Abstract

Flexible endoscopes commonly use coherent fiber bundles with high core density to facilitate in vivo imaging. Small, closely spaced cores are desired for achieving a high number of resolvable pixels in a small diameter fiber bundle. On the other hand, closely spaced cores potentially lead to strong core-to-core coupling. Based on numerical simulations, it was previously explained that image fiber bundles can successfully transmit images because of nonuniformities in the core size that reduce coupling. In this paper, we show numerically and experimentally that, due to the randomness of the structural nonuniformity, significant core-to-core coupling still exists in fiber bundles that are routinely used for imaging. The coupling is highly dependent on the illumination wavelength and polarization state. We further show that the resolution achievable by a fiber bundle depends not only on the core density, but also on the inter-core coupling strength. Finally, we propose that increasing the core-cladding index contrast is a promising approach to achieve a fiber bundle with low core coupling, high core density, and effectively single moded propagation in individual cores.

© 2008 Optical Society of America

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References

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2007 (1)

2005 (3)

2004 (3)

C. Amatore, A. Chovin, P. Garrigue, L. Servant, N. Sojic, S. Szunerits, and L. Thouin, "Remote Fluorescence Imaging of Dynamic Concentration Profiles with Micrometer Resolution Using a Coherent Optical Fiber Bundle," Anal. Chem. 76, 7202-7210 (2004).
[CrossRef] [PubMed]

W. Göbel, J. N. D. Kerr, A. Nimmerjahn, and F. Helmchen, "Miniaturized two-photon microscope based on a flexible coherent fiber bundle and a gradient-index lens objective," Opt. Lett. 29, 2521-2523 (2004).
[CrossRef] [PubMed]

J. Fini, "Perturbative numerical modeling of microstructure fibers," Opt. Express 12, 4535-4545 (2004).
[CrossRef] [PubMed]

2003 (3)

2002 (2)

V. Dubaj, A. Mazzolini, A. Wood, and M. Harris, "Optic fibre bundle contact imaging probe employing a laser scanning confocal microscope," J. Microsc. 207, 108-117 (2002).
[CrossRef] [PubMed]

T. P. White, B. T. Kuhlmey, R. C. McPhedran, D. Maystre, G. Renversez, C. M. d. Sterke, and L. C. Botten, "Multipole method for microstructured optical fibers. I. Formulation," J. Opt. Soc. Am. B 19, 2322-2330 (2002).
[CrossRef]

2001 (2)

E. Beaurepaire, M. Oheim, and J. Mertz, "Ultra-deep twophoton fluorescence excitation in turbid media," Opt. Commun. 188,25-29 (2001).
[CrossRef]

J. Knittel, L. Schnieder, G. Buess, B. Messerschmidt, and T. Possner, "Endoscope-compatible confocal microscope using a gradient index-lens system," Opt. Commun. 188, 267-273 (2001).
[CrossRef]

1999 (1)

1993 (1)

1987 (1)

S.-L. Chuang, "A coupled-mode theory for multiwaveguide systems satisfying the reciprocity theorem and power conservation," J. Lightwave Technol. 5, 174-183 (1987).
[CrossRef]

1986 (1)

E. Marcatili, "Improved coupled-mode equations for dielectric guides," IEEE J. Quantum Electron. 22, 988-993 (1986).
[CrossRef]

1972 (1)

Amatore, C.

C. Amatore, A. Chovin, P. Garrigue, L. Servant, N. Sojic, S. Szunerits, and L. Thouin, "Remote Fluorescence Imaging of Dynamic Concentration Profiles with Micrometer Resolution Using a Coherent Optical Fiber Bundle," Anal. Chem. 76, 7202-7210 (2004).
[CrossRef] [PubMed]

Aziz, D.

Beaurepaire, E.

E. Beaurepaire, M. Oheim, and J. Mertz, "Ultra-deep twophoton fluorescence excitation in turbid media," Opt. Commun. 188,25-29 (2001).
[CrossRef]

Brenner, M.

Buess, G.

J. Knittel, L. Schnieder, G. Buess, B. Messerschmidt, and T. Possner, "Endoscope-compatible confocal microscope using a gradient index-lens system," Opt. Commun. 188, 267-273 (2001).
[CrossRef]

Chen, Z.

