Large polarization mode dispersion in fiber optic cables

The recently observed difference in polarization mode dispersion (PMD) between spooled and cabled single-mode optical fibers is investigated experimentally. To discriminate between a large polarization mode-coupling length or a large birefringence as a cause of high PMD, both parameters are measured. The results show a factor of 50 difference between the mode-coupling lengths of spooled and cabled fibers, which accounts for the larger PMD's of cabled fibers. It is suggested that cables with a loose tube design especially suffer from large polarization mode-coupling lengths. Internal stress is shown to be the dominant source of birefringence in standard telecommunication fibers by observing the shift of the PMD spectrum over a wide wavelength interval as a function of temperature.<
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