X-ray microtomography for the characterization of optical fibers.
Crocco M.C., Ferraro M., Crocco M.C., Mangini F., Jonard M., Sangiovanni F., Zitelli M., Filosa R., Beltrano J.J., De Luca A., Barberi R.C., Agostino R.G., Couderc V., Wabnitz S., Formoso V.
The full characterization of glass optical fibers consists of determining the value of the refractive index within their entire volume. In this framework, optical techniques present some limitations, $e.g.$, these require the absence of plastic coating. The latter, in fact, absorbs the optical radiation, thus preventing light from reaching the glass fiber, hindering its post-coating characterization. In order to overcome these limits, we propose to exploit the X-ray absorption properties of glass, thus demonstrating a new tool for the measurement of the 3D spatial profile of the refractive index of standard optical fibers. In particular, by means of absorption contrast X-ray microtomography, we characterize both microstructured ($e.g.$, photonics crystal fibers) and standard optical fibers, whose core/cladding refractive index difference is provided by doping either the core or the cladding. In order to confirm the validity of our approach, the results obtained are compared with complementary characterization techniques, based on electron spectroscopy and multiphoton microscopy.