Cheung, E.

B. Flusberg, E. Cocker, W. Piyawattanametha, J. C. Jung, E. Cheung, and M. J. Schnitzer, "Fiber-optic Fluorenscence Imaging," Nature Methods 2, 941 (2005).
[CrossRef] [PubMed]

Chovin, A.

C. Amatore, A. Chovin, P. Garrigue, L. Servant, N. Sojic, S. Szunerits, and L. Thouin, "Remote Fluorescence Imaging of Dynamic Concentration Profiles with Micrometer Resolution Using a Coherent Optical Fiber Bundle," Anal. Chem. 76, 7202-7210 (2004).
[CrossRef] [PubMed]

Chuang, S.-L.

S.-L. Chuang, "A coupled-mode theory for multiwaveguide systems satisfying the reciprocity theorem and power conservation," J. Lightwave Technol. 5, 174-183 (1987).
[CrossRef]

Cocker, E.

B. Flusberg, E. Cocker, W. Piyawattanametha, J. C. Jung, E. Cheung, and M. J. Schnitzer, "Fiber-optic Fluorenscence Imaging," Nature Methods 2, 941 (2005).
[CrossRef] [PubMed]

Descour, M. R.

Donaldson, L.

Dubaj, V.

V. Dubaj, A. Mazzolini, A. Wood, and M. Harris, "Optic fibre bundle contact imaging probe employing a laser scanning confocal microscope," J. Microsc. 207, 108-117 (2002).
[CrossRef] [PubMed]

Feng, X.

Finazzi, V.

Fini, J.

Flusberg, B.

B. Flusberg, E. Cocker, W. Piyawattanametha, J. C. Jung, E. Cheung, and M. J. Schnitzer, "Fiber-optic Fluorenscence Imaging," Nature Methods 2, 941 (2005).
[CrossRef] [PubMed]

Follen, M.

Garrigue, P.

C. Amatore, A. Chovin, P. Garrigue, L. Servant, N. Sojic, S. Szunerits, and L. Thouin, "Remote Fluorescence Imaging of Dynamic Concentration Profiles with Micrometer Resolution Using a Coherent Optical Fiber Bundle," Anal. Chem. 76, 7202-7210 (2004).
[CrossRef] [PubMed]

Gmitro, A. F.

Göbel, W.

Guo, S.

Harris, M.

V. Dubaj, A. Mazzolini, A. Wood, and M. Harris, "Optic fibre bundle contact imaging probe employing a laser scanning confocal microscope," J. Microsc. 207, 108-117 (2002).
[CrossRef] [PubMed]

Helmchen, F.

Hewak, D.

Hopkins, M. F.

Jung, J. C.

B. Flusberg, E. Cocker, W. Piyawattanametha, J. C. Jung, E. Cheung, and M. J. Schnitzer, "Fiber-optic Fluorenscence Imaging," Nature Methods 2, 941 (2005).
[CrossRef] [PubMed]

Kerr, J. N. D.

Knittel, J.

J. Knittel, L. Schnieder, G. Buess, B. Messerschmidt, and T. Possner, "Endoscope-compatible confocal microscope using a gradient index-lens system," Opt. Commun. 188, 267-273 (2001).
[CrossRef]

Koshiba, M.

Kuhlmey, B. T.

Liang, C.

Malpica, A.

Marcatili, E.

E. Marcatili, "Improved coupled-mode equations for dielectric guides," IEEE J. Quantum Electron. 22, 988-993 (1986).
[CrossRef]

Maystre, D.

Mazzolini, A.

V. Dubaj, A. Mazzolini, A. Wood, and M. Harris, "Optic fibre bundle contact imaging probe employing a laser scanning confocal microscope," J. Microsc. 207, 108-117 (2002).
[CrossRef] [PubMed]

McPhedran, R. C.

Mertz, J.

E. Beaurepaire, M. Oheim, and J. Mertz, "Ultra-deep twophoton fluorescence excitation in turbid media," Opt. Commun. 188,25-29 (2001).
[CrossRef]

Messerschmidt, B.

