Refractive index profiler for characterization of optical fiber preforms

• Subject Area: Systems Engineering
• Term: Funded in 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 455750705

Quantum technology and sensors are the main research areas of the associated scientific groups at the Hannover Institute of Technology (HITec). The goal of these activities is the development of new sensor concepts, which will increase the sensitivity and the precision beyond the limits of classical physics, in particular for application in optical clocks, atom interferometry, relativistic geodesy or laser interferometric distance measurement in spacecraft missions. In this context, optical fiber technology is considered as a key technology. It enables the development of highly efficient, ultra-compact and stable beam sources, which are required for the aforementioned applications and beyond. The quality of the provided laser sources define the characteristics of the sensors. However, the development of active optical fibers for these highly specialized applications requires an extremely precise process control along the production chain of the optical fibers.At HITec, optical fibers are produced in a two-stage process - the fabrication of fiber preforms using the modified chemical vapor deposition (MCVD) and the subsequent drawing of the preforms to optical fibers. The concentration profile of the dopants – and accordingly, the refractive index profile of the fiber, which defines the optical transfer properties of the optical waveguide – is already determined during the preform fabrication. However, the process control of the preform deposition is quite complex and requires an iterative optimization in order to meet the demands. Furthermore, the geometric and optical properties of the fiber preforms must be characterized comprehensively such that subsequent processing steps can be planned properly. For this purpose, a refractive index profiler for the non-destructive characterization of fiber preforms enables a highly precise determination of the radial dopant concentration. Especially, the requested device shall be used in three projects: (i) for the production of nanoparticle-doped optical fibers, (ii) for the production of aperiodic multicore fibers for ultrashort pulse applications in endoscopy and (iii) for the investigation of the molecular structure of dopants and the quantitative dopant profiling via Raman spectroscopy. The purchase of the refractive index profiler is absolutely essential for the progress of future projects. This will strengthen the scientific orientation of the HITec, and therefore the science location Hannover in general.

• DFG Programme: Major Research Instrumentation
• Major Instrumentation: Brechungsindexprofilometer zur Charakterisierung von optischen Faserpreformen
• Instrumentation Group: 4190 Spezielle Geräte der Mikrosystemtechnik
• Applicant Institution: Gottfried Wilhelm Leibniz Universität Hannover
• Leader: Professor Dr. Detlev Ristau