We have investigated the system performance of an experimental Praseodymium Doped Fibre Amplifier (PDFA) in an optical transmission system operating at 1.3 μm. Experimental evaluation of the PDFA, based on Bit Error Rate (BER) measurements, is presented for the PDFA in copropagating and bidirectional configurations as a function of both wavelength and optical input power. The performance is analysed for both NRZ and RZ modulation format at a bitrate of 10 Gbit/s. The polarisation dependency of the PDFA is less than 0.2 dB. The results of an experimental analysis of the PDFA in an optical recirculating loop are shown for a NRZ modulated pseudo random data stream at 622 Mbit/s. A total span of approximately 2000 km is covered. Furthermore, the results of transmission experiments using the optical circulating loop at 10 Gbit/s are presented.