscopy and taper down its illumination branch until the optimal ratio d/mode field diameter (MFD) is obtained (see Fig. 2(a))
Summary
Endomicroscopy is an emerging medical imaging technique combining the flexibility of endoscopy with the advantages of confocal microscopy, namely micrometric resolution and optical sectioning. For single fiber based systems, this translates into using double-clad fibers (DCFs) where the SM core transmits illumination light and the inner cladding acts as a larger collection aperture. This speckle reduction technique was successfully implemented in wide field endoscopy [12]. We present a method for using DCFs in confocal endomicroscopy for preserving the optical sectioning while benefiting from signal increase and speckle reduction This is done by adding an achromatic double-clad tapered fiber (DCTF) at the imaging branch of a DCFC which allows precise adjustment of the collection to illumination ratio for single fiber confocal endomicroscope. We test this device for imaging of biological tissue in a spectrally-encoded confocal microscopy setup
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