Photonic crystal fibers technology provides us with new way to obtain fibers with much higher non-linearity than
conventional techniques. Upper limits of non-linear coefficients obtainable in silica-based photonic crystal fibers have
been already investigated. Unique dispersion characteristic and enhanced non-linearity make this kind of fibers an ideal
candidate for non-linear optical devices in telecommunication applications, for measurement and sensing and for
supercontinuum generation. However, there are limitations given by material properties, which obstruct us from
achieving theoretical limits of these fibers. Extremely small core and high air-filling fraction are here needed for reach
higher non-linearity, so when material properties of conventional silica restrict us, there is a requirement on a novel
matter. This could be poly-methyl metacrylate (PMMA), a common material for plastic optical fibers manufacturing.
These microstructured polymer optical fibers are a recent technology, which gives us with new possibilities in core size,
fiber geometry and related air-filling fraction. By this kind of fiber, we could be closer to ideal non-linear fiber, which is
core strain surrounded by air, than even before. But new kind of fiber brings new issues, like which effect in fiber will be
dominant or how will be coupled light affected by outer influences - and what difference will be between predicted and
real values in general. This is a large task and hopefully, there will be answer at least for a small part in this paper.