Optimal suppression of higher-order modes (HOMs) in hollow-core antiresonant fibers comprising a single ring of thin-walled capillaries was previously studied, and can be achieved when the condition on the capillary-tocore diameter ratio is satisfied (d/D ≈ 0.68). Here we report on the conditions for maximizing the leakage losses of HOMs in hollow-core nested antiresonant node-less fibers, while preserving low confinement loss for the fundamental mode. Using an analytical model based on coupled capillary waveguides, as well as full-vector finite element modeling, we show that optimal d/D value leading to high leakage losses of HOMs, is strongly correlated to the size of nested capillaries. We also show that extremely high value of degree of HOM suppression (∼1200) at the resonant coupling is almost unchanged on a wide range of nested capillary diameter dN ested values. These results thus suggest the possibility of designing antiresonant fibers with nested elements, which show optimal guiding performances in terms of the HOM loss compared to that of the fundamental mode, for clearly defined paired values of the ratios dN ested/d and d/D. These can also tend towards a single-mode behavior only when the dimensionless parameter dN ested/d is less than 0.30, with identical wall thicknesses for all of the capillaries.
We compare, thanks to a Sagnac interferometer, the phase sensitivity to strain of different microstructured
optical silica fibers (MSF) that we design and fabricate. Our results show that when a same elongation is applied
to different MSF, the induced phase change is equal or lower than the one obtained for a standard fiber, showing
no advantage on this parameter for sensing applications.
Proc. SPIE. 7503, 20th International Conference on Optical Fibre Sensors
KEYWORDS: Multimode fibers, Optical fibers, Tunable lasers, Structured optical fibers, Single mode fibers, Near field scanning optical microscopy, High power fiber lasers, Modal analysis, Light wave propagation, Near field optics
We propose and demonstrate two methods for modal decomposition in multi-mode fibres. Linearly polarized modes
propagating in a slightly multi-mode fibre are easily retrieved from intensity measurements at the fibre output surface.
The first method is an improvement of the so-called spectrally and spatially imaging technique, which is limited to largemode-
area optical fibers. The second method is a new, simpler and faster solution for the characterization of any kind of
optical fibre, thus attractive in comparison to previously reported methods, which are cumbersome, time-consuming
and/or limited to large-more-area fibres. Different kinds of multi-mode optical fibres are characterized. A large-modearea
photonic-bandgap fibre, a photonic-crystal small-core non-linear fibre, and a standard index-stepped multi-mode
fibre are characterized successfully.
KEYWORDS: Optical fibers, Photonic crystal fibers, Polarization, Birefringence, Dispersion, Optical microscopy, Single mode fibers, Reflectometry, Near field scanning optical microscopy, Near field optics
We present the structure of photonic crystal fibers and give a characterization results in birefringence and
chromatic dispersion using scanning near field optical microscopy and low coherence interferometry.