Kerr-induced polarization attraction in Telecom fibers

Within the research activity performed during my Ph.D., I investigated an all-optical fiber-based device for the ultra-fast control of the polarization of optical signals. Such a device is thought to be implemented within the transparent all-optical networks of future generation. Within these networks, the processing and the regeneration of the signal will be performed in the optical domain, as opposed to the current optical networks where the processing/regeneration is performed in the electrical domain, thus providing an increase in the processing speed and in the overall network bandwidth. Among the different polarization controller devices that can be taken in consideration (e.g., ideal polarizer, polarizer based on photorefractive materials, active polarizer, etc.), I focused my attention on the (fiber-based) nonlinear lossless polarizer (NLP), that is the most recently investigated technology, with experimental demonstration appearing only few years ago (2008). Since the NLP allows to perform a fast control of the polarization, while preserving the signal intensity, it represents a promising solution to be employed in transparent all-optical networks of future generation. In my Ph.D., I investigated the original counter-propagating configuration of the NLP and I contributed massively to the introduction of the co-propagating configuration, which has been proved to be more flexible and power efficient. Moreover, based on the NLP, I proposed a novel all-optical noise cleaning device able to almost double the optical signal-to-noise ratio of a (possibly depolarized) signal affected by unpolarized additive noise.