Flat gain EDFA are key devices in long haul DWDM systems. A flat gain is needed to ensure an adequate signal to noise ratio evolution between channels during transmission. The dissipative filter introduced between two sections of doped fiber inside the amplifier can have a small residual reflective contribution at a particular wavelength. We have investigated the impact of such a back-reflection and shown it is negligible for EDFA operation. The gain equalization filter is composed of several slanted Bragg gratings. Slanted Bragg gratings are gratings where the pitches ar enot perpendicular to fiber axis. So, a strong coupling between fundamental mode and the cladding modes occurs. They are written with a CW UV laser in photosensitive cladding fiber in order to lower the coupling between the two contra-propagting modes (reflectivity). For each slanted grating, we have measured the peak wavelength of reflectivity. The strongest back reflection is observed at 1539.88 nm with a 13 dB power level. The average gain was measured at 17 dB for an input level of-1 dB with a gain excursion of 1 dB over 3- nm wavelength range. A BER measurement at 10 Gbit/s shows no penalties are observed for the peak of back reflection.
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