A polarization mode dispersion (PMD) emulator with tuneable first-order PMD and constant second-order PMD

We design a polarization mode dispersion (PMD) emulator with fixed second-order polarization mode dispersion (50-PMD) but varying first-order PMD (FO-PMD). The emulator constitutes of an optical delay line (ODL). a polarization controller (PC) and a fixed number of randomly concatenated polarization maintaining fibre (PMF) segments. An understanding of the SO-PMD equation is the first vital step to consider before designing such an emulator. The control of the differential group delay (DGD) statistics with wavelength proves to be the key measure for this design. Results show that the mean DGD (or the mean magnitude of the FO-PMD vector ((tau) over right arrow)) of the emulator is biased towards the dominant wavelength-independent (tau) over right arrow of the ODL This is provided the dominant (tau) over right arrow is by far greater than FO-PMD contributions from the other cascaded sections. Experimentally it is shown that when the DGD (Delta tau) is wavelength-independent due to the absence of mode coupling, or when the wavelength-cle pendent DGD spectra do not change with time due to fixed mode coupling, there is negligible influence on the SO-PMD. The PC angle is controlled at an angle 0 to ensure that the sub-emulator (tau) over left right arrow is always parallel to the ODL (tau) over right arrow. Thus by rotating the mode coupling angle 0, we change the wavelength-dependent DGD spectra thereby ensuring SO-PMD variation. (C) 2009 Elsevier B.V. All rights reserved.