J. Knittel, L. Schnieder, G. Buess, B. Messerschmidt, and T. Possner, "Endoscope-compatible confocal microscope using a gradient index-lens system," Opt. Commun. 188, 267-273 (2001).
[CrossRef]

Monro, T.

Mukai, D.

Nimmerjahn, A.

Oheim, M.

E. Beaurepaire, M. Oheim, and J. Mertz, "Ultra-deep twophoton fluorescence excitation in turbid media," Opt. Commun. 188,25-29 (2001).
[CrossRef]

Petropoulos, P.

Piyawattanametha, W.

B. Flusberg, E. Cocker, W. Piyawattanametha, J. C. Jung, E. Cheung, and M. J. Schnitzer, "Fiber-optic Fluorenscence Imaging," Nature Methods 2, 941 (2005).
[CrossRef] [PubMed]

Possner, T.

J. Knittel, L. Schnieder, G. Buess, B. Messerschmidt, and T. Possner, "Endoscope-compatible confocal microscope using a gradient index-lens system," Opt. Commun. 188, 267-273 (2001).
[CrossRef]

Reichenbach, K. L.

Renversez, G.

Richards-Kortum, R.

Rouse, A. R.

Sabharwal, Y. S.

Saitoh, K.

Sato, Y.

Schnieder, L.

J. Knittel, L. Schnieder, G. Buess, B. Messerschmidt, and T. Possner, "Endoscope-compatible confocal microscope using a gradient index-lens system," Opt. Commun. 188, 267-273 (2001).
[CrossRef]

Schnitzer, M. J.

B. Flusberg, E. Cocker, W. Piyawattanametha, J. C. Jung, E. Cheung, and M. J. Schnitzer, "Fiber-optic Fluorenscence Imaging," Nature Methods 2, 941 (2005).
[CrossRef] [PubMed]

Servant, L.

C. Amatore, A. Chovin, P. Garrigue, L. Servant, N. Sojic, S. Szunerits, and L. Thouin, "Remote Fluorescence Imaging of Dynamic Concentration Profiles with Micrometer Resolution Using a Coherent Optical Fiber Bundle," Anal. Chem. 76, 7202-7210 (2004).
[CrossRef] [PubMed]

Snyder, A. W.

Sojic, N.

C. Amatore, A. Chovin, P. Garrigue, L. Servant, N. Sojic, S. Szunerits, and L. Thouin, "Remote Fluorescence Imaging of Dynamic Concentration Profiles with Micrometer Resolution Using a Coherent Optical Fiber Bundle," Anal. Chem. 76, 7202-7210 (2004).
[CrossRef] [PubMed]

Sung, K.-B.

Szunerits, S.

C. Amatore, A. Chovin, P. Garrigue, L. Servant, N. Sojic, S. Szunerits, and L. Thouin, "Remote Fluorescence Imaging of Dynamic Concentration Profiles with Micrometer Resolution Using a Coherent Optical Fiber Bundle," Anal. Chem. 76, 7202-7210 (2004).
[CrossRef] [PubMed]

Thouin, L.

C. Amatore, A. Chovin, P. Garrigue, L. Servant, N. Sojic, S. Szunerits, and L. Thouin, "Remote Fluorescence Imaging of Dynamic Concentration Profiles with Micrometer Resolution Using a Coherent Optical Fiber Bundle," Anal. Chem. 76, 7202-7210 (2004).
[CrossRef] [PubMed]

White, T. P.

Wood, A.

V. Dubaj, A. Mazzolini, A. Wood, and M. Harris, "Optic fibre bundle contact imaging probe employing a laser scanning confocal microscope," J. Microsc. 207, 108-117 (2002).
[CrossRef] [PubMed]

Xie, T.

Xu, C.

Anal. Chem. (1)

C. Amatore, A. Chovin, P. Garrigue, L. Servant, N. Sojic, S. Szunerits, and L. Thouin, "Remote Fluorescence Imaging of Dynamic Concentration Profiles with Micrometer Resolution Using a Coherent Optical Fiber Bundle," Anal. Chem. 76, 7202-7210 (2004).
[CrossRef] [PubMed]

Appl. Opt. (1)

IEEE J. Quantum Electron. (1)

E. Marcatili, "Improved coupled-mode equations for dielectric guides," IEEE J. Quantum Electron. 22, 988-993 (1986).
[CrossRef]

J. Lightwave Technol. (1)

S.-L. Chuang, "A coupled-mode theory for multiwaveguide systems satisfying the reciprocity theorem and power conservation," J. Lightwave Technol. 5, 174-183 (1987).
[CrossRef]

J. Microsc. (1)

V. Dubaj, A. Mazzolini, A. Wood, and M. Harris, "Optic fibre bundle contact imaging probe employing a laser scanning confocal microscope," J. Microsc. 207, 108-117 (2002).
[CrossRef] [PubMed]

J. Opt. Soc. Am. (1)

J. Opt. Soc. Am. B (1)

Nature Methods (1)

B. Flusberg, E. Cocker, W. Piyawattanametha, J. C. Jung, E. Cheung, and M. J. Schnitzer, "Fiber-optic Fluorenscence Imaging," Nature Methods 2, 941 (2005).
[CrossRef] [PubMed]

Opt. Commun. (2)

J. Knittel, L. Schnieder, G. Buess, B. Messerschmidt, and T. Possner, "Endoscope-compatible confocal microscope using a gradient index-lens system," Opt. Commun. 188, 267-273 (2001).
[CrossRef]

E. Beaurepaire, M. Oheim, and J. Mertz, "Ultra-deep twophoton fluorescence excitation in turbid media," Opt. Commun. 188,25-29 (2001).
[CrossRef]

Opt. Express (6)

Opt. Lett. (3)

Other (2)

A. Snyder, and J. Love, Optical Waveguide Theory (Kluwer, London, 1983).

A. F. Gmitro, A. R. Rouse, and A. Kano, "In vivo fluorescence confocal microendoscopy," in Biomedical Imaging, 2002. Proceedings. 2002 IEEE International Symposium on (2002), pp. 277-280.
[CrossRef]

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Figures (8)

Fig. 1.
Fig. 1.

Experimental set-up: Obj1 is an objective with NA=0.30, Obj2 is a 100x objective. The image inset is an SEM micrograph of a fiber bundle endface.

Fig. 2.
Fig. 2.

Numerical (A) and (B), and experimental (C) and (D), results for the power in two cores as a function of wavelength. The numerical results are calculated at a propagation distance of z=0.3 m. Fiber type 500N is shown in (C), while type 350S is shown in (D). Images (E)-(H) are of the transmitted light through the image fiber 350S at different wavelengths; the images are approximately 7 µm square. The illumination source for images (E)-(G) is a CW tunable laser, while in image (H) the source is broadband.

Fig. 3.
Fig. 3.

The numerical (A) and experimental (B) results for the power distribution in two cores of fiber 350S when a half-wave plate is rotated 360 degrees.

Fig. 4.
Fig. 4.

Experimental set-up: Obj is an objective with NA=0.50. Both fibers (Fujikura 500N and 350S) are tested at three different wavelengths 630, 768, and 978 nm

Fig. 5.
Fig. 5.

Images taken at three different wavelengths. A: Images taken with Fujikura 350S. B: Images taken with Fujikura 500N. C: Images taken without a fiber bundle. Images in the left, middle, and right columns in each panel are taken at 630nm, 768nm, and 978nm, respectively.

Fig. 6.
Fig. 6.

The average coupling efficiency for data sets of 30 two-core fibers is plotted versus the percentage core-size variation for A) FIGH-10-350S and B) FIGH-10-500N at three different wavelengths. The lines have been added to more clearly show the trends in the data. Note that the horizontal scales in the two plots differ.

Fig. 7.
Fig. 7.

The average inter-core coupling efficiency for data sets of 30 two-core fibers (pitch 2.5 µm, core diameter 2 µm at wavelength 0.8 µm) is plotted versus the core radius percentage variation at four different index contrasts.

Fig 8.
Fig 8.

Simulation results of the relation between effective index difference and core-cladding index contrast of a fiber core with a 2.5 µm pitch, 2 µm core diameter at wavelengths from 630nm to 980nm.

Tables (1)

Tables Icon

Table 1: parameters of the Fujikura fiber bundles 500N and 350S

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