Two-dimensional refractive index profiling of optical fibers by modified refractive near-field technique

El Sayed, Ali; Pilz, Sönke; Ryser, Manuel; Romano, Valerio (2016). Two-dimensional refractive index profiling of optical fibers by modified refractive near-field technique. In: Jiang, Shibin; Digonnet, Michel J. F. (eds.) Optical Components and Materials XIII. Proceedings of SPIE: Vol. 9744 (97440N). SPIE 10.1117/12.2211002

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The refractive index distribution in the core-cladding region of an optical fiber plays an important role in determining the transmission and dispersion properties of the waveguide. The refracted near-field technique (RNF) is among the most widespread techniques used for measuring the refractive index profile of optical fibers and is based on illuminating the end-facet of a fiber with a focused beam whose vertex angle greatly exceeds the acceptance angle of the fiber, which is immersed in an index matching liquid. What one observes are then the refracted unguided rays rather than the guided rays. Nevertheless, the standard refracted near-field technique cannot be applied to a wide range of optical fibers e.g. if their shapes are not axially symmetric. In this work we demonstrate a modified method which allows 2-D imaging of the refractive index profile and thereby overcoming the axial symmetric limitation of the standard RNF. The new system is operating at 630 nm and based on the same principle of the RNF, but the optical path is reversed so that the light at the fiber end-facet is collected by an objective lens and detected by a CCD camera. The method does not require scanning over the fiber end-facet. Thus the system is faster and less sensitive to vibrations and external conditions compared to the standard RNF, furthermore it allows averaging to improve the signal to noise ratio. The spatial resolution of the system is determined by the numerical aperture of the objective and by the resolution of the CCD camera. To calibrate the setup, a reference multi-step index fiber provided by National Physical Laboratory was used.

Item Type:

Book Section (Book Chapter)

Division/Institute:

08 Faculty of Science > Institute of Applied Physics
08 Faculty of Science > Institute of Applied Physics > Lasers

UniBE Contributor:

El Sayed, Ali; Pilz, Sönke; Ryser, Manuel and Romano, Valerio

Subjects:

600 Technology > 620 Engineering
500 Science
500 Science > 530 Physics

Series:

Proceedings of SPIE

Publisher:

SPIE

Language:

English

Submitter:

Simone Corry

Date Deposited:

13 Jul 2017 10:16

Last Modified:

11 Sep 2017 20:55

Publisher DOI:

10.1117/12.2211002

BORIS DOI:

10.7892/boris.96982

URI:

https://boris.unibe.ch/id/eprint/96982

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