We experimentally demonstrate novel hybrid photonic crystal fibres incorporating a single ring of high-index
inclusions surrounded by several rings of holes. These fibres are designed to exhibit large bandwidths of guidance
combined with periodic group velocity dispersion zeros. While the multimode character of these fibres limits
their use, they are an ideal platform to experimentally demonstrate the emergence of photonic bandgaps.
We demonstrate a method of local spectral enhancement of an ultrafast soliton pulse. We use an in-line acoustic long-period
grating (LPG), a periodic structure modifying both the phase and the loss of the propagating light, and which is
readily tuned by simple adjustment of an applied electrical signal. The soliton perturbed by this narrow-band filter
evolves with nonlinear propagation into an intense localised spectral peak. Our setup consists of creation of a red-shifted
optical soliton by propagation of pulses from a fibre laser in standard single-mode optical fibre, followed by imposition
of a spectrally narrow LPG near to the soliton peak, and then continuing propagation. The wavelength and the peak value
of the resulting local enhancement can be tuned by adjustment of the applied acoustic frequency and amplitude. The physics of the observed local spectral enhancement will be discussed in detail here.