Home > Research groups > Holographic Microscopy (Tessier) > Projects

Ultra-low roughness measurement in photonic bandgap optical fibers

Within the European project ModeGap, the development of hollow core Photonic Band Gap Fibers (PBGF) aims at providing next generation fibers for low loss and long haul optical telecommunications. The main limitation to efficient transmission in these fibers is currently associated to surface roughness in the core of the fibers, which induce scattering losses. We have developed an interferometric microscope which is able to measure differential roughness profiles with vertical sensitivities of a few picometers. Using oil immersion, this system is now able to measure roughness inside unopened fibers. Our results indicate that roughness on flat glass surfaces is mainly driven by cappillary waves statistics at the liquid-air interface in molten glass, during the glass fabrication processes. In the special case of optical fibers, we are currently studying other processes which might dominate roughness statistics.

Differential optical profilometer for picometer-scale roughness measurements inside unopened hollow PBGF. Electron microscopy image of a PBGF section.