Communications performance of a multimode EDFA

We report an investigation of a multimode EDFA used as an optically preamplified receiver. A two-stage amplifier pumped at 982 nm shows gain of up to 40 dB at 1553 nm. We study the communications performance of the receiver at 10 Gb/s and compare it with theory. The measured sensitivity is 220 photons per bit at a bit error rate of 10/sup -9/ and data rate of 10 Gb/s. This is 4.5 dB from the quantum limit of 75 photons per bit for a 56 mode amplifier.