Optical low-coherence reflectometry for characterization of specialty fibers and photonics crystal waveguides

The emergence of new fibers families induces considerable requirements in terms of characterization and metrology such as group delay, chromatic dispersion, birefringence, bending losses, etc ... Unlike classical characterization techniques such as the well-known phase shift method, optical low-coherence reflectometry (OLCR) technique requires only short fiber samples (i.e. <50cm). Characterization results concerning different types of specialty fibers including erbium-doped fibers, few-modes fibers, photonic crystal fibers will be presented. Unique dispersive properties of higher-order mode fibers offer novel solutions for dispersion compensation and nonlinear effects management. OLCR can allow each LP mode characterization without the requirement of mode converters. A new method, called "Time-wavelength mapping", based on the process of the OLCR interferogram is demonstrated as a versatile method to determine chromatic dispersion of each guided LP mode whatever their group index. Different characterization results concerning photonic crystal fibers with guiding based on to the conventional total internal reflection principle - high index guiding or photonic bandgap effect - low index guiding - will be presented. Finally, we show that the versatility and deep physical insight of OLCR technique can play a key role in the study of photonic crystal waveguides in terms of structural disorder, losses, group delay in highly dispersive region and emphasizes the unique role of this technique in the understanding of their properties.