Partners and International Organizations
(English)
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A, B, CZ, DK, FIN, F, D, I, P, SK, E, S, CH, GB
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Abstract
(English)
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This is the final report for the COST265 action on Photonic Crystal Fibers. 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. For the novel PCFs, the emphasize was put as much on their characterization as on verifying the applicability of standard measurement methods. The latter is interesting because the guiding mechanism in PCF is different from that in standard fibers. Due to a large change of the effective cladding refractive index with wavelength, measurement methods based on wavelength averaging (e.g. PMD measurement) are to be analyzed critically. In a first study, chromatic dispersion and PMD was measured by 4 different COST265 participants. Two very different commercial PCF fiber samples were used in this round-robin, an endlessly single-mode fiber (ESM, core size 15 um, L=20 m) and a nonlinear PCF (NL, core size 1.7 um, L=19m). Whereas reasonable agreement was found for the ESM for both CD and PMD, measurements on the NL fiber proofed to be difficult. This was due to the large insertion loss (~35 dB) and due to an extremely large PMD. Therefore, standard measurement methods did not work for this fiber, and only with some modifications we were able to determine the large PMD of 17.1 ps/m. In general however, the standard measurement methods were found to work well. We additionally measured several other parameters (fiber loss, insertion loss, coupling loss, PDL, beatlength, Rayleigh level, etc). The corresponding results showed that although these were state-of-the-art PCFs, the losses are still large, fiber homogeneity is not great (leading to large PMD and PDL), and the Rayleigh level, due to scattering at the silica-air interfaces of the holes, is much larger than in telecom fibers. Consequently, these fibers still have some way to go for telecom applications. However, for specific applications such as white-light generation, they can be advantageous. In a second study, we analyzed PCFs of large core dimension. These fibers are useful for high energy applications, as -contrary to standard fibers- they can still be single-moded, thereby conserving a good mode quality allowing proper focusing after the fiber. The investigated fiber samples were of considerable length (100 m) and quality. The transverse symmetries e.g. were much better than what was found in the PCFs of the first study. In one case, the PMD was lower than what is obtained in the best standard fibers. Another interesting point is that the PMD dropped quite a bit for higher temperatures.
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