Partner und Internationale Organisationen
(Englisch)
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A, B, CZ, DK, FIN, F, D, I, P, SK, E, S, CH, GB
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Abstract
(Englisch)
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This is the final report for the COST265 action. The main emphasis of our efforts in Geneva within the COST265 framework are the investigation of the influence of polarization on data transmission, and the analysis of methods for distributed measurements. In the third and last year of the project, following the project proposal, the main efforts were put on the investigation of the interaction between PMD and nonlinear effects in fiber transmission, on work related to PMD compensation, and on Photonic Crystal Fibers (PCF). Analysis of the interaction between PMD and nonlinear effects led to the insight that for measurement methods exploiting nonlinearity, PMD can lead to important performance degradations. In chromatic dispersion (CD) mapping, based on the measurement of the backscattered four wave mixing (FWM) signal power, PMD was found to alter the characteristic power fluctuations used to extract the CD. This is because PMD leads to a different polarization evolution of the different frequencies involved, thereby changing the FWM efficiency. On the other hand, the interaction between nonlinearities and PMD can also be exploited. The dependence of the nonlinear change of the polarization state (nonlinear polarization rotation NPR) on PMD -or, more precisely, on the polarization coupling that determines the PMD statistics- can be exploited to get a better description of the polarization characteristics of the measured fiber. Regarding PMD compensation, we refrained from building a compensator ourselves. As outlined in the previous report, a lot of research groups are active in this area, and the problems are rather of technical than physical nature. Instead, a PMD emulator was developed. Such emulators can be used to test PMD compensators and allow to determine the impact of PMD in transmission systems. The specificity of our 2nd order PMD (or more precisely differential group delay) emulator is that it allows to investigate in a simple way the low probability events important for PMD system penalty. The investigation, started during the second year, was finished by optimizing and fully characterizing the emulator. Moreover, a novel technique to measure the degree of polarization (DOP), used as a feed-back parameter for PMD compensation, was developed and thoroughly analyzed. This DOP-meter is both physically intriguing (it is one of the first practical implementations of a coherent 2 photon measurement) and of high practical interest provided that some technical flaws can be overcome.